1. In phase-shift control method the control is carried out by varying the of grid voltage ?

magnitude

polarity

phase

any of the above

Answer: phase

Explanation:


2. Which of the following mercury arc rectifier will deliver least undulating current ?

Six-phase

Three-phase

Two-phase

Single-phase

Answer: Six-phase

Explanation:


3. The advantage of mercury arc rectifier is that ?

it is light in weight and occupies small floor space

it has high efficiency

it has high overload capacity

all of the above

Answer: all of the above

Explanation:


4. The potential drop in the arc, in a mercury arc rectifier, varies ?

0.05 V to 0.2 V per-cm length of the arc

0.5 V to 1.6 V per cm length of the arc

2 V to 3.5 V per cm length of the arc

none of the above

Answer: none of the above

Explanation:


5. The voltage chop between the anode and cathode, of a mercury arc rectifier comprises of the following ?

anode drop and cathode drop

anode drop and arc drop

cathode drop and arc drop

anode drop, cathode drop and arc drop

Answer: anode drop, cathode drop and arc drop

Explanation:


6. Mercury, in arc rectifiers, is chosen for cathode because ?

its ionization potential is relatively low

its atomic weight is quite high

its boiling point and specific heat are low

all of the above

Answer: all of the above

Explanation:


7. In which of the following equipment direct current is needed ?

Telephones

Relays

Time switches

All of the above

Answer: All of the above

Explanation:


8. Normally, which of the following is used, when a large-scale conversion from A.C. to D.C. power is required ?

Motor-generator set

Motor converter

Rotary converter

Mercury arc rectifier

Answer: Mercury arc rectifier

Explanation:


9. In a single phase rotary converter the number of slip rings will be ?

two

three

four

six

Answer: two

Explanation:


10. Asynchronous converter can be started ?

by means of a small auxiliary motor

from AC. side as induction motor

from D.C side as D.C motor

any of the above methods

Answer: any of the above methods

Explanation: