AC electric motor rewinding for EV use

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AC electric motor rewinding for EV use

Post by BigMouse » Tue, 23 Jul 2013, 05:22

PlanB wrote: I'm stuck with a 50 kw 650v electric transaxle I can't do much with because most of the controllers & EC accessories (pumps, aircon, etc)are 420v. I'd get it rewound if I knew what size wire to go for & could find someone with the know how to do it. Some background here
I would love to see a rewind done on a Toyota hybrid IPM motor. I'm planning to get a hold of a 1st generation Prius transaxle some day and have a go at rewinding it myself. From what I can see it would be interesting to do. The stator is removable so that would improve access, but the slot openings are very narrow, meaning it could be fun getting the wire in if winding many in-hand.

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AC electric motor rewinding for EV use

Post by mizlplix » Tue, 23 Jul 2013, 05:35

One thought to ponder:

The Prius only uses the electric drive up to a point (not sure), when the I.C.E. motor takes over.

So even when you got it working OK alone, you will have at best a 30-35 MPH car.

If you can over freq. the motor, you might pick up some RPMs there too.

If rewound to 6 or 4 pole to pick up torque, it would worsen the problem.

(Not trying to put a dampner on it)

I would like to try one myself.

Miz
Last edited by mizlplix on Mon, 22 Jul 2013, 19:37, edited 1 time in total.
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AC electric motor rewinding for EV use

Post by BigMouse » Tue, 23 Jul 2013, 05:44

mizlplix wrote: One thought to ponder:

The Prius only uses the electric drive up to a point (not sure), when the I.C.E. motor takes over.

So even when you got it working OK alone, you will have at best a 30-35 MPH car.

If you can over freq. the motor, you might pick up some RPMs there too.

If rewound to 6 or 4 pole to pick up torque, it would worsen the problem.

(Not trying to put a dampner on it)

I would like to try one myself.

Miz


The ICE never "takes over" in the Prius. It only comes on above certain speeds, and always works with the electric motors. The big motor (MG2) is coupled to the drive wheels by a fixed gear ratio, so rotational speed isn't an issue. The motor is capable of spinning (and commutating) at any speed the car is capable of. Otherwise it wouldn't be able to regen at freeway speeds.

The purpose of the rewind would be to lower the voltage in order to maintain constant torque to a higher RPM. It's not really over freq'ing the motor because it commutates at these speeds anyway during normal use, just not with as much current. The rewind would just push the torque fall-off knee to a higher RPM.

I would suspect that the motor can't be rewound to a different number of poles because the rotor has 8 poles with permanent magnets.
Last edited by BigMouse on Mon, 22 Jul 2013, 19:46, edited 1 time in total.

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AC electric motor rewinding for EV use

Post by mizlplix » Tue, 23 Jul 2013, 06:35

Cool, I am far from knowledgeable on these.

I DO know, there are several converters in California doing the plug in thing by removing the ICE and related stuff and adding another pack to the car. So, I would assume the electric motor will RPM just fine.

The first group to do this is a bunch of engineering students. I guess the hardest part was a new VCL for the controller, which they wrote.

(And I suck at)

After reading that PDF on the operation, it seems that a planetary is instrumental in keeping the electric motor within it's RPM range no matter what the ICE does.

It acts as a priority power flow divider and each power trane can operate at it's own speed without interference from the other.

Like the ICE can shut off locking it's input source allowing the Electric motor to provide 100% of the motive force. OR both can operate allowing the power flow to combine to one output source.

If this is correct, then the electric motor will not throttle up and down with the ICE, but run within it's own range. I wonder what that is?

Miz

Last edited by mizlplix on Mon, 22 Jul 2013, 20:42, edited 1 time in total.
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AC electric motor rewinding for EV use

Post by PlanB » Tue, 23 Jul 2013, 16:12

Tnks for the rewind info offer Miz. The tritium controller I'd use is 450VDC and 368ADC input and 320VAC and 300Arms output. The IPM is currently 8 poles & I'm not sure that's alterable because of the permanent magnets?

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Post by BigMouse » Tue, 23 Jul 2013, 17:44

mizlplix wrote:After reading that PDF on the operation, it seems that a planetary is instrumental in keeping the electric motor within it's RPM range no matter what the ICE does.

It acts as a priority power flow divider and each power trane can operate at it's own speed without interference from the other.

Like the ICE can shut off locking it's input source allowing the Electric motor to provide 100% of the motive force. OR both can operate allowing the power flow to combine to one output source.

If this is correct, then the electric motor will not throttle up and down with the ICE, but run within it's own range. I wonder what that is?
The Prius transaxle has two electric motors. One (the big one and the one of interest for EV conversions) is coupled to the differential via a fix gear ratio. It always spins at a constant multiple of the wheel RPM.

The smaller electric motor isn't much use for an EV conversion. It's just there to start the ICE, and transfer the ICE's torque to the wheels when required. It is coupled to the differential via the planetary gears and its RPM is a ratio between the ICE RPM and the wheel RPM (determined by the planetary ratio). It's what gives the transmission its "continuously variable" nature, and serves a role similar to a brake band in a normal automatic transmission, but does its job magnetically rather than through friction.

In a PEV conversion of a Prius, the ICE would be removed, and the smaller electric motor would either be removed as well or the planetary would be welded to allow the two motors to work together. This seems like way more work than it's worth as you'd need a second controller for it and it wouldn't add much power.

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AC electric motor rewinding for EV use

Post by Johny » Tue, 23 Jul 2013, 17:48

Just in case you haven't seen this, it may be a helpful visualisation aid.
Scroll down the page a bit - then play with the controls.
http://eahart.com/prius/psd/

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AC electric motor rewinding for EV use

Post by coulomb » Tue, 23 Jul 2013, 18:41

BigMouse wrote: In a PEV conversion of a Prius, the ICE would be removed, and the smaller electric motor would either be removed as well or the planetary would be welded to allow the two motors to work together. This seems like way more work than it's worth as you'd need a second controller for it and it wouldn't add much power.

I don't know why you'd want to ignore a motor that is 60% of the power of the main motor (30 kW verses 50 kW, though it's hard to find definite numbers for MG1). 50 kW peak, with much less continuous, is pretty light on for a Prius sized car with an EV sized pack. 80 kW peak is much more reasonable.

It's a pain having to drive the two motors with two controllers, but the car comes with two water cooled inverter back ends already matched to the motors (before rewinding, of course). So if you can deal with a 500 VDC pack (you'd need 650 VDC on later models), you get two inverter back ends for free. You do need to provide the inverter front ends, but that's "just software" and a microcontroller.

I'm a little surprised that no-one seems to have done this yet. Perhaps it's the pack voltage.
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AC electric motor rewinding for EV use

Post by Johny » Tue, 23 Jul 2013, 18:49

coulomb wrote:I'm a little surprised that no-one seems to have done this yet. Perhaps it's the pack voltage.
If I rememeber correctly the later Prius' pack is around 200 VDC and they use an up-convertor to 650 VDC. So a DIYer would not have to fiddle with the 650 VDC side. I agree - it's a little surprising that given all the reverse engineering that's taken place on the Prius that a BEV hasn't been done this way.

Edit: looked up and changed battery pack voltage
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AC electric motor rewinding for EV use

Post by BigMouse » Tue, 23 Jul 2013, 19:13

coulomb wrote: I don't know why you'd want to ignore a motor that is 60% of the power of the main motor (30 kW verses 50 kW, though it's hard to find definite numbers for MG1). 50 kW peak, with much less continuous, is pretty light on for a Prius sized car with an EV sized pack. 80 kW peak is much more reasonable.


Remember that 50kW number is before the re-wind. Rewinding for even 1/3rd the voltage could push that up to 150kW. Seems hardly necessary to go through the added trouble to integrate MG1 in to it when you have a 150kW 400Nm beast of a motor already connected to the differential.

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Post by Johny » Tue, 23 Jul 2013, 19:35

...I think I'm starting to understand (again) why no-one bothers to play DIY BEV with the Prius.
Bigmouse, that 150kW is only valid if you can use the extra Revs.

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Post by coulomb » Tue, 23 Jul 2013, 19:37

Johny wrote: If I rememeber correctly the later Prius' pack is around 200 VDC and they use an up-convertor to 650 VDC. So a DIYer would not have to fiddle with the 650 VDC side.

But the boost converter has a limit of ~ 20-25 kW (2004 and 2012 models respectively), as provided. I suppose you could beef up the size of the boost converter; that might be less trouble than dealing with 500 or 650 V packs (for the 2004 and 2012 models respectively).
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Post by Johny » Tue, 23 Jul 2013, 20:04

coulomb wrote:But the boost converter has a limit of ~ 20-25 kW (2004 and 2012 models respectively), as provided. I suppose you could beef up the size of the boost converter; that might be less trouble than dealing with 500 or 650 V packs (for the 2004 and 2012 models respectively).
It's getting too hard isn't it. So much reverse engineering when you might as well go from scratch in a car you actually like driving. (IMHO)

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Post by BigMouse » Tue, 23 Jul 2013, 20:05

Johny wrote: ...I think I'm starting to understand (again) why no-one bothers to play DIY BEV with the Prius.
Bigmouse, that 150kW is only valid if you can use the extra Revs.
The gear reduction between the wheel and MG2 is 4.113:1 for the 2004 model (3.905:1 for the previous model).
With the standard configuation and the high voltage, the rated torque of 400Nm is available until 1540rpm. Assuming a 0.3m radius on the wheel, that corresponds to 42km/hr.

A re-wind which would allow constant torque to 4000 motor rpm on a reasonable battery voltage would take you to 110km/hr and produce about 168kW.

An 8-pole motor at 1540rpm is operating at 100Hz. For 500V supply, that's 5Vdc/Hz. (note: using DC values for simplicity)

To maintain that Vdc/Hz to 4000rpm (267Hz), we'd need to supply 1335V. Therefore, if we want to accomplish this with a battery pack of say 365V, we'd need to re-wind the stator for about 1/4 the voltage. This would be 1/4 the number of turns per coil and 4x the number of wires in hand, right?

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AC electric motor rewinding for EV use

Post by T2 » Tue, 23 Jul 2013, 23:34

I say that rewinding IPM Prius machines deserves its own thread..
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AC electric motor rewinding for EV use

Post by mizlplix » Wed, 24 Jul 2013, 04:27

"To maintain that Vdc/Hz to 4000rpm (267Hz), we'd need to supply 1335V. Therefore, if we want to accomplish this with a battery pack of say 365V, we'd need to re-wind the stator for about 1/4 the voltage. This would be 1/4 the number of turns per coil and 4x the number of wires in hand, right?"

Yes, but with an increase in wire gauge also. That thin wire is not up to the higher currents I am afraid. There again, 18 Ga seems the best trade off.

You can simply unwind it and count the coil turns and the in hand bundle. Divide the turns by 4 and mulitply the in hand bundle by 4.

Figure that in hand amount in circular mills and convert it to the 18 gauge wire equivalent. (Use an online chart)

Length (Turns) stays the same at 1/4 the original, inhand count gets smaller, (but really stays the same in circular mills.)



"I say that rewinding IPM Prius machines deserves its own thread.."

Agreed.

It is a worthy subject all on it's own.

Miz
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Post by BigMouse » Wed, 24 Jul 2013, 17:04

mizlplix wrote: "To maintain that Vdc/Hz to 4000rpm (267Hz), we'd need to supply 1335V. Therefore, if we want to accomplish this with a battery pack of say 365V, we'd need to re-wind the stator for about 1/4 the voltage. This would be 1/4 the number of turns per coil and 4x the number of wires in hand, right?"

Yes, but with an increase in wire gauge also. That thin wire is not up to the higher currents I am afraid. There again, 18 Ga seems the best trade off.

You can simply unwind it and count the coil turns and the in hand bundle. Divide the turns by 4 and mulitply the in hand bundle by 4.

Figure that in hand amount in circular mills and convert it to the 18 gauge wire equivalent. (Use an online chart)

Length (Turns) stays the same at 1/4 the original, inhand count gets smaller, (but really stays the same in circular mills.)



"I say that rewinding IPM Prius machines deserves its own thread.."

Agreed.

It is a worthy subject all on it's own.

Miz


I also agree it deserves its own thread. One last comment here for continuity though. The slot openenings through which the wire is inserted is very narrow on the prius stator. 18 guage wire may not fit. Continued discussion in new thread.

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Post by BigMouse » Wed, 24 Jul 2013, 17:20

Prius stator rewind thread HERE.

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AC electric motor rewinding for EV use

Post by 7circle » Thu, 31 Jul 2014, 23:05

BigMouse wrote: My motor was purchased from Jon, yeah. 48vac @50hz. I'm told it's rated for 200a continuous current, so 3x current overload shouldn't be outrageous. There are LOTS of parallel conductors per phase. I will have an electric fan on it, so not relying on the integral fan. I've considered putting a water jacket around it too, but I haven't come up with a reasonable method to do that yet. I don't expect that I'd be pulling full current for more than 10-20 seconds at a time.

It's a WEG 132M frame motor, 4 pole. 9.2kw original rating. I don't know what the winding configuration is, other than it being 4 pole and delta. Next time I have the end bell off, I'll take a picture. Jon may or may not release the winding details. I doubt it though.

EDIT: Checked original rating

BigMouse wrote: Miz: That sounds about right. What sort of results did you get with that motor? Seat of your pants is fine ;-)

What frame size is that? Your phase windings coming out look even bigger than mine (hence the 300a cont I suppose).
Stiive wrote:That'd be a great winding if only you could run it at 400V to get the RPM you want/need.


Like I'm doing! Getting excited now :-)

I've actually got another identical motor on the way now for another EV project, but with the same goals and same controller I'll be using on my own car. I'm hoping to connect them together to make a dyno so I can actually get some performance numbers and help with tuning. I have all the bits to connect them together (heavy duty flexible element couplings). The hard part is measuring the torque. I need to come up with a clever way to fit a load cell in there. I wonder if I could just glue a strain gauge to one side of the motor's feet and calibrate it with a known torque applied to the motor case. I was planning to support the load motor by its shaft and measuring the torque using a load cell at the end of an arm attached to the case, but there's too much fabrication and danger with that method.

Stiive, is it possible to determine rotor time constant for FOC using a locked rotor and adjusting the time constant in software until maximum torque is produced? I'm considering doing this with the motor both hot and cold to get two values, then interpolating between those points based on actual motor temperature. Not as accurate as online identification perhaps, but requires much less processing power.


@ bigmouse
Did you detirmine any of the motor parameters?

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Post by mizlplix » Fri, 01 Aug 2014, 06:44

I have actually tested another motor in my car. It is an exact model of the same 20HP motor, except it is a 2 pole (originally) making the back iron slightly more and the stator has fewer but bigger slots, allowing more in-hand and a total wire length in between all of those we have done in the past. (some 12 different winds)



The same Curtis controller was used and it was optimized on Ivan's dyno before being placed in my car.

Image


It has good low end torque and has 5,100 RPM top speed. It allows my direct drive car at 1,900 Lbs to take off better than traffic and have a 70 MPH top speed. (Pretty good for a 20 year old motor with "old tech" alloy in the stator plates.


Ivan is testing a 2 year old 10HP core that he rewound that has 225 Ft/Lbs of torque. A big difference .....1/2 the size and slightly more torque.   (Locked rotor torque) Leading me to believe that a newer motor is a better starting place. We will see when he completes testing.

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Re: AC electric motor rewinding for EV use

Post by pirpy » Tue, 22 Oct 2019, 04:36

Hello
How much peak power would a 50 Hz 7.5kW 4 pole motor with 400 V windings produce with 48 V battery and custom rewind to lower voltage at 75 Hz ?
to what voltage should I rewind it?
I want to convert small tractor to EV, max speed is 2300 rpm.
thank you

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Re: AC electric motor rewinding for EV use

Post by Richo » Tue, 22 Oct 2019, 12:38

48V is pretty low.

So
50Hz-1500RPM 7.5kW nominal 18-22kW peak
75Hz-2250RPM 11.2kW nominal 28-33kW peak
It would have to be rewound to 22Vac.
Very unlikely.
So the short answer is NO but the long answer is YES.
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Re: AC electric motor rewinding for EV use

Post by Richo » Tue, 22 Oct 2019, 12:40

At those power levels and RPM and voltage you are bettor off with an etek motor(DC magnet motor) or mars motor (AC magnet motor).
So the short answer is NO but the long answer is YES.
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Re: AC electric motor rewinding for EV use

Post by Richo » Tue, 22 Oct 2019, 12:43

You are better off starting a new thread and say:
"I want to convert this"
[insert picture]
"I want it to do this...blah blah blah"
"what do you suggest".
So the short answer is NO but the long answer is YES.
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Re: AC electric motor rewinding for EV use

Post by T1 Terry » Wed, 23 Oct 2019, 12:53

At least this thread brought up the link to the Prius rewind thread that I didn't realise even existed, so not all was a loss :lol:

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