Question { 25355 }

what is a relay?

Answer

relay is protective device which is first find or determine
the fault in the section and initiate the circuit breaker
for isolate the faulty section from healthy section.

Question { 15835 }

why rotor resistance starter is not suitable for
squrielcage induction motor?why it is suitable for slipring
induction motor?

Answer

in squrielcage induction motor the rotor bars are short
circuited. there is no provision of including resistances
on rotor side.
but in slip induction motor, the rotor bars are connected
to slip rings for providing and an external resistances.
thats why tha rotor resistance starter can be used in
only slip ring induction motor.

Question { APTransco, 15246 }

IN TWO WATTMETER METHOD WE GOT W1,W2,WE KNOW V.HOW TO FIND
Q????????????

Answer

reactive power Q= sqrt3 (W1-W1)

Question { Eskom, 9261 }

what is power factor

Answer

Power Factor is the ratio of Active Power to Apparent Power


Power Factor= Active Power (kw)/ Apparent Power(kva)



or


The cosine angle between voltag and current is called
power factor

Question { 6153 }

In which connection the distribution T/F is connected?

a) ▲ / Y b) Y / ▲ c) ▲ / ▲ d) Y / Y

Answer

the answer is delta/star. bcoz in distribution system we
use always step down tranformer and in the system netural
point is more important for industrieal loads. suppose we
connect transformer in star/delta connection, no neutral
point is comming.

Question { Power Grid, 8007 }

can we connect both delta and star to the transformer
secondary and for what reason?

Answer

suppose in transformer one side of coil of each phase can
connect to ground potential. It means that the insulation
strength of transformer can be reduced compared with Delta
connection . It realize cost down of transformer. Delta
connected coil need same insulation strength on both side
of coil, so it need more cost for insulation. But in Star
connection, harmonics problem will appear. In case of Delta
connection, harmonics current is circulating in delta-
connected coils and not appear in distribution line. If the
harmonic current was there, it will be a cause of over heat
of lead-phase capacitor, lag-phase inductance and
transformaer.

Question { 7870 }

At which time Synchronous generator act as a Synchronous
Condenser?

Answer

synchronous generator can be operated in overexited at no
load condition. then it acts as a synchronous condenser.

Question { 9219 }

how to reduce humming noise in transformer?

Answer

following methods are there:
1) reduction of induction in the core.
2)adequate design and costruction of core.
3)insertions of vibrations insulating comonents inthe
transformer tank.
4)adequate construction of tank.