Re: PFC on MOT Pair

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "J Whyte by way of Terry Fritz <twftesla-at-qwest-dot-net>" <xoom321-at-hotmail-dot-com>




>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: PFC on MOT Pair
>Date: Sat, 02 Feb 2002 19:55:33 -0700
>
>Original poster: "Matthew Smith by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><matt-at-kbc-dot-net.au>
>
>Hi All
>
>College was a long time ago and I can't remember how to work this out -
>anyone help?
>
>Two MOTs - primaries in parallel, secondaries in series; they are rated
>for 240V input and both have approximate turns ratio of 1:7.95, each
>giving approximately 1.9kV.
>
>Mains frequency is 50Hz.
>
>I have determined the primary restistances to be 2.7 and 3.0 Ohms and
>the secondary resistances 85 and 109 Ohms respectively.  These figures
>were measured using a Wavetek 27XT and confirmed using decade resistance
>+ Wheatstone Bridge of a "traditional" Megger tester.  (The inductance
>didn't half make the needle vibrate at low cranking speeds - like trying
>to measure AC with a DC voltmeter.)  I attempted to measure inductance
>using the Wavetek, but it was either two low or too high to register.  I
>have yet to check primary current since I currently lack a CT and don't
>like using DMMs directly for current measurement! (I've had one fry 
>before.)
>
>I guess that is not enough data to calculate the value of a PFC
>capacitor but I would like to know
>
>a) is there a rule of thumb value for capacitor sizes for an array like
>this?
>b) what is the actual formula that I should be using, if I had the
>inductance figures (which is what I guess that I'm missing)?
>
>Cheers
>
>Matthew Smith
---------------------------------------------------------------------
I'm not sure about your PFC value in uF...but a standard 240VAC motor 
starting capacitor should do fine with two MOT's in series. I just hook my 
240 volt MOT's directly to the 240 volt socket with a 30 amp power bar. It 
seems to work fine without current limiting.
Each MOT is rated at 2300 watt output at 2.2 kVAC seriesed to give 4.4 kVAC 
at a KILLER 900 mA short curcuit current!!!
I have ran a Tesla Coil off that supply and I am getting 105" arc from my 
secondary!!!

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