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pfc caps and vsd for plastic injection machines


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#1 jan

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Posted 27 February 2003 - 03:06 AM

do i have to install both to get maximum reduction in electricity consumption?

#2 marke

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Posted 27 February 2003 - 09:05 AM

Hello Jan

welcome to the forum.
pfc capacitors are used to improve the power factor of induction motors and thereby reuce any power factor or KVA penalty that you may be paying. They will not reduce the kw drawn by the motor. If you use a vsd, you can not use pfc capacitors. pfc capacitors across the motor will cause the vsd and/or the capacitors to fail! You must use either one or the other but not both.

Best regards,

#3 jan

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Posted 27 February 2003 - 10:50 PM

so which one will give me more benefits?

or can i have a vsd and still use bulk pf correction?

#4 marke

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Posted 02 March 2003 - 09:57 AM

Hello Jan

To give you a definative answer, we would need to have a lot more information.
Fitting a VSD will only save energy if you are going to operate the motor at reduced speed. I would expect that this is not the case in this application, so you could actually end up using more energy by fitting the VSD.
Yes, you can use a VSD and still have bulk correction at the point of supply, but the input current to the VSD is very rich in harmonic currents and could cause an increase in the capacitor current and premature capacitor failure. I would recommend that if you are using bulk correction on the same supply as you have VSDs connected, that you fit detuning inductors to the capacitors.
Best regards,

#5 Daniel

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Posted 30 October 2003 - 01:14 PM

Is the detuning inductor same as detuning reactor?If not, I think we should connect the reactor in series to the capacitor but not inductor, am I right?

#6 marke

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Posted 30 October 2003 - 01:43 PM

Hello Daniel

The reactor is an inductor, so yes they are the same thing.

Best regards,

#7 jhun

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Posted 06 February 2004 - 02:18 AM

vsd is good option. but if you want to install the pfc. you must really study about the consequent of pfc.
you must take a look the harmonic thd. by installing pfc you might be magnifying the distortion.




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