# Choice of AC induction motor



## Coulomb (Apr 22, 2009)

ACEVS4US said:


> I'm pretty keen on operating at a high voltage because the batteries are the most critical thing in an EV (I reckon) and a high voltage pack significantly lengthens the life of the batteries because of the reduced current draw.


Well, but you need lower capacity cells to get enough of them to fit in the car and still make the high voltage. So you still need 3-6 C to get decent performance out of them, and that's with a large (circa 30 kWh) pack; for smaller (circa 10-15 kWh) packs, you need a higher discharge rate. These figures are largely independent of pack voltage.

What you do get with the lower current draw is less voltage drop across the links and cables (and you need less thick cable, which is cheaper, easier to work with, and slightly less weight). But not longevity, unfortunately.


----------



## ACEVS4US (Jul 21, 2011)

Thanks for pointing that out Coulomb. Yep, I don't know that much about batteries technologies and had incorrectly assumed that higher voltage and lower current is better. But on reflection I guess it's the total power the pack has to deliver that really matters. C ratings generally seem to be the same for any pack size.

In one sense though higher voltage should be less demanding on the pack simply due to the increase in efficiency resulting from less I-squared R loss in the motor and cabling.

I'm kind of thinking somewhere around 35kwhrs for batteries, which would put my cell size at 60ah. 

At the moment though I really want to focus on getting a spec for a motor so that I know what rating the controller will need to handle.

Chris


----------



## Tesseract (Sep 27, 2008)

ACEVS4US said:


> ...
> In one sense though higher voltage should be less demanding on the pack simply due to the increase in efficiency resulting from less I-squared R loss in the motor and cabling.


Not so fast, buster... if you go to higher a voltage pack then you will almost certainly use smaller diameter wire, so you might not save all that much in i²r loss. Then in the actual power electronics you're going to find out that higher voltages result in higher switching losses (just like higher currents result in higher conduction losses). There's no free lunch... anywhere. More specifically, higher voltages require slower switching speeds and a lower frequency to keep dV/dt and switching losses within reason. High dV/dt wreaks havoc with those DSPs, makes it impossible for your product to coexist peacefully with other devices like, say, the car radio, and more insidiously, damages the windings and bearings in the motors (from capacitively coupled currents).



ACEVS4US said:


> At the moment though I really want to focus on getting a spec for a motor so that I know what rating the controller will need to handle.


That depends on the breakdown torque of the motor in question... Resident motor guru "major" knows more about this, but 3-5x full load torque seems typical. Thus, you can reasonably expect to overload an AC motor by ~4x its continuous rating. I'd suggest finding an AC motor with at least a 20kW continuous rating if you want to propel a car while anything above 50kW is going to be too heavy unless it was specifically designed for EVs (and then it ain't gonna be cheap - think UQM). This isn't gospel or anything, just my opinion on the matter.


----------



## Martijn (Aug 17, 2010)

Hi,

would you consider a Siemens motor ?

We are using a 45Kw(nominal power) Siemens AC motor with a weight of 80 Kg.
But we have a whole range of siemens motors available. 

If you want more info, i have a pdf with specifications.

Not sure where you are located, we are in the EU.

Regards,
Martijn


----------



## hbthink (Dec 21, 2010)

I purchased this bad boy on ebay recently but it is probably a bit undersized for pushing my 83 VW Rabbit convertible. I want to build a controller for it, I have build smaller ones for RC model planes so I'm planning to scale up that design for higher power. This motor has the following specs:

10.5 kW
22.2 N/m 
4500 rpm
54.5 Volts
136 amps

but when I check the data:

http://perm-motor.de/fileadmin/user...en_Englisch/PMS120_W_TD-E_technical_specs.pdf

it appears I can get 12.5 kW out of it at 96v and I suspect thats at closer to 6000 rpm. Still a bit lightweight, maybe I can get the next motor up in size. This one would work well in my Ford Think 

Steve


----------



## jhuebner (Apr 30, 2010)

Tesseract said:


> Not so fast, buster... if you go to higher a voltage pack then you will almost certainly use smaller diameter wire, so you might not save all that much in i²r loss. Then in the actual power electronics you're going to find out that higher voltages result in higher switching losses (just like higher currents result in higher conduction losses). There's no free lunch... anywhere. More specifically, higher voltages require slower switching speeds and a lower frequency to keep dV/dt and switching losses within reason. High dV/dt wreaks havoc with those DSPs, makes it impossible for your product to coexist peacefully with other devices like, say, the car radio, and more insidiously, damages the windings and bearings in the motors (from capacitively coupled currents).


Well, operating at high voltage is somewhat comparable to operating at high rpm: everything gets lighter and smaller. Though it introduces other problems.

I did a quick simulation of inverter losses at Semikrons website for operating at 25kW (8kHz switching):
- 177Vac and 98A -> losses 878W
- 354Vac and 49A -> losses 516W
So using higher voltage does pay off here.

Cheers,
Johannes


----------



## Tesseract (Sep 27, 2008)

jhuebner said:


> I did a quick simulation of inverter losses at Semikrons website for operating at 25kW (8kHz switching):
> - 177Vac and 98A -> losses 878W
> - 354Vac and 49A -> losses 516W
> So using higher voltage does pay off here.


I don't know that your examples really prove anything, Johannes, since both operating conditions can be handled by 600V silicon and you didn't specify the input voltage in each case. I was referring to comparing doubling the input and output voltages while halving in the input and output currents. If those two operating conditions can be handled by the same, e.g., 600V silicon then both could occur at any time with the same inverter/motor combination. This comparison only gets interesting, and informative, when you compare 600V and 1200V devices.

For example, I ran two simulations in Semisel comparing 50kW output with 8kHz switching and 40Hz motor at a high PF of 0.95.

SEMiX 600V Si (HDs)
400V in, 300V out, Psw = 37W/IGBT, 7.8W/FWD; Ptot = 585W

SEMiX 1200V Si (Vs)
800V in, 600V out, Psw = 57W/IGBT, 19W/FWD; Ptot = 617W

All in all, fairly similar, but with a slight edge to the lower voltage situation.

If I switch to E4 Si (1200V) then the total losses are slightly better at high voltage than low voltage (520W).

Which leads me to another point: you can use simulation to prove almost anything... within the narrow confines of the simulator's worldview, anyway.


----------



## jhuebner (Apr 30, 2010)

I see your point.

I ran my simulation at 500Vdc and 250Vdc, both with the same 1200V IGBT (6-Pack).

I guess if lower system voltage allows you to switch to a 600V type IGBT you will indeed reduce inverter losses.

I reflected about my choice of a high voltage system a bit. The root is my decision to use an industrial AC motor without rewinding it.

Its a commodity item and thus rather cheap. In my current electric car it works just fine.

/Johannes


----------



## Salty9 (Jul 13, 2009)

Have you checked etischer's thread?

http://www.diyelectriccar.com/forums/showthread.php/converting-2001-passat-15363.html

It seems similar to your project.


----------



## tomofreno (Mar 3, 2009)

There's eve:
http://www.electro-vehicles.eu/default.asp?content=1,67,56,0,0,Electric_Motors,00.html

and these (no idea on price and availability to diyers):
http://www.evo-electric.com/products/electric-motors/


----------



## ACEVS4US (Jul 21, 2011)

Thanks for those links, That second link (EVO Electric) shows some pretty impressive specs.

The AFM-240
Power density of 4.2Kw/KG!!!
Peak power for 60 secs is 335KW - holy crap!
Torque up to 1200 Nm - holy crap!
80kG
Great link - I'm going to chase this up to find out the costs of their motors.

The eve motors also look pretty good

The M3-AC50 has a 60s peak power of 90kW for 60s and it costs $2990 euro which I reckon is not a bad price. The weight is 80Kg.

I note the EVO motors are permanent magnet, whereas the Eve are pure induction.


----------



## Coulomb (Apr 22, 2009)

ACEVS4US said:


> Great link - I'm going to chase this up to find out the costs of their motors.


I've seen the smaller brother of the AFM-240, the AFM-140. With 167.5 kW of peak power, it might do your job. The prices are reported here:

http://forums.aeva.asn.au/forums/forum_posts.asp?TID=2300&PID=29147#29147

as well as some other AC motor options you might want to consider. In case you can't get to that page, the AFM-140 was £6000, and the AFM-240 £10,000, in October 2010. So these are not cheap, but good performance motors. I believe that these are ironless motors.

Unfortunately, the poster lost his donor vehicle in the January floods here in Brisbane, Australia. He still has the motor and Tritium controller. He's since moved to Sydney, Australia, and has a replacement donor vehicle (identical, as it happens), but is challenged for workshop space. So unfortunately, there won't be any performance results from him for a while. Although the motor has been spun up on a Tritium controller at the Tritium factory, so there may be some dynamometer results to be had. (A quick search didn't result in any; you may need to contact the poster directly).

So at least, these motors are available to hobbyists like us, at least for upper end conversions.


----------



## ACEVS4US (Jul 21, 2011)

Tesseract said:


> There's no free lunch... anywhere. More specifically, higher voltages require slower switching speeds and a lower frequency to keep dV/dt and switching losses within reason. High dV/dt wreaks havoc with those DSPs, makes it impossible for your product to coexist peacefully with other devices like, say, the car radio, and more insidiously, damages the windings and bearings in the motors (from capacitively coupled currents).


I must admit I don't really share this view. Higher voltage does have advantages which are "a free lunch". Specifically, with high voltage you get a much wider dynamic range (higher torque at high rpm's) because you don't get into the field weakening region as early. This is a significant performance advantage.

As for EMI wreaking havoc with DSP's in the inverter and other low voltage electronics. Yes and no. Yes, there is a lot of EMI, but EMI at a frequency of 10kHz or so is very easy to deal with - primarily through shielding.


----------



## Tesseract (Sep 27, 2008)

ACEVS4US said:


> I must admit I don't really share this view. Higher voltage does have advantages which are "a free lunch". Specifically, with high voltage you get a much wider dynamic range (higher torque at high rpm's) because you don't get into the field weakening region as early. This is a significant performance advantage.


It's not an opinion or a view that I have, it's simple physics. Switching losses go up with the square of voltage while conduction losses go up with the square of current. A good designer seeks to strike a balance between those two....

And the only way you get higher torque at higher RPM is with higher voltage (and frequency for AC motors) AND higher current. But higher voltage means more Volt-seconds across the motor windings which means more turns of smaller diameter to avoid saturation. But higher amperages means more Amp-turns which means less turns of larger diameter to avoid saturation. Ergo - TANSTAAFL.



ACEVS4US said:


> As for EMI wreaking havoc with DSP's in the inverter and other low voltage electronics. Yes and no. Yes, there is a lot of EMI, but EMI at a frequency of 10kHz or so is very easy to deal with - primarily through shielding.


Board-level shielding employed for anything besides RF front ends/mixers is, to me, the sign of defeat. Almost all problems that get solved with shielding could have instead been solved with better board layout and circuit design. Note that putting the entire device into a metal (ie - shielded) box to meet EMC regulations is a separate issue; I'm talking about soldering bits of folded sheet metal over parts of a pc board to enable it to function properly.

That said, the PWM frequency isn't the source of the EMI here, rather, it's the switching transitions that send the emissions spectrum out into the MHz range. The rule of thumb is to divide the transition time in microseconds by 0.5 to get the knee frequency in MHz. E.g. - switching in 200ns results in emissions extending out to ~2.5MHz.


----------



## arber333 (Dec 13, 2010)

Martijn said:


> Hi,
> 
> would you consider a Siemens motor ?
> 
> ...


Hi, i am interested in buying a Siemens 40KW motor?
Can you send me the documents/prices?
[email protected]

tnx

Arber


----------



## ACEVS4US (Jul 21, 2011)

I would also be keen to get a quote for the 45kw motor.
[email protected]

Thanks


----------



## E30_Dave (Apr 19, 2012)

Hi Chris,

Did you make a decision about your motor afterwards ?

In light of my chosen siemens motor being unavailable, I spotted this at the Bosch Rexroth site:

MSS162F-0310

http://www.boschrexroth.com/dcc/Vor...anguage=EN&VHist=g97568,g96068&PageID=p146808

It's from a different range I know - synchronous as opposed to asynchronous... I understand what these terms mean, but is there a preference for EV applications ?

Best Regards

Dave


----------



## niallm (Aug 31, 2021)

Hi , i have four large rexroth 3 phase motors 30kw – 46 kw e.g model “Bosch Rexroth induction motor 3 phase mad130d-0200-sa-m0-fg0-05-n1 “ two of them seem brand new and two reconditioned, so worth putting into something, they very heavy 160kg. i am wondering if these are candidates for EV conversions, i am passionate about working on cars and would even go for and old rolls or bentley , came across these motors in one lot at an auction and bought them with no idea what to do with them , hence i am here any advice even if not for EV, for green energy production wind turbine etc.. i have them and want to use them. 
thanks in advance 
niall


----------



## arber333 (Dec 13, 2010)

niallm said:


> Hi , i have four large rexroth 3 phase motors 30kw – 46 kw e.g model “Bosch Rexroth induction motor 3 phase mad130d-0200-sa-m0-fg0-05-n1 “ two of them seem brand new and two reconditioned, so worth putting into something, they very heavy 160kg. i am wondering if these are candidates for EV conversions, i am passionate about working on cars and would even go for and old rolls or bentley , came across these motors in one lot at an auction and bought them with no idea what to do with them , hence i am here any advice even if not for EV, for green energy production wind turbine etc.. i have them and want to use them.
> thanks in advance
> niall
> 
> View attachment 123483


Well can see those motors were made in Slovenia, probably in Škofja Loka where Bosch has its factory . I can ask about motor performance if you like.
It is quite heavy! Generally it is Pnom 31kW motor nominal. It could go up to 47kW, but i think that is more like industrial rating. For dynamic rating i am sure it could go for 3x nominal power.
I see it was wound for 600Vrms. This means it will require quite HV battery to develop full RPM. 

Can you check what kind of sensor it has in the back? If it has normal resolver you could go for Openinverter drive and use either Prius gen3 inverter or Volt gen1 inverter.
If resolver is amplified (some Tamagawa...) then you would need to replace this. I dont think it would be worth the trouble.


openinverter forum - Index page


----------

