# 36v motor at 144v problem



## aredxwrestler (Oct 10, 2011)

I am having a hard time understanding how putting all of that extra voltage into a motor. I will be using a 9in by 15in motor in a 3000lb car at 144v and 500a


----------



## major (Apr 4, 2008)

aredxwrestler said:


> I am having a hard time understanding how putting all of that extra voltage into a motor. I will be using a 9in by 15in motor in a 3000lb car at 144v and 500a


Hi ared,

The nameplate rating on the motor was 36V. The motor itself doesn't know that. You can apply different voltage to the motor and it will respond accordingly. Higher voltage commands higher RPM.

Back to your application. You have a 144V battery. There is a controller between the battery and motor. You have to limit the RPM of the motor for mechanical reasons, let's say to 5000 RPM. All this means that the motor may never see 144V. The controller will reduce the voltage from the battery and keep the motor operating in the safe zone, that is within the current and speed limits.

I think I saw where you have a series wound motor. This type of motor has a characteristic performance where the RPM decrease with load for a given voltage. So in your application, you may find that the controller will need to apply higher motor voltage at high loads (meaning at current limit when accelerating) but then needs to reduce the motor voltage at cruising speed to keep the RPM within limits.

Your concerns are valid. You simply cannot connect 144V to a 36V series motor without a limiting controller. It would either overspeed to destruction (as Yabert found out) or arc itself to death from overcurrent if the shaft was restrained.

Regards,

major


----------



## aredxwrestler (Oct 10, 2011)

Thank you very much The motor was the last piece of my puzzle.


----------

