# Motors: AC or DC?



## Manntis (May 22, 2008)

yes. AC motors tend to run more efficiently and provide superior brake regen, but require more complicated & expensive controllers. In the event of a failure, they stop working.

DC motors can be used with less sophisticated (cheaper) controllers but usually require more cooling and, in the event of a failure, can 'run away'; spinning up to max power independent of the throttle control.


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## megajoules (Jun 1, 2008)

Thanks, and sorry for the delayed reply.

Do some DC installations use additional air or liquid cooling?

I'm assuming that a kill switch would be advisable if these have a chance of running away.


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## mattW (Sep 14, 2007)

I think for motorbikes at 72V the advantages of AC get smaller and smaller. we're getting 88% efficiency out of the motor, and regen is easy since they are PM motors and there is no brush advance problems at these low voltages. Unless you have a specific tendency towards AC or want more power than the Pm motors offer then just go with the Etek or equivalent.

Kill switch is a good idea, I might duct a little air onto the motor on my bike but it depends on how hot it gets. I haven't seen liquid cooled DC though...


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