ASI input filters

Hi!

We have a project which includes ASI-bus systems. We still got one problem left. On VFD controlled motors we use "clixons". This is a bi-metal contact in the motor. This contact opens when the motor is to hot. This contact is wired to a standard Siemens 4xInput ASI block. When I use an ASI analyser to check the quality of the bus, I see that all ASI blocks with "clixons" on it have communication problems. (Retry counter increases over time). We concluded that the "dirty" motor signals are transfered to the ASI bus via the "clixon" input.

We contacted Siemens they gave as two options:

1) Check ASI power at the end of the bus. If the power drops to low use ASI power uppers.

2) Use an interface relay for the "clixon" contacts.

We will install option 1. Option two sounds stupid. We can't put interface relays all over the plant just to solve this problem.

My question is does this sound familiar to anyone?

Are there some kind off filters/seperators which can be screwed on top of the ASI connectors of the ASI block?

Any other possible solutions? (Beside of just getting rid off the "clixon" inputs)

I have done numerous retro fits of interposing relays to isolate the clixons from the drive. Your VFD noise is usually impressed on the over temp switch, as I am used to calling them and the digital inputs to the drive do not like the noise. By using a relay's dry contacts, you ISOLATE the noise from the drive inputs.

Doing the relay thing may sound stupid, but if FIXES an annoying problem and that is NOT stupid.

OK, I know it fixes the problem but is doesn't fit in the ASI philosophy. What you are proposing is relays in terminal boxes and run an ASI cable along the boxes to get the inputs on ASI. I'm looking for a "clean" solution without relays and boxes. (Relays in some kind of screw connector between the ASI input block and the clixon contacts sounds ok to me. Anybody seem something like this?

Hello werner;

Sorry I don't have an answer to your query. But maybe these guys can help out:
http://www.as-interface.com/techforum/default.asp?cid=1

Hope this helps,
Daniel Chartier

Werner

I have no solution or suggestion to make, but my memory was jogged by your mention of 'clixon'. I haven't come across these things for over 20 years! As far as I know it is (was) spelled Klixon, and was a trademark of Texas Instruments. I don't think it was the PLC part of TI that made these items, but a totally different division of the business that was in to metal working etc. Do you still get them from TI, or have they been divested like the PLCs were?

Thanks, Werner, for blowing the dust off part of my aged memory.

Regards

Ken.

We use SEW motors. The (C/K)lixons are an option we can order at SEW. I don't know if they buy the (C/K)lixon part from TI or that it is something made by SEW. As programmer I just get a motor list from our mechanical engineers. For me it is just an input on the plc which I need to incorporate in my program.

Sorry...

One solution i use is to feed the Klixon directly into the drive normally to the Klixon / PTC temp input and config the drive software to mimic the Klixon on an isolated digital output.

But this depends on the drive as to wether you can do this, i use SSD (Formally Eurotherm Drives) 690+ for all AC apps where i can do this.

Been There Done That!

While I do not know which drive model you are using I have used the following method with success.
Wire the Klixons to a drive input.
Configure this input as motor overload status to monitor the status of the Klixon.
Wire a drive output status to the ASI module input.
Configure the Drive output to change state when the Klixon changes state.