Answer / k.prakashchandra

AC does not have fixed polarities

Answer / k.prakashchandra

Dc is not applied continuously. It is just touch and go, to
create momentary flux.

Answer / raj

then how we are using dc on test ..dc wont step up or step
down.., hw dc is craeting current that was shown in galvano
meter . please explain briefly..?

Answer / er dhananjay kumar

Actually in dc genertae constant flux. When we puch on buttons the contant have to travel from one side of ct (p1) to another side of ct (p2) and in this traveling. The flux is cut by ct winding all this event exist for micro second and this will induce a little potential across secondary side and in unidirectional that's why meter sow a little deflection

Answer / raghavendran.r

I think for Polarity testing AC is being used in power transformers.Let me explain the circuit for the same .Keep the secondary side open.But short one of the terminals of the secondary side with the primary side, so that the primary current flows through the secondary.Now adjust the primary voltage using variac and note down the secondary voltage.If primary voltage is greater than secondary then the polarities are different.
If secondary voltage is more than primary then the polarities are same.
This is how polarity is tested in power transformers and Motors.
The same may apply to CT also.

Answer / gopi

IN AC LOSSES HIGH. BUT DC LOSSES IS LOW

What is skin effect?

2 Answers  

george phenomenon of synchronous machine

0 Answers   JU,

what happens in the short circuited secondary transformer,if the resistance of the short circuit is increased gradually?

0 Answers   IIT,

how to calculate knee point voltage for pt?

1 Answers   Amec,

I have a current transformer with 1 main reading meter with transformer outside the building and a control panel having 5 CT reading meters with black round coils inside the building. I want to know, A) when current pass through the Transformers, will the current be reduced or be the same and after that B) when current pass through the CT meters with black round coils, will the current be reduced or be the same. C) in the above process will the reading of the main meter be same or different, from the total reading of all the 5 CT meters.

0 Answers  

What happen when switch yard one pole not tripe when you tripping the breaker

3 Answers   Adani,

if the diameter of a conductor is 'R' then what is the distance between two bundle conductor in a phase?

1 Answers   NTPC,

Can i use the B-curve MCB instead of C-curve MCB

0 Answers  

A 230V dc shunt wound motor has an armature resistance of 0,15Ω.When operating on no load at 650 rev/min the armature current is 6A . The motor takes a full load current of 85A. Calculate the full load speed if the field flux is (i) maintained constant (ii)reduced by 0,03

0 Answers  

what do you mean by PF correction. A motor is rated at 15 kw,415 volts, 0.7 pf and eff of 0.92. The powerfactor is improved to 0.98 by adding capacitors at the bus. calculate the current drawn by motor under full load condition before and after pf correction

5 Answers  

why current is constant on d.c?

0 Answers  

why the transformer was not rotating like a motor?

5 Answers   TATA,