Ch 7

Synchronous motors are similar to induction motors in that both have stator coils that produce a rotating magnetic field.

• T

• F

If the synchronous motor is overloaded to the point where the rotor is pulled out of step with the rotating magnetic field, no torque is developed and the OSR takes the motor off-line.

• T

• F

A synchronous motor has a three-part rotor.

• T

• F

The amortisseur winding of a synchronous motor is generally smaller than the squirrel-cage winding of a comparable induction motor because the winding is only used for starting and is not expected to dissipate heat from continuous operation.

• T

• F

At approximately 95% of synchronous speed, DC excitation is applied to the wound rotor section.

• T

• F

An M-G set can be mounted at a remote location from the synchronous motor and cannot be used with more than one synchronous motor at a time.

• T

• F

The exciter rotor output to the single-phase bridge controls the level of excitation in the main rotor DC field winding.

• T

• F

When starting a synchronous motor, the final step is to simultaneously remove the discharge resistor from the circuit and apply the DC voltage to the field windings on the rotor.

• T

• F

Synchronous motors cannot be protected from damage caused by the loss of excitation.

• T

• F

Many older synchronous motors included a back-up component for times when the discharge reisistor failed.

• T

• F