50A SSR Problem

[abltech]

Deleted (Double Post)

 

[abltech]

johnnyboy

Labview allows you to create/control logic and PID controls. Its a very expensive software package but if your a student there is a student version you can download for free (maybe for limited time). It has very little difference to the full version and is fully functional.

 

[Darkwood]

Well, after being back on site I have found there is continuity between the load supply and the output wire to the element without the relay connected. There is also slight continuity between L-E (and hence TN-C-S slight continuity barely readable with earth). I could not fully isolate the unit today to test as it is installed in a 24hr McDonalds that has a load of other appliances running off the circuit which they could not afford to go down and at the moment the elements are giving out 52 degrees which is not quite the 66 set point, but they would rather have that than me turn it off for 30mins!!

However all that said if the relay is bypassed and supply to load is connected directly then the elements heat correctly which I was expecting anyhow. The controller is definitely fine - it gives out a steady 24VDC supply and energises and de-energises the load upon the correct input signals.

This leads me to believe there is an insulation problem somewhere along spaghetti junction - but still does not explain why this one relay gives out 120V with the fault and a brand new replacement gives out 0V. The relay which I did remove and tested works perfectly well on the bench.

I suppose there could still be a faulty element - just because it heats doesn't mean it isn't leaking somewhere.

My heads melted with this now!

Is the SSR protected by a semiconducting fuse ... is their is any kind of fault on the element?

There is alot to ask but rather than go through a long winded Q&A session give this link a read and apply it to your situation and see if it high-lights anything.
http://www.omron.com/ecb/products/pdf/precautions_ssr.pdf

 

[silva.foxx]

I have found there is continuity between the load supply and the output wire to the element without the relay connected.
However all that said if the relay is bypassed and supply to load is connected directly then the elements heat correctly which I was expecting anyhow. The controller is definitely fine - it gives out a steady 24VDC supply and energises and de-energises the load upon the correct input signals ... but still does not explain why this one relay gives out 120V with the fault and a brand new replacement gives out 0V. The relay which I did remove and tested works perfectly well on the bench.

You sound absolutely certain on the controller.

What is your method of bench-testing the SSRs?

What is the complete part numbers of the SSRs?

regards
s.f

 

[Gage]

Sorry to jump in, but does anyone have any simulation software for PID control. It's a subject that we haven't covered on my HNC (even though weirdly I'm one assignment away from a distinction in this module).
It's something I'd like to understand fully, not just the textbook version of how they're supposed to work.

Get an old eurotherm tc from eBay and play around yourself you'll learn better that way

 

[Knobhead]

Sorry to jump in, but does anyone have any simulation software for PID control. It's a subject that we haven't covered on my HNC (even though weirdly I'm one assignment away from a distinction in this module).
It's something I'd like to understand fully, not just the textbook version of how they're supposed to work.

Can’t help with that one John.
I learnt by writing parallel networks in Modsoft and watching the results on live programs. The program would be running with my bits running parallel on the side with comparator registers showing any difference.
Eventually I came up with my own algorithm that used half the registers of Schneider PID2. The other lads liked it as they could see what has happening rather than just a DX block giving answers.
I also did deceleration algorithms which again the other lads could follow what was happening.

 

[plugsandsparks]

Have you measured V across the two output terms of the SSR in the "off" state and "on" state. This may give an idea if the SSR is being pulsed, also have you measured the current against the expected for the heater size.
Just had another thought - if one of the output gates is not firing you will only get half of the waveform coming through on the output, you may pick this up with a voltmeter on DC. As for the new one not working at all - pass