P-Flex525 with Safety Relay for PLe

I feel like this should be obvious, but I'm not seeing it:

A vendor is building us a machine that has a spindle controlled with a PowerFlex525.

The spindle is enclosed by a removable guard that employs dual-channel safety switches. PLe is required for the hazard.

This would be a straightforward application for safe-torque-off *except* that we will have a jog circuit to turn the spindle at low speed when the guard is open and the operator is depressing a Schmersal enabling switch. The idea is that in jog mode with the guard open the spindle would be limited to very low speed.

I'm hung up on how to "enforce" that the drive will run at low speed. I can imagine how the jog-enable would provide the required inputs to enable the drive and the safe-torque-off, but I don't know how you insure the drive can only run at X% speed.

They are currently not using the ethernet interface at all...all hard wiring to the I/O board and analog input for speed control.

Of course any robot can do this, but that velocity-limiting seems to be "built in", and I've never given any thought to how that is controlled.

Has anyone seen this / done this before? Is this even possible to do?

Thanks!

What you are describing is called a Safe Speed Monitor function. You do not have that option on a PF525, it's only avaialable on the PF750 series by adding a 20-750-S1 card. The option card for the 525 is not available but has been talked about as a future enhancement however that does you no good right now. Your only viable option at this point is the 750.

Or Siemens drives...they also have safe speed

Or redesign the process so the operator doesn't need to move the spindle without guarding.

jraef said:

What you are describing is called a Safe Speed Monitor function. You do not have that option on a PF525, it's only avaialable on the PF750 series by adding a 20-750-S1 card. The option card for the 525 is not available but has been talked about as a future enhancement however that does you no good right now. Your only viable option at this point is the 750.

Click to expand...

I actually just happened to run into our AB distributor down on the plant floor and he just told me the same thing......thank you!

AustralIan said:

Or redesign the process so the operator doesn't need to move the spindle without guarding.

Click to expand...

That's a great suggestion....we racked our brains on this one and we just couldn't get away from it, but you're right that it's always better to keep the operators out of these hazards completely.

Thanks again everyone.

It doesn't really help with your problem but I believe STO on PF525 is rated PLd/SIL2 Cat 3 (not PLe)
PF527 is PLe rated.