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Earth Leakage On Star-delta Close Transition


Gavin

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I have a system using a star-delta close transition with resistor and capactior starter.

 

During the starting stage the earth leakage is about 9.6Amp! Is pretty high isn't it? The earth leakage relay is using a differential CT to measure my 3Ph 4 Wire, that is why it can detect the earth leakage during starting. After running it is back to normal zero leakage.

 

Wire is fine and motor is fine.

 

What could have causes the leakage current?

 

 

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  • 3 weeks later...

Hello Gavin

 

There should not be any earth leakage with a closed transition star delta starter.

Earth leakage current would suggest that either the CT is in the wrong place, or there is a fault in the starter.

 

Chris, for information on the closed transitions star delta starter, look here http://www.lmphotonics.com/star_delta.htm

 

Best regards,

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  • 2 years later...
Hello Gavin

 

There should not be any earth leakage with a closed transition star delta starter.

Earth leakage current would suggest that either the CT is in the wrong place, or there is a fault in the starter.

 

Chris, for information on the closed transitions star delta starter, look here http://www.lmphotonics.com/star_delta.htm

 

Best regards,

 

Hello Marke,

 

I am having the same problem as Gavin. However, I am using a auto-trans (closed transition) starter and there is nothing wrong with the starter.

 

Any idea why there is an Earth Leakage only during the starting procedure before change over? Why is there such a high earth leakage during starting? The earth leakage was measured using a clamp meter at the earth wire.

 

Could you kindly advise me on how I can resolve this problem?

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Hello bringit

 

Switching will cause transient and step voltages which can be capacitively coupled to the frame of the motor.

If there is a single impulse at the time of the switching, it is due to the capacitance between cables and earth and the motor windings and the motor frame. This is normal and not a problem.

 

Best regards,

Mark.

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