synchronous motor

Question 1

Name the synconus motor characteritics

Answer 1

• Constant-speed motors, rotor turns at synchronous speed
• Salient-pole rotor construction
• Polyphase synchronous motors start as squirrel-cage induction motors
• When rotor speed reached 92-95% of synchronous speed a DC voltage is applied to the rotor
• DC can either come from an external supply via two slip rings & brushes, or from a shaft-mounted “brushless” exciter

Question 2

WHat are the advantages of syncronus motor

Answer 2

• Constant speed

* Ability to improve system power factor by acting capacitively (leading power factor), saving energy costs

Question 3

WHat are the disadvantages of syncronus motor

Answer 3

• Higher initial cost
• More complicated & more expensive starting equipment
• Higher maintenance costs

Question 4

What happens to torque angle when load increases

Answer 4

It will increase

Question 5

What is the relationship of phase between rotor and rotating magnetic feild

Answer 5

Rotor lags the magnetic feild