# 1 AC motor vs. 4 motors - same looses?

1696 Views 2 Replies 2 Participants Last post by  CroDriver
If we have four motors we'll loose some energy on every motor and controller but the energy from the battery is also split between them... So will the looses be basically the same no matter how many motors we use...?

I'm not counting in the better regen capability of a car if it has one AC motor on every wheel.
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If we have four motors we'll loose some energy on every motor and controller but the energy from the battery is also split between them... So will the looses be basically the same no matter how many motors we use...?
Hi Cro,

Basically correct. If you have one motor which is 90% efficient and converts 100 kW, the system losses will be the same as four 90% efficient 25 kW motors. However it is likely that the larger motor can have an increased efficiency over the smaller motor. So the 100kW motor might be 93%, which would then favor a single larger motor versus 4 smaller ones.

Also, a single motor may benefit from a reduced mass versus the total mass of four smaller ones. Things like bearings and housings will not be 4 times larger on the single motor. Also, the gear reducers will benefit from economy of scale making one larger one superior to 4 separate units. But offsetting that would be the mechanical power transmission to the wheels, assuming all 4 wheels need to be driven, or even just 2 from a single motor.

From an electromechanical energy conversion efficiency viewpoint, the situation favors a single machine, in my opinion. But packaging, power management (traction), handling (weight distribution), economics, etc. will influence the design decisions.

BTW, check the NEDRA site. Someone is trying to contact you.

Regards,

major
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Hi Cro,

Basically correct. If you have one motor which is 90% efficient and converts 100 kW, the system losses will be the same as four 90% efficient 25 kW motors. However it is likely that the larger motor can have an increased efficiency over the smaller motor. So the 100kW motor might be 93%, which would then favor a single larger motor versus 4 smaller ones.

Also, a single motor may benefit from a reduced mass versus the total mass of four smaller ones. Things like bearings and housings will not be 4 times larger on the single motor. Also, the gear reducers will benefit from economy of scale making one larger one superior to 4 separate units. But offsetting that would be the mechanical power transmission to the wheels, assuming all 4 wheels need to be driven, or even just 2 from a single motor.

From an electromechanical energy conversion efficiency viewpoint, the situation favors a single machine, in my opinion. But packaging, power management (traction), handling (weight distribution), economics, etc. will influence the design decisions.
I agree.

BTW, check the NEDRA site. Someone is trying to contact you.
Oh thanks. I haven't seen that. I just called him.
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