# Electrical machines

Electrical machines
Question:-
Option (A)
Field resistance is higher than critical resistance
Option (B)
There is no residual magnetism in the field circuit
Option (C)
Field winding has got wrongly connected
Option (D)
There is a fault in armature circuit
Correct Option:
C
Question Solution:
If shunt field resistance is more than the critical field resistance, there will be no voltage buildup beyond residual voltage but voltage would not be zero
Question:-
Option (A)
efficiency is higher
Option (B)
power factor is higher
Option (C)
Slip is larger
Option (D)
Starting current is lower
Correct Option:
D
Question Solution:
The outer cage has high resistance and low reactance while the inner cage has low resistance while the inner cage has low resistance and high reactance. Therefore at starting and high reactance. Therefore confined to the outer cage with a consequent decrease in starting current and an increase in starting torque.
Question:-
Option (A)
Locking
Option (B)
Plugging
Option (C)
Crawling
Option (D)
Cogging
Correct Option:
C
Question Solution:
Refer, harmonic asynchronous (induction) torques. Running stably at low speed (around 1/7th normal motor speed) is known as crawling
Question:-
Option (A)
40A
Option (B)
44A
Option (C)
400A
Option (D)
440A
Correct Option:
A
Question Solution:
Ea = V-IaRa
Ea = 200 = 220-Ia x 0.5 Þ Ia = 40A
Question:-
Option (A)
{sin(g/2)/m sin (mg/2)}
Option (B)
{sin(mg/2)/m sin(g/2)}
Option (C)
{m sin(g/2)/sin(mg/2)}
Option (D)
{sin(mg/2)/sin(g/2)}
Correct Option:
B
Question:-
Option (A)
Stator field strength and torque angle
Option (B)
Stator field and rotor field strengths
Option (C)
Stator field and rotor field strengths and the torque angle
Option (D)
Stator field strength only
Correct Option:
C