Some EE Questions

Q) For eleiminating 5th harmonics in a three phase AC system, the winding pitch should be?

Choices:   2/3, 4/5, 5/6, 6/5

Q) Magnetic circuit is saturated, delivering full load current at rated volt and current. n= constant, brushes at interpolar axis. When load is switched off, terminal voltage would?

Choices:  remain same , increase, decrease, will become 0.

Q) Under which of the following conditions dc motor with compensating winding is used?

Choices:
A) Wide range of speed control above normal
B) Wide range of steady load variation with no speed control
C) Wide range of rapid variation in load

Q) What happens when field of DC shunt motor gets opened?

Q) Match?

Interpoles.................Commutation in D C machine.

Three pt. starter.........DC shunt motor

Dummy Coils............Wave Winding

Equaliser Ring...........Lap Winding

Q) The phase sequence of alternator will reverse when

a) If ( field current) is reversed, keeping direction of rotation same.
b) If remains same, direction of rotation is reversed.
c)If reversed, number of poles is doubled.
d) Number of poles doubled, If same.

Electrical titbits

Q) What is efficiency of Electric Locomotive compared to Steam?

Ans) Steam loc 6 %, Electric Loco 45 %

Q) Which load forms sizeable base load for grid?

Ans) Electric Traction

Q) What is effect of low frequency on motor?

Ans) It improves commutation of DC machines and p.f. and efficiency is also increased.

Q) What is advantage of DC series motor vs ac series motor?

Ans) DC series motor develops more starting as well as running torque for same size than ac motor.

Some Rapid Fire Questions on Electrical Engineering

Q) Which machines have parabolic characteristics?

Ans) Fans and Pumps

Q) Which machine has linear load characteristics?

Ans) Screw Feeders

Q) What is difference between NEMA and IEC?

Ans) NEMA is American and IEC is Indian standard.