# CVTs worth considering?



## tylerwatts (Feb 9, 2012)

First thought is the torque of the motor is not suitable. For a high revving motor where you want rpm to multiply the motor's low torque that would be better. BLDC or high frequency AC might be good.

There are some higher torque CVTs but I don't know much about them. A weak link is the centrifugal clutch many have, but ideally the electric motor wouldn't need it. Next concern would be belt tension or slip! Worth looking not for lighter applications though. Could have good efficiency advantages for lower speed operation too.


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## cts_casemod (Aug 23, 2012)

tylerwatts said:


> First thought is the torque of the motor is not suitable. For a high revving motor where you want rpm to multiply the motor's low torque that would be better. BLDC or high frequency AC might be good.
> 
> There are some higher torque CVTs but I don't know much about them. A weak link is the centrifugal clutch many have, but ideally the electric motor wouldn't need it. Next concern would be belt tension or slip! Worth looking not for lighter applications though. Could have good efficiency advantages for lower speed operation too.


I just hate those fiats and smarts with the clutch. You have to rev the motor and then it suddenly locks and moves forward. I think you loose control when you want to do a gentle move...

But other than that, torque can be limited on the controller, knowing the RPM.s On a Ac is even easier. From a point of efficiency wouldn't it be better?


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## poprock (Apr 29, 2010)

Re CVT Volvo: Originally the Dutch DAF. Bought out by Ovlov c1980's and marketed in Australia as the V360


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## PaulS (Sep 11, 2012)

An electric motor is it own transmission. With a good controller you can set the torque to whatever the motor will produce at any given setting. Why add the weight of a transmission that you don't need. It adds complexity (more maintenance) and weight (which costs you mileage, acceleration and handling). Stop thinking like you are using a small gas engine and remember that you have your maximum torque at any rpm programmable through the controller.


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## cts_casemod (Aug 23, 2012)

PaulS said:


> An electric motor is it own transmission. With a good controller you can set the torque to whatever the motor will produce at any given setting. Why add the weight of a transmission that you don't need. It adds complexity (more maintenance) and weight (which costs you mileage, acceleration and handling). Stop thinking like you are using a small gas engine and remember that you have your maximum torque at any rpm programmable through the controller.


True but from an efficiency point oif view its not efficient to drive the motor at a non optimun speed. As it has been discussed before an AC motor wont perform so well at low revs and it will have extra iron losses at high frequency/speed.
A DC motor on the other hand has a lot of low end torque but with low efficiency due to the added current flowing on the brushes and has more drag an losses that an equivalent AC Motor at high speeds.

Just because you have a much higher power available from standstill unlike an ICE doesnt mean you dont need to run the motor in its optimun power band.


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## tylerwatts (Feb 9, 2012)

CTS I agree with you here, lots of potential with the CVT and your AC motor, but you MUST ditch the stupid clutch. I expect you know that though How easily can you get one of these Volvo transmissions? My experience with Volvos is the are stubborn belligerant beasts that refuse to die, which is good, except getting spares might be difficult.


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## Coulomb (Apr 22, 2009)

PaulS said:


> An electric motor is it own transmission.


More or less, yes. In a Prius, the "transmission" is a pair of electric motors and controllers.

You might get 5-10% more efficiency by running the motor at its optimum speed, then lose that 5-10% in the CVT, and you are still carrying the weight and using space that would be better served with a bigger pack, or payload.

Edit: even so, there are many situations where using a transmission makes sense. It depends on the characteristics of the motor, mainly its speed range.


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## tylerwatts (Feb 9, 2012)

Coulomb are you saying the benefit for an AC motor is not great then? What about over-speed on the AC to get a decent top speed? If it is single reduction then you have to decide a compromise there don't you?


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## Coulomb (Apr 22, 2009)

tylerwatts said:


> Coulomb are you saying the benefit for an AC motor is not great then?


To be able to lose the transmission, you need a motor with a large speed range, and that's most easily achieved with an AC motor. You can go transmissionless with DC by oversizing the motor, but that adds weight and cost, and uses extra space.



> What about over-speed on the AC to get a decent top speed?


Exactly; an interior permanent magnet (IPM) AC motor, for example, gives a wide almost-constant-power region, so you don't need a transmission.


> If it is single reduction then you have to decide a compromise there don't you?


Yes, you will usually need a fixed ratio transmission, and this involves some compromise. But the fixed ratio can more or less be part of the differential, and is more efficient than a multi-speed gearbox. I'm not aware of how efficient CVTs are. Perhaps they are as efficient as a single speed reduction, or very nearly so; if so, I retract my statement and you might get some real benefit from a CVT. A quick search seems to indicate that they are not as efficient as a single speed reduction.


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## tylerwatts (Feb 9, 2012)

Edit:
Coulomb,
End.

Given your explanation of the flexibility of the ac motor I'd hesitate the single speed reduction with a suitable motor would be as or more efficient than cvt. I was not aware the ac motors could be so flexible, I apologize. Thanks for educating me!

Do tell about this IPM motor please. I have not heard of these, unless they are BLDC motors. If not, what are the differences please? Is it simply the sine versus trapezoidal bemf that is different? If so, how easily can a controller be switched for use between one and the other? Is I simply a programming change?

cts, seems there's mileage in your direct ratio transmission. I'd open the gearbox, remove excess gears and selectors etc and keep only the gear you need fixed onto the shafts. Saves weight and reduces drag. Also allows opportunity to mod the input so your AC motor can fit. Oh, problem was diameter, wasn't it? I'd look to have a special casing machined then, keeping the stock gears with a custom ratio maybe, to attach to your motor and keep your driveshafts in the stock position.


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## cts_casemod (Aug 23, 2012)

Coulomb said:


> To be able to lost the transmission, you need a motor with a large speed range, and that's most easily achieved with an AC motor. You can go transmissionless with DC by oversizing the motor, but that adds weight and cost, and uses extra space.
> 
> 
> Exactly; an interior permanent magnet (IPM) AC motor, for example, gives a wide almost-constant-power region, so you don't need a transmission.
> ...


Permanent magnet AC motors are just brushless DC's really, if someone knows a difference other than marketing please let me know. The prius inverter uses a Square wave for their "AC" MG1 and MG2. They may have better torque and less weight, but are quite expensive and are not so easy to find. It would be great if someone came up with a modified rotor for a STD induction motor. I can tell you the rotor itself is about 30% of the unit weight.
Again, over speeding on both AC and DC will incur in some extra losses, which might neglect the advantage of running without a gearbox in the first place.

The idea of a CVT was to have a constant optimal motor speed, where the efficiency could go to 92%, instead 20 to 40% at non optimum revs, OVER a standard gearbox or a Direct Drive approach. You will have a 10% loss on the transmission, unlike 20% on fixed gear types, but you can have a smaller motor that a Direct drive approach, hence lighter and with better acceleration, which I believe would be the most advantageous solution of the three, all factors considered. Also it should eliminate clutch-less gear change time and its pretty easy to control only with vacuum or air pressure.

Anu thoughts?


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## Coulomb (Apr 22, 2009)

tylerwatts said:


> Do tell about this IPM motor please. I have not heard of these, unless they are BLDC motors. If not, what are the differences please? Is it simply the sine versus trapezoidal bemf that is different?


IPM motors typically use sine wave excitation, whereas BLDC (by definition? It's comfusing) use trapezoidal. I believe it's possible to drive either motor with either type of excitation; there is a paper on this somewhere.

My shallow understanding is that the interior permanent magnets change the motor characteristics considerably, and are basically what gives them the wide power range. So this is what you find, I believe, in a Leaf or Prius. I think that Toyota developed the technology somewhat in the Prius.



> If so, how easily can a controller be switched for use between one and the other? Is I simply a programming change?


I'm not a motor controller expert; there are others who could answer that. I think that motor controllers that support both can swap from one to the other by checking a tick box in the controller's configuration; the Tritium WS200 has this for example. So its "just software", but there is a lot of work in getting that software right. IPMs are synchronous machines (no slip), so you certainly can't use a controller designed for induction machines.


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## tylerwatts (Feb 9, 2012)

Ah so here is where my understanding of ac motors shows its limitations. It seems though, that the IPM motor is better suited to single reduction drive. A few questions then:
Can an ac motor be modified with a PM rotor for this application? I'm thinking along the lines of an HPEVS motor, maybe even with Liquid cooling for the stator.
Does anybody know of sources for suitable controllers?
You say an induction controller can't be configured to drive an IPM motor, could a BLDC like the Scottdrive or Wavesculptor power such a motor?
Does anyone know how the Tesla makes such good use of an induction motor?
Would an IPM suffer a weight penalty versus the induction motor?
Are there heat issues for the PM rotor that risk demagnetising the rotor?

Thanks for the guidance!

PS, you seem to be up late Coulomb!


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## cts_casemod (Aug 23, 2012)

Coulomb said:


> IPM motors typically use sine wave excitation, whereas BLDC (by definition? It's comfusing) use trapezoidal. I believe it's possible to drive either motor with either type of excitation; there is a paper on this somewhere.
> 
> My shallow understanding is that the interior permanent magnets change the motor characteristics considerably, and are basically what gives them the wide power range. So this is what you find, I believe, in a Leaf or Prius. I think that Toyota developed the technology somewhat in the Prius.
> 
> ...


Coulomb,

My Experience is that the square or sine wave has nothing to do with efficiency or motor type. The problem is how an inductive load releases its energy when the power is suddenly removed, creating a peak 3 or 4x the supply that can burn mosfets. - This is what happens on cheap square wave inverter and this is what has created a myth that square wave is no good. If you can clamp this you are okay. Even in an induction.

Now the only of these motors that its a true AC is the induction, the PM types can be classed as each.

I know by experience if you drive a car alternator with DC controller you have to apply DC to the field. If you drive it with AC you can either short the field and it will self magnetize, turning into an induction motor or drive the same field with DC, creating a synchronous motor. Note that this type needs to be taken up to speed by an external motor or the controller needs to have an encoder, just like a DC and unlike an induction. 

As far as I know controllers are interchangeable, but you can not run an induction motor with DC, it has to be inverting (Even square or triangle) because of the magnetizing rotor. Other than that, yes, a VSD can run an PM, provided you use an encoder to know the actual position - This will be a synchronous motor, but again, thats what a DC brush less is 

PM motors also have a drawback - Field weakening. They are limited in their maximum speed due to this, they have high torque but big losses at high RPMs and LOW load for this reason. Its like a DC series wound and shunt wound. The first will go any speed as the field collapses, the second will have a steady speed.
Actually the prius gearbox is limited by MG1 which runs at 3x the ICE speed.

Now coming back again to efficiency on this website http://www.falconev.com/E-Bikes.html
you can see the performance of a PM DC. 









As I said you have low efficiency (less than 50%) at low torque levels due to iron losses. As the torque increases to 50% the efficiency goes to >90% and stays there, now limited by the increasing copper losses. On an induction motor the field is reduced and exchange of torque by speed happens as the frequency the rotor sees is smaller and hence the rotor current and field also decrease.

By far the best motor you can have is a synchronous motor with a powered field (slip ring on the field coil). You power this coil for high torque and reduce the field for high speed. In my car alternator experiences Ive driven an alternator from 1Hz to about 10.000RPM with this setup. In a motor so small you can easily make [email protected] with about 36V. The bearings are the limit to the actual power you can take out of it. 
10HP at 144V is not out of the question all all with about 1HP per 1000revs out of a typical 70-90Amp car alternator that weights a few kilos. The current should be limited and the torque is constant and HP is proportional to speed just like an ICE. They run up to 15.000RPM in an ICE (usually 3-1 on a Diesel and 2 to 1 on a Petrol)

Each motor is different. Hence the gearbox question in the first place


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## Coulomb (Apr 22, 2009)

I'll just respond to a couple of points here.



cts_casemod said:


> PM motors also have a drawback - Field weakening. They are limited in their maximum speed due to this, they have high torque but big losses at high RPMs and LOW load for this reason.


My understanding is that an appropriate controller can control the field, in a process that is sometimes called flux weakening (as opposed to field weakening; the latter term seems to be preferred when you control the field more directly). This would appear to be the case with the Prius IPM motors, for example. Their base speed is around a quarter or a fifth of maximum speed; operation beyond base speed presumably requires field weakening.



> Actually the prius gearbox is limited by MG1 which runs at 3x the ICE speed.


? MG1 in a Prius has no fixed speed relative to the ICE speed. It's used to start the ICE, for example; it could not do that if its speed was a multiple of that of the ICE. (Three times zero is zero.) MG1 can spin up to 10 000 RPM, though it seems to be limited in software to lower speeds when the ICE is not running.


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## Coulomb (Apr 22, 2009)

tylerwatts said:


> Can an ac motor be modified with a PM rotor for this application?


The stator of an induction motor and an IPM motor are much the same, though I suspect that the windings are often optimized for a particular back EMF shape. So I would say that it could be done, but it likely would not be practical.



> You say an induction controller can't be configured to drive an IPM motor, could a BLDC like the Scottdrive or Wavesculptor power such a motor?


The Wavesculptor 200 certainly can and does drive IPM motors; Tritium's founders came from the Solar Car world, where such motors are valued for their high efficiency.

An induction controller could drive an IPM motor if it had the right software and the right speed information (from an encoder or resolver or the like). My apologies if I gave the wrong impression.



> Does anyone know how the Tesla makes such good use of an induction motor?


The Tesla induction motor is merely a more refined version of an industrial induction motor. I believe that the main differences are a smaller air gap, requiring greater tolerances, a copper rotor for efficiency, and suitable construction (bearings, etc) to allow high speed operation (to 14,000 RPM).
This article may be of interest: http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors .



> Would an IPM suffer a weight penalty versus the induction motor?


I don't believe that weight makes a lot of difference between these two.

[quote[ Are there heat issues for the PM rotor that risk demagnetising the rotor? [/quote]
There are. My understanding is that under normal circumstances, this issue can be ignored.



> PS, you seem to be up late Coulomb!


No, I'm from Down Under.


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## tylerwatts (Feb 9, 2012)

Thanks Coulomb and CTS

Coulomb, I'm in the UK, so thought you were not far enough ahead to be morning yet, but just realised you must already be up when i'm heading to bed.

Very interesting reading and learning, thanks gents. My first motive is my Rav4 has size limitations for AC motors, if you know gdirwin's conversion thread, he barely squeezed a Warp9 in, with clearance issues due to the transverse transfer case for the 4wd. I want to keep the 4wd also. Ruckus's BLDC motors, though very enticing are simply way too large for my application. I looked on metricmind.com, and the siemens motors, as oribinally used in the RavEV are very power dense and would fit nicely if orientated properly, they are a very slender square profile, 240mm across. I don't quite understand how they achieve this slim profile, but it would work well for me. limitations, high voltage to drive them, cost of motors, and cost of associated controllers.

So then this discussion stemmed the idea, could an HPEVS AC-75 frame be modified to hold an IPM rotor? Would this be of much benefit? What are the limitations to me building my own custom AC motor, having it properly wired etc? The first answer I got was that I can't build the iron cores myself, so am stuck. Unless I 'recycled these form another suitably sized frame and rehoused them in a custom jacketed Al case, and built a custom rotor, not sure if AC induction or IPM.

Then I read somewhere that ironless DC motors are very promissing, this is a PM stator with specially wound brushed rotor as I understand it. Then we're back to brushes though, and the rarity of these motors. So I'm circling a drain it seems.

And before I'm told we're off topic, at the back of my mind whilst understanding these things I'm thinking which motor is best suited to a CVT? So...

It seemed the AC Induction had starting torque limitations, enter the CVT to give a BIG work advantage at start-up and maintain the motor at its peak torque/power/efficiency rpm (delete as applicable). but then is all this necessary if I can just show horn in a more affordable (potentially) Scott drive 200kW BLDC setup and twist the crap out my drive train and not worry about the little bit of starting efficiency loss. BUT, my application involves mostly commuting, adn start stop between traffic lights and idiot ICE drivers who have all day to miss the change of the lights and leave everyone racing to the last second only to miss them (high accel repeatedly for shorter periods at worst/lowest speeds and take-off). So that inicial eficiency isue is bigger than first thought. I'm not blessed with open space in the UK! Miss it horribly (born and bread South African, sorry Coulomb...).

So my dilemma grows... BUT enter CTS with modding a VFD drive to use an industrial motor, but again, they get big (frame size) quickly! And are only air cooled. So could I maybe house an industrial AC motor in a custom casing (maybe even integrate a reduction ratio irect drive to my transfer case, but getting expensive and complicated very quickly) and rn it off a modified VFD?

My biggest limitation, I'm a Mechanical Engineer, not EE, and amseemingly cursed with Electrical ignorance... But I learn fast!

So, the big question then:
*With all these motor/drive options, is there any mileage to having a CVT transmission versus say a 2/3 speed transmission versus a constant HP AC/BLDC single speed reduction drive (eg Brusa transaxles)?*

What does anyone think? Sorry about long post...


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## cts_casemod (Aug 23, 2012)

tylerwatts said:


> Edit:
> Coulomb,
> End.
> 
> ...


tylerwatts,

I have thought about that before and I got to the conclusion that due to my limited available power I rather keep the gearbox, the clutch and all the gears, reason being efficiency. I have most power in the 1000-1500RPM range.
I should recover my losses to spin the flywheel with the Regen and it could also help as I could spin the flywheel before the car starts moving to make it easier on the motor.

Regarding to the gearbox I will simply get a different one. I am not adept of modifying something when I can get it already done, that can easily be replaced, if required. Drive-shafts are the easiest part.


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## cts_casemod (Aug 23, 2012)

Coulomb said:


> I'll just respond to a couple of points here.
> 
> 
> My understanding is that an appropriate controller can control the field, in a process that is sometimes called flux weakening (as opposed to field weakening; the latter term seems to be preferred when you control the field more directly). This would appear to be the case with the Prius IPM motors, for example. Their base speed is around a quarter or a fifth of maximum speed; operation beyond base speed presumably requires field weakening.
> ...


Coulomb,

Think of it this way if you get a magnet close to a metal part it will attract. This is the same with the motors. Either you keep the field on so it will repeal (like its suppose to do in a motor) or you have a drag. If you want this motor to free rev. you need power to overcome this losses.
Its like trying to move a stepper. They offer a high resistance. It WILL always have a drag unless you can switch the field of. You cant on a permanent magnet. Try it and let me know.
Check the bikes forums. They have a clutch bearing to avoid this drag if you are pedaling without the motor assist, but you loose Regen. The Drag is quite considerable. I have built and electric bike before the car project.

In Regards to the Prius, yes, the MG1 Speed is dependent on several factors and CAN go up to 3 times the ICE speed. Its not easy to explain, but it does not only act as a starter. 

http://eahart.com/prius/psd/

Take a look at this website. Its for the 1st generation prius. The later ones have a DC DC and MG2 can now move the car up to 100mph or so without the ICE, but the concept is similar.


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## cts_casemod (Aug 23, 2012)

tylerwatts said:


> Thanks Coulomb and CTS
> 
> Coulomb, I'm in the UK, so thought you were not far enough ahead to be morning yet, but just realised you must already be up when i'm heading to bed.
> 
> ...



tylerwatts
It all depends how much you want to spend. 
If we think about direct drive an Induction motor can be rewired to have great power but this costs money. Also the acceleration may be slower that with a gearbox and you need a powerful controller and battery pack.

At 640V you have 200LiFe Batteries. The BMS is very complicated and expensive, the chargers are expensive as well, fuses cost a lot, individual batteries may fail and are hard to locate, etc.
Its hard to find a BLDC for this power levels and if they overheat they may loose magnetization of the magnets, rendering the motor useless. If you go with a lower voltage, like a DC system, make sure your batteries are rated for this peak. You will now have to be cautious with the instalation due to the currents involved. Depending on the power you need you may have to find a compromise between amps and volts. 96Vx1000A is 96KW, but will your batteries hold a discharge of 1000Amp? Will you have suitable cable for that? What will your losses be at this current? Only 1.5V loss at 1000Amp means 1.5KW you're wasting!!!

Everything is a compromise.

Mechanical and Electronic Engineering are not that different, and as an Electronic Engineer I also need quite a lot of mechanical background. Most Universities have a common curriculum with diferences on last year, but you need to make yourself familiar with simple terms like HP, KW, Amps... This is all about maths really. You need to do your calculations. The same power you need for the ICE you need to have in an Electric vehicle, the power bands may be different, but other than that its all the same.

You need to observe your driving and calculate how much output your engine is producing at a given speed/condition - you wont need the full power, but you will need to calculate how much you use on acceleration and make it available on the electric motor. Can you live with less acceleration? Do you need a certain top speed? Whats the lowest speed you are willing to go on hills?

Do you research, see what motor suits you better. Go with DC or Induction and forget the rest they are hard to find.
In Induction you can design your own controller, use a commercial controller and motor, rewind an existing motor... you have several options.

On DC don't use nothing less than a solitron. Check my other topic here http://www.diyelectriccar.com/forums/showthread.php/controller-failure-full-power-output-traffic-77961.htmlIf the controller fails you are in problems, so make sure you have a good one.

So in resume:

*Get to know your car* - power needs, driving habits, gearbox suitability...
*See how much you would like to get along with the project:* You may want to actively participate on the project and learn in between or you may just want to buy something already tested (in response to the needs you found before)
*Start planing your budget*- See how much the components you need will cost, define priorities, so you can install them or make brackets for them, etc.
*Make sure you have another car.* You will have to think a lot, so your car will be stopped for a while. You need a garage or an off road space.
Start putting everything together. You will find small problems along which you will solve with time like bracket fabrication, things that don't work, etc.


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## tylerwatts (Feb 9, 2012)

Thanks CTS

Still deciding alot of this. Want a 'real world' conversion, ie no loss in performance rom my vehicle. So I expect some improvement due to better torque characteristics of electric motors. My current is a Diesel though, so good torque from at least 1500rpm through 3500rpm. So I'd want a motor capable of same torque continuously to at least teh same rpm, and if a good AC motor, to maintain power to higher rpm as torque drops off. Alo of BLDCs have a steep drop off in torque, but I noticed some ACs have a smoother decrease which maintains a constant power rating as revs rise, eg the Brusa motors.

I'm pondering a few things. forgive me if I mislead, I have a decent 'layman's understanding' of EE, but more advanced stuff like AC motor control I must learn and relearn to consolidate befoer I fully understand it. I can visualise and conceptualise how the motor works, but how you instruct/program the controller to produce this motor performance I am still understanding. I'll post a new thread regarding motors.

Re the CVT, my thought was that since the AC motor has a 'comfurt zone' or efficient rpm range, like you said, then a CVT would keep the moor in this range over a wider range than a normal transmission. And if you were changing your transmission you could look to fit a CVT, perhaps from teh Volvo, or from some smaller city cars. Not sure which, but Google will educate. I know the big Nissan Murano SUV had a 3,5ltr V6 with a CVT, so this would certainly handle EV torque output, but fitting it in a small car is a different question...

I still think there may be some decent benefit to running an AC motor through a cvt. Especially if the motor could operate a fixed speed (within say 200rpm range, and the CVT can be controlled to change the vehicle speed and the motor's torque change according to demand. Maybe I am complicating it too much. Seems a bit excessive for DIY thinking of it.

I'll post the other thread.


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## Stiive (Nov 22, 2008)

tylerwatts said:


> I still think there may be some decent benefit to running an AC motor through a cvt.


This paper shows a 10% increase in overall efficiency (and therefore range) when using a CVT.
http://link.springer.com/chapter/10.1007/978-3-642-24145-1_30




tylerwatts said:


> Seems a bit excessive for DIY thinking of it


I'd say so. Its very easy to not implement the CVT effectively and end up with a net loss of energy. For the extra cost and complication, i don't think its worth it for DIY. Leave it to the OEMs.

I would however recommend AC over DC. DIY people always downplay the effect of regen, but you could easily get 10%+ increase in range if you use it effectively, and even more in city driving.
IM also have great overload characteristics (with the right controller) which means you can get good performance off the line.


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## cts_casemod (Aug 23, 2012)

tylerwatts said:


> Thanks CTS
> 
> Still deciding alot of this. Want a 'real world' conversion, ie no loss in performance rom my vehicle. So I expect some improvement due to better torque characteristics of electric motors. My current is a Diesel though, so good torque from at least 1500rpm through 3500rpm. So I'd want a motor capable of same torque continuously to at least teh same rpm, and if a good AC motor, to maintain power to higher rpm as torque drops off. Alo of BLDCs have a steep drop off in torque, but I noticed some ACs have a smoother decrease which maintains a constant power rating as revs rise, eg the Brusa motors.
> 
> ...


Second time to write the post... lets start again!
Your car is not very heavy you should be Ok with something capable of 60HP or more.
What gearbox do you have? Auto? If you have a manual don’t even worry. keep their clutch for better performance.
A Diesel has its optimum power band at 2000-3000RPM, starts to cut fuel at 3500 and has a maximum speed of 5000RPM at no Load. This is easy to get with an AC Conversion.
DC is hard to find here in the UK, you will have to import from the USA, together with the controller, pay shipping, taxes, etc. Forklift motors for the power you want are hard to find and also expensive, although I know of some members got some at the scrap yard for 50 or 100£. but they are good for maybe 40W peak at low speeds and you need to mess with them: Change brush angles for higher voltages, etc.
Commercially an AC 50 is the minimum you want to use.
If you want to go DIY look for industrial motors. You want one with:
208V Delta 415V Star Connection – make sure its not 415V Delta!!
Aluminium Frame
Flange and foot mounting (Yes both)



You can look for a new or used VFD. Power will depend on your tastes 
From the motor you can get 6 times the power.
7.5KW = 15KW nominal, 45KW (60HP) peak (100nm nominal from 1400 to 2900RPM, 300nm @ 0RPM)
11KW = 22KW nominal, 66KW peak (150...)
15KW = 30KW nominal, 90KW peak (120HP) (200...)
Note that a 120HP Diesel does about 250nm at 200-300RPM, yet at 1000-1500 it may do 150, while your electric motor is delivering 600 right from a stop and some 350 at 1000RPM (idle).
Don't worry with the CVT this are only concerns about efficiency in regards to other automatic gearboxes. As a rule of thumb you can use 2nd gear on city and 4th gear on motorway. If you want the best performance use a clutch. If you want to use an Automatic keep the motor Idling at 500RPM. The Gearbox will take care of the rest. You will loose some efficiency due to the idling, on the other hand you can keep your AirCon on and power steering (Cant remember if your car is electric or hydraulic) You will also loose most of the regeneration capabilities. 
Batteries for your car should be about 15KW for each 60 miles (or 17 if you use an Auto gearbox)
Again, evaluate what you need or want.


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## tylerwatts (Feb 9, 2012)

Thanks CTS

My current vehicle is a 4.2 Rav4. The transverse transfer case limits motor diameter to ~9". THis is my biggest limitation and hence why I'm asking the questions about a hybrid motor. Plus I like to do my own thing and bend the rules a bit 

Thanks for all the advice, I'll have to see what size motor I can fit, then work back to the power available. Mine has max ~250ftlbs/320Nm? from 2-3000rpm, but is chipped so has more currently across a wider RPM range. It doesn't run out of puff until after 4k rpm adn then it is gradual. Good engine!

To conclude the Thread then if I may:
*CVTs are not practical as a DIY mod unless your vehicle already has one, and then it may still not be ideal for your type of motor used. Not rule out completely, but complicated for little benefit except maybe space and weight.*


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## cts_casemod (Aug 23, 2012)

For a 9" motor you are quite limited in terms of options. Is it exactly 9"? Mine is a 7.5KW and its 9.5" not counting the flange (You can get a flange that is only the motor diameter).

The best you could do was rewire to 115VAC. You would have about 100nm from 1500 to 6000RPM (80HP). And thats the most you can squeeze from a motor of this size.

You would need a rewind and the rotor balanced for this speed.
Ist a compromise between power and size.

Your conclusiuon is right but it may be possible to change to a CVT if your gearbox is damaged and you want to invest on another one as well. It does happen


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## tylerwatts (Feb 9, 2012)

This image shows my transfer case. Because the trasnmission an engine are transverse in th engien bay, the transfer box must turn 90deg twice to get around front diff and motor to go backward to rear diff. Not sure if the link works...

If not, it is here.

And per gdirwin/s conversion, even teh 9,25" Warp 9 motor was too big without some heavy modification. I thought of replacing my transmission with a transaxle much like a Subaru unit keeping 4wd but giving all the space in front of the transmission for almost any diameter motor. Then a short BLDC like Ruckus is using with the Scott drive would fit perfectly  But this is significant modification.


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