A triggering circuit such as shown on p4 of:
www.qsl.net/g3uvr/4cx250/G4AJW-psu.pdf
could do the job. Multiple secondary windings could feed stacked
thyristors so no added PSU needed, and an extra one to feed
something to shut off the mains breaker.
Farnell have 1.6kV 70A thyristors at $8.
Steve
I wonder if any US readers use a crowbar circuit as described in the Eimac
paper to really cut down on the energy a valve has to endure during an arc?
There is the outline of a circuit using a string of thyristors (SCRs) in
figure 2 here
http://www.qsl.net/oe5jfl/flashover.htm
although the circuit does not offer protection during the first half
second, until the gate trigger reservoir capacitor has charged up. It also
may not keep the thyristors triggered for 20ms or more, until after the
primary-side relay/breaker/contactor has dropped out. A better approach
might be to use transformer coupled gate triggering, driven from the low
voltage DC supply that is already provided for the control logic. Some kind
of pulse train circuit (NE555?) would be needed to keep the thyristors
triggered during the "follow on" phase.
73, Alan G3XAQ
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|