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RE: Using SCR's For Regulating Input Current

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 11:15 AM 2/1/2005, you wrote: 
Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx>

Thanks Jim.  For this part of the project, the load is transformer only
(no gap and cap).  It seems some sort of RC circuit would have to be
attached to the block to give the pulses to the gate to fire the SCR's.
Do you know any site that shows schematics of such a firing circuit?

Thank you

Carl
Any of the usual phase control circuits works.. R & C with a neon bulb or DIAC to the gates. If you can find old Motorola or GE Power Semi applications notes there are circuits in there.

Looks just like a lamp dimmer. And, in fact, a lamp dimmer with a lightbulb or resistor load might work very well. You can use a pair of diodes and some resistors(to limit the gate current) to take the voltage from across the lamp into the SCR block.




-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Monday, January 31, 2005 6:12 PM
To: tesla@xxxxxxxxxx
Subject: Re: Using SCR's For Regulating Input Current


Those modules are just two back to back SCRs (which works much better
than
a single device TRIAC, particularly on inductive loads).

They're sort of a grown up light dimmer, and use phase control.  You
send a
pulse to the gate at the right time, relative to the zero crossing.

Using such devices to control the very unusual load of a transformer
charging a capacitor with a spark gap is sort of dicey.

If you wanted to control voltage in a DC coil, with a big filter (or
with a
6/12 pulse rectifier), they might work.