AC motor controlers

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GreatPotato88
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AC motor controlers

Post by GreatPotato88 » Wed, 18 Jan 2012, 02:06

Ive been looking into AC motor controllers and I have come to several conclusions.

Firstly the Tritium Wavesculptor 200, seems immensely popular, and it also seems quite powerful.

The other is that there don't seem to be many other AC controllers at all.

I remember reading long ago, that the Wavesculptor was in fact designed as a 200kW (or was that 200kva?) controller, but it was running on a reduced load, as it was still "under testing" and that a firmware update would liberate that performance. Is there any truth to that? Will it happen?

The other is, does anyone know of any notable and effective AC controllers, particularly ones more powerful than the Wavesculptor that are suitable for EVs?

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woody
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Post by woody » Wed, 18 Jan 2012, 16:39

The only AC controllers more powerful that I've heard of are industrial ones, but they are big, heavy and make the Wavesculptor look like a bargain.

If you want more power maybe two Wavesculptors + two motors is the way to go.

Curtis make a lower voltage AC controller, (1238?)
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coulomb
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Post by coulomb » Wed, 18 Jan 2012, 17:31

woody wrote: The only AC controllers more powerful that I've heard of are industrial ones, but they are big, heavy and make the Wavesculptor look like a bargain.
There are others, like UQM, but they make industrial controllers look cheap Image Performance costs.
Curtis make a lower voltage AC controller, (1238?)
Yes, but limited to around 130 VDC and 650 A RMS, so perhaps 80 kW (mechanical) maximum, or around 101 kVA to compare it to the WS200's 165 kVA. I think that the Curtis controllers have master/slave capability, so a pair of them should be able to play nicely.

There is also the 144 V nominal Curtis AC controller coming, due about the second quarter this year. But its current limit is probably going to be around 500 A; see DIYelectriccar for a discussion. A pair of these may be more attractive, since the voltage will be a bit higher and the peak currents won't be as extreme.
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AC motor controlers

Post by GreatPotato88 » Wed, 18 Jan 2012, 18:46

Thanks for the help, Ive never seen those UQM controllers before.

Did I understand that last bit right? About the 144v Curtis controllers and the master/slave capability? It looked like you were saying that two of them can be used in tandem on one motor, or did you mean two controllers, two motors? (would 2 144V controllers mean 288 v at the motor?)

Yea I know many of the more powerful drives are big heavy and expensive, it seems that the Wavesculptor is the best controller for the job. Its a shame that there are not more options.

When I compare the Wavesculptor to the Curtis controllers, I see that the Wavesculptor is capable of much higher voltage, but lower amps.

For example the Curtis 1238 can only handle 80v, compared to the Wavesculptor's 450v. However the Curtis 1238 can do 800 Amps, whilst the Wavesculptor can only do 368 amps. (or was it 300?)

Why the difference? What I really would love to see, would be the Wavesculptor do 600Amps, though the more the better.

What are the reasons why this is not so? (Ive also noticed that some DC controllers can do 1000+a, is this down to some intrinsic difference between DC and 3 phase AC?)

Thanks guys, your a huge help.
Last edited by GreatPotato88 on Wed, 18 Jan 2012, 07:47, edited 1 time in total.

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Post by woody » Wed, 18 Jan 2012, 19:26

I think the difference between the DC + AC voltage/amps stems from the history of the different motors used.

There's a bit of a chicken + egg problem - you need a motor which will work with your controller, so it makes sense to use one which is already available.

In DC the motors are descended from fork lifts and golf carts and so work on low voltage (48V and up) but with huge currents.

In AC there are a gazillion industrial AC induction motors built to work using 240/415V AC, so the controllers tend to work with them.

There are problems with both extremes: high current requires lots of copper to conduct the current with low resistance. High voltage requires insulation and is a big scary number.

In an EV:
high voltage means lots of batteries in series => lots of connections => lots of BMS.
high current means fat wires and meaty connections.

Electrical Power is Amps x Volts, so 300 Amp @ 200V is more or less the same as 200 Amp @ 300V = 60kW.

3 Phase AC current messes this up, you multiply the phase current by sqrt(3), i.e. 200 Amp * 1.73 @ 300V = 104kW :-/
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coulomb
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Post by coulomb » Thu, 19 Jan 2012, 00:04

GreatPotato88 wrote: It looked like you were saying that two of them can be used in tandem on one motor, or did you mean two controllers, two motors?
I meant two controllers, two motors.
(would 2 144V controllers mean 288 v at the motor?)
No, 144 at each motor.
For example the Curtis 1238 can only handle 80v, compared to the Wavesculptor's 450v.
I believe that the Curtis 1238 that we are looking at is 96 V nominal; the 1238R-75XX and -76XX models are different from the rest of the 1238 series. The 96 V nominal has an upper limit of 130 V. So people put 35, even 36, even more 3.2 V nominal cells on them.

http://www.curtisinstruments.com/index. ... prodid=529
However the Curtis 1238 can do 800 Amps, whilst the Wavesculptor can only do 368 amps. (or was it 300?)
The 1238R-7501 is capable of 550 A RMS output peak, and the 1238R-7601 is capable of 650 A RMS output peak. The 800 A model is limited to 80 V nominal, I believe.

The Wavesculptor is 300 A RMS per phase output, and would go to 350 A (or just over perhaps) if it is re-rated to 200 kVA.
Why the difference? What I really would love to see, would be the Wavesculptor do 600Amps, though the more the better.
It's the size of the IGBT modules. With an AC controller, you need 6 IGBTs (switching elements); for DC you need either one and a diode or two. So you have to be a bit careful with the silicon budget.

A Wavesculptor with 600 A silicon would be larger and would require more cooling. I guess they thought that 200 kVA would be enough for most applications. Hopefully, the 165 kVA limit will be increased to 200 in the future, I haven't heard anything more about it. I think it would help if some OEM (say Blade) would use a bunch of WS200s; then the cost would come down and maybe there is more chance that they'll have enough thermal data to increase the power limit.
is this down to some intrinsic difference between DC and 3 phase AC?)

Not really. As has been pointed out, DC usually needs more power because typical DC motors can't handle the higher voltage. A larger AC controller could be designed; it would just cost more for the six larger IGBTs.

Another thing you could consider is the Tumanako open source AC controller; you can build one yourself with basically as high power as you want, if you can find the modules large enough.

http://sourceforge.net/apps/mediawiki/t ... e=Inverter (that might not be the best link for this project)

It has been slow progress, but some of them seem to be getting motors to turn now.

There are also Brusa and MES controllers, e.g. from Metric Mind:

http://www.metricmind.com/category/ev-a ... inverters/

I think Jack Rickard was using a TIM controller, and had some weird problems. See the evtv.me site for details.
Last edited by coulomb on Wed, 18 Jan 2012, 13:04, edited 1 time in total.
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AC motor controlers

Post by GreatPotato88 » Thu, 19 Jan 2012, 01:59

Thanks for the info its exactly what im looking for, the Bursa looks good, wonder how much more it is than the Wavesculptor... (edit: Found their price list, isnt it sad how much these things cost... (several times the cost of the Wavesculptor for anyone following at home))

This is a different topic but I was just looking at the ABB catalogue for their motors, and it seems they have dropped the most powerful versions of their 132 frame motors.

The most powerful 132 2 pole is 18.5kW, but this was 22kW last year. (I believe thats the one you ordered for the MX-5 coulomb.)

Likewise the most powerful 132 4 pole is 15kW but this used to be 18.5kW.

Dropped due to low sales volume perhaps? I wonder if they could still be ordered?

Edit:

Oh that reminds me, woody I believe when you ordered your motor you got the 12 wires option, with the s voltage. This resulted in having:

400v star/230v delta OR 200v star 115v delta, in parallel.

Do you run it in parallel? If so are there any compromises? Do you think the motor could be wired for other voltages inbetween (say 170-180), with or without rewireing?

Thanks again guys, I'd be completely lost without this forum and its members.
Last edited by GreatPotato88 on Wed, 18 Jan 2012, 15:15, edited 1 time in total.

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Post by coulomb » Fri, 27 Jan 2012, 14:10

coulomb wrote: There is also the 144 V nominal Curtis AC controller coming, due about the second quarter this year.

It may have been cancelled, though:

DIYElectriccar "HPG AC30/31/50 owners thread" .
Last edited by coulomb on Fri, 27 Jan 2012, 03:11, edited 1 time in total.
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Post by Adverse Effects » Fri, 27 Jan 2012, 17:56


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coulomb
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Post by coulomb » Sat, 04 Feb 2012, 14:54

coulomb wrote:
coulomb wrote: There is also the 144 V nominal Curtis AC controller coming, due about the second quarter this year.

It may have been cancelled, though...

And it may still be coming and due in July 2012:

DIYElectriccar: "HPG AC30/31/50 owners thread"
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