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Post by Richo » Tue, 16 Jul 2013, 00:15

Just remember the varnish won't be good for your health when heated.

Interesting that the motor is 230V delta and 400V star.
Normally 3kW is the biggest in this format so you already have a benefit there.

Yeah scrubbed up real nice. Image
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Post by Johny » Tue, 16 Jul 2013, 02:32

Nice work. Thanks for the detailed description.

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Post by peskanov » Tue, 16 Jul 2013, 05:27

Thanks guys; I should have made some pic of our "lever" system, but I got my hands full of dirt at that point.
Richo, what's the advantage of the 230/400 rating?

Also, does anybody know why this motor has a high power factor (0.9)?
Last edited by peskanov on Tue, 16 Jul 2013, 03:12, edited 1 time in total.

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Post by BigMouse » Tue, 16 Jul 2013, 20:52

Great info. Are you going to re-use the slot papers and inter-winding papers, or have you found a source for new ones? Very interested to see this process.

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Post by Stiive » Wed, 17 Jul 2013, 00:14

peskanov wrote: Next, we cut the front heads using a small grinder. We used a cutting disc, very thin. Initially, the disc was too wide to enter the motor. We cut some old iron until the diameter was reduced a few milimeters.
Image
Windings after cutting.
Image
At this point we removed the small insulation bands using pliers (just the front ones).
Image


Seems like such a waste cutting all that copper...
Did you try map out the windings to see if you could parallel them below your 100V first?
Could have been a good test mule if the rotor is indeed damaged.
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Post by peskanov » Wed, 17 Jul 2013, 02:50

BigMouse,
we threw the old insulator away. About 5 or 6 slots contain burned insulator (we still have to found a way to clean them). Anyway, even if all the insulators were OK, I plan to use higher heat resistant materials.
I asked a pair of professional rewinders where do they get their supplies; it's a local shop (http://www.crisama.com/). I will go there and check the prices; if they are too expensive I will search on internet.

Stiive,
I didn't think too much about parallelizing coils. The motor must go down to 48v or even 36v (I am going to use a Curtis limited to 100V DC); too low for parallelization, right?
I still have the coil heads, cut from the motor as a solid block, and will try to draw the scheme from it.


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Post by peskanov » Wed, 17 Jul 2013, 07:57

Comedic gold:
- First repair ship: the guy test my rotor using a growler he made himself. Unfortunately he kept forgetting to plug it, an even when plugged the device was so loosely attached it was difficult to know if it was ON. :
Verdict: this squirrel cage is completely broken.
Quote for rewind: suggested 700E. Lowered the price a bit after some discussion.
- Second repair ship: the guy takes a look at the rotor: "this rotor is completely in working order. It bears marks from a broken bearing, but that's ok. I don't have growlers or cheking tools, I check it after rewinding the motor".
Quote for rewind: about 500E, because we already removed the old windings. He said he would use varnish for 180C.

At this point I think I will have to look for some squirrel cage testing method, because it seems I cannot trust in any local professional for this!

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Post by T2 » Wed, 17 Jul 2013, 17:14

Peskanov, on July 5th you wrote

To be fair, "2 pole motors have more back iron" is an ambiguous sentence.

On Pg 2 "14000rpm Machines" thread there is a post from Weber dated Oct 12th 2012 depicting data from the ABB motor catalog Dec 2010.

Observe 131-002, 132-002   7,5Kw 2 and 4 pole resp.

Observe motor weight ............      43 & 49Kg resp.

Observe rotor inertia kgm^2.....     0.016 & 0.038 resp.

What does that tell you about rotor sizes re 2/4 pole machines ?

Also torque/mass ratios for those embarking on a rewind. Which motor would you choose ? Hint - the torque (Nm) values are adjacent to the mass (Kg) values if you care to go back and look.
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Post by Richo » Wed, 17 Jul 2013, 20:38

peskanov wrote:Richo, what's the advantage of the 230/400 rating?


Since you are doing your own rewind nothing.

But if you were doing a 400Vac system and ran the motor in the 230V configuration you get 1.73x the power without doing anything.
So you'd have a 15kW motor.
Peak perhaps about 50kW which suits a micro car.
peskanov wrote:Also, does anybody know why this motor has a high power factor (0.9)?
The extra power from a 7.5kW size motor to 9kW output the extra power has to come from somewhere.
So seems reasonable that the pf would be better on this motor.
Last edited by Richo on Wed, 17 Jul 2013, 10:40, edited 1 time in total.
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Post by peskanov » Thu, 18 Jul 2013, 00:43

T2,
that's right, those inertia values means the 4 poles has a bigger diameter. Still, how much iron do they have is unknown.
But torque also depends on rotor diameter, not just back iron. So I still think 4 poles should be a better bet.

Richo,
I have to study where the power factor comes from, as this a bit of a mistery to me.
But I suspect the extra 1.5kw comes from the length of the rotor as you suggested. It's 21 cm long, and I think it's noticeably longer that another rotor from a 132m motor I saw previously.

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Post by jonescg » Thu, 18 Jul 2013, 05:09

Is there a risk the cleaning process removes the coating on the laminations? this would serve to increase eddy currents to some extent I guess?
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Post by T2 » Thu, 18 Jul 2013, 11:49

BTW, Peskanov, thanks for this thread. I know, chances are, most of the time you are positioned to be on the receiving end of unintended brickbats rather than bouquets ! I have been finding the images from your motor teardown to be both interesting and instructive.

The story so far. We know the motor weighs 60kg rather than the 68kg stated in the catalog which raises the question - Does this particular motor more likely possess the IE2 ( High Effcy) designation, rather than the more favourable IE3 (Premium Effcy) rating ?

Then you anticipate this 9Kw 4-pole 48 slot machine will achieve 50Hp (37.3Kw).

But whatever the 4-pole rewind pattern chosen, the nominal torque will remain at the original 59 Nm but now overclocked to ~6000 rpm (200Hz) to achieve that goal of 37.3Kw (continuous).

That being so, two pieces of information are missing.

............The V/Hz

............The overall gear ratio.

Can you give us an indication of what these two values are to be ?

It would assist others who may want to duplicate your work.
Last edited by T2 on Thu, 18 Jul 2013, 18:59, edited 1 time in total.
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Post by peskanov » Thu, 18 Jul 2013, 14:10

jonescg,
I only used soap and water in the case, I think it's better to avoid water entering the iron core. I know for a fact that ACIMs will work with water on the insides for a long time, but I don't know about the impact in the efficiency.
I performed some light brushing in the internal side, didn't use soaps or oils.

I don't know too much about the coatings, wiki says for AC motors a varnish is used between laminations. I think it's a very weak insulator, because that's all that is needed to contain eddy currents.

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Post by peskanov » Thu, 18 Jul 2013, 14:48

T2,
thanks for your interest. I feel quite comfortable writing in this forum, people here is quite friendly imo.

I did not found precise info about this motor; it seems it was built in 2008, but can't find a catalogue from those years.
The closest spec I found in Leroy-Somer catalogues is:

IEC1
Effi. ~87%
Tm/Tn 3.1
Tn    59.1 nm
Moment of inertia 0.023 kg*m2

Not sure it's the same motor; weight is pretty close but power factor differs.

I don't understand why do you say I am limited to nominal torque. My Kawasaki conversion has a 4kw motor rewound to 48ac; nominal torque is 26nm, but I have calculated 65nm from measured acceleration. That's a 2.5x torque, pretty common for ACIMs, right?
We have a Curtis 1236 there, which is a FOC controller I think.

For this conversion I have a Curtis 1238, max 500A. & 100VDC.
Unfortunately, with this controller I cannot go for high RPM!

About the gear ratio: I plan to keep original transmission & gears, I think I will need them to get the most of this controller.

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Post by Richo » Thu, 18 Jul 2013, 20:50

If the controller is 100VDC ie ~70Vac.
A rewind at 36Vdc (25Vac@50Hz=0.5V/Hz) would suggest peak at 4,000RPM.
Now 9kW continuous becomes 25kW continuous.
Short peaks of 75kW (100HP)
Assuming the controller could put out that current.
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Post by Richo » Thu, 18 Jul 2013, 20:53

Given the controller will only do 500A it will be current limited a lot.

25kW should keep most cars at 100kph/60mph.
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Post by peskanov » Fri, 19 Jul 2013, 07:16

25kw continuous is more than I need, it would suck out all the energy of the battery in half and hour Image.

I am not sure about 25VAC and 4000 RPM using a Curtis. It seems Ivan Bennet & friends didn't have much luck following that path.
Has anybody tried than conf.?
This scheme would be really nice, even I could go direct drive .

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Post by T2 » Fri, 19 Jul 2013, 07:45

-peskanov you wrote That's a 2.5x torque, pretty common for ACIMs, right?

Yes sure.

I don't understand why do you say I am limited to nominal torque

It's just that when discussing the rewind, I had expected you would prefer discussion with nominal values only, since the replacement wire must be capable of producing the original mmf. Torque multipliers are intrinsic to the design whether they be 3.1 or 3.7 but they will not effect the choice of the wire size.

And while on the subject, I agree the nominal torque for a 9Kw motor is indeed 59.1Nm, not 49Nm. I have since corrected my previous post which erroneously assumed a 7.5Kw motor. Image

Unfortunately, with this controller I cannot go for high RPM!
That Curtis 1238 is pretty much top of the line. It will go to 300Hz which is plenty.

Its use with a 60Kg motor is going to be very interesting, particularly if you can take the opportunity to use as much of the available 9000rpm while remaining in one gear.

Richo has suggested winding for V/Hz = 0.5 which will have you peaking around 4000 rpm. This will occur at approximately 20mph in first gear and 33mph in second.

If I had "skin in the game" I would be opting for 70Vac/200Hz V/Hz = 0.35 which will have you peaking around 6000 rpm. This will occur at approximately 27mph in first gear and 50mph in second.

The difference being that for the same acceleration the "0.35" motor will be pulling 40% more motor current. The battery current will be the same in both cases of course. From 33mph onwards the "0.5" motor will keep up due to the controller which will allow the motor slip to be increased. At 50 mph both the torque and motor current will start to noticeably drop off and a change into third gear may be necessary.
At the same time the "0.35" motor will now have attained its peak and will continue to draw full current - no gear change will be necessary.

Well that is the idea anyway. One more thing, do any of those rewinders have setups for rotor balancing ?

Edit for better clarity
Last edited by T2 on Fri, 19 Jul 2013, 01:12, edited 1 time in total.
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Post by Johny » Fri, 19 Jul 2013, 15:30

peskanov wrote: 25kw continuous is more than I need, it would suck out all the energy of the battery in half and hour Image.

I am not sure about 25VAC and 4000 RPM using a Curtis. It seems Ivan Bennet & friends didn't have much luck following that path.
Has anybody tried than conf.?
This scheme would be really nice, even I could go direct drive .
Hi peskanov. The Vogue is direct drive and I'm currently only able to deliver 159NM to my drive shaft with a 4.22:1 rear end. The car is quite drivable and has good acceleration above 20km/h. But getting to 20km/h it feels like a slug - even though the acceleration is constant. We are all used to having those gear thingys to multiply torque at lower speeds. I have a second controller which will, when finished, deliver 255NM and I think that's close to a minimum for the 1070kg car that I have.

By the same token, I'm getting 111wh/km on occasion and generaally 125 to 130 wh/km - battery to wheel. With a gearbox I don't think it would be as good.

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Post by peskanov » Sat, 20 Jul 2013, 02:39

T2,
the problem with going low voltage/high revs is that rewinding the motor is difficult. You have to know the art pretty well and unfortunately I don't.
I understand that rewinding for 9000rpm with some torque available is the same than rewinding for 12VAC (using my 100VCD/70VAC controller). That means big coils of 1 turn, and probably in parallel.
Any poorly soldered connection would change the resistance of one coil, leaving the motor unbalanced...and that can happen easily when you are stripping and soldering >20 wires in one go!

The guys at Ivan Garage's could probably try something as unusual, but I don't feel myself prepared to perform that kind of extreme rewind, sorry.

Yep, I have access to a rotor balancing.


Johny,
what you tell me sounds pretty similar to what I experienced with the Kelly controller. However, you have a good controller with vector control...Looking at your transmission, car weight and motor torque, you should have decent acceleration.
Maybe we have different opinions on what is good acceleration? Image

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Post by peskanov » Sat, 20 Jul 2013, 02:42

Well, I moved the rotor to another shop which I feel is more professional. They use a commercial growler to test squirrel cages and repair all kind of strange motors.

They told me they "think it's broken". They seem a bit unsure, like the first guy checking it.

I guess I must move on and look for another one. But I am tempted to rewind this one also, just to see how it behaves. It's a pity copper is so expensive now, and the slots would be too small for aluminum wire. Image
Last edited by peskanov on Fri, 19 Jul 2013, 16:43, edited 1 time in total.

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Post by T2 » Sat, 20 Jul 2013, 11:29

About the gear ratio: I plan to keep original transmission & gears, I think I will need them to get the most of this controller.

I would point out one thing, something I think Richo would agree with also, is that the 7.5Kw frame size is too large. Going forward with a low voltage rewind would transform a 5.5Kw frame into a machine quite capable of absorbing all the current that your Curtis controller can supply. Providing you restrict operation to first and second gears I doubt you could come even close to burning out the stator.

With 5.5Kw nominal torque will drop to 36Nm. At 6000rpm this represents 22.6Kw which is already three times what is needed just to cruise at 50 mph and that is before considering those Tm/Tn multipliers.

Regarding parallel wires. Siwastaja's 7.5Kw frame used 3 in hand for 34 turns/phase. A total of 102 wires of 20awg per slot. Each wire carried 3.1 amps nominal. Wiring them all in parallel gives a 316 amps nominal capability @ 19Vac 50Hz. Clearly your 650 amp controller could only permit a Tm/Tn ratio of ~ 2.0 (650/315). In this case, clearly, the Curtis will not have quite the capability to drive this motor to its full potential.

OTOH a 200Amp stator winding would give you the Tm/Tn ratio of ~ 3.2 (650/200)that you seek.

Right now I am thinking that a 5.5Kw frame with 36 slots would provide 12 slots/phase with each slot accomodating 75 20awg wires in parallel.

The use of a consequent 4-pole layout would divide each phase into four groups of three slots that are separated by 90 degrees around the periphery of the stator. So you would take the bundle of 75 wires and visit the first slot in each group in turn. When you finally return to the first group of slots, the next adjacent slot is selected and the winding continues as before, using the next adjacent slot of each group.

Finally on return to the first group of slots, the third and last slot (for that group) is filled and so on around the machine until the last slot in the last group is filled, at which point the phase exits the stator.

I ask you, how difficult is that ?
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Post by peskanov » Mon, 22 Jul 2013, 03:33

T2,
I have the "older" model of the 1238, it will take only 500A peak and 155A continuous.

I like your idea of using a 5.5kw, as they are lighter and cheaper. In fact, I have an 5.5 kw motor available.
But what about efficiency and durability? Lighter motors usually have an smaller eff. factor.
And what about gears and bearings, are they rated to work 4000-6000 rpm continuosly?
Many 5.5kw motors weight about 40-43 KG, while 7.5KW weight just 10 KG more.
I would say that playing a bit conservative here is a better option, if you have the space.

Honestly, I cannot say how difficult your proposed wiring scheme is as I have never rewound a motor before. I would like to see the scheme for that, if you have one.

I am adding a few pics of both motors (5.5kw & 9 kw) for size comparison. The 9kw weights about 18 kg more than the 5.5kw.

Image
Image
Last edited by peskanov on Sun, 21 Jul 2013, 17:35, edited 1 time in total.

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Post by peskanov » Mon, 22 Jul 2013, 03:55

Some news about my latest findings:
- One of the rewinders told me the small cracks in the body of the rotor were probably caused by squirrel cage crack and arcing.
- Another one told me no shop can properly diagnose an squirrel cage, no matter what they say. His says the only way to check the cage is to test in an stator that is known to work correctly. If the amp draw of all 3 phases is similar, the cage is ok; if any bar is broken, the current will be unbalanced.

Yesterday I tried to determine the config of the windings. 1st lesson: using just the cut head of the coils is not a good idea. I think it would have been easier to try it before cutting anything.
Image

Anyway, I was able to count the wires and find a matching wiring scheme. It is pretty similar to the one used in our previous conversion, also a Leroy-Somer. Number of slots differ, but it is the same pattern.
Here it is:
Image
You can easily see the similarity with coil heads
Image

This is what I got, if anybody see something suspicious in my numbers please let me know.
There are 56 wires in each slot, 4 in-hand, single layered.

So, a "simple" way to lower the voltage would be using the same scheme, but 28 wires in-hand. That would result in 32vac. Right?
Last edited by peskanov on Mon, 22 Jul 2013, 03:11, edited 1 time in total.

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Post by jonescg » Mon, 22 Jul 2013, 04:42

So the number of turns will be 4, even though it's distributed across 8 slots? I find distributed windings very confusing Image
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