Quiz on DC Machines

Which components in DC machines need to be replaced or re-conditioned due to wear?

• Stator and rotor

• Commutator and brushes

• Bearings and shafts

• Windings and coils

What is the characteristic of an asynchronous motor?

• Rotates faster than the supply

• Rotates slower than the supply

• Rotates in time with the supply

• Does not rotate

What does the alternating supply create in the stator coils of a synchronous motor?

• Static magnetic field

• Rotating magnetic field

• Pulsating magnetic field

• Constant magnetic field

What happens to synchronous motors if they do not run at synchronous speed?

• They accelerate.

• They stall.

• They reverse direction.

• They increase torque.

Why are synchronous motors not self-starting?

• Due to their rotor design

• Due to their stator design

• Because they are too heavy

• Because they have no windings

Which component of the motor is directly affected by the applied supply?

• Rotor

• Stator

• Commutator

• Armature

What is one advantage of a wound rotor compared to a cage rotor?

• Lower starting torque

• Higher starting torque

• Simpler design

• Lower efficiency

What component is used to add external resistances to the rotor windings in a wound rotor?

• Gears

• Belts

• Slip rings/brushes

• Pulleys

In the diagram, which component is directly connected to the slip rings?

• Stator

• External resistors

• Wound rotor

• Line

What is a universal motor?

• A motor that operates only on solar power

• A commutated series-wound motor

• A motor that operates only on wind power

• A motor that does not require any power supply