S71500 Card 6ES7531-7PF00-0AB0

Hi,

Can anyone tell me the difference between this 1500 card against the older S7-300 model 6ES7331-7PF01-0AB0 in relation to the Glass Furnace Industry.

We think we have identified a major flaw in the new 1500 card where we are experiencing up to 90 V AC on the thermocouples when the thyristors fire across the glass at 1200degC. We never had this issue when using the S7-300 cards. The website states this is a suitable replacement.

https://support.industry.siemens.com/cs/ie/en/view/109482719

Any advice or help appreciated as we are getting very little response from Siemens.

Thanks.

What filtering do you use (or did you use) on the S7-300's 331-7PF01 TC inputs?

What filtering do you use on the s7-1500's 531-7PF00 TC inputs?

I suspect your S7-300 system was not responding fast enough to notice any problem, but on the s7-1500, things are much faster, which resulted in your measuring the high common mode voltage induced from the induction furnace powered by the thyristors.

If you measured the s7-300 system at the same time in the same way, what voltage would you see?

If you do not know, perhaps you can assume it is 90 VAC.

Are you using shielded TCs?  Are you following the Siemens suggestions for wiring of TCs with the sense lines, proper terminal times, proper wiring type, or did you just swap hardware and hook it back up?

daveoc

Hi,

Can anyone tell me the difference between this 1500 card against the older S7-300 model 6ES7331-7PF01-0AB0 in relation to the Glass Furnace Industry.

We think we have identified a major flaw in the new 1500 card where we are experiencing up to 90 V AC on the thermocouples when the thyristors fire across the glass at 1200degC. We never had this issue when using the S7-300 cards. The website states this is a suitable replacement.

https://support.industry.siemens.com/cs/ie/en/view/109482719

Any advice or help appreciated as we are getting very little response from Siemens.

Thanks.

Thank for the response.

We have set the smoothing at weak. Would it make a difference to set this to strong?

In relation to the installation, this is a new install and the thermocouples do not have any shielding used as the installer claims this causes earth faults,

We can only assume the other installations has the same 90V AC on the TC as it is by the same company.

I have requested to get the negative of the TC to ground as per the manual.

Any other ideas?

The smoothing is not going to change the induced voltage.  Shielding and cable management affect that.

If they are causing "earth faults", they need larger grounding, or more appropriate grounding for the frequency.  For induction heating, I would think the grounding would be configured to shunt the high frequency used by the induction furnace to ground around the TCs and any other instrumentation.  Specially designed braided ground straps in the area around the furnace is what I have seen in the past, "tuned" to the output frequency of the furnace induction system (in case the input is tuned to a different frequency at a lower current).

Another option is to use TC signal & galvanic isolators between the PLC analog input and the TC.

That last option is what I have used the most.

daveoc

Thank for the response.

We have set the smoothing at weak. Would it make a difference to set this to strong?

In relation to the installation, this is a new install and the thermocouples do not have any shielding used as the installer claims this causes earth faults,

We can only assume the other installations has the same 90V AC on the TC as it is by the same company.

I have requested to get the negative of the TC to ground as per the manual.

Any other ideas?

Thanks,

We were afraid of having to change the cards to 4-20mA cards and fir Isolators. We have 48 TC's so not a cheap solution.

Thanks for the help.