Which part of a motor needs maximum attention for maintenance?

Rotor of a motor is usually supported on _________ bearings.

A. Ball or roller

B. Needle

C. Bush

D. Thrust

When the load is above _________ a synchronous motor is found to be more economical.

A. 2 kW

B. 20 kW

C. 50 kW

D. 100 kW

For derris and winches which of the following drives can be used?

A. Pole changing squirrel cage motors

B. D.C. motors with Ward-Leonard control

C. A.C. slip ring motors with variable resistance

D. Any of the above

Which of the following motors is preferred for traction work?

A. Universal motor

B. D.C. series motor

C. Synchronous motor

D. Three-phase induction motor