# Dirt Cheap Electric Drive System ---seriously



## Beyonder (Sep 18, 2008)

Ok, first off I don't know a whole lot about electric vehicles. An ICE however I'm a little more knowledgable. So here is my thinking, looking at my wifes sewing machine, there is no big fancy controller, etc like in an EV. And yes I realise you need one in an EV, however. Thinking about this, couldn't you "for arguements sake" use a sewing machine type setup hooked to a distributor from a car, hooking the plug wires to relays, running them to a brushless DC motor. Now obviously the sewing machine is AC, but I'm only using that as an example here. My thinking being that the faster the "Sewing machine" circut ran the distributor, the faster the EM would run and slow down as you slowed the sewing machine circut down? This seems it would be an extremely simple setup so I know there has to be something wrong with it...I'm eager to learn so if it wont work, PLEASE explain why. 

I'm not to good at explaining things so plz forgive me if it doesn't make a lot of sence.

Clarence


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## vgslimo (Oct 21, 2008)

someone smarter than i could probably answer better or more clearly but i think all this would acomplish is your "pulses" of electricity would not only be more strung out (farther apart in time) than is normal but also hard on and hard off which is never good in my opinion. also you would still have the tremendous heat losses in your "controller" and foot pedal "pot box". but i could be wrong and if i am someone will tell both of us i'm sure. lol. good luck.


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## vgslimo (Oct 21, 2008)

also forgot to mention you would also be using more energy to power the second motor and this too would lead to inefficiency. i'm a firm believer in any thing can be made to work, it's just a matter of cost versus result.


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## mattW (Sep 14, 2007)

I'm pretty sure there is a controller in the sewing machine and a pot box in the pedal on the floor. Its may not be big and fancy but it is probably scaled down and internal. I don't see the major difference.


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## Beyonder (Sep 18, 2008)

vgslimo : 
- Thankyou...i knew i was missing something. But, I dont think the pulses would be further apart than normal because they would speed up and slow down with the distributor type setup. Same as in an ICE for firing the cylinders. ( could be wrong though, lol )
- What do you mean by hard on / hard off?
I'm not sure if I understand what you mean, but doesn't a electric motor normally do this as the brush's go from coil to coil? If I'm wrong, would a small constant current to each coil solve this problem?

- The foot pedal shouldn't heat up any more than say a normal sewing machine operation. I'm not talking about running the current through the foot pedal ( not 100% ). My thaughts were to run whatever normally runs though it...say whatever it takes to turn a distributor or distributor style device, 1/8 HP...I'm guessing really, but I wouldn't imagine it would take a lot. And thats ....93watts ( I think ). The plug wires would run into relays which would switch on and off sending current from the battery bank to the motor. So if I am correct in my thinking an EM with 6 coils running 30KW ( approx 100km/hr ), each coil would require 5KW per hour. And running at say 144Volts I'd need 35amp relays for each coil? 

mattW :

- Ok, obviously there is a controller in a sewing machine. However...what i meant was compared to a controller for an EV it is a very simple device. Nothing extremely complicated. The biggest difference is that a sewing machine would cost you...69.99 at walmart if it dies...how much does a new unit for an EV cost? ( I think someone on here posted around 900.00, I could very well be wrong though ) Walmart is for most people within an hours drive, how long do you have to wait for a new controller? 


A quick question for anyone who can answer, how much power does a normal EV controller consume? Is it more than 93 watts? Based on my idea if it is, would this be more efficient? ( Please explain if not )

Question #2 ...Does anyone know how hot an electric motor gets?

Clarence


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## vgslimo (Oct 21, 2008)

Beyonder said:


> vgslimo :
> - Thankyou...i knew i was missing something. But, I dont think the pulses would be further apart than normal because they would speed up and slow down with the distributor type setup. Same as in an ICE for firing the cylinders. ( could be wrong though, lol )
> - What do you mean by hard on / hard off?
> I'm not sure if I understand what you mean, but doesn't a electric motor normally do this as the brush's go from coil to coil? If I'm wrong, would a small constant current to each coil solve this problem?


ok if i understand you the pack would flow directly through the distributor to the motor. so what if you stopped rotating the distributor and it came to rest in a contacted posistion. since an electric controled coil is continously pulsing there is no way in the distributor normally to stop energy flow if it came to rest in a contacted position therefore your drive motor would essentially be at full throttle. also hard on off means full voltage and amps not a reduced value like a standard controller. so at a dead stop your drive motor looks like a short but its gonna get every thing your battery pack has right now! lol also the pedal has very fine control in rotating the sewing machine. even if you sped up the start velocity it would still provide volts/current measurable in seconds while standard controllers measure in nano seconds. i think thats right. lol


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## vgslimo (Oct 21, 2008)

Beyonder said:


> A quick question for anyone who can answer, how much power does a normal EV controller consume? Is it more than 93 watts? Based on my idea if it is, would this be more efficient? ( Please explain if not )


from what i understand, i've seen controller ratings anywhere from 90 - 98% efficiency. that should ideally mean that the consumption rate is the portion missing from 100%. so if 98% efficient that means that 2% of the used power is lost due to the controller. hope that helps.


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## Beyonder (Sep 18, 2008)

vgslimo said:


> ok if i understand you the pack would flow directly through the distributor to the motor. so what if you stopped rotating the distributor and it came to rest in a contacted posistion. since an electric controled coil is continously pulsing there is no way in the distributor normally to stop energy flow if it came to rest in a contacted position therefore your drive motor would essentially be at full throttle. also hard on off means full voltage and amps not a reduced value like a standard controller. so at a dead stop your drive motor looks like a short but its gonna get every thing your battery pack has right now! lol also the pedal has very fine control in rotating the sewing machine. even if you sped up the start velocity it would still provide volts/current measurable in seconds while standard controllers measure in nano seconds. i think thats right. lol


 Hmm, the current doesn't flow directly through the distributor. The current from the distributor flows to relays, the main current flows from the bat bank to to the relay to the motor. Also, the distributor generates the voltage when spinning. Or at least a distributor type device could be built that way. So the motor wouldn't think it was supposed to be on.

One problem I can already see, like you said is start up...but, setting up the motor to idle like an ICE would solve that for the getup and go. Say a smaller 2HP motor ( like a starter in an ICE ) to make it idle. Could be hooked upto a 12V clutch ( like an AC compressor style clutch ) to run when Idle, and shut off during acceleration. This would solve the volts/current needed to start acceleration wouldn't it? 

For the hard on/hard off...you want max voltage for the motor dont you controlling speed via current? Or am I completely off in outter space with this? But if I am correct, as the distributor spins turning on and off the relays, wouldn't the amperage flow be regulated by this? E.G. if you have say 60 amps per coil at max acceleration, that's 1 amp per minute... so 1 RPH would equal 1amp per hour, and 30 RPH would equal 30 amps per hour?

Please explain if I'm wrong, or you have any suggestions, I know this might be getting a little out there, but talk is a lot cheaper than finding out the hard way, lol. 

Clarence

Question : if its looksing 2%, at 30KW per hour, does that mean the controllers consuming 600 watts per hour?


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## vgslimo (Oct 21, 2008)

to be perfectly honest i'm far from an expert but i do know i have seen answers to most of these type questions on this site before under various threads. use the search feature and you can locate them. having said that now as i try to understand your config. it probably would be best in my opinion to try to have your sewing machine spin a generator that produced correct volt/amps directly to the motor. fused of course and cut out all the relays. then you could be using a sewing machine as your speed and everything. probably a good pma could function like this and would only cost you around 200 or so bucks. i would be concerned about over currenting the motor but if you used correct pully ratio at max rpm of sewing machine to max rpm of alternator to below max rating of motor. it should work fine. i have no idea how efficient it would be as the sewing machine is a complete unknown to me for obvious reasons. ( i'm male lol) your really want to stay away from idle because it only costs you range. any power you can save increases range. the real trick is figuring out how much juice the sewing machine is pulling, (and either needs to actually run on dc or you will need inverter which will cause loss of more power.)and at what rpm max it's spinning. here is alink to a pma that gives more volt and current the faster it is spun. scroll down the page to see all the info _http://cgi.ebay.com/HighAmp-PMA-Perm...QQcmdZViewItem_


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## vgslimo (Oct 21, 2008)

Beyonder said:


> For the hard on/hard off...you want max voltage for the motor dont you controlling speed via current? Or am I completely off in outter space with this? But if I am correct, as the distributor spins turning on and off the relays, wouldn't the amperage flow be regulated by this? E.G. if you have say 60 amps per coil at max acceleration, that's 1 amp per minute... so 1 RPH would equal 1amp per hour, and 30 RPH would equal 30 amps per hour?
> 
> Please explain if I'm wrong, or you have any suggestions, I know this might be getting a little out there, but talk is a lot cheaper than finding out the hard way, lol.
> 
> ...


answer to question.. i didn't check your math but in general yes i believe that you understand. and no the pwm controller is feeding lower volts and controlling the width of the pulses to get speed control. ie.. if you want to continuosly go 20 mph you only need x volts @ y current. not all volts or all current available. someone on here said think about volts as your rpm and current as your torque. i think i got that right. lol so thats what the controller does in as efficient means as possible.


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## elevatorguy (Jul 26, 2007)

Beyonder said:


> Ok, first off I don't know a whole lot about electric vehicles. An ICE however I'm a little more knowledgable. So here is my thinking, looking at my wifes sewing machine, there is no big fancy controller, etc like in an EV. And yes I realise you need one in an EV, however. Thinking about this, couldn't you "for arguements sake" use a sewing machine type setup hooked to a distributor from a car, hooking the plug wires to relays, running them to a brushless DC motor. Now obviously the sewing machine is AC, but I'm only using that as an example here. My thinking being that the faster the "Sewing machine" circut ran the distributor, the faster the EM would run and slow down as you slowed the sewing machine circut down? This seems it would be an extremely simple setup so I know there has to be something wrong with it...I'm eager to learn so if it wont work, PLEASE explain why.
> 
> I'm not to good at explaining things so plz forgive me if it doesn't make a lot of sence.
> 
> Clarence


One obvious flaw in this is there is no physical connection from the rotor to the distributor contacts, it is a air gap that the spart jumps across.
Every conversion is a loss, controllers are pretty efficient. A sewing machine motor and controller setup is pretty low current, as the current goes up so does cost, that is why commercial motor controllers for large motors cost 10-15 thousand. 
If your motor is any kind of size to drive a vehicle, I think your relays would have a short life switching even 36 volts at any current would quickly destroy them even if you got the rotary switching to work.


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## TX_Dj (Jul 25, 2008)

What you're talking about here is essentially the same as if you used a light switch to turn on and off a heavy load rapidly.

When you "energize" your "relay" from a dead stop, you are doing nothing to limit the current to the motor. At a stop, the motor appears as a short in the electrical system. When you go to try and turn this off, you will weld the contacts of the "relay" closed from it arcing, and lock the motor into a full-on condition with no current or speed limitation.

Yes, your idea of using an ignition distributor "pulses", but it does not modulate. A motor controller is a pulse width modulator. I.E. it "changes the size and number of terminals of the distributor on the fly"

A dead simple PWM controller is easy enough to build, and there are plans galore on this site and the web in general.

I would not recommend attempting to control a DC motor with the setup you've described.


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## 1clue (Jul 21, 2008)

One thing I haven't seen here (I skimmed all the posts but did not closely read them) is a general description of what you're doing here.

A brushless DC motor is basically a permanent magnet DC motor with an external commutator. OR, a permanent magnet AC motor. You can look at it either way.

So your sewing machine/distributor proposal is basically an external commutator which is driven by a separate motor, without feedback from the traction motor. Leaving the circuitry details out of it for now, let me explain what goes on in a real motor, and why they made brushless DC in the first place.

A brushless DC motor is basically a permanent magnet 3-phase AC motor. You could literally clamp a commutator onto the shaft and feed DC into it, and it would be a permanent magnet DC motor.

Now here's the scoop about 3-phase AC motors: They are very simple, very reliable motors which, when running at full power are very efficient if all other things are equal. There is no arcing from the commutator because it doesn't have a commutator. As well, many of the other problems with DC motors are gone.

The problem is, the current draw for a 3-phase AC motor running off wall current which is running at no load is identical to the same motor running at full load. It turns no faster, and uses the same amount of current which means the same exact cost to run.

So what they did is, over time, they evolved an external commutation system which controls voltage and frequency in order to keep that motor always very near full load, at whatever speed it needs to go. The frequency determines RPM of the motor, the voltage is controlled in order to make best use of the current.

Your sewing machine setup is a variable frequency drive. In other words, your motor would get square-wave pulses of full voltage electricity timed with this distributor. On-off-on-off-on-off. You're controlling one of the critical factors, but right now even stationary motor applications are putting in variable voltage/variable frequency controllers because it's economic to do so. Meaning, the controller very clearly pays for itself over the life of the system. A mobile, battery operated setup will be much more sensitive to lost power.

Yes, your setup would _work._ It would not be efficient.


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## Beyonder (Sep 18, 2008)

A lot of info here, thank you.



> to be perfectly honest i'm far from an expert but i do know i have seen answers to most of these type questions on this site before under various threads. use the search feature and you can locate them. having said that now as i try to understand your config. it probably would be best in my opinion to try to have your sewing machine spin a generator that produced correct volt/amps directly to the motor. fused of course and cut out all the relays. then you could be using a sewing machine as your speed and everything. probably a good pma could function like this and would only cost you around 200 or so bucks.


 I tried the search and didn't find anything on this type of setup. If I understand what your saying correctly it wouldn't work because if I ran a sewing machine motor running a Altinator i would be limited to the power input of the sewing machine motor. But, I think this might have merrit with an ICE in say a series hybrid.



> One thing I haven't seen here (I skimmed all the posts but did not closely read them) is a general description of what you're doing here.
> 
> A brushless DC motor is basically a permanent magnet DC motor with an external commutator. OR, a permanent magnet AC motor. You can look at it either way.
> 
> ...


 It was just an idea I had. I'm in the process of planning a house that is to be completely off grid. I am planning on converting as much as possible to DC loads, e.g. tv, computer, washing machine,etc. Even the coffee pot, this allows me a much smaller inverter. I had been looking at the sewing machine considering converting it as well.

So if I understand you right, ( sorry if I sound dumb ) your saying that if the draw is 100 amps, the current to the motor is 100 amps no matter what, whether your doing 10 or 100. And the RPM is controlled by the voltage alone? And so if thats the case a simple device like this could be configured to increase / decrease the voltage?

I do realize that this is an extremely impractical idea to actually put into anything, now it's more a matter of curiosity. 

I'm going to look up these controllers you guys mentioned, the DIY ones. If you have any links or anything I'd greatly appreciate them  Thankyou


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## major (Apr 4, 2008)

1clue said:


> The problem is, the current draw for a 3-phase AC motor running off wall current which is running at no load is identical to the same motor running at full load. It turns no faster, and uses the same amount of current which means the same exact cost to run.


Hey 1clue,

That statement is incorrect. The motor will draw more current as it loads up. An induction motor will have increased current, increased power factor and increased slip as it is loaded. In will consume more power loaded versus unloaded.

Regards,

major


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## 1clue (Jul 21, 2008)

Beyonder,

It sounds like I might have to get some facts straight before I answer your question.

Major,

I thought I was quoting a text book. If what you say is correct, then why have they gone to the effort of making variable voltage, variable current drives?

Beyonder,

Whether my assumptions about full current all the time are correct or not, I can deduce from the existence of this type of drive that a lot of energy is wasted if you run full voltage even at partial load.

Current provides torque, and frequency provides speed. That's good so far as it goes.

However, the idea of the VVVF drive (variable voltage, variable frequency) is to do the following things:


Control the speed of the motor.
Use as little energy as possible to get the job done.
If there isn't enough current to generate the torque you need to go the proper speed, then the motor "skips a tooth" which probably isn't much of a problem for the motor as much as it is for the stuff attached to it. I understand it can be bad.

As I said, current provides torque. The motor is a transformer of sorts, or an electromagnet. It has inductance and capacitance. In any given situation, it has fairly static conditions: If you want more current to flow through, you need more volts. The characteristics of the motor change with the speed of the motor somewhat, and the controller is keeping track of all that.

http://www.diyelectriccar.com/forums/showthread.php?t=6535

This is a link to more info, it's on the WIKI. As wrong as the rest of my post might be, the wiki is probably fairly close to right.


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## major (Apr 4, 2008)

1clue said:


> then why have they gone to the effort of making variable voltage, variable current drives?


Hi 1clue,

You answered your own question. Oppps. I see. Above you said variable current, below you say variable frequency.

The load commands the current. The more load, the more current. The controller may have a current limit which sets the maximum current for the motor. In which case, if the load exceeds the torque corresponding to that set current limit, the motor speed is reduced to reduce the load or it simply stalls.

Unless you have some special application with a fixed, unchanging load, all motor controllers are variable current. Certainly all controllers for EVs are variable current devices. And it is the load that determines the current. Light loads, low current, like driving slowly on the level. High loads, more current, like driving up hill.

Regards,

major




> However, the idea of the VVVF drive (variable voltage, variable frequency) is to do the following things:
> 
> 
> Control the speed of the motor.


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## 1clue (Jul 21, 2008)

major said:


> Hi 1clue,
> 
> You answered your own question. Oppps. I see. Above you said variable current, below you say variable frequency.
> 
> ...


OK, you basically answered a typo. I'm talking about VVVF drives. Thanks for the heads up, especially when somebody else is trying to learn from those typos. 

I know that slippage goes up with load on an induction motor which technically affects RPM, but I was fairly certain that current stayed constant until such time as the core saturates. Or rather, scratch out "fairly." Up until your post, I was _certain_ that it stayed constant. If you have a link that illustrates what you're talking about, it would probably be interesting for both Beyonder and me.


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## Beyonder (Sep 18, 2008)

Thankyou for the information. I ran my printer out of ink printing the wiki, lol.

But I cant find anything on these homebuilt simple controllers that were mentioned earlier...maybe I'm doingsomething wrong, I dunno..lol. Can anyone point me in the direction of this information?


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## major (Apr 4, 2008)

1clue said:


> If you have a link that illustrates what you're talking about, it would probably be interesting for both Beyonder and me.


Sorry, did a quick google and came up empty. Try any text book on energy conversion or electrical machinery. Also, motor manufacturers' web sites may have tutorials. Like Baldor, Marathon, Reliance, Lesson and the like.

Regards,

major


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## Beyonder (Sep 18, 2008)

Thankyou


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