# Speed of a Cumulative Compound DC Motor

by mobin.abrar
Tags: compound, cumulative, dc motor, electric machines, torque-speed
 P: 1 I came across an equation for the Speed ω in Radians/seconds of a Cumulative Compound DC motor. ω= K(Vt-IA[RA+RF)/($\Phi$P+$\Phi$S) How would we calculate K in this equation? Shouldn't the Terminal Voltage Vt be replaced by Armature Voltage Ea? I came across a lot of varying torque speed curves. WIll the curve be exponentially decaying or linear?
Mentor
P: 10,519
Maybe you should explain your formula and the used variables, or at least give its source.
My guess: K is some constant given by the geometry of the motor.

 I came across a lot of varying torque speed curves. WIll the curve be exponentially decaying or linear?
I don't think that any of these curves are perfectly exponentially or linear. In addition, it might depend on the motor (e.g. how its internal friction depends on the angular velocity).

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