JE electrical model question and answers Part 3

JE electrical model question and answers with explanation

Part - 3

1. What is the factor of safety used for

current ratings in a power installation?

2

Explanation: - Factors of safety is also known as (and used interchangeably with) safety factor (SF), is a term describing the load carrying capacity of a system beyond the expected or actual loads.

2. Which among these is a method of wiring?

Joint box system or Tee system

Loop in system wiring.

Explanation: -

Surface or open Conduit type wiring

Recessed or concealed or underground type Conduit wiring. Cleat Wiring, Casing and Capping wiring, Batten Wiring (old wiring system), Lead Sheathed Wiring,Conduit Wiring,

3. Which among these is a part of distribution

system?

A. Feeders

B. Distributors

C. Service mains

D. All the above

Explanation: -

A distribution system originates at a distribution substation and includes the lines, poles, transformers and other equipment needed to deliver electric power to the customer at the required voltages.

4. What is the maximum span up to which the

wooden poles can be used?

60 m.

5. For what voltage is the H-type of poles

used?

130 kV

Explanation: -

1.    Wooden poles :- cannot be used for voltages higher than 20 kV.

2.    Steel poles: - Substitute for wooden poles. The steel poles are of three types (i) rail poles (ii) tubular poles and (iii) rolled steel joints.

3.    RCC poles: - R.C.C. poles for single and double circuit.

4.    Steel towers for 110 kv span 320 m and other

one 220 kv span 320m.

6. To prevent the decaying owing to snow and

rain, the wooden poles are protected by

_________ cap at the top.

A. Aluminium

B. Zinc

C. Cement

D. All the above

7. The squirrel-cage winding of a single-phase

motor is placed in the_________.

rotor

8. NEMA standards rate motors according

to__________.

frame number

Explanation: -

National Electrical Manufacturers Association (NEMA).

9. Which of the following motors is most

suitable for signalling devices and timer?

Reluctance motor.

Explanation: -

A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on the ferromagnetic rotor. The rotor does not have any windings. Torque is generated through the phenomenon of magnetic reluctance.

10. The purpose of skewing of rotor slots in

induction motor is_________.

to reduce the locking tendency of rotor.

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