[Collins] 32V Series Relay Info Wanted

[Dr. Gerald N. Johnson, electrical engineer]

The arcing, if any is mostly on opening, not closing. 120 volts just
doesn't leap out when the contacts are close, they have to touch, of
course, they will bounce. Two breaks in series always breaks the arc
better than one because they both eventually get wide.

I don't know the 32V to know the relay style or the wiring diagram, but
I can think of some safety reasons for having contacts on both ends of
that HV transformer primary. Back in the days of the 32V, line cords for
120 volts (115 or less) were not polarized, so one could not use a
single set of contacts and be certain that there was no voltage to
ground with the relay (or a single pole line switch) open. Sure one
contact would kill the HV, but if it was in the neutral side of the
primary circuit, it would leave 120 volts to ground for ALL the primary
wiring except the wire from the switch/relay to the neutral pin on the
line plug. And if a ham is reaching in to work on THAT circuit thinking
its off, its safe, he gets fried on the 120. Might survive, might not. 

Now if the primary can be wired for 240, again one open will kill the HV
but leaves the entire primary wiring at 120 volts from ground, hence as
unsafe as breaking the neutral on 120 volts.

If the relay is like that used for VOX in the S-line, its a short form
telephone type that has very little contact motion and it might truly
take two points in series to get enough gap to interrupt 120 volts. I
much prefer the clapper type of relay because it generally has greater
contact motion, hence better clearance when open, doesn't have to be
individually adjusted at the factory (and then again after the wiring
terminals have been moved around to allow hooking and soldering wires to
them), and with the extra contact travel it gets a bit of sliding at the
contact to clean oxidation or arc debris.

For a 5 amp line circuit, I'd use a relay similar to the Potter &
Brumfield KUP, KUMP, KUHP, or KRPA series. Nearly every relay
manufacturer makes an equivalent relay, enclosed in a rectangular
plastic housing with parallel blade terminals or an octal/11 pin octal
style base. They do make a socket to take the parallel blade terminals
because these relays are used a great deal in industrial controls and
its hours faster to have a socket than to have to rewired a soldered in
relay and a few seconds to replace a relay vs an hour can mean a whole
lot of production saved.

73, Jerry, K0CQ, Technical Advisor to the CRA
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.