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Join Date: Mar 2008
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# 3 Phase AC Capacitor

09/11/2017 2:06 PM

I have a capacitance measurement question.

I have a three phase AC capacitor rated 480 volt ac 700 uf +/-3%.

Measuring between all three terminals on a new cap I get 1.5 X 700 uf. = 1050 uf on all terminal combinations.

I am using a Escort capacitor meter EDC-110R set at 2000 uf.

Seems I recall this many years ago that this reading is correct but if it is I can't recall why.

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Join Date: Dec 2008
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#1

### Re: 3 Phase AC capacitor

09/11/2017 2:41 PM

Two 700 uF capacitors in series is what equivalent single capacitor, 700/2 uF.

Any two capacitors in parallel is the sum of those two capacitors. (700 +350) uF = bingo.

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#2

### Re: 3 Phase AC Capacitor

09/11/2017 2:56 PM

I am not sure if the cap is delta or Starr so I sketched both configurations.

I should have done that first makes it very clear. Thanks for jogging old brain cells.

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#3

### Re: 3 Phase AC Capacitor

09/11/2017 2:58 PM

From the result you gave, it's star configured.

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#4

### Re: 3 Phase AC Capacitor

09/11/2017 5:55 PM

Delta configuration, I would say. Across each pair of terminals is one cap in parallel with two in series.

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