3 PHASE MOTORS AND INVERTERS

What is the main advantage of three-phase motors over single-phase motors?

• Higher resistance

• Three times the torque

• Lower voltage

Which feature makes three-phase motors useful for aircraft servos?

• Self-cooling

• Easily reversed

• Low slip

What type of motor is most widely used in AC systems?

• Synchronous motor

• Induction motor

• Universal motor

Why do induction motors not need brushes or slip rings?

• The rotor is stationary

• No electrical connection to rotor

• They use DC power

What determines the fixed rpm of an induction motor?

• Design and frequency

• Rotor resistance

• Load torque

What creates the rotating magnetic field in a three-phase stator?

• Changing flux density

• Phased AC voltages

• Permanent magnets

What is “slip” in an induction motor?

• Rotor lags behind stator field

• Speed of stator field

• Electrical angle difference

Synchronous speed is defined as:

• Slip percentage

• Actual rotor speed

• Speed of stator rotating field

Slip speed equals:

• Brushes and commutator

• Synchronous speed – rotor speed

• Poles and coils

When three-phase AC is applied to the stator, what is produced?

• DC excitation

• Stationary flux

• Rotating magnetic field