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mohsinhamid
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Join Date: May 2011
Posts: 91

Reactors

08/16/2011 1:41 AM

why we are using reactors before capacitors banks.....?????

i heard tat it reduses harmonics is tat true....??? if it is how it reduces pls any one explain clearly.......
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kvsridhar
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#1

Re: reactors

08/16/2011 2:48 AM

Capcitors, when switched on, act as a short-circuit momentarily. A single uncharged capacitor can draw 30 times its rated current, this being limited by the supply impedances.

When multiple capacitors are being switched, the already charged capacitors will discharge into the new one, and, impedances being very low now, the current drawn can reach 150 times the rated current ! Since it is also at 10-15 kHz, reactors are used to attenuate this high inrush.

A good explanation is available in NEMA ICS 2. It is available for free download, please download and study.

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mohsinhamid
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#2
In reply to #1

Re: reactors

08/16/2011 3:00 AM

tnks for ur valuable reply....

sir how could the capacitor acts as short circuit when switched on for sme tym..???
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kvsridhar
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#3
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Re: reactors

08/16/2011 5:03 AM

A closer look at that extract of NEMA ICS2.....

i was also taught this in college

Similarly, if you apply a voltage to an inductor, the current doesn't flow immediately.... it rises exponentially as per the time-constant of the inductor {I = Imax*(1-e-Rt/L)}

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kvsubramanyam
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#4
In reply to #1

Re: reactors

08/16/2011 5:20 AM

GA, there are many ways of explaining but this is good.

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kvsridhar
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#5
In reply to #4

Re: reactors

08/16/2011 5:54 AM

Thanks, you made my day

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electricalexpert65
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#6
In reply to #1

Re: reactors

08/16/2011 10:20 AM

But, KVS! Therea are also reactors used in series with capacitors, to supress harmonics, as in tuned filters and in de-tuned filters.
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kvsridhar
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#7
In reply to #6

Re: reactors

08/16/2011 11:52 AM

Of course

But i don't know them ! If the OP asks, you will have to answer !

As you know, i am a switchgear guy, and i love that beautiful product, the capacitor-switching contactor ! So, will you excuse me on harping on what i know....

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kvsubramanyam
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#8
In reply to #6

Re: reactors

08/16/2011 11:33 PM

The company in which I am working now use battery charger-cum-regenerative-dischargers. There are 4000 to 6000 circuits at each of our manufacturing facilities. These equipment leads to very high harmonics generation (VTHD 6 to 8% % & up to ITHD 36%). I am able to handle these harmonics with out using any filter. Idle would be "Active Filter" but very costly. As you said correctly, reactors are used to prevent frequencies other than fundamental reach capacitor and damage them.

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