PowerFlex 525 and Safe Torque-Off Circuits

[drforsythe]

JaxGTO listed the fix in post #3 of this thread (t105). We use STO on our drives and that parameter is changed to prevent the fault.

 

[beethoven_ii]

Brilliant, thanks. I missed that before I replied.

 

[Geospark]

PF525 Pld...maybe PLe...?

FYI you can get PLe from Cat 3...

...Also if you look at the PF525 safety data...it can get PLe as well?...

Hi,

There is no maybe...

You may have not read or missed the meaning in some of my earlier statements but I had already stated that you can achieve PLe using a PowerFlex 525 with STO, but not on its own. To explain it again more simply and without the functional safety data calculations you have provided...

...the PowerFlex 525, using Safe Torque-Off, can achieve SIL 2 Category 3 /PLd alone...

This means when used on its own the PowerFlex 525 can achieve a maximum Performance Level of PLd.

However...

...To achieve SIL 3 Category 3 / PLe, STO would have to be used in conjunction with other Safety measures to achieve this higher Performance Level.

You need to know which Performance Level (PL) you require here before deciding whether or not it is permissible to use STO only on these drives.

That is, you may or may not need Safety contactors here. PLd, for instance, may permit the use of no contactors here...

What this essentially means is that if PLd is required, then the PowerFlex 525 with STO can achieve this Performance Level without using Safety contactors. If Performance Level PLe is required then the PowerFlex 525 with STO can be used in conjunction with Safety Actuators i.e. Safety contactors.

So yes, Performance Level PLe is achievable using the PowerFlex 525 as part of an overall Safety Function.

But now, back to the functional safety data calculations...

522301 - How do I achieve PLe with a PowerFlex 525 drive
Access Level: Everyone

From here we can see that it is possible to achieve SIL 3 Cat 3 PLe based on a Probability of dangerous Failure per Hour (PFHd) scoring of 5.8 e-8. This equates to a Probability of dangerous Failure per hour of < 0.00000058%

"e"asy...

Regards,
All Green