[Prev][Next][Index][Thread]

RE- Cap Confusion


From: 	Robert Michaels[SMTP:robert.michaels-at-online.sme-dot-org]
Sent: 	Sunday, November 16, 1997 6:26 AM
To: 	tesla-at-pupman-dot-com
Subject: 	RE-  Cap Confusion

        The use of power-factor correcting a capacitor is of very
        limited usefulness in a single-phase circuit.

        Power-factor capacitors earn their keep in 3-phase power
        systems and then only in the cases where the power is
        supplied via delta-wound transformers.  (a very commonplace
        situation)

        Inductive loads with less than unity power-factors cause
        "reactive currents" in the windings of 3-phase transformers.

        These currents are registered on the power company's
        kilowatt-hour meters and hence are billed to the customer.
        However, the reactive currents do nothing but circulate
        around in the 3-phase windings, generating heat therein, and
        contributing absolutely nothing to the useful load.

        In a factory-full of reactive loads (most typically motors)
        the use of power-factor correction can save a bunch on one's
        utility bills.

        In the case of a lone experimenter and a single-phase load,
        they are hardly worth discussing.

                                           More power to you, from
                                           --- Detroit, USA

                                           Robert Michaels


TL>From:  Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
TL>Subject:  Re: Cap Confusion

TL>On Friday, November 14, 1997 11:56 AM Andrew Chin
TL>[SMTP:chinny-at-ozemail-dot-com.au] wrote;

TL>> Hey all.
TL>>
TL>> I am trying to build a Tesla coil, and while my mechanical and
TL>> electrical knowledge is fairly sound, I have no idea how to size all the
TL>> capacitors used in a Tesla coil driver.
TL>>
TL>> There are at least 3 capacitors I would like explained:
TL>>     -Power Factor Correction capacitors (I think these go on the mains
TL>> side of the transformer)

TL>The formula to calculate power factor correction on neon sign transformers
TL>is;
TL>                                  10^9
TL>              C = Corrected kVA  ------
TL>                                 2(pi)fe^2

TL>   C = required capacitance in microfarads
TL>   f = frequency of applied voltage
TL>   e = applied voltage

TL>CORRECTED kVA is determined by dividing the corrected power factor output of
TL>the neon sign xfrmr (Volt-Amps below) by 1000

 [ ... ] [ ... ] [ ... ]