# A DIY AC motor?



## tylerwatts (Feb 9, 2012)

So, background. Been discussion various encarnations of AC motors with cts_casemod and coulomb in this thread, and have some ideas. This link coulomb posted about teh Tesla AC motor suggests the stator of all our EV motors are very simple... So:

Could you convert a simple DC motor by building a custom rotor and dropping the brushes, say converting a strong forklift motor? Options:
*1*. build a permanent magnet rotor using Neodumium magnets, with good heating ducts and CF fan for cooling (not really needed but would aid weight reduction also).
*2*. build an induction rotor custom wound/made or stripped and remounted from a scrap industrial motor.

*Question*, is an interpoled Kostov rotor at all similar to an induction rotor? I suspect the DC rotor is all copper bus bars, and the Induction is special ferritic iron structure...
*Question*, does the (once DC) stator ned rewiring or modifying in some way to operate correctly for AC?

Big questions, but this is the DIY forum, so we like to Do It Ourselves  Trying to think outside the box to come up with a recycled hybrid motor to give us DIYers the performance and options for AC motors no afforded us currently unless modding either DC forklift type systems, or modifying industrial drive motors. 

Any thoughts/brainstorming/suggestions/criticism accepted. Towards the concept that is. If you think Im crazy, your no different to those who chastised Tesla 120 years ago adn screwed the world out of a healthy future


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## Siwastaja (Aug 1, 2012)

My opinion;

If you are going to do your own stator winding...

Junkyards, Ebay etc. are full of old AC induction motors. There you have the surely-compatible stator slots ready, and a suitable rotor. It will surely be easier than modifying a DC motor.

See http://www.diyelectriccar.com/forum...nduction-motor-rewinding-questions-77776.html for my on-going experiment on this... (It's running now, higher power limits to be tested.)

Try to find aluminum frame, and drill holes to cool it internally by forcing air through the air gap.

There are some reports that apparently upping the power by 3x by "overclocking" is possible. We will try this theory, but it will still take some time (need to first get money for batteries to start the conversion). This way, our 7.5 kW frame weighing 52 kg would become 22.5 kW continous, maybe 40 kW peak, if everything goes as expected.

Our rewinding process has been a bit painful but not _difficult_. The next motor will be easy as we have learned from our mistakes.


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## Tesseract (Sep 27, 2008)

tylerwatts said:


> ...
> *Question*, is an interpoled Kostov rotor at all similar to an induction rotor? I suspect the DC rotor is all copper bus bars, and the Induction is special ferritic iron structure...
> *Question*, does the (once DC) stator ned rewiring or modifying in some way to operate correctly for AC?...


The rotor in (most) AC motors is the field so the stator is the armature (yes, AC motors have fields and armatures, too). So, no, you cannot use the rotor from a DC motor with the stator from an AC motor.


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## tylerwatts (Feb 9, 2012)

Still plenty to weight up and think about then. Initially:

Is there benefit to rehousing an industrial AC motor in a smaller Alu frame from the behemoth steel frame of original, and designing in air/liquid cooling channels?

Is liquid cooling necessary? I've toyed with using a small DC driven Air Con system to 'charge cool' the cooling airflow for the motor, should offer a stepped improvement in the motor's performance, but do the trades add up? Maybe for higher continuous power when moving and airflow over the AC radiator is good...

Do people know of a reliable source of second hand industrial motors and controllers, or could suggest where to find them? I noticed at work the other day a warehouse full of old/surplas machinery and noticed a few fairly big motors, but I doubt I could just load one up into my car and head home ha ha. Would be nice to find out though!

Ignoring the system losses, could an industrial 3 phase (or whatever) AC input controller not be modified to operate an AC motor, assuming it could be fead the required AC input? I know in reality we'd want to feed it DC from the Batts, but this is a theory question. Say I was hooked up to an AC tram power supply in the road or something. Just hypathetical...

I'm sure I'll bludgeon the forum with many more strange and wild questions and ideas, I'm the typoe to exhaust my thoughts before deciding what I like best, and am good at pushing boundaries to find new ideas or approaches. Mayby I'm just a baligerant pain who likes to go against the grain, I apologise if it annoys, but hopefully it will also discover some new ideas for everyone too!


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## mizlplix (May 1, 2011)

Every question you have raised is covered in GREAT detail in many complete threads that have beat them to death.



> Is there benefit to rehousing an industrial AC motor in a smaller Alu frame from the behemoth steel frame of original, and designing in air/liquid cooling channels?


 YES-Been done-IS being done:

This is a steel housing being replaced with an aluminum/water cooled shell. It is also being rewound to lower voltage and a higher amperage.




> Ignoring the system losses, could an industrial 3 phase (or whatever) AC input controller not be modified to operate an AC motor, assuming it could be fead the required AC input? I know in reality we'd want to feed it DC from the Batts, but this is a theory question. Say I was hooked up to an AC tram power supply in the road or something. Just hypathetical...


 http://www.diyelectriccar.com/forum...nduction-motor-rewinding-questions-77776.html
http://www.diyelectriccar.com/forums/showthread.php/ac-induction-motor-thoughts-73807.html
http://www.diyelectriccar.com/forums/showthread.php/another-homebrew-ac-controller-45909.html
http://www.diyelectriccar.com/forums/showthread.php/diy-ac-motor-controller-3-phase-78085.html
http://www.diyelectriccar.com/forums/showthread.php/open-source-ac-vfd-conversion-72000.html 
Most of these links are dealing with the issue of converting an industrial controller to EV use, although a couple deal with building your own from scratch.


My advice is to read....lots. Then it will begin to dawn on you the vast wealth of good information here on this forum.

Asking "Newb" questions repeatedly will get you less and less answers from the members.

Addressing one issue at a time is a wise approach to your quest.


Miz


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## tylerwatts (Feb 9, 2012)

Thanks Miz

Have tried various searches before which is why I started asking my questions. I'll definately try those threads, and see if I'm just searching the wrong terms.

I fully appreciate the vast knowledge and support of the forum, thank you! Maybe after a while I'll try compile a sticky of all this information to avoid mroe people asking the same questions.

Thanks all!


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## Coulomb (Apr 22, 2009)

tylerwatts said:


> So, background. Been discussion various encarnations of AC motors with cts_casemod and coulomb in this thread, and have some ideas. This link coulomb posted about teh Tesla AC motor suggests the stator of all our EV motors are very simple... So:
> 
> Could you convert a simple DC motor by building a custom rotor and dropping the brushes, say converting a strong forklift motor?


No. A typical DC motor has 4 poles; a typical AC motor has 4 poles *per phase*. So you need three times the number of poles in the stator.



> *Question*, is an interpoled Kostov rotor at all similar to an induction rotor?


No. An interpoled DC motor is the same as an ordinary DC motor, but has special, smaller poles inserted between the main poles. Since these are not the same size as the main poles, they can't be used as active poles.



> I suspect the DC rotor is all copper bus bars, and the Induction is special ferritic iron structure...


From vague memory, the DC rotor is turns of thick wire in slots; the DC rotor actually looks more like an AC motor's stator than does the DC motor's field windings. The induction motor stator has the classic squirrel cage structure; the essential part of it are shorted turns.



> *Question*, does the (once DC) stator need rewiring or modifying in some way to operate correctly for AC?


Yes; one essential change is that it needs three wires compared to two  Also, the laminations for DC use would probably be wrong for AC, and a host of other problems.



> ... or modifying industrial drive motors.


That's more practical. The modifications needed of an industrial motor are basically to rewire or rewind for a lower voltage, balancing for higher speed, and possibly replacing bearings for higher speed. But this will not reduce the air gap; to reduce the air gap, the motor needs to have been built to tighter tolerances from scratch. So this will only ever result in a moderately wide speed range motor (say up to 6000 RPM), not wide enough to be ideal for direct drive (where at least 10,000 RPM is needed, possibly up to 14,000 RPM).

Modifying an induction motor to become a permanent magnet AC motor is possible, but I don't think it's worth the hassle. For one thing, strong magnets are a pain to work with; there are severe thumb squashing hazards, and spinning the motor will always generate a voltage; you can't turn them off. It seems unlikely that a hobbyist could manufacture an IPM rotor with typical home facilities, and even less likely one that could reach 10,000 RPM.

There are people that modify certain types of washing machine motors to turn them into wind generators; just search. But I don't think that any of those are in the power range needed for a typical EV.


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## tylerwatts (Feb 9, 2012)

Thanks Coulomb.

You say for direct (reduction) drive at least 10krpm is needed. IN the previous direct drive thread CTS says the right motor will happily make plenty torque with a 0-6k rpm range, with max torque to about 4k and peak power from 4-6k. This would be more suited to use with a manual transmission (4th gear). Unless of course a lower gear were used.

Is it reasonable to expect to be able to over clock an industrial motor to such high rpm?

If rewinding the stator, does the rotor design make a difference? Ie would a rotor from say a 2 pole motor operate well in a rewound 6+ pole motor?

Forgive me if I ask questions already answered, not had chance to do all my reading up (thanks Miz ).


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## shortbus (Sep 27, 2011)

tylerwatts said:


> If rewinding the stator, does the rotor design make a difference? Ie would a rotor from say a 2 pole motor operate well in a rewound 6+ pole motor?
> .


If you want an AC motor to turn faster you are going at it wrong. The higher the number of poles the slower the RPM. To get higher speed from an AC motor, the frequency of the AC is what is changed.


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## Siwastaja (Aug 1, 2012)

shortbus said:


> If you want an AC motor to turn faster you are going at it wrong. The higher the number of poles the slower the RPM. To get higher speed from an AC motor, the frequency of the AC is what is changed.


Today, we have variable frequency drives -- most motors for those are designed for 4 or 6 poles/phase. 2 pole/ph motor simply has torque too low (you need to gear it down more, and have higher mechanical and windage power loss), AND an additional I^2R loss due to the fact that most of the copper is not in the slots but in the ends. 4 poles/phase is pretty much considered optimal, or possible 6 poles/phase on larger motors. Instead, if high rpm is needed, it can be more productive to use thinner laminations to allow running at high frequencies. A 4 poles/phase motor produces 12000 rpm at 400 Hz. This keeps motor size down and still gives pretty high torque.

I'd say, forget very high RPM's on a DIY motor. Those 10 000 RPMs are needed in a Tesla-type design, where very high top speed is needed together with fixed single gearing. Are you going to do a 120-150 mph racer, or a "normal" car to move from place A to place B efficiently and conveniently? If the latter, you won't need more than 6000 rpm.


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## tylerwatts (Feb 9, 2012)

Siwastaja

Yes, no high rpm needed. Hence why perhaps rewinding to more poles. But the a larger motor would have more poles anyway.

Shortbus

My question relates to rewinding a 2 pole motor for 4 poles and keeping the same rotor. Would this be ok? Does rotor design vary much? 

Regarding my space constraints, in the spirit adopted by DC guys, could a Siamese Bogor be built for low diameter but twice the torque of the single? That is, timing and locking 2 induction rotors onto the same shaft right next to one another and rewinding 2 matching staters into one longer motor with same voltage (actually lower with longer copper runs right?) and current acting over a larger area? I expect voltage would need to go up to compensate for more copper present.

Any ideas? Thoughts are that say 2 x 10kW rotors alone are short and could be build together onto one shaft for a small increase in length and double the torque, and the stators rewound for the intended application and controller output. Is there any sense in this theory?


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## Siwastaja (Aug 1, 2012)

tylerwatts said:


> Siwastaja
> 
> My question relates to rewinding a 2 pole motor for 4 poles and keeping the same rotor. Would this be ok? Does rotor design vary much?


I have been told that the rotor is ok.

However, the stator teeth are typically much more narrow in a 2-pole design. It may or may not be OK. OTOH, there is more "back iron" in 2-pole.



> That is, timing and locking 2 induction rotors onto the same shaft


Without modification to the motor structure, with two separate controllers, yes.



> right next to one another and rewinding 2 matching staters into one longer motor with same voltage (actually lower with longer copper runs right?) and current acting over a larger area? I expect voltage would need to go up to compensate for more copper present.


You mean getting two identical stators and joining them end-to-end to get double-length stator, and the same for two rotors, and then do single, long windings through both stators like it would be one big stator? At least to me, this sounds like a very good plan. Can't imagine any problems, if you just can remove the stators from the motor housings and build a new housing, and join the rotor shafts without any offset and angle. Of course you would also want to minimize the gap between the stators, hence, you would need to cut the rotor shafts before joining them. Hey, if you can do the machining and fit the long motor (for example, for a rear-wheel drive car in the middle of the car), it sounds pretty good.

The good part here is that these "components", ACIM rotors and stators, are abundant. But if you need two identical, the scrapyard option may become more difficult. Still, these are not _so_ expensive even if you had to buy them new.


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## mizlplix (May 1, 2011)

The ideal AC motor to use for an EV seems to be a 15-20HP, 2 pole, TEFC, inverter duty one designed for a pump. 

They have more back iron, a 50% longer stator, a finned aluminum body for lighter weight, A "C" face plus a second shaft that can be used for the encoder.

The one motor shop gave a cost of $500 to rewind it for EV duty with the Curtis 1238R controller. (rewound to 4 pole) 

Plus the encoder for about $150

SO, $200 for a used core
$500 to rewind
$150 for encoder
__________________
$850USD (approximate cost)

I see the 500amp Curtis 1238 controllers on Ebay sometimes for $900- up.

For $2,000 or so you can have a nice set up.

(These prices are for my area in the Phoenix east valley) Miz


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## Coulomb (Apr 22, 2009)

shortbus said:


> If you want an AC motor to turn faster you are going at it wrong. The higher the number of poles the slower the RPM.


Yes, but a higher pole count means more "headroom" for overclocking before hitting the RPM limit for the motor. By using say a 6-pole motor, you also reduce the fixed ratio you will need, which can end up cheaper and/or more compact.

I agree with others that a 4-pole would usually be about ideal for direct drive.


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## subcooledheatpump (Mar 5, 2012)

Just my $.02, (and I may be wrong on this) 

Wether or not you want 4 or 6 pole depends on your final gear ratio,(like Coulomb said)
and how much current your inverter can output. 
With a higher pole count, you get more torque for less current. A 4 pole motor, to me, seems like it doesn't allow as much slip as a 6 pole does. That (slip) can be useful for stall conditions like a hill start

I agree, for the most part that unless you have a transmission/gearbox, a 2 pole motor is out of the question. Maybe if you have a giant 2 pole motor and a very high current inverter you could use direct drive with a 2 pole motor


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## PStechPaul (May 1, 2012)

The four pole motor seems to be the ideal choice for EVs for several reasons. First, it provides twice the torque in a size equal to or slightly larger than its 2 pole equivalent of the same HP. It also offers the ability to be overclocked at least 2x for twice the HP at a safe RPM of 3600 which is similar to the top end of most ICE vehicles. And, for the DIY project, 4 pole motors are perhaps the most numerous on eBay and surplus sources.

From what I have read, rotor design is somewhat of an art, involving certain ideal ratios of rotor to stator slots, and the degree of "skew" or twist of the rotor laminations. But I have rewound a couple of single phase motors with 24 and 36 slots, to make 3 phase motors of about 10 VAC with 6, 8, and 12 poles. I got them to run, and overclocked up to 4x, but I don't know their efficiency or actual power output. Stator winding is also somewhat tricky, but the safest way is to rewind the same way as the motor was wound originally. And even better may be to use the original windings, but change from star to delta, and use a high voltage battery pack (as high as 600-750 VDC).


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## tylerwatts (Feb 9, 2012)

Thanks all.

So we're saying a rewind of 2 identical stators abutted together to lengthen the stator would work well, and similarly abutting the Rotors onto a single shaft in line with the stators would double the torque, and over-clocking the same amount as a single would give double the increase, ie 4x clocking = 8x power! Iiinterestiiiing! My homework is set then...

Regarding controllers, my intent is to use a reprogrammed Scottdrive controller, probably in higher voltage spec like Ruckus has gotten hold of, so 450VDC and peak 600A. Then if rewinding, the stators would be a new single stator so only require a single controller. BUT I have an interesting question, if I found motors not NEEDING a rewind for this controller, which is quite likely if I'm going single speed reduction (almost direct drive...) and I kept the original windings and the stators abutted together, could I connect them both in Wye and in parallel (like a DC setup) to handle the high current output of this controller and give more torque (iron losses the limiting factor of course).

This is getting too exciting! Great recycling like this... Looks like some building and concept proofing is required!

Read somewhere about larger industrial motors running ~4000VAC. Battery requirements ignored, would there be any benefit to running a system at this voltage? How doies it produce torque if (I'm assuming) it uses little current?

Thanks all!


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## Coulomb (Apr 22, 2009)

I think I can answer this part.



tylerwatts said:


> Read somewhere about larger industrial motors running ~4000VAC. Battery requirements ignored, would there be any benefit to running a system at this voltage?


No, not at the power levels needed for EVs. Plus, 4000 VAC is getting seriously dangerous, and the insulation needed for everything would take up a lot of space.



> How doies it produce torque if (I'm assuming) it uses little current?


Many turns of wire, one-in-hand (none paralleled). That way, you get many amp-turns per amp, and torque is proportional to amp-turns. You also get a lot of back EMF that way, which is fine when you are running 4000 VAC. In other words, you increase the Kv a lot; this gives more torque per amp, at the cost of more volts to overcome the back EMF. Another way of putting it: you wind the motor for higher voltage, the opposite of what we often need to do.

You don't get into this sort of voltage range until the tens of megawatt power level. BTW, the "little" current may run to thousands of amps. A small power station generator (a synchronous AC wound rotor motor run as a generator) might produce 2000 V at 2000 A, or about 6.9 MVA. (And that's its continuous rating .) So the many turns would be of very thick wire or bar.


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## tylerwatts (Feb 9, 2012)

HAHA ok lets steer clear of those vehicle-sized motors then... Not trying to drag race!

Any advice/guidance on my other ponderings? Am I pushing my luck, or is there very reasonable sense in trying this?


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## shortbus (Sep 27, 2011)

To all - my statement of poles was directed at the 10,000 RPM requirement. As far as I've found, the stator core is the same for 2, 4 ,and 6 pole motors. The difference is in the actual windings. Most of these motors use a 36 slot stator, or at least the ones I'm familiar with. Even motors within a certain frame size use the same stator core and just change the physical windings to make the different horsepower and RPM ratings in that frame size.


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## Tesseract (Sep 27, 2008)

shortbus said:


> .. As far as I've found, the stator core is the same for 2, 4 ,and 6 pole motors...


This might be the case, but it shouldn't be. The higher the pole count the more "back iron" is needed in the stator. This is because torque is proportional to flux and the more flux required the more iron area is required to support it without saturating. This also means that higher pole count motors tend to weigh more for a given power output.


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## tylerwatts (Feb 9, 2012)

Shortbus, Tesseract

I think you might both be right. In some cases for manufacturability and mass production each frame size could easily use the same stator core with different windings and the lower pole motors just be nowhere near saturation point.

additionally I expect higher end/quality motors made more bespoke will have specific designs for their intended applications so likely be designed more specifically to maximize performance.

so we all agree locking rotors and aligning stators is feasible. What about timing the rotors to one another? Is there anything to be aware of and ensure correct alignment of?


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## major (Apr 4, 2008)

Tesseract said:


> The higher the pole count the more "back iron" is needed in the stator. This is because torque is proportional to flux and the more flux required the more iron area is required to support it without saturating.


Hi Tess,

I usually stay off the roll-your-own motor threads, but couldn't resist correcting you (or your terminology)  BTW, it was a pleasure to have finally met you.

Back iron is the steel in the yoke in between the poles. In the typical AC stator, as you find in the NEMA induction motors, the back iron would be the material of the stator between the bottom of the slots and the outer diameter. 

As the pole count increases, the minimum requirement of back iron cross section decreases for a given diameter rotor and therefore the stator outer diameter can actually decrease while holding the slot geometry the same. More poles mean less back iron flux for the same total air gap flux.

More poles means smaller poles which means less flux in the magnetic path connecting the poles.



> This also means that higher pole count motors tend to weigh more for a given power output.


Higher pole count AC motors for mains frequency (like 60 Hz) run slower and therefore "given power output" motors are larger so they can produce greater torque. Even with this increase size, the actual back iron mass theorectically could remain the same.

Regards,

major


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## Tesseract (Sep 27, 2008)

major said:


> ...
> I usually stay off the roll-your-own motor threads, but couldn't resist correcting you (or your terminology)  BTW, it was a pleasure to have finally met you.


Well, I ought to know better than to comment on motor threads in general... 

Likewise on meeting you, and congrats on the best-in-show win for that bad-ass open-wheel roadster you built.



major said:


> Back iron is the steel in the yoke in between the poles.
> ...
> More poles means smaller poles which means less flux in the magnetic path connecting the poles.


Err... I am having a tough time with this one. Is it not true that each pole will exert the same net force on the rotor in a 6 pole 10hp motor as each pole in a 2 pole 10 hp motor? Ie, the torque in the 6 pole motor will be 3x higher and the speed will be 3x lower. 

As for the reduction in needed back iron cross sectional area as pole count goes up, I can sort of see that happening because the back iron only has to support the vector summation of the flux from each pole, but that still means there will be areas of higher and lower flux density, no?

I don't know why I bother arguing with you about motors... I'm always wrong, you're always right...


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## major (Apr 4, 2008)

Tesseract said:


> Likewise on meeting you, and congrats on the best-in-show win for that bad-ass open-wheel roadster you built.


Thanks. First time I saw your handiwork up close and personal. Nice lookin' boxes. You won the dynamometer contest, didn't you  Like 350 HP 



Tesseract said:


> Err... I am having a tough time with this one. Is it not true that each pole will exert the same net force on the rotor in a 6 pole 10hp motor as each pole in a 2 pole 10 hp motor? Ie, the torque in the 6 pole motor will be 3x higher and the speed will be 3x lower.


Hmmm. Might be a loaded question. I guess so, but the poles in the 6-pole motor would be the same size as the poles in the 2-pole motor. 



Tesseract said:


> As for the reduction in needed back iron cross sectional area as pole count goes up, I can sort of see that happening because the back iron only has to support the vector summation of the flux from each pole, but that still means there will be areas of higher and lower flux density, no?


Sure. It is practically impossible to shape the motor magnetic circuit for consistent flux density.


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## PStechPaul (May 1, 2012)

I think one reason higher pole count motors are larger is that there is more overlap of adjacent poles. When I wound my 36 slot stator, each slot had two sets of windings which had phases of:

A+C'
C'+B
B+A'
A'+C
C+B'
B'+A

And this repeated 6 times which made a 12 pole motor (6 pole pairs).

If you add the vectors of these pairs, which are 60 electrical degrees apart, the resulting current (I think) is 1/2 the magnitude of each. So this may explain the lower HP for the same frame size in smaller motors with the same slot count. 

I have three motors of equal size, and one is 2HP 2 pole, another is 1.5HP 4 pole, and I have a 1 HP 8 pole. But when I looked at larger motors (20-100HP) I found no size difference between 2 and 4 pole, and little to no difference for 6 and 8 pole. I think this is because they have more slots (probably 72 or more), so the winding pattern is more efficient.

Another reason might be that a motor with more torque needs a stronger frame.


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## Tesseract (Sep 27, 2008)

major said:


> Thanks. First time I saw your handiwork up close and personal. Nice lookin' boxes. You won the dynamometer contest, didn't you  Like 350 HP


356hp, but who's counting? 

This was limited by the battery pack, of course, which is comprised of 6p96s of 8Ah Headway cells. Battery current in each controller was limited to 750A so we "only" punished them with a peak discharge current of ~31C... 

Of course, the same could be said for your "Ariel Atom" lookalike, right? Those Hawkers hold up pretty well under high amp loads but lithium really is "all that and a bag of chips"...



major said:


> Hmmm. Might be a loaded question. I guess so, but the poles in the 6-pole motor would be the same size as the poles in the 2-pole motor.


Oops... I didn't finish writing what I intended to write there. I meant to add that each pole in the 6 pole motor has to be as large as each pole in the 2 pole motor to contribute the same net force to the rotor at the same flux concentration and amp-turns, so the stator has to be bigger, right?


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## shortbus (Sep 27, 2011)

Tesseract said:


> This might be the case, but it shouldn't be. The higher the pole count the more "back iron" is needed in the stator. This is because torque is proportional to flux and the more flux required the more iron area is required to support it without saturating. This also means that higher pole count motors tend to weigh more for a given power output.


The one thing you may have missed in my post was the words, " certain frame size". This means that for a given NEMA frame size the dimensions are the same physical size. And within that frame size there are several different RPMs (pole numbers) and horsepowers (winding wire diameter is the big difference in this).


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## tylerwatts (Feb 9, 2012)

My head hurts! Anyone know a tutorial with illustrations please? I just can't visualize this...

Thanks!


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## shortbus (Sep 27, 2011)

I know this thread is about AC motors, but for a DIY motor the best and easiest is a SRM. I am biased though as that is what I have researched and going to build.

The can be made using a stator from a induction motor, by cutting out the unwanted teeth. They are wound with salient poles. They have an almost flat torque level at all RPMs, from a stand still to over 10,000 or more RPM if needed. They require no magnets or windings in the rotor. 

The controller is really no harder than an AC motor controller or BLDC controller. And there is no "cogging" torque like a PM or BLDC motor.

Sorry to hijack the thread but so far not too many people are familiar with the SRM.


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## major (Apr 4, 2008)

Tesseract said:


> 356hp, but who's counting?
> 
> This was limited by the battery pack, of course, which is comprised of 6p96s of 8Ah Headway cells. Battery current in each controller was limited to 750A so we "only" punished them with a peak discharge current of ~31C...
> 
> Of course, the same could be said for your "Ariel Atom" lookalike, right? Those Hawkers hold up pretty well under high amp loads but lithium really is "all that and a bag of chips"...


The roadster did pretty well in the autocross. Took 1st. But you big boys stayed on the strip. The 270 hp Tesla came over and bested our time by a second or 2, but then he wasn't a conversion, so didn't count. I was pleased with the performance on Pb. We were still in break-in mode, about 60% settings, IIRC. Being the only Pb there I was glad to see no discrimination.



Tesseract said:


> Oops... I didn't finish writing what I intended to write there. I meant to add that each pole in the 6 pole motor has to be as large as each pole in the 2 pole motor to contribute the same net force to the rotor at the same flux concentration and amp-turns, so the stator has to be bigger, right?


Yeah, really all the pole count does is set the frequency. When it comes to torque, size matters


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## Tesseract (Sep 27, 2008)

tylerwatts said:


> My head hurts! Anyone know a tutorial with illustrations please? I just can't visualize this...
> 
> Thanks!


This site appears to have some good animations:

http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

And this short youtube video looks helpful:

http://www.youtube.com/watch?v=nf0RPtkJnpE

It's tough to wrap your head around how an induction motor works, so don't feel bad if it gives you a headache


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## Tesseract (Sep 27, 2008)

major said:


> The roadster did pretty well in the autocross. Took 1st. But you big boys stayed on the strip.....


Seb never drove the 911 on the autocross track? Probably for the better, since all day he was running on just one controller and motor (the other one was faulting off with a 12V too high error because of a ground loop... can't have anything to do with the car being 34 years old, can it?).



major said:


> Yeah, really all the pole count does is set the frequency. When it comes to torque, size matters


Yep. I think we'll leave it at that... no sense diving into even more esoteric details like that higher pole count motors tend to require more magnetizing current (ie - have lower power factor) and such...


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## tylerwatts (Feb 9, 2012)

Thanks Tess!

Woah woah, Shortbus!

Please do hijack and share! Your motor doesn't sound too different to an AC motor from a DIYer's perspective so please share your information. Not to seem pessimistic, but it sounds almost too good to be true. Please share what you know.

Thanks!


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## tylerwatts (Feb 9, 2012)

Shortbus

Doing my homework and this says the main drawback of these motors is torque ripple. Looking on Google says this is exactly what ICEs have, pulses of torque. Fine with me, I'll hold onto my dual mass flywheel then to keep my trans in good shape. 

So do tell of this motor then please.


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## mizlplix (May 1, 2011)

As long as we are dreaming:

I would take 2 identical pump duty motors. About 10 HP or so. Strip them for parts. 

Trim one end of the rotors of their little fins so they would sit closer together and somehow couple them as one unit, OR make a new shaft and put the two trimmed rotors on it. Phased as close as possible.

Using that, I would put the two stators together with a spacer in the middle to keep their spacing same as the rotors. I am not sure if the spacer needs to be steel/laminated or aluminum.

Custom make an aluminum housing for them and use the two "C" face end caps. 

I would then wind BOTH stators as though it were one big one. Mount an encoder to one end. 

Maybe it would be just as easy to have custom rotor and stator plates cut and make your own instead...

Miz


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## tylerwatts (Feb 9, 2012)

Well this seems very informative. How to find one aftermarket though...

Does anybody know whether an AC controller, say a Scottdrive  , could simply be reprogrammed to drive one of these SRM motors? I'm quite interested in these now. Though building one looks tough, would have to buy one, ideally 3 Phase to match an AC motor.

Any thought folks?


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## Salty9 (Jul 13, 2009)

mizlplix said:


> Maybe it would be just as easy to have custom rotor and stator plates cut and make your own instead...
> 
> Miz


But not cheaper. Check http://endless-sphere.com/forums/viewtopic.php?f=30&t=41576&start=75

A fairly decent motor building thread.


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## Siwastaja (Aug 1, 2012)

shortbus said:


> I know this thread is about AC motors, but for a DIY motor the best and easiest is a SRM. I am biased though as that is what I have researched and going to build.
> 
> The can be made using a stator from a induction motor, by cutting out the unwanted teeth.


But if you need an induction motor stator for the build, you could be easier off using the rotor too, and just rewind the stator...

Just saying. Of course, if you _want_ to make a reluctance motor for any reason over induction motor, then it is of course a great idea and probably easier than cutting and insulating the laminations from scratch.

Industrial ACIM are just so abundant that it still seems like a winner solution to me in relative easiness. But it's not the time for me to celebrate yet. The rewind was a bit PITA but we got it done and having learned from our mistakes, the next one will be much easier. (Don't use wire too thick...)


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## PStechPaul (May 1, 2012)

I tried to use a rotor from an ACIM for a SRM. The stator seemed perfect, having six individually wound poles, except for the problem that it was a shaded pole motor which has split pole pieces with a shorted turn to create phase shift. However I figured I could cut the shorted turn and the extra small slot would not be a problem.

However, the rotor consisted of a stack of skewed laminations with aluminum end caps and aluminum rods through slots in the laminations. I was able to cut the caps off and I could pry some of the laminations loose, but the aluminum rods made it difficult. The laminations and skewed slots made it impossible to cut notches to make a switched reluctance rotor.

I looked into having laminations custom made, and the cost is on the order of $500 to $1000 for a 2-5 HP motor.

While searching for more information I came across some interesting articles:
http://www.grc.nasa.gov/WWW/RT/2005/RX/RX48S-morrison.html (novel SRM with maglev bearings)
http://ddmotorsystems.com/ElectricVehicles.php US made EV DC motors and controllers
http://www.reliance.com/mtr/mtrthrmn.htm (some good motor theory info)
http://www.phonature.com/education_DIYMotor.htm (DIY motors, PCB motors)
http://www.cedengineering.com/upload/AC Generators and Motors.pdf (Motor and Generator principles)


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## Salty9 (Jul 13, 2009)

Paul,

Good find of that NASA site. In checking the parent URL I found a treasure trove of info. 

Chuck


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## shortbus (Sep 27, 2011)

tylerwatts said:


> Thanks Tess!
> 
> Woah woah, Shortbus!
> 
> ...


There's another thread started by PStechPaul, on the forum that has a lot of information and links to SRM motors. I kind of hijacked that one too.

The Srm controller is similar to a BLDC controller but with out the need of reversing the direction of current. The Flux reversal in the stators of both ACI and BLDC motors is one of the biggest heat producers of the motor.

The SRM has next to no end windings in the stator so not any where near as much "copper loss". And as said earlier. the iron loss in both stator and rotor is also much lower. I was a skeptic too about the SRM until I started researching them. Was going to try a BLDC but the more I read about them and magnet prices and the problems holding magnets onto the rotor in a "in-runner" type motor, The SRM seems a lot better.

Most of the problems with the SRM due to torque ripple and noise in them, is in reference to there use in appliances and small applications like that. Like you said they are similar to the ICE. But even those problems have work arounds to them, and really not a problem in a vehicle.


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## tylerwatts (Feb 9, 2012)

Well I've missed a lot over the weekend! Thanks for all the info folks. I'll try find the other thread, and also how easily I can locate a used SRM and go from there.

I wonder whether an SRM industrial drive can be hacked for torque drive in an EV like is done with VSDs for induction motors, part of my homework then.

Catch up soon.


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## shortbus (Sep 27, 2011)

Here's a link to Paul's thread on SRMs - http://www.diyelectriccar.com/forums/showthread.php?t=77483&highlight=switched+reluctance+motor

As far as a torque drive I don't think that is needed with a SRM. The torque curve is so flat with a SRM. The SRM is made for variable speed, not like an ACIM that is a "synchronous" motor and only operates a peak torque in a small RPM range.


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## Coulomb (Apr 22, 2009)

shortbus said:


> As far as a torque drive I don't think that is needed with a SRM. The torque curve is so flat with a SRM. The SRM is made for variable speed, not like an ACIM that is a "synchronous" motor and only operates a peak torque in a small RPM range.


Huh? An induction motor (ACIM) is asynchronous, and has a flat torque curve from zero to base speed. I don't get your point.


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## tylerwatts (Feb 9, 2012)

Yes, *Shortbus* please clarify why you say that. I agree with Coulomb, the ACIM is asynchronous an dproduces flat torque to base speed.

Also, torque drive controls how much torque, regardless of speed, so if I apply 50% torque and going down hill it is sufficient to accelerate speed it will, but goign up hill if load exceeds torque outputted at 50% the car will slow down until torque is sufficient to maintain/accelerate again. Torque will not change. To accelerate I need excess torque, and how much acceleration and how much torque are directly proportional (at a given speed, before I get told...) so torque control is what's needed to 'manually control the vehicle speed similar to how an ICE does.

Someone correct me if I am wrong please.


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## Tesseract (Sep 27, 2008)

tylerwatts said:


> ...I wonder whether an SRM industrial drive can be hacked for torque drive in an EV like is done with VSDs for induction motors, part of my homework then.....


The circuit for for driving switched reluctance motors is very different from the usual 3ph. inverter. It essentially uses a "two switch forward converter" to drive each phase, rather than a fully controlled half bridge.

SRMs are also very difficult loads to drive from an electronics standpoint because the stator inductance is a function of the alignment angle between salient rotor and stator poles (as the poles approach alignment the stator inductance shoots up and as the poles recede from each other the stator inductance drops down again). Since torque depends on stator current and stator current depends on inductance and pulse width, you can see that the microprocessor in the SRM drive has a pretty heavy workload. Much more so, even, than doing FOC of an induction motor.

For all their ills and woes, SR motors are very cheap to make, so there is no doubt they will be used more and more in the future. However, they will likely occupy the same niche as the econobox 4-banger, and not that of the V-8, in automotive applications.


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## tylerwatts (Feb 9, 2012)

Well, out of curiosity I came up with a simple Axial Flux Switched Reluctance motor design... I will post a couple images in a second.

For the wiring and cooling, I will use heavy gauge and heavy insulation wiring first around the stator cores, most likely in 2 layers to equal aprox 5mm thick all round adn then also insulated dia 5mm heavy walled copper tube for cooling which will be cooled by a simple AC cooling system rather than liquid cooling. But I am not sure this will be more efficient than liquid cooling but since the AC cooling lines can almost freeze I'd expect them to have better heat transfer.

Alternatively a more radical design I've thought of is to use the heavy gauge (approx 1mm wall) copper tube as the conductor for the coils also and have 2 layers per the wiring route but the AC coolign system would directly cool the wiring then, and also the iron cores so potentially offer higher power density. But this would only be used if I could get a robust and reliable design to work with this route.

What do people think?




The controller scares me a bit but I was thinking of a simple 'brute force' design where the coil pulses are simply controlled by the timing of the rotor relative to the stators and the variation in output is controlled by high frequency pulse width modulation similar to a DC controller being switched across different poles according to the timiing of the motor.

Tesseract, all others

Do you think this approach, almost like a modified DC controller and 'electronic points' switching the output to the necessary stator coils to drive the motor. the points of a distributor are a good analogy for this control method. What do folks think?


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## tylerwatts (Feb 9, 2012)

AFSRM:








AFSRM with flange for mating to transmission:









This is the transfer box on my transmission that i must clear with my motor, hence being limited to a Dia220mm motor and why I figured a well designed Axial Flux SR motor might be a perfect fit.









Can't seem to get the pictures to link properly... Moderators, please!


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## PStechPaul (May 1, 2012)

The links seem to work:
http://www.diyelectriccar.com/forums/album.php?albumid=198&pictureid=1153

If you right-click on the picture from that link, select "Copy", and then "Paste" into the post, you get this:


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## tylerwatts (Feb 9, 2012)

Wow who knew it was so simple! Thanks Paul!

Post updated... Thoughts?


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## tylerwatts (Feb 9, 2012)

Well, I had my own thoughts after posting that. If thinking of it as a distributor, or the rotor of a dc motor one could almost design a motor that mechano-electronically triggers the phase switching through hall sensors or similar with the correct triggering duration to match the angular rotation for each phase. and power could be supplied by a regular dc controller.

Actually I'd use a less than regular, or rather extraordinary Soliton controller and large IGBTs to switch the phases. Perhaps the trigger sensors would need to trigger a driver circuit to properly trigger the IGBTs but that is a small additional requirement.

Have I got my wires crossed or does this over simplification of SRM control seem feasible?


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## tylerwatts (Feb 9, 2012)

So nobody seems to be interested in my hair brained schemes ha ha. All forgiven...

Well I've had another one. What do folks think of the idea of using the cooling medium or liquid as the conductor for the coils? I was thinking that flowing the liquid through insulative tubing like a high temp plastic with cathode and anode connection each end of the piping around the coil and the long cooling path to the rad meaning the current will obviously take the shortest route through the motor coils with only a small amount of loss through the rad.

Sound crazy?


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## PStechPaul (May 1, 2012)

I've thought about your ideas but I need to do more with my prototype to comment with any confidence. I do not think using the coolant as a conductor will work. I think copper has far better conductivity than any liquid (except perhaps molten metal).

My prototype motor did not use any position sensing, and it worked, but not very well. I thought maybe a simple sensor to detect the position of the rotor might work. The algorithm I used provides a rotating sequence of electromagnetism and once the rotor is synchronized it runs. So it may be that a simple speed sensor may suffice to adjust the drive frequency as it accelerates. I think it will self-start if the sequence is slow enough.

I may get back to my experiment in a while, but I'm working on something else at the moment.


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## tylerwatts (Feb 9, 2012)

Thanks Paul

Glad I'm thinking along rational lines then. I'm more concerned with what to use for laminations, or where to get proper ones cut.

Do you know a reasonable way to calculate the potential performance of a motor, what the torque would be at given current (current translated to magnetic flux, minus losses, translated into rotational force, equals torque, and maybe a theoretical power band) please?


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## shortbus (Sep 27, 2011)

To get the most out of a SRM the phases have to be timed correctly. The most important is the turn-off timing. It has to be turned off slightly before the rotor is fully aligned with the stator pole. If not the rotor will then start to generate a BEMF and slow down its rotation.


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## PStechPaul (May 1, 2012)

shortbus said:


> To get the most out of a SRM the phases have to be timed correctly. The most important is the turn-off timing. It has to be turned off slightly before the rotor is fully aligned with the stator pole. If not the rotor will then start to generate a BEMF and slow down its rotation.


It seems like that could be done with a shaft position sensor that can be adjusted almost like the timing on a distributor. It could also have a centrifugal advance if the timing needs to change with speed. Of course that could also be done electronically.

There is also a change in inductance as the rotor approaches and crosses the stator pole. Perhaps an AC signal could be superimposed on the DC drive to detect the inductance more precisely. And it might be done on an unused rotor pole, although my idea is to use all of them. 

My concept requires bipolar drive of the stator poles, which means an H-bridge per pole pair and the associated problem of cross-conduction unless you have dead-time. But if I am correct, my concept will provide much more torque than the standard design, where only one or two pole pairs are energized simultaneously.


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## tylerwatts (Feb 9, 2012)

Paul
Could you direct me to some info on bi polar srm please, I don't understand the concept or how an srm rotor could be bi polar.

Thanks


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## PStechPaul (May 1, 2012)

In my thread http://www.diyelectriccar.com/forums/showthread.php/switched-reluctance-motor-77483.html I show my idea. It essentally makes the rotor an electromagnet whose polarity follows that of the poles of the stator. It may not work as well for a short path SRM. The short path concept may work better for large diameter "pancake" motors where many poles may reside on the periphery while the bulk of the rotor may be of lightweight non-magnetic material. For a "sausage" design, the single pole rotor may be used with a longer path through the center. Depends largely on the speed/torque requirements and the physical shape that best fits an EV.


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## shortbus (Sep 27, 2011)

tylerwatts said:


> Thanks Paul
> 
> Glad I'm thinking along rational lines then. I'm more concerned with what to use for laminations, or where to get proper ones cut.


Another saving grace with a SRM is that the laminations don't have to be nearly as thin as with an AC or brushed DC or BLDC motor. Since the polarity doesn't reverse directions there is a much smaller amount of eddy current/iron loss in the motor core.

Haven't tried it yet, but I'm betting 16ga hot rolled steel would work good for the laminations.


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## PStechPaul (May 1, 2012)

I think it would be worthwhile to try steel wire which can be formed to match the ideal magetic flux path, and then sealed with epoxy. I have seen information about toroidal current transformers that were made this way. It may be easier for a DIY project, since all you need is wire cutters. It may be possible to make a mold from flexible tubing and then push the wires through it until it's a tight fit, then fill it with epoxy or other binding material. Finally you would mount the pole pieces onto the rotor, which could also be a molded assembly with a steel axle. Then chuck it in a lathe and grind the surface to fit the stator. The stator pole pieces could be made in a similar manner. If you can make both of them in a shape like a cut toroid it may be most efficient.

I could not find the website, so here are some references to the topic:
http://www.electro-tech-online.com/...iews/40181-homemade-toroidal-transformer.html
http://amasci.com/elect/mcoils.html
http://www.jfe-steel.co.jp/en/products/electrical/supercore/index.html (worth considering for high frequency motors)
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4717740
http://www.worldofsteel.com/resources/electrical_steel.htm (general info about electrical steel properties)


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## tylerwatts (Feb 9, 2012)

Hey very nice idea with the wire! Woudl hve to find out where to get the right type from, and insulate it somehow. One of those links mentioned the wire needs insulating from neighbouring strands to prevent eddy currents and cross-currents so this could be a headache. But some spray paint insulation would do the trick in this case, before sealing the wire with epoxy.

Would probably assemble the cores in a nylon or similar template to allow them to set etc before insulating and assembling into the motor and wiring the stator.

Anyway, any thoughts ont eh layout I showed earlier? Based it on Axial Flux SRM with diameter limitted by clearance in my vehicle. Wondered if I could calculate potential power capability to know whether I'd want to stack 2 or 3 stages of motor to get good power output. Worried that limited rotor diameter will limit the torque output of the motor. Contemplating using a fixed or 2 low ratios and a high rpm or V/rpm winding arrangement to carry the potentially limited torque over a wider rpm range with a better mechanical advantage in the lower ratios.

But I'd need to estimate the power output first. Wouldn't like to machine that whole lot to try it to find out the torque output is too low for my 4wd system...


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## shortbus (Sep 27, 2011)

tylerwatts said:


> But I'd need to estimate the power output first. Wouldn't like to machine that whole lot to try it to find out the torque output is too low for my 4wd system...


If your good at math, the links I posted in Paul's thread have the formulas to figure out just about everything for a SRM.


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## tylerwatts (Feb 9, 2012)

Awesome, thanks Shortbus! Will do my homework this evening!


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## shortbus (Sep 27, 2011)

About the steel wire for a motor core/rotor. How would it resist the magnetic forces and in the rotor the rotational forces? Don't quite understand how it would even be formed to make stator or rotor.

Even with an epoxy matrix around it there is a lot of force involved. Don't forget your moving a vehicle with this, a lot of force trying to tear the motor apart.

I was a die maker/machinist for 45 years and worked in some small shops with pretty primitive equipment some times, so had to be creative. How about using sheet metal and just band sawing the shapes needed for laminations? If they were made slightly (~1/64 - 1/32 inch) undersized they could the be assembled and coated with epoxy where the windings are put in the slots. That would make them smooth and insulate them from the windings at the same time. Then the bore and outer diameter of the stator would be the only critical machined areas. The same could be done with the rotor profiles.

When first starting out on this quest, I was going with a design that used "E" laminations from a transformer to make the stator. It was a design that I found in the patent office files. Even went as far as buying the laminations to use. They are ,to me, expensive. A six inch stack of laminations was $230. The plain blank lamination steel is very hard to find. They want to only sell it by the coil, and a two ton coil at that. 

Since the SRM is a straight unipolar motor, lamination steel isn't even necessary. Many commercially made motors both AC and DC just use low carbon steel in the laminations.


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## tylerwatts (Feb 9, 2012)

Ah so just thin low carbon steel sheet would work? Would if need to be insulated between laminations?

Is there not a lower weight magnetic material that can be used for the laminations?


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## PStechPaul (May 1, 2012)

It may be worthwhile to contact some companies who specialize in magnetic materials and transformer laminations:





 
and here is how it's done with laser cutting:





 
and a DIY version:





 
http://www.cnc-laser-cutter.com/

You can get a 40W laser cutting machine for about $1500:
http://www.amazon.com/Desktop-40Wat...510390&sr=8-2&keywords=Laser+Cutting+Machines

A larger one for $2700:
http://www.ebay.com/itm/New-USB-Las...789?pt=LH_DefaultDomain_0&hash=item1c2cf92d0d

or for $10k:
http://www.ebay.com/itm/CAMFive-Cut...060?pt=LH_DefaultDomain_0&hash=item2a25ae055c

But many of these machines seem to more for engraving to a depth of about 0.1 mm in steel, and may only be able to cut materials like wood and plastic.

A serious machine (1 kW) is more like $45K:
http://www.ebay.com/itm/Trumpf-304-...135?pt=LH_DefaultDomain_0&hash=item2ebe95f0af


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## shortbus (Sep 27, 2011)

Here's a link to a good read about electrical lamination steel - http://www.aksteel.com/pdf/markets_products/electrical/Mag_Cores_Data_Bulletin.pdf


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## tylerwatts (Feb 9, 2012)

Wow thanks guys! I'll catch up on the readin gand think about what I might do. Forgive the slow progress, this project takes a back seat to daily life unfortunately!

BUT thanks for all the help! Really appreciate it!


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## Arlo (Dec 27, 2009)

Lots of great info here thanks mitz.


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## Reactor1967 (Oct 23, 2014)

I have been reading a old timer book on how to build a dynamo/electric motor. The book shows how to calculate horse power, watts, and what-not. Stuff I already know but for the beginner this would be greatly beneficial in building their own AC or DC motor for an electric car or truck. Now, as with old things the language is English but in their day they phrased their wording much differently than we do today. We are talking way back when Edison and Tesla were alive and doing well.

Now, the reason I am writing this post is because these old books show and tell how to build a motor from the ground up from scratch pretty much at home. And, using things that are so simple that a person could run to their hardware store and get and make it work in the motor.

Now, these old designs would need some tweaking to make them work in an electric car or truck but it is a matter of building the parts to the right size and specifications plus doing the math calculations so the motor produces the right horse power and consumes the correct voltage and watts for the horse power calculated. Plus the design allows for the connections to be changed around so things can be changed. Which again is another reason I am writing this post. The old designs could be tweaked to the individual person. A sort of old timer OPEN SOURCE HARDWARE. YES BACK THEN THEY DID NOT KNOW IT WAS OPEN SOURCE SO THEY CALLED IT OTHER THINGS. OPEN SOURCE HAS BEEN AROUND A LONG TIME.

A lot of these motors can be built with a simple DIY AT HOME iron,steal, and aluminum foundry, a 3d printer, and a cnc machine and the average person could sit at home and build motors for electric cars or trucks all day long. Well with a little help from a good online electronics store too.

Now, most people may prefer a good DC motor but AC motors work best but they are more complicated. I have seen designs where a person would need 4 or more castings and some cuttings that have to be treated and stacked and then the person could wound by hand or build a simple winder out of a few pieces of wood and a handle to wind the coils. Plus either a lath or few tools to smooth off ruff spots then the home built EV motor could be built.

So, yes most people like advance technology but my post here is to tell people to look at earlier technology from books that they can get for free like I did with my e-reader or from their local library and they could build their own damn AC/DC motors for their electric car and not spend very much money in the process.

Just look at what you need for a motor. Coils on the outside. A round thing that turns on the inside with coils. Brushes that provide power to the thing turning on the inside so the coils have power. No I am not using correct terminology because I need most people reading this to understand. 

In the old days they would wind their coils on much simpler devices than we have today with terminal post for the connections between coils, insulation, varnish, wax and cotton, and make all that stuff work to make a motor or generate power.

So, no the average person at home does not need to go out and spend $5000 to $8000 dollars. Yes they can buy a simple forklift motor and do 50 miles an hour on the interstate or build a cheaper better motor and do 70 on the interstate plus pull their boat or climb that mountain to get to deer camp with a EV car or truck.

I guess what it all boils down too is common sense and know how. The older books on how to build dynamos and electric motors is all one needs to build a motor for an electric care. I wish everyone luck on their projects.


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## major (Apr 4, 2008)

Reactor1967 said:


> Just look at what you need for a motor. Coils on the outside. A round thing that turns on the inside with coils.
> <snip>
> Yes they can buy a simple forklift motor and do 50 miles an hour on the interstate or build a cheaper better motor and do 70..........


Hi Rea,

Welcome to the forum. I guess you got it figured out. You're so confident you can build from scratch a motor which would out perform a forklift motor, I dare you. Double dare you. Why didn't you just do it before writing that post? That would have have been impressive. Otherwise you have meaningless rambling from a guy who has looked at some pictures and diagrams in an old text book without a clue as to the physics involved in electromechanical energy conversion.

suggestion: Read or lurk on the ES forum. There are a couple of guys over there who are serious about scratch building motors albeit for bicycles. Like members Miles and Lebrowski. http://endless-sphere.com/forums/viewforum.php?f=30 Then figure out what it will take to better the fork motor and do 70 in an EVcar on the interstate. Get real.

Dream on,

major


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## Ivansgarage (Sep 3, 2011)

Thats the funniest thing I have read in a long time.


Major, your just a dream wrecker. LOL


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## Reactor1967 (Oct 23, 2014)

Well I can really tell that I am in a place where people have a lot of respect and truely care for others. I can really feel the love here. That being said, I love the post someone made that just AUTOMATICALLY assumed I have never built a motor before coming here and posting. 

Well, that could not be further from the truth. My topic here today was to try to help others understand how to build a motor at home and yes better than a fork lift motor.

You see, I use to build motors for a living. In fact I have built the heck out of them. I had to operate the machines to make the shafts for the motors. I had to wind the coils. I had to varnish the coils. I had to look at blue prints. I had to put everything together including winding the coils. I learned that there were many ways for a motor to be bad. So, I just have to say that reading the previous post to my orginal post is the FUNNIEST THING I HAVE READ IN A LONG TIME.

But, I was trying to let my readers know that the best place to start was with the older books because they tell how to do things the DIY way. Newer books don't do that or do not do that very well.

For starters the watts the motor is going to be running at has to be calculated first. That would be the voltage times the amps. That gives watts. And, the size of the wire in the motor has to be calculated to handle the current the motor is suppose to use.

Now 1 horse power = 745.699872 watts. So, with a car you need to know how many horse power the motor is going to use. Convert that to watts. Then that the voltage you plan to run in that motor and calculate the current for the motor. That tells you the size of the wire to use in the motor

Now, after the size of the wire is calculated how many rolls per square inch can you do with that wire? Figuring this out will tell you how big to make your parts in the motor.

Now another thing. When winding the coils a winder can be made with some wood and a handle to help wind the coils. Now, funny thing about coils. You need to know if the coil you are winding is going to be N pole, S pole, or flip back and forth. There is a left hand right hand rule for winding to get the correct poles.

There is so much more a person needs to know to make their own motors at home. Now, I have my own foundry and cast my own parts but if you can not do that the parts can be ordered from a machinist. Now days with the Internet that is real easy to do.

So, please everyone do not let a few disgruntled people ruin your day by trying to tell you that someone can not make their own EV motors at home. It can be done. The cores for these windings now whether they are all iron or laminated iron stacked up will effect the heat the motor puts out so depending on the size of the motor getting a good core is important because the motor can heat up enough to melt the wire so good planning is important. Know they core before you use it.

Now the design of the motor. There are many designs. you certainly do not have to build the design that commercial motors use. That is why I like the older books. Some of the books I read told me what to buy at the hardware store to make the motor. They used post to tie, solder, or wax wires too. 

It told me how to make my own wire insulation. It told me how to varnish my cores. It told me how to fix problems like the core being winded too tight and the wire cutting into the core causing a leak in the current. That causes the current to bypass the coil. Two wires wound too hard together can cause another problem.

The books told me what equipment to use to check my windings electrically as I wound the motors. Now, before when I made motors I checked all that at the end and if it was bad I had to take the whole thing apart and test it but no, you can test things as you build it. If there is a mistake simply unwind and fix the problem. That is if the winding is being tested electrically as the winding is built.

So, here you go. Now, I have built motors before for a living but I am still working on getting the EV on my dreams. I am looking at doing something different on my batteries and power source but that is a post for another day.

On the books I have a nook and I shopped for how to make electric motors and I got the ones with the FREE PRICE. But, yeah they are free but they are old. I like learning when it comes to building.

Now I know this is a EV forum but if you build a drone (yes I do that too) there is no direct way that I know of to convert horse power to thrust but typically propellers will convert 50% to %70 percent of the horse power to thrust depending on your propeller design. So, this post is food for thought 

I was trying to give back to the public for the advice the forum puts out and trying to add my knowledge to the knowledge here. I hope others who read this will appreciate it. Everyone have a good day. Reactor1967 over and out.


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## major (Apr 4, 2008)

It should be easy enough for you to post a couple of photos of this motor you built which is better than the forklift motor for driving an EV car. Please do so. All here would love to see it.




Reactor1967 said:


> Well I can really tell that I am in a place where people have a lot of respect and truely care for others. I can really feel the love here. That being said, I love the post someone made that just AUTOMATICALLY assumed I have never built a motor before coming here and posting.
> 
> Well, that could not be further from the truth. My topic here today was to try to help others understand how to build a motor at home and yes better than a fork lift motor.
> 
> ...


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## Ivansgarage (Sep 3, 2011)

Reactor1967 said:


> Now, after the size of the wire is calculated how many rolls per square inch can you do with that wire? Figuring this out will tell you how big to make your parts in the motor.
> Reactor1967 over and out.


How many rolls per square inch?

Yes I would like to see some pics of your windings.


Ivan


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## PStechPaul (May 1, 2012)

Yes, some pictures would be nice. Also links to the books or more specifics for title, author, publisher, and date. Old motor books are very good and much of the technology of AC induction motors has not changed a lot in the last 100 years. But until recently (1980 or so) efficiency was not a major factor, because electricity and energy in general was cheap. 

As for making your own DIY AC motor, it is probably much easier to get a motor similar in size to what you need and rewind it, unless the mechanical requirements dictate a special shape or mounting. For an EV, you need a motor that is designed to work well with a VFD (inverter duty) and capable of overclocking at least 2x and maybe 4x or more.

If you have a lot of experience rebuilding and rewinding and testing motors, perhaps you could offer those services to the EV community, but that depends greatly on where you are located, as large motors are expensive to ship.

AC motor design involves much more than simplistic formulas for HP, watts, volts, and amps. Motors are rated for a particular duty cycle and temperature rise, and also have characteristic curves for speed, slip, torque, power, and efficiency. Some designs can achieve as much as 4x nominal torque, while others may be no more than 2x. There is also the issue of power factor, which tells you how much more current the motor will draw than that derived from the DC special case where W=V*I. 

Sorry if some of us seem gruff or disrespectful, but most people here already know a great deal about motors and control systems as used in EVs, and there have been a lot of EE wannabees that jump right in with posts like yours that offer simplistic advice and claims of superior knowledge without the credentials, experience, or evidence to back them up. It is also good forum etiquette to make a first post as an introduction with some information about your location, experience, and intentions.


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