[Amps] [Moon-net] Solid state relay

[TexasRF@aol.com]

In a message dated 8/28/2005 2:58:20 P.M. Central Standard Time,  
k8isk at comcast.net writes:

Hello to  the group,

Has anyone in the group ever used solid state relays for  controlling the AC 
input to a power supply for a 1500w amplifier? I  recently acquired some 
really nice 50A @ 480VAC solid state relays and  they would work great in a 
power suppy but never using this type device  before, I am somewhat hesitant.

Thanks for any info.

73, Terry  



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Hi Terry, I have used many Solid State Relays for HV power supplies over  the 
years with excellent results. At first I tried 25 amp units and had a couple  
of failures due to the very high peak currents in my capacitor filter power  
supply. After switching to 40 amp units no more problems.
 
I do use fault sensing in the amplifier to interrupt the control voltage to  
the relay in the hope that quick hv turn off will help keep more components  
(including the relay) from failing.
 
The only other comment is that the solid state units need to be mounted in  
such a manner to help remove self generated heating. There is a voltage drop  
across the relay of about .7 as I recall and you can see that with large peak  
currents some heating will happen. The relays I have used have a small leakage 
 when turned off that leaves a few volts ac on the transformer primary. This  
means you could have a bit of voltage left on the hv side when you might 
think  there is none. Beware, shorting the filter is deceptive: it will just 
charge  right back up.
 
73,
Gerald K5GW