An induction motor is_______ - Three-Phase Systems in Power Applications

Electrical and Electronic Engineering (EEE) : Three-Phase Systems in Power Applications - Quiz(MCQ)

An induction motor is_______

Requires external supply

Self-starting

Both (A) and (B)

None of the above

Correct Answer : Option (B) : Self-starting

Explanation : As the rotation of the rotor conductors are initiated normally due to the force produced because of interaction between induced current and rotor magnetic field, no external supply is required and the Induction motor is self-starting.

Recently Updated in Three-Phase Systems in Power Applications Questions

In a three phase, delta connection

Line current is equal to phase current

Line voltage and line current is zero

Line voltage is equal to phase voltage

None of the above

Correct Answer : Line voltage is equal to phase voltage

Explanation : A delta connected AC circuit is achieved by connecting the start end of a winding to the finish end of another winding such that all three windings form a mesh. Since each end of the windings forms the line connection, voltage across each winding is equal to the potential difference between the corresponding lines taken from that winding. Hence the phase voltage is equal to the line voltage.

For a three-phase delta connected load, fed from a star connected network, the power transferred to the load is_

3 KW

4.7 KW

5 KW

7KW

Correct Answer : 4.7 KW

Explaination :

For a balanced three phase, three wire system with input power of 10kW, at 0.9 power factor, the readings on both wattmeter are ________ respectively

7kW, 3kW

5000W, 5000W

6350W, 3650W

7600W, 1200W

Correct Answer : 6350W, 3650W

Explanation :

Let reading of one Wattmeter = W1

Reading of second Wattmeter = W2

Input Power, P = W1+W2 = √3V_LI_Lcosφ = 10000………………1

Power Factor, cosφ = 0.9

Phase angle, φ = 25.8 degrees

Therefore, W1 = V_LI_Lcos(30-φ) = 0.99V_LI_L = 6350W