Answer / samy

DC supply gives constant , steady magneticflux.
but AC supply gives an alternating flux. so in alternators
field give to dc supply.

Answer / saeid

The answer is because these alternators are synchronuse
generators. The philosophy of electrical synchronuse
generators is based on DC excitation in the rotor and
synchronuse vontages in stator.

However,there are some application for induction generators
such as wind generators that have AC excitation like other
induction motors.

As a reslut, if alternator is synchronuse generator it has
to have DC excitation and if alternator is induction
generator it has to have AV excitation.

Answer / a.kossay

THATS BECAUSE IN GENERATORS THERE IS A TURBINE WICH CAUSE
ROTATION TO THE ROTOR SO WE ALREADY HAVE ROTATING ROTOR SO
THERE IS NO NEED FOR A ROTATING FIELD, AND IF SO IT WILL BE
HARD TO CONTROL THE SPEED OF THE FIELD

Answer / ajay kumar yadav

no ripple factor in DC excitation but there is ripple factor
in AC

Answer / xengso0nax

alternator is sync. machine which not self start,so we need
dc excitation to get const field

Define relative stability.

0 Answers  

how i meggar value of 11kv alternator winding.and with meggar.

1 Answers  

How to calculate the input cable rating for 10kva ups (3phase input and single phase output and also 3phase output, battery rating 65Ah)provide the formula also.thnx

0 Answers   Bhel,

Basic philosophy of applying 3P tripping for uptill 132KV switchyards & for 132KV & above 1P/3P tripping is used.

1 Answers   L&T,

wat is d first thing to be seen 2 lay a cable in a particular area??

1 Answers  

IN THE CASE OF AN ELCB, IF THERE IS ANY UNSTABILITY BETWEEN PHASE AND NEUTRAL IT MAY TRIP. BUT MY QUESTION IS WHEN A LOAD IS CONNECTED IN BETWEEN P AND N, THE LOAD CONSUMES SOME POWER AND THERE IS A DIFFERENCE IN NEUTRAL WITH RESPECT TO THE PHASE. THUS ACCORDING TO ME, THE ELCB WILL AUTOMATICALLY OPERATES WHEN EVER THE LOAD CONSUMES-- I KNOW IT IS WRONG. BUT THE SOLUTION IS?????????

1 Answers   KSEB,

What are the factors which influence the choice of specific magnetic and electric loadings of a synchronous machine?

0 Answers  

How to test the vector groups of 3 winding transformer & phase displacements

2 Answers  

why capacitor using the induction motor?

5 Answers  

in small capacitor we use uf( micro farad) and in big quantity we used kvar. i want to know that in 1 kva how much will b uf(micru farad).

2 Answers  

an electric bulb or lamp can operate on ac and dc, if yes then why

5 Answers  

why batteries are rated in ampere hour

1 Answers