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Current limiting using microwaves.
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To: "'Tesla List'" <tesla@pupman.com>
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Subject: Current limiting using microwaves.
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From: Tesla List <tesla@stic.net>
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Date: Wed, 11 Feb 1998 23:53:38 -0600
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Approved: tesla@stic.net
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From: Malcolm Watts [SMTP:MALCOLM@directorate.wnp.ac.nz]
Sent: Wednesday, February 11, 1998 5:01 PM
To: Tesla List
Cc: Nasalharp@Aol.com
Subject: Re: Current limiting using microwaves.
Greetings:
> From: Nasalharp@aol.com [SMTP:Nasalharp@aol.com]
> Sent: Tuesday, February 10, 1998 8:13 AM
> To: tesla@pupman.com
> Subject: Current limiting using microwaves.
>
> Greetings
>
> My power supply is a 5500v 350mA ex physics lab transformer -
> big no current shunts, connected to ground and then to a 2000v
> 500mA microwave transformer. Giving me about 7500v at 350mA plus.
> Primary capacitor is 0.09uF. Mains is 230v 50 Hz here.
>
> I had been using a 2500w electric convector heater for current limiting.
> But I tried instead using the primaries of microwave oven transformers,
> with the secondaries shorted out. I now use 2 of these in series with a
> 110v variac used as a variable inductor. I can now control the current from
> just under two amps (12" arcs) to over 10A (32" arcs - limited by the space
> in the garage).
>
> To use a variac as a variable inductor just connect to one end of the coil
> and to the wiper. They won't do on their own as past a certain point they
> tend to saturate and effectively become a dead short.
>
> Curiously when I tried to suppliment these inductors by putting a resistor in
> parallel with them - the coil output dropped - I must have some benevolent
> resonance / voltage rise / wierdness happenning through the inductors.
Indeed you are. The loose inductance is resonating with the
transformed primary cap value as seen at the primary of the
transformer. A consequence of this is that the secondary of your
transformer will go to a far higher voltage than SQRT(2) x 5500V if
your gaps allow it.
Malcolm
> Nice though - more output and control.
>
> Microwaves are current limited but probably at about double the value
> you might expect from their power rating.
>
> Have fun,
>
> Alan Sharp (UK)
>
> till I am sure that my mail is working please
> contact me at:
>
> 100624,504@compuserve.com
> and
> Nasalharp@Aol.com
>
> My web site is at:
> http://ourworld.compuserve.com/homepages/AlanSharp
>
>
>