In Reply to: Delay Relays posted by Triode_Kingdom on May 2, 2017 at 21:14:51:
You said
"One potential issue with delay relays has to do with the relatively small contacts"
Correct that also includes SS time delay relays.
You said
"The delay relay will power a main relay, and that one will be wired so it latches electrically. In addition, one set of contacts will be wired to disconnect the delay relay. So, once the amplifier is fully operational, the delay relay will power down and cool off. Not only will its contacts only need to pass a few mA to activate the HV, its heater will only be used for a minute or so each time the amplifier is turned on"
The disconnection of the delay relay is simply overkill I've run a similar scenario using 24V/30A relay activated from SS delay mains relay / timer for 10 yrs without fault. You can safely derate the DC current rating by 50% into a inductive load ie transformer and still be well under the DC rating. Relay coil DCR for 12-24V are under 1k ohm so the current requirement are small. But install a diode - reverse biased across relay coil to absorb back EMF on turn on / off. Seriously this configuration has been used in cross bar / step by step electro-mechanical telco exchanges for generations....bullet proof.
Johno
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Follow Ups
- Re: Disconnecting Relay sound like over-kill - Johno 03:24:55 05/03/17 (2)
- Re: Disconnecting Relay sound like over-kill - Tom Bavis 07:35:06 05/03/17 (1)
- Re: Disconnecting Relay sound like over-kill - Triode_Kingdom 08:32:06 05/03/17 (0)