Operate Alternators, Generators. Test 6

What will happen when push-button 2 is pressed?

The bulb L will give a pulsating light.
The relay coil A will activate as long at the button is pressed.
The relay coil A will activate and remain activated even after the button 2 has been released.
The switch T will cause the coil to de-activate.

What can cause etched or burned bands on the contact faces of brushes in a DC motor?

High mica segments.
Brushes improperly positioned.
Copper embedded in the brushes.
Copper drag on the commutator.

In the event of total immersion of an electric motor in sea water what corrective action should you take to make the motor operational again?

Clean with air, wash with fresh water and heat by lamp.
Wash with tetrachloride, heat to 80
Wash with fresh water, wipe dry and re-varnish windings.
Wash with tetrachloride, wipe dry and re-varnish windings.

What is the result if a motor runs at a frequency higher than its designed operating frequency?

It will run slower with too high a current.
It will run faster and overspeed.
It will run faster and be overloaded.
It will run slower and at too high a voltage.

If the insulation fails on a major distribution cable, which alternator breaker trip will operate?

The high/low frequency trip.
The short circuit protection.
The overload trip.
The reverse current trip.

An unidentified feeder supplies three motors with full load currents of 15, 40 and 52 Amps each. What is the minimum size of the motor feeder in 'AMPACITY '?

350 Amps.
120 Amps.
235 Amps.
175 Amps.

Why are interpoles fitted to DC generators?

To enable the same size generator to carry more load.
To counter field distortion.
To prevent burning of the brushes.
To prevent shaft magnetism.

Review Answers