Lrc

[bob14]

Hello forum members,

 

I know that the lock rotor current of an inductio motor varies between 7-12 times the flc. My question is as follows: Is the LRC dependent on the mode of starting? Star/delta and DOL application?

Thanks.

 

Bob

 

 

[marke]

Hello Bob

 

Yes, the LRC (or LRI) is the current drawn under full voltage starting conditions.

If you reduce the voltage, you reduce the current.

If you connect a delta motor in star, you are reducing the voltage acros each winding so you reduce the effective LRC also.

 

Best regards,

Mark.

[bob14]

Thanks Mark, which means that a circuit breaker with a lower magnetic setting could be used instead.

 

Bob

[marke]

Hi Bob

 

I presume that you are considering an application using a star delta starter.

 

In this case, while the initial current in star is lower, the initial current when you change to delta is commonly higher than the normal delta LRC.

This is due to the open transition switching transient. There are other posts on this topic.

I would use the same magnetic trip, possibly higher.

 

Best regards,

Mark.