[Amps] Hotswitching

[Peter Chadwick]

Rich said:
>My guess is that a $1 MOV would have prevented this glitch.<
Maybe. What I read was that during ground testing, the supply was unregulated, and went up to around 70 volts, causing the thermostat to arc because the  voltage it was trying to switch was too much - in terms of DV (Direct Voltage -  you really can't have a 'Direct Current Voltage', now, can you?). The MOV would probably have just burnt out. What is clear (and I think Rich is saying this, too) that underating switches, thermostats, relay contacts and solid state switches etc. is a poor idea.
20 odd years ago, VMOS devices were touted as ideal for relay drivers and the like, but it turned out that they needed VERY fast diode protection compared with bipolars....


73
Peter G3RZP (I've been away all week, and haven't read all the items, so there's something I should have responded to, let me know)