VSD's with Cat3 Input

Have many of you used this option before?

We are looking at an app where we will have 10x vsd's, but whilst the manual shows a connection example for a single drive, we have not been able to find for multiples.

Rule of thumb would suggest that a separate safety channel is used for each drive, but then this would add considerable cost, especially if more were required!

We could look at suitable force guided relays, which will reduce it slightly, but it does seem more intensive rather than the double-dump method on the line side, which then makes us ask, why use the cat3 option?

I don't want this to become a discussion on safety implementation, moreso common practice if a cat3 option like this is to be used.

Those of outside New Zealand probably don't know what Cat3 involves. Thus we can't help you much.

Maybe, if you describe Cat3 and it's intended purpose, we could participate.

http://www.automation.siemens.com/m...afety-integrated/Pages/safety-integrated.aspx

Siemens do safe stop options for Cat 3 (link above shows the G series)

I'm sure they do it on some other drives also, am at home now so haven't got the catalog's to hand

What are you trying to achieve as you can do this with standard safety equipment and a normal drive (in most cases)

DickDV said:

Those of outside New Zealand probably don't know what Cat3 involves. Thus we can't help you much.

Maybe, if you describe Cat3 and it's intended purpose, we could participate.

Click to expand...

Sorry, was not aware of the differences in the US. This helps to explain it a bit.
http://www.safety-relay.com/monitoring_relay.html
Basically, we are using Danfoss FC302 Automation drives, and the requirements for the application are Cat3 safety. Standard way was to have a double-dump type arrangement on the Line side of the VSD's.
As these drives have a Cat3 input, we have thought about using that. (See attached image)
What we are not sure of, is how is best to handle multiple drives using this method. Should we provide a separate safety channel for each drive, or can we parallel up the drives? (I not sure if the parallel method would be the best option. ..?)

504bloke said:

http://www.automation.siemens.com/m...afety-integrated/Pages/safety-integrated.aspx

Siemens do safe stop options for Cat 3 (link above shows the G series)

I'm sure they do it on some other drives also, am at home now so haven't got the catalog's to hand

What are you trying to achieve as you can do this with standard safety equipment and a normal drive (in most cases)

Click to expand...

The FC302 is a standard drive, with the Cat3 input as standard. What we are trying to do, is utilise this feature, rather than having to have the double-dump on the line side.
The key is in the implementation for multiple drives, what is the best method?

Now I understand that the Cat3 you are referring to is the safety stop circuit. There are other uses for the Cat3 terminology.

I would definitely recommend a separate stop circuit for each drive.

What you are talking about doing is wiring one safety output to more than one drive safety input, correct?

If you do that, and there is a problem with that particular signal, none of the drives will stop. I know the likelihood is very low, but what if one of the drives creates a problem on that signal...now it will affect any others on that same wire.

I am not an expert in this area, but I would use a separate safety relay output for each drive. You will already see a lot of space and money savings just by getting rid of the contactors...don't push it too far...

Just my opinion.

Lostcontrol

Are you planning to use a bus system or just hardwiring?

If a bus is a option then using profinet ethernet you can do profisafe which is the safety protocol over ethernet which is sil 2 or 3 and cat 4 rated without using relays.

We have i system similar to this. Some sinamics drives are cat 3 and some cat 4. I thought all the new revisions of sinamics were cat 4 though?

We use this setup with AB and contrologix CIP safety over ethernet / ip with powerflex 755 drives with safe torque off and safe speed options.

Estops and safety gate switches,etc can go into safety i/o modules and there is not much ned for safety relays.

AB system is sil 3 rated. To give you a idea most stamping presses do not exceed sil 3.

Sil 3 rated equipment will handle the 90% of safety applications.

You could also use ASISafe on an ASi Net system

Siemens also support this, i have use it alot, with great success. Its a lot cheaper than Profisafe and works with siemens drives.

Originally posted by OkiePC:

If you do that, and there is a problem with that particular signal, none of the drives will stop. I know the likelihood is very low, but what if one of the drives creates a problem on that signal...now it will affect any others on that same wire.

Click to expand...

While this cannot be argued conceptually it doesn't follow with standard machinery design today. If this point were extrapolated through a design it would require a separate dual safety contact on each output point and redundant supply contactors on every load. As we design now we typically have redundant line side contactors for multiple drives and control a rack's worth of outputs off a single safety relay. I don't see why implementing this concept at the drive control level should be any different. We generally will control multiple drives' safe off circuits from a single safety relay.

What I do question is the image that shows only a single safety input into the drive. I thought Cat3 equired redundancy.

Keith

kamenges said:

While this cannot be argued conceptually it doesn't follow with standard machinery design today. If this point were extrapolated through a design it would require a separate dual safety contact on each output point and redundant supply contactors on every load. As we design now we typically have redundant line side contactors for multiple drives and control a rack's worth of outputs off a single safety relay. I don't see why implementing this concept at the drive control level should be any different. We generally will control multiple drives' safe off circuits from a single safety relay.

What I do question is the image that shows only a single safety input into the drive. I thought Cat3 equired redundancy.

Keith

Click to expand...

Agree