[TR] Off topic...electric motor speed

[Randall]

> Anyone enlighten me on what determines the speed of an 
> unloaded electric 
> motor?  House current and or 12v auto?

Depends on the motor type.  Most brushless AC motors run slightly below
synchronous speed, with how much below determined by their load; so they
don't change much when unloaded.  Most AC motors with brushes and many DC
motors are series-wound, which have basically no inherent top speed, their
maximum speed is determined only by when the output of the motor matches the
bearing drag and/or wind resistance of the armature.

Parallel-wound and permanent magnet DC motors have an inherent top speed
(for a given voltage) determined by the motor design ... basically they act
like generators and oppose the applied voltage until the armature current
drops to nearly zero.

Randall