Current limiting using microwaves.

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: Current limiting using microwaves.
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 11 Feb 1998 23:53:38 -0600
Approved: tesla-at-stic-dot-net

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From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Wednesday, February 11, 1998 5:01 PM
To:  Tesla List
Cc:  Nasalharp-at-Aol-dot-com
Subject:  Re: Current limiting using microwaves.

Greetings:

> From:  Nasalharp-at-aol-dot-com [SMTP:Nasalharp-at-aol-dot-com]
> Sent:  Tuesday, February 10, 1998 8:13 AM
> To:  tesla-at-pupman-dot-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-at-compuserve-dot-com
>           and
> Nasalharp-at-Aol-dot-com
> 
> My web site is at:
> http://ourworld-dot-compuserve-dot-com/homepages/AlanSharp
> 
> 
>