RE: Using SCR's For Regulating Input Current (fwd)

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Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Thu, 3 Feb 2005 17:07:26 -0600
From: Carl Litton <Carl_Litton@xxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: RE: Using SCR's For Regulating Input Current (fwd)

I got some general information on this from the TCML.  I cannot seem to
find a specific site that shows a **simple** circuit for this type
application, however.

There is one guy on the net that shows what appears to be a common light
dimmer circuit connected across the gates and a capacitor connecting the
K (cathode) terminals.  

http://www.dansworkshop.com/00-index/14-Amps%2C%20Volts%2C%20and%20Watts
/15-Homebuilt%20arc%20welder/10-Electrical%20Schematic%2C%20wiring%20dia
gram.gif


He is using this to control the input current to a homemade 250 Amp
welder!  Does know whether such a thing would really work or not?

Any comments welcome

Carl


---------- Forwarded message ----------
Date: Mon, 31 Jan 2005 10:57:56 -0600
From: Carl Litton <Carl_Litton@xxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Using SCR's For Regulating Input Current


Would someone please explain how the brick-like high current 'power
module' blocks containing 2 SCR's are used to regulate current?  We are
interested in pursuing this as an alternative to heavy/bulky variable
inductors.

We have such a module rated at about 250 Amps continuous and 1200 Volts.
It has the 3 main terminals: 1 for AC in and 2 (+/-) used to connect the
SCR's and provide output.  It also has four small terminals, 2 to the
gates of the SCR's and 2 to the cathodes of the SCR's.

We have been given to understand that such a module may be placed in 1
leg of the AC input line (along with a potentiometer and such) to
regulate the input current as a sort of pulse width modulator.  Current
demand on our input line is about 80-120 Amps and we would like to
restrict it to a variable 25 to 60 Amps with this type of setup.

We would appreciate a brief description of such a control circuit or a
link to the explanation and/or a schematic.

Thank you,


Carl Litton