[Amps] Serious design stage

[R.Measures]

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=20=

>> stage of a 4-1000A linear.  The power supply, because of its size is=20=

>> to be external and connected by a cable.
>>
>> In the first design I was going to bring the 6500VDC power through a=20=

>> cable to the linear.  But then it occurred to me that since the main=20=

>> reason for the separate supply was the size...which is MOSTLY the=20
>> 12KVA transformer I am using.  It might be safer to just make the=20
>> transformer external and have the rectifiers and filter capacitors in=20=

>> the transmitter case thus allowing the only the transmission of AC,=20=

>> at a lower potential, (using a voltage doubler circuit) in the cable.=20=

>>  Thus, by just turning off the input power I could eliminate the=20
>> potential on the cable instantly...or almost so...while the filter=20
>> capacitors which are the biggest danger would be in the transmitter=20=

>> cage and would be connected to shorting circuits controlled by the=20
>> safety switches on the lid of the transmitter.
>>
>> There must be some reason this is not a good idea as I have never=20
>> seen it done.
>>
> It's mostly the inconvenience of running several high-voltage,=20
> high-current cables - and also multiple redundant safety ground=20
> bonding.
>
> You also need to think *very* carefully about the right locations for=20=

> mains and HV-AC fuses, to protect against a short if any wire=20
> breaks... or any pair of wires... or...

=F0  How would a HV fuse protect better against a short than the extant=20=

circuit breakers in the primary of the HV transformer?
>
> ...
Rich Measures, AG6K, 805.386.3734.  www.somis.org/