### Author Topic: A question about capacitor?  (Read 985 times)

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#### 928928

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##### A question about capacitor?
« on: December 19, 2018, 08:56:34 am »
Recently, I have learned something about capacitor and learned a lot about it.A few days ago, I read an article about capacitor, which talked about the functions and definition of the capacitor. I think it’s useful and it helps me a lot when I studied the capacitor.( to know more about this article, one can visit the website:http://www.apogeeweb.net/article/114.html )
However, now I am meeting a problem, which is in the following picture.
I have this capacitor in my hand, four binding posts, who can give an explanation? In addition, how is its internal wiring method? Y type or △ type? It is written as 299uf, but the one-three and one-four-column measurement is 98uf, the one-two-column measurement is 45uf, the second and third-column measurement is 32uf, and the reverse is the same. How is the capacitance calculated? How to calculate the withstand voltage as a DC capacitor?

#### helius

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##### Re: A question about capacitor?
« Reply #1 on: December 19, 2018, 09:29:55 am »
RF Power capacitors are designed with special considerations and operating limits.
You can read more from Vishay: https://www.vishay.com/docs/22071/geninfo.pdf

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##### Re: A question about capacitor?
« Reply #2 on: December 19, 2018, 09:36:15 am »
https://www.vishay.com/docs/13181/phahvac3phase.pdf

But the star and delta configuration still have 3 pins.

http://www.etigroup.eu/images/userfiles/en-GB/documents/products/building_industry/Three-phase-capacitor.pdf

You could show us the photo of your capacitor ?  i saw on one photo they sometimes use the case as ground (4th pin ??) or simply a way to attach it somewhere
« Last Edit: December 19, 2018, 09:40:16 am by coromonadalix »

#### capt bullshot

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##### Re: A question about capacitor?
« Reply #3 on: December 19, 2018, 09:50:08 am »
That is a typical power capacitor used for power factor correction in industrial environments.
Internally, it would consist of three capacitors in delta configuration, each one at a rated (299 / 3) uF. Quite uncommon to specify that total capacitance, usually only nominal voltage and kvar rating is given. Sometimes these three capacitors are manufactured as one large bobbin with internal taps, for larger power one usually finds three seperate capacitors.
Three pins are to be connected to the three phases, the fourth one might be protective earth (not connected to the capacitors).

DC rating will be at least sqrt(2)*nom. AC voltage, usually more since these are supposed to withstand surges etc.
Anyway, current rating is rather poor, so running them at larger currents than given on the type plate will overheat or degrade them. Definitely no good for pulse discharge experiments and similar fun.
Safety devices hinder evolution

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#### Gregg

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##### Re: A question about capacitor?
« Reply #4 on: December 19, 2018, 08:36:08 pm »
The capacitor label indicates this is used for delta three phase.  Sometimes the center of one leg of the delta is center tapped and referenced to grounded neutral.  This may explain your readings on the 1,2 and 2,3 terminals.
The #2 terminal may be a midpoint tap of the capacitor with the 1,3 terminals
« Last Edit: December 19, 2018, 08:37:53 pm by Gregg »

#### maginnovision

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##### Re: A question about capacitor?
« Reply #5 on: December 19, 2018, 09:26:30 pm »
When posted at xcore.com this looked like absolute spam, glad to see you made it here.
« Last Edit: December 19, 2018, 09:29:05 pm by maginnovision »

Smf