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Anonymous Poster #1

Power Factor Compensation

08/25/2017 3:08 AM

Why power factor compansatition capacitor should not connect between VFD and motor..?

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#1

Re: Power factor compansatition

08/25/2017 3:53 AM

Because that cable will be correctly sized for the duty and protected by fuses.

Power factor correction is aimed at balancing better the relationship the power source experiences further upstream so as to reduce current. The only justification for it is to reduce the reactive power component in the charging tariff.

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#2

Re: Power Factor Compensation

08/25/2017 3:07 PM
  1. The VFD has capacitors on the DC bus already and will present a corrected PF of .95 to the source, rendering the motor PF irrelevant.
  2. Charging of the caps on the load side of the VFD would look like a short circuit to the transistors, and the PWM output would contain so much high frequency harmonic content to the caps that it becomes a race to see which one fails first; the caps or the VFD.
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#4
In reply to #2

Re: Power Factor Compensation

08/25/2017 3:58 PM

I am saying it is a good way to let the smoke out (agree with you).

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#3

Re: Power Factor Compensation

08/25/2017 3:57 PM

Because the motor/VFD combination will not work with a capacitor connected between them. Is that simple enough?

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#5

Re: Power Factor Compensation

08/26/2017 2:15 AM

Pl. refer here which appeared 8 years back in this cr4 forum. You may search further in this forum or EEP portal for more details.

http://cr4.globalspec.com/thread/35965

One senior ABB official informed during discussions that Capacitors should not be connected since at low speed operation of VFD the frequency is low and capacitive reactance will be very high and inductive reactance will be low leading to higher terminal voltage and lead to problems.

DHAYANANDHAN.S

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#6
In reply to #5

Re: Power Factor Compensation

08/28/2017 9:21 AM

In so many words, NO, it won't work, don't do that. We already know it will not work.

You (the OP) will put your eye out with that thing!

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