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

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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 -
coordinate system are shown for the case of open-loop and closed-loop operation. The motor torque is proportional to the
component of the current vector
. In the case of closed-loop operation the current vector is always parallel to the
axis.
Contributed by: Frank Brechtefeld (April 2012)
Open content licensed under CC BY-NC-SA
Snapshots
Details
The current of a non-salient pole synchronous motor fulfills the equation
.
In this equation is the supply voltage,
is the back-EMF,
is the resistance,
is the reactance, and
is the imaginary unit.
The voltages ,
,
, and
are represented by phasors in the
-
coordinate system. The
axis, which is the imaginary axis, is parallel to the phasor of the back-EMF
. The
axis, which is the real axis, is perpendicular to the phasor of the back-EMF
.
Reference
[1] J.R. Hendershot and T.J.E. Miller, Design of Brushless Permanent-Magnet Motors, Hillsboro, OH: Magna Physics Publications, 1994.
Permanent Citation