On Apr 21, 2004, at 12:08 AM, Ian White, G3SEK wrote:
Jim Isbell wrote:
After collecting parts for most of a year I am in the serious design
stage of a 4-1000A linear. The power supply, because of its size is
to be external and connected by a cable.
In the first design I was going to bring the 6500VDC power through a
cable to the linear. But then it occurred to me that since the main
reason for the separate supply was the size...which is MOSTLY the
12KVA transformer I am using. It might be safer to just make the
transformer external and have the rectifiers and filter capacitors in
the transmitter case thus allowing the only the transmission of AC,
at a lower potential, (using a voltage doubler circuit) in the cable.
Thus, by just turning off the input power I could eliminate the
potential on the cable instantly...or almost so...while the filter
capacitors which are the biggest danger would be in the transmitter
cage and would be connected to shorting circuits controlled by the
safety switches on the lid of the transmitter.
There must be some reason this is not a good idea as I have never
seen it done.
It's mostly the inconvenience of running several high-voltage,
high-current cables - and also multiple redundant safety ground
bonding.
You also need to think *very* carefully about the right locations for
mains and HV-AC fuses, to protect against a short if any wire
breaks... or any pair of wires... or...
How would a HV fuse protect better against a short than the extant
circuit breakers in the primary of the HV transformer?
...
Rich Measures, AG6K, 805.386.3734. www.somis.org/
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