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Why does a motor take 1 ampere when current passes through auxiliary contacts, whereas it takes 10 ampere?

Question asked by Kumar Sahoo in #Coffee Room on May 10, 2019
Kumar Sahoo
Kumar Sahoo · May 10, 2019
Rank E1 - BEGINNER

motor takes 1 ampere when current passes through auxiliary contacts it takes 10 ampere why?

Posted in: #Coffee Room
Ramani Aswath
Ramani Aswath · May 10, 2019
Rank A1 - PRO

The question is not clear. A sketch of the circuit may help.


Kumar Sahoo
Kumar Sahoo · May 10, 2019
Rank E1 - BEGINNER

A single phase  1 HP motor connected  with a DOL starter which  having  2 push buttons one is start(green) another one is stop (red). As per the  principle  of W= √3VIcosΦ the motor should take 1.48amps but it's taking  10 Amp.  How? 


Ramani Aswath
Ramani Aswath · May 10, 2019
Rank A1 - PRO

In a single phase motor, W= VxIx cos(phi).

Full load current of a 1 hp induction motor will be about 8 amps taking into account power factor.

You seem to be taking the formula for the single phase current of a 1 hp three phase induction motor.

Please see here:

https://www.engineeringtoolbox.com/elctrical-motor-full-load-current-d_1499.html

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