NuB AB SSrelay?

[gr8scot]

First time post...
I have an AB SLC5/04 PLC trying to turn on a Crouzet GAO 3 phase solid state relay. I have tried using a relay output and a solidstate output. 24Vdc. Neither has worked. I can force the output on and the relay will turn on but when used in automatic the relay will turn on every now and then.
I have taken the output module power straight to a 24 Vdc power supply and tied the common from the control of the SS relay to the same supply. Still nothing. I have extended the automatic signal time from 200 mS to 1.5 S still nothing. Any other suggestions?

Link to relay data sheet:

http://www.crouzet.com/catalogue_web/int/eng/637/Solid-state-relays-GA-three-phase-ENG-26.htm

 

[jraef]

... but when used in automatic the relay will turn on every now and then. ...Still nothing.

So the problem is that it turns on sometimes when you DON'T want it to, or it fails to turn on sometimes when you do? You seem to have mixed up your tenses here.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[gr8scot]

To clarify, the PLC output turns on for 1.5S, every 10 seconds, but the SS relay only turns on for a fraction of a second, once every other minute.

I raised the turn on time from an original setting of 0.2 S to 1.5 S, trying to eliminate that as one of the factors.

I can take a piece of wire and pulse the SS input, as quick as possible, directly from the 24 V supply and the relay will respond correctly. For some reason pulsing the SS from the AB output module doesn't turn on the input of the SS.

 

[jraef]

But you said you tried a hard contact relay output on the PLC and it did the same thing?

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[gr8scot]

Correct. I was using an AB relay output card with the same results. I switched to a dc sourcing output but that didn't change anything.

This is why I posted here, I have tried everything I can think of.

 

[jraef]

I can see that as a problem with a triac output in the PLC because the load on the SSR may not be great enough for it, and you would typically solve that with a burden resistor or use the PLC triac to drive a slave relay. But if you used a real relay output contact on the PLC, that should have solved it. That really only leaves a defective SSR or a glitch in the PLC programming.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[waross]

Look for a circuit race in your programing.
I haven't been close to a PLC for a long time, but I used to have a demonstration circuit that behaved totally differently on three different models of PLC depending on how they did their internal processing. You may have a problem not with the timers directly but with some programing associated with the timing. Relay equivalent; A relay, when energised, starts the timing cycle. A circuit race turns the relay off at the same time as it turns on.
Try a different program to control the SSR.
Use a manual input to turn the SSR on. Then use the same manual input to start a timer. Verify the operation of the new timer. Use the new timer to turn the SSR off after a delay. When you get that working, start shortening the time to see if your timing is less than the PLC can comfortably handle.
yours