Comparing Open-Loop and Closed-Loop Operation of a Synchronous Motor

torque

1.

⟶ back-EMF E

⟶ voltage drops at resistance and reactance R I + j X I

⟶ supply voltage V

⟶ current I

This Demonstration compares open-loop and closed-loop operation of a non-salient pole synchronous motor. Non-salient implies that the reactance is equal along every axis due to the uniform airgap between stator and rotor. The voltage vectors and the current vector in the

d

-

q

coordinate system are shown for the case of open-loop and closed-loop operation. The motor torque is proportional to the

q

component of the current vector

I

. In the case of closed-loop operation the current vector is always parallel to the

q

axis.