What’s the minimum time for STO Safety to be ready again after consecutive activations?

Question from a colleague:

Good morning ,

“(my boss) addressed me to you for a question about STO Drive Safety”

Our costumer is asking : “ what’s the minimum time for STO Safety to be ready again after consecutive activations ? “

Behind this question “normally”, in my opinion, we have a customer who is misleading the Safety purpose which is “monitor / prevent” and not “acting”, unless something goes wrong of course.

I say that because, when safety activates customer’s actual concern should be check whether somebody got injured and not how long it takes to reactivate safety. ( anyway seconds or below )

Probably, he aims to programmatically stop the machine with STO instead writing the right code in PLC program.

This is a very common case for us. I’ll call the customer to clear up the topic. So, I did with other customers too.

Therefore in many situation talking is not enough.

Do you have any datasheet or piece of documentation to share with me to support my communication to the customer ?

“don’t hesitate to correct my understanding of the safety purpose”

 

I thank you in advance for your support.

 

Cordiali Saluti / Best regards,

 

Best reply by AllAutomation

Hello!

The answer I promised:

The IndraDrive SafeTorqueOff documentation (section 4.4.3 "Performance") provides a deselection time of 20 ms for IndraDrive Cs, C, M and Mi and 120 ms for ML. Keep in mind that this is only the time to get the drive into normal operation state. It does not cover the time spent inside the safe relay circuits around!

On the opposite side the IndraDrive SafeMotion documentation (section 4.4 "Performance") shows the activation of Safety functions with a typical value of 4.5 ms. The very same time is needed to come back to normal operation mode, since it is only (safety) software. Similar to the STO case this is just the time from detecting the signal edge at the IndraDrives "system boundary". Every delay outside of the drive system (e.g. relay delays, FSoE copying delays for I/O, Safe PLC, etc.) is not included.

Bottom line:

It is reasonable to look at the concrete configuration in the application. With SafeMotion it is not only smarter and faster safety (effectively safer with same distance) or allows more compact machines, but in a programmatically controlled (deterministic) machine cycle SafeMotion can safe time and costs.

The very same (maybe marginal changes) will be valid for ctrlX DRIVE SafeTorqueOff (T0) and for ctrlX DRIVEplus SafeMotion (M5).

HTH and if it really helped, then please mark this posting as a solution!

Best regards

The ctrlX SAFETY Team

View original
2 replies