A synchronous motor converts AC electrical energy into mechanical work while keeping its rotor speed synchronized with the supply frequency. This lesson introduces the magnetic interaction that produces rotation and the main motor components.
The stator is the stationary part of the motor. AC in its windings produces a rotating magnetic field. The rotor is the rotating part and carries permanent magnets or an electromagnet that creates magnetic poles. When the rotor locks to the stator's rotating field, it turns at the same rate as that field.
All flashcards
Synchronous speed
The rotor speed locked to the supply frequency and pole count: Ns=120f/p, where p is the total number of poles.
Permanent-magnet synchronous motor (PMSM)
A synchronous motor whose rotor-mounted permanent magnets create its magnetic field.
Reluctance motor
A synchronous motor whose salient rotor develops torque by moving toward positions of lower magnetic reluctance.
Hysteresis motor
A synchronous motor in which lagging rotor magnetization produces torque; it can start itself.
Steady-state stability limit
The greatest load torque a synchronous motor can carry without losing synchronism.
Quiz questions
What produces aligning torque in a reluctance synchronous motor?Answer: The salient rotor moves toward alignment with lower magnetic reluctance.
What creates torque in a hysteresis motor?Answer: Lagging magnetization in the rotor as the stator field rotates.
How does a squirrel-cage winding help start a large synchronous motor?Answer: It accelerates the rotor like an induction motor before synchronism.
What power-factor effect can an overexcited synchronous motor provide?Answer: It can operate at a leading power factor and help correct lagging loads.
At fixed supply frequency, what happens to synchronous speed when the total pole count increases?Answer: Synchronous speed decreases.
Based on the Wikipedia article Synchronous motor, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.