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[Amps] SSR in amp PS not working as expected

To: Amps reflector <amps@contesting.com>
Subject: [Amps] SSR in amp PS not working as expected
From: Ulf Tjerneld <ulf@sm0nor.com>
Date: Sat, 5 Jan 2019 11:59:17 +0100
List-post: <mailto:amps@contesting.com>
Hi All,

I start with the question:
Is there anything around SSR:s in general or anything in particular around the 
Crydom CSD2525P that I don’t’ understand when used as breakers and step -start 
in a HV PS? 

And the background:
After a few years off the reflector and amp building I recently dusted off my 
big-ultimate-amp-project and took up the work again.
This winter’s focus is the PS. I thought it could be nice to use SSR:s in the 
AC-circuit for breaking and step-start. I have never used SSR:s before, but I 
expected it to work as planned as I perceive them as pretty simple devices. 
Anyhow, I bought three surplus SSR:s off Ebay, Crydom CSD2525P rated at 25A, 
and built a standard breaking and step-start circuit around them. 
Everything was tested with a low voltage 230/12 Volt small transformer on the 
bench. It works as expected; the two SSR:S in the 230V line switches on and the 
third SSR shortens the inrush resistor after about a second of delay.

But, when testing with the HV-transformer, it doesn’t work. 

The HV transformer is boxed in the chassis and disconnected from all secondary 
loads. The HV-output is isolated and off from anything in the circuit. I 
measure voltage on the 105 volt secondary winding. The only things outside of 
the box is the multimeter and the 12Volt DC control voltage. After applying 
control voltage the SSR:s in the AC line actuates and the transformer starts to 
hum, which it shouldn’t, and after a second the step-start SSR actuates and the 
transformer starts to hum loudly. The reading on the 105V secondary was close 
to zero.

The transformer in itself is a custom made 2KVA toroid beast wound for me in 
Germany in 2013. With the breaking circuit out of the loop, the transformer is 
almost inaudible and delivers as expected in the 105V secondary,

So, the question is: is there anything around SSR:s in general or anything in 
particular around the Crydom CSD2525P that I don’t’ understand? Please advise! 😊

/73’s SM0NOR - Ulf





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