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why must a synchronous motor never be started when DC excitation is applied to the rotor

why must a synchronous motor never be started when DC excitation is applied to the rotor

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Rotor becomes and acts as an electomagnets on the application of DC exitation in synchronous motor. Rotating magnetic field starts turning at synchronous speed after the stator is enerzied due to which alternate attraction and repulsion of electromagnets takes place by stator rotating magnetic field. As a result of this, rotor does not rotate and rotor and power supply might damage due to high induced voltages. Thus, synchronous motor never be started when DC excitation is applied to the rotor.

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