Answer / madhusudhan

inorder to produce constant magneticfield we required to
apply D.C rather than A.C. which gives variable magnetic
field

Answer / shantanu mishra

The DC current also called field current or excitation
current is given to produce magnetic field in which rotor of
the generator rotates and produces EMF. the EMF can be
varied by regulating field current.

Answer / mahesh

we need a rotational magnetic field of sine wave for the
emf to be induced . if dc is given, the field that is
produced in the air gap is almost a sine wave with constant
magnitude. for ac excitation the air gap flux is not a sine
wave .

Answer / u.vijay bhaskar reddy

for producing constant flux on the rotor

Answer / nagarjunacharya

to produce emf in the stator either we should apply
alternating flux or dynamic(rotating) conductor.as already
we are rotating rotar by prime mover ,wewe have to apply.

Answer / venkatrao chowdary

the dc current produce constant magnetic field.when rotor
conductors are rotated this conductors cuts the magnetic
lines of flux than emf is induced.this emf is called
dynamically induced emf.when ac is given to the alternater
it induces statically induced emf.the operation of
alternater we need dynamically induced emf.so ac is not
given to the alternater.

Answer / u.v.subhashreddy

alternator is an speeed machine. the dc current gives
exication current is given to produce a magnetic field so
giving d.c supply to field of an alternator.

Answer / y.srinath

dynamically induced e.m.f requires fixed polarity& magnetic flux .if we given a.c to field the polarity of a particular pole is not fixed .if one pole behaves as north pole for +ve half cycle & same behaves as north pole for negative half cycle to.that's why we are using d.c supply for alternator.

Answer / b madhu sudhan reddy

alternator is a constant speed machine.i.e it always runs
at synchronus speed.so,for producing constant speed we
require constant excitation.so,for the constant excitation
we require constant supplly.i.e d.c supply

Answer / pravallika

for magnetising poles in rotor

an amazing situation was faced when an alive distribution panel with 415 volts and carrying almost 200Amps has become short and this metal cubical showing 220 volts against neutral and earth. to redress any confusion i checked the panel with help of single 200watts test lamp which also glowing with max.intensity b/w neutral & metal body of DB. amazing situation is that i hold the DB firmly more than once with necked foot means without insulated shoes but not received any electrical shock. whereas our all running gen sets neutral points also proper grounded and this short DB was completely earthed , this is beyond my understanding . any body explain how is it possible . our running gen set neutral also grounded firmly

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