Which of the following is the reason behind an ideal synchronous motor not developing any starting torque?
- A. The relative velocity between stator and rotor mmf is large at starting
- B. The rotor is extremely heavy in these machines
- C. The stator winding is concentrated winding
- D. The rotor winding has a very high reactance
Answer: A. The relative velocity between stator and rotor mmf is large at starting
Explanation: At standstill the stator field sweeps past the rotor at synchronous speed, so the rotor torque alternates and averages to zero: no starting torque.