Question { NTPC, 17191 }

In a Synchronous generator, Can AC voltage be used instead
of DC voltage in field winding of rotor to produce AC power?

Answer

No.....AC voltage cannt be used in field winding of rotor
of synchronous machines for following reasons....

1)AC produce poles on rotor whose strength is varying
sinusoidally.It is undesirable because the magnetic locking
between two fields in this case are not achieved troughout
the cycle.At current zero of AC there is no locking at
all.So synchronism will be lost.

2)Field winding is designed for DC. It has higher
resistance.According to Lenz law emf is induced in field
winding.so current flowing through through winding will be
very low.Pole strength is very weak.

Question { 10765 }

What is the basic difference among Circuit
breaker,Contractor and Isolator?
Are they different names of same device/equipment?

Answer

circuit breaker can make,break and carry current under
normal,short circuit and overloaded condition..It operates
automatically.

contactor can make,break and carry current under normal and
overloded conditions only but not in short circuit
condition.It can operates more no of times without
maintenance.

Isolator can break currnt only through that part of circuit
which is bot carrying any current.It is manually operated..

Question { 6527 }

Classical power system stability was mainly focussed on
rotor angle stability but modern power system stability has
more focus on voltage stability.Why?

Answer

Yes...Arvind.
Your proposition is right.
I had just made a relative analysis with two stabilities
involved.It does not means that the rotor angle is of no
importance today.It just establish the fact that now we
MORE FOCUSSED towards volyage stability.

Question { 131037 }

What is the difference between Type test and Routine test?

Answer

Thanks Dhiraj for appreciating the answer.
I am sure you people will not allow me to make mistake.
If you find any discrepencies in any of the answer posted
by me,please let me know.I will sure rectify them.

Question { 7348 }

What is the meaning of coupling and decoupling in the
context of power flow?

Answer

Dear Anil
Thanx for appreciating the answer.

Question { 5672 }

Without seeing the nameplate descriptions of a rotating
machine,Is it possible to say which one is a motor and
which one is a generator?
How would you certain this?

Answer

Dear Amit,
Your statement is right except the last line.As long a
machine is in motoring mode it will only take electrical
energy as input not the mechanical enegry.

In the question asked, the intention was to find the
difference on a practical ground.We all are very much aware
of the difference on various techanical grounds but a
laymen would not understand the terms like stator,magnetic
field,armature etc.For them FULLY CLOSED and SEMI CLOSED
are quite easy to interprete.Hope now you agree.

Author:arbelectbit@yahoo.com

Question { HCL, 41212 }

why microprocessors are named as 8085 ,8086 etc?
what's the reason for this???

Answer

Dear Shyam,
There must be some reason behind other series of
microprocessors which i dont know.What i shared with you is
true for 8085.
Since every manufacturer choose their product name on a
separate basis so it is quite difficult to keep track of
nomenclature guidlines of each and every products.However
we can keep abrest with few important names.

Author:arbelectbit@yahoo.com

Question { 4763 }

Why machines are avoided to work is saturation region of B-
H curve?

Answer

Thanks..Nithi for elaborating the answers

Author :arbelectbit@yahoo.com