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Capacitor Bank On Vfd Output / Soft Starter Output


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#1 dip04051978

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Posted 18 December 2008 - 10:50 AM

WHAT WILL HAPPEN IF VFD IS CONNECTED ON MOTOR WHERE ALREADY PF CORRECTION CAPACITOR CONNECTED.
What will be the effect on Soft starter with the same case ??

#2 jraef

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Posted 19 December 2008 - 11:46 PM

QUOTE (dip04051978 @ Dec 18 2008, 02:50 AM) <{POST_SNAPBACK}>
WHAT WILL HAPPEN IF VFD IS CONNECTED ON MOTOR WHERE ALREADY PF CORRECTION CAPACITOR CONNECTED.
What will be the effect on Soft starter with the same case ??

Usually a race between the capacitor or the power switching devices to see which one can fail faster.
"He's not dead, he's just pinin' for the fjords!"

#3 dip04051978

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Posted 22 December 2008 - 05:44 AM

Thanks for rpely Jreaf.
We know it is not recommanded to connect capacitor on the output side of the Drive / Softstarter.
But can you please explain in detail how it will fail.

#4 marke

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Posted 23 December 2008 - 12:57 AM

Every time you turn ON the IGBTs in a VFD or the SCRs in a soft starter, they have to carry the charging current to the capacitors which look like a short circuit until charged.
This causes very high currents to flow through the switching device and these high currents damage the switching devices (IGBT SCR)

Best regards,
Mark.




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