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#1 bob14

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Posted 29 November 2009 - 10:38 AM

Hi,

We are planning to install a dozen of VSDs, 7.5 kW 400 V, on a new site. The panel powering the VSDs are loaded with a power factor correction capacity bank. The bank is permanently powered. Having been through the forum, I am wondering how the local capacity bank could affect the performance of the VSDs. The VSDs are of the Siemens micomaster type.
Thanks.

Bob

#2 marke

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Posted 29 November 2009 - 05:45 PM

Hi Bob

When you say that the capacitors are permanently powered, I assume by that you mean that they are not switched at all. This is most unusual!!

The action of the capacitors will be to amplify transients which could be enough under some conditions to damage the inputs to the VFDs, and also to increase the transient fault current so that the VFDs, when hit by a line transient, are more likely to be damaged due to the current magnitude.

I would recommend fitting AC line reactors if the capacitors are closer than 50M in cable length from the VFDs.

Best regards,
Mark.

#3 AB2005

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Posted 30 November 2009 - 04:09 AM

QUOTE (marke @ Nov 29 2009, 10:45 PM) <{POST_SNAPBACK}>
I would recommend fitting AC line reactors if the capacitors are closer than 50M in cable length from the VFDs.

Best regards,
Mark.


Hello Mark,

Great info. But if capacitors are switched through PF controller then?? It too need to install line reactor under such installation?


"Don't assume any thing, always check/ask and clear yourself".

#4 marke

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Posted 30 November 2009 - 08:16 AM

Hello AB2005
Yes, the act of switching the capacitors creates transients and the low impedance causes the transient currents to be high enough to cause problems.

Best regards,
Mark.




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