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omkar_991
Associate

Join Date: Jun 2007
Posts: 25

Magnetising inrush phenomenon

06/15/2007 2:43 PM

We have learnt that high capacity devices like huge transformers or induction machines are never started directly at the rated voltage due to the phenomenon of the magnetising inrush current. In our lab, we have started an induction machine by slowly increasing the applied voltage through an auto-transformer. Then in that case how can the auto-transformer itself be switched ON directly from the supply mains? Wont the same above mentioned phenomenon take place in the auto-transformer?
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jack of all trades
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New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
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#1

Re: Magnetising inrush phenomenon

06/18/2007 5:11 PM

No, because the autotransformer itself doesn't have a high inrush current (no large core to magnetize). When the output voltage of the autotransformer is set low the windings of the autotransformer (which are in series with the load being driven) act to limit the inrush into that load by limiting the voltage the load sees (a bit like a resistive potentiometer or voltage divider network).

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