Which statement describes a Synchronous Motor?

Which statement describes a Synchronous Motor?

• A. Runs at constant speed; used in timing or where speed needs to be constant
• B. Variable speed control
• C. High starting torque
• D. Not suitable for precise speed

Answer: (A)

Synchronous motors run in step with the electrical supply frequency, so they spin at a fixed, predictable speed known as synchronous speed. The speed is determined by the supply frequency and the number of poles, and the rotor locks to the rotating magnetic field, resulting in very little slip under load. Because of this locking to the constant rotating field, the motor maintains a nearly constant speed even as the load changes, which is why it’s used in timing applications or anywhere speed needs to stay constant. Other statements don’t fit as well: speed control that’s easily varied describes motors intended for variable-speed operation, which isn’t the main feature of a synchronous motor. High starting torque isn’t a defining trait, since synchronous motors aren’t self-starting and typically don’t rely on high starting torque. And a machine known for precise speed aligns with the idea of staying at synchronous speed, not the opposite.

Synchronous motors run in step with the electrical supply frequency, so they spin at a fixed, predictable speed known as synchronous speed. The speed is determined by the supply frequency and the number of poles, and the rotor locks to the rotating magnetic field, resulting in very little slip under load. Because of this locking to the constant rotating field, the motor maintains a nearly constant speed even as the load changes, which is why it’s used in timing applications or anywhere speed needs to stay constant.

Other statements don’t fit as well: speed control that’s easily varied describes motors intended for variable-speed operation, which isn’t the main feature of a synchronous motor. High starting torque isn’t a defining trait, since synchronous motors aren’t self-starting and typically don’t rely on high starting torque. And a machine known for precise speed aligns with the idea of staying at synchronous speed, not the opposite.