Question { 8382 }

in trains i have seen the terminal which is connected at
the top of the train is positive .where is negative ?
track? i dont think so

Answer

Actually,it is good to refer it as Phase & neutral
itself,since,as per Indian railways we use 25kV,1 phase ac
system.The terminal at top ie called panthograph takes power
in to loco and track acts as neutral

Question { 17325 }

if two bulb of 50w &30w apply in series having 230v the
which bulb glow bright ,why

Answer

P=VI,
So this combined 80w load will draw approx. 0.34 amp from
the 230 v supply

So when the same current flow through the bulbs,the highest
resistance one,ie 50w bulb will glow bright.

Question { 4380 }

tell how current tranfomer works

Answer

We know it as a measuring device.But it can act as
protecting device also.

It is basically a step-up transformer.It raises the
voltage thereby reducing the current(as high as 100A or
more) in a circuit so that it can be measured using a std 5A
or 1A ammeter.Primary is the conductor containing the
circuit in which the current is to be measured.

Question { GIL, 20550 }

Why HT motors are connected in star.

Answer

I think we need a clarification to answer 1.Actually the
starting current will be 2-3 times the Full Load current,not
load current.

Question { 8120 }

why D.C excitation is given to sunchronous motor?

Answer

Like all DC motors,a synchronous motor also requires DC
excitation,since,a conductor placed in the field can only
produce some torque on the conductor.

Question { 6460 }

What is mean by hormonics?

Answer

Harmonics are the unwanted frequencies present in the
supply.It can affect the equipments connected in the system
adversely.It can be removed by using filters.Usually odd
harmonics produce more harm to loads,while even harmonics
,will be suppressed by itself.

Question { Shreem Electric Ltd, 23501 }

What is mean by power factor?

Answer

The angle created between voltage & current is referred to
as Power Factor.It depends mostly on the load.This plays a
great role in determining the power a load takes.