Ch 6

The stator of a wound-rotor motor is different than the stator of a squirrel-cage induction motor.

• T

• F

The rotor of a wound-rotor motor is constructed be placing solid conductor bars in the slots instead of the insulated coils of wire used in the squirrel-cage induction motor.

• T

• F

Wound-rotor stator windings are not short-circuited, they are wye connected, with the free end of each winding connected to slip ring.

• T

• F

A pigtail connects the slip ring to the power supply.

• T

• F

Brush material is typically composed of a mixture of carbon and graphite for high-voltage machines and of graphite and metallic powder for low-voltage machines.

• T

• F

Resistors used in a wound-rotor motor are often referred to as secondary resistors, because the rotor is the secondary of the motor.

• T

• F

The M1 connection is the outside slip ring, the M2 connection is the middle slip ring, and the M3 connection is closed to the motor windings.

• T

• F

A wound-rotor motor is never started with full resistance in the circuit.

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• F

Resistance is increased as the motor accelerates in order to shift the point of maximum torque.

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• F

When no resistance is applied to the rotor circuit the starting torque is about 125% of the full-load torque (FLT)

• T

• F