# Need advice about an industrial AC motor



## Terror_V (Jan 26, 2011)

Hi guys I've found this motor. And im wondering if it will do the trick.

http://www.elektromotory.cz/goods/index/id/404

I'm thinking on a conversion up to 1500kgs.
What kind of performance should i expect compared to ICE of 75kW?

What should i keep in mind when using industrial motor?
Can I go over the nominal 3000 RPM?
Isn't the nominal voltage of 400V a little bit high?
What kind of Controller/Inverter should i use with this motor?

Thanks in advance!


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## Coulomb (Apr 22, 2009)

Terror_V said:


> Hi guys I've found this motor. And I'm wondering if it will do the trick.


It would work, if you had the space, and a suitable controller, and a suitable high voltage pack.



> http://www.elektromotory.cz/goods/index/id/404What kind of performance should i expect compared to ICE of 75kW?


It would be good compared with the ICE, provided that the battery and controller were up to it, and you could overvoltage/overfrequency it.



> What should i keep in mind when using industrial motor?


1) The motors are cheap but the controllers are expensive.
2) Industrial motors often don't optimise for weight or space. This one is 100 kg (not too bad, but heavy) and in a 160L frame. That means it's huge: 320 mm diameter, and probably over 500 mm long.
3) Industrials tend to be wound for higher voltage than is convenient in an EV. For 400 VAC, you need a minimum 570 V pack, preferably higher. You might be able to get the same motor in a "400 V star" version, meaning it would be 230 V delta. You would still drive it with a 500+ V pack, however. We do this in our MX-5 (build thread here). We're running into safety issues; it's very difficult to maintain the "one millimetre per volt" separation of conductors that has been suggested (google that phrase if you are interested; it goes back to how "plasma boy" got his name).
4) The market is rather limited with AC controllers at present. Industrial controllers (drives) are plentiful, but not cheap new, and again don't bother to optimise for space or weight. We started with a controller that was 830 mm long (from poor memory) and 55 kg in weight. 20 kg of that was three inductors, which we could possibly have removed. In the end, we decided it really was too big to fit in our small donor vehicle.



> Can I go over the nominal 3000 RPM?


Yes, it will do almost 3600 RPM at 60 Hz, so it's designed to do 3600 RPM all day every day. But its design limit is probably 4500 RPM or so; you could perhaps push it to 6000 RPM with balancing (we intend to do that).



> Isn't the nominal voltage of 400V a little bit high?


Yes, see point 3) above. You can get the motor rewound for a lower voltage, but that will likely cost almost as much as the motor new (doubling the cost of the motor).



> What kind of Controller/Inverter should i use with this motor?


As per point 4) above, it's difficult. If you get the motor rewound for lower voltage, say 100 VAC, then you could use a Tritium Wavesculptor 200 (450 V model). This controller will put 300 A RMS per phase into our motor, but we'd need good cooling to do that more than briefly. You could wait for the 900 V version of this controller. You could use an industrial controller; they can be found at reasonable prices on ebay, but you can't guarantee finding a suitable one. You could also get a small industrial motor, and upgrade the IGBTs and drivers to get a higher power model in a reasonable size. Etischer did this for his Volkswagen. There may be other options that I don't know about.

In short: finding a relatively cheap 400 V motor is not all that difficult, but with AC, the motor is the cheapest part of the system. The other problems as noted above mean that there are few AC conversions around at present. The Curtis 1238-7501 and its recent upgrade (-8501?) are good, but are only about 50-60 kW, which is good for a smaller conversion, but not great for heavier donors. They are 96 V nominal, with a strict 130 VDC limit. What the world really needs is a 144 VDC nominal AC controller capable of at least 500 A RMS AC. You'd still need to find low voltage wound motors (they are available), or rewind a smaller frame industrial (ours is 132 frame) for lower voltage. I note that the smaller frame industrials, like ours, cost more (like about 2.5x) than the standard sized ones.


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## Terror_V (Jan 26, 2011)

Hi Coulomb

Thanks a lot for the in depth response. Gave me a food for thought...

Few more questions emerged in my mind...
Although i found some info about the delta and the star configurations i didn't get it about the 400V star being 230V delta (can you please explain it or give me a thread link that explains it ...it will be much appreciated).

These motors look quite customizable(most of the things that can be customized i honestly don't understand :S) and one of the things that can be changed is the motor voltage. They provide quite a diverse list of configurations but yet again i'm incompetent to choose (or at least to understand them....).

As you mentioned the problem with finding a controller i took a deeper look at the same site and they are offering a product that translates to something like frequency converters. And if that is the controller then you are right its quite bulky (roughly as big as the motor...don't know how much does it weight).
I was also wondering about the power rating of the controller. How powerful controller do i need for this 26kW motor ?

The Tritium Wavesclupto 200 looks quite promising. I'm starting to wonder if it can push my motor.
If i have seen it right you are using 730V battery pack... and the Wavescluptor 200 is rated for 450V DC.. how does it handle it ?


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## Coulomb (Apr 22, 2009)

Terror_V said:


> I didn't get it about the 400V star being 230V delta ...


This is standard 3-phase theory; just google "three phase" or similar. Basically, when you have 6 wires to your 3-phase load (as you do with all industrial motors, and most motors made for EVs, especially if you are prepared to open them up), there are two sensible ways to connect the loads: star and delta. It turns out that with delta you split the currents at the join points; with star (in the US, more commonly called Y or wye) you split the voltage among the loads. The split turns out to be the square root of 3 in each case. So a controller output that is 400 V line-to-line can be connected to a star load, such that the loads will see 400 / 1.7321 ~= 230 V each. With either load, the total power is always line voltage time line current times the square root of 3 (because there are 3 loads, but either the voltage or the current will be split by a factor of the square root of three, so you end up with 3 times the voltate time the current divided by sqrt(3), which is the same as the voltage times the current multiplied by sqrt(3).

That does't mean you can connect a motor or other load delta or star and end up with the same power. For the same source voltage, delta will draw more power than star. So if you have a 400 V motor wired in star, then if you rewire it in delta, each coil that was getting 230 V is now getting 400 V. Looking at it the other way, if you only have 230 V from your controller, changing from star to delta will make each coil see 1.73 times as much voltage as before (the full 230 V it was designed to run at).



> These motors look quite customizable (...) and one of the things that can be changed is the motor voltage.


Motors have fixed voltages, apart from the ability to connect in star or delta. Some motors have extra windings that you can wire in series or parallel, but these are rare.

But you can take a motor designed for only 230 V say, and apply 400 V to it at a higher frequency, and you will get more power from it (provided it doen't goo too fast and disintegrate, or break down the insulation with too much voltage. But most motors will run safely to about 4500 RPM (6000 RPM with extra rotor balancing), and about 480 V AC.



> I was also wondering about the power rating of the controller. How powerful controller do i need for this 26kW motor ?


A lot more than 26 kW. If you put a 26 kW controller on to it, it will deliver 26 kW continuous, and about 150% of that for a minute, or 39 kW. That's not a lot of power for a car. You probably want something like a 75/55 kW controller (that means 75 kW for maybe 5 minutes, but 150% of 55 kW or 83 kW for a minute or less). This fits the profile of power demand in a small electric vehicle.



> The Tritium Wavescluptor 200 looks quite promising. I'm starting to wonder if it can push my motor.
> If i have seen it right you are using 730V battery pack... and the Wavescluptor 200 is rated for 450V DC.. how does it handle it ?


Oh, right. We are going to split our pack into two 365 V halves, and run them in parallel for now, and put them back in series if and when Tritium bring out their 900 V controller (much the same thing but with 1200 V silicon instead of 600 V silicon). The current will decrease, of course, but not quite by half, and this should be able to drive our nominal 22 kW 230 V delta motor to well over 100 kW mechanical.

If you could get the motor at the start of this thread in 400 V star form (so you can just change some jumpers in the connector box to make it a 230 V motor), then yes you can probably push 300 A into that motor with a Wavesculptor 200 at around 400 V. It may well need a lot of cooling in this configuration, compared to a higher voltage controller, since you'll be getting your power by higher current rather than higher voltage, and that will increase the copper losses (proportional to I^2.R, i.e. to the square of the current).


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