Ultra 3000 Category 3 Safety

[LURBY 1]

I was wondering if anyone had any experience with Category 3 safety requirements and the Ultra 3000. I am building a machine and am trying to satisfy some safety concerns. I will be using AB Guardmaster safety relays and a number of E-stops. I will have dual channel inputs. All of my outputs will also have "duality." My hydraulic pump will have two contactors in series. I will be using AB Powerflex 40P drives with the added "safe-off" option for my spindles. I also have an AB Ultra 3000 servo drive and motor. How do I integrate this into the system??? They do not appear to offer a "safe-off" option on the Ultra. I can't seem to find any documentation where it describes how to integrate this drive. One thought I had was to wire the enable thru one output and add a contactor in between the output of the drive and the servo motor. I can't be the only one who has ever wanted to do this, can I??

[drforsythe 15]

Ultra 3000 does not have a 'safe-off' option, so on jobs I have done in the past, I utilized redundant power contactors between the drive output and the motor. These contactors were controlled by a safety relay with a time-delayed output module. When an e-stop was pressed or a guard was opened, the system would go into an emergency stop mode that worked as follows: 1) Immediate outputs of main safety relay would initiate a stop command to the drive. (The drive needs to be set up with a high deceleration rate.) 2) The time-delayed outputs would be wired to a) the enable on the drive and b) the coils of the redundant contactors. These outputs of the safety relay would be set up to open after the deceleration would theoretically be over. (example: servo set to decel load in .25 seconds, therefore the safety relay would be set up to open time-delayed contacts after 0.375 or 0.5 seconds). Of course, the contactors would need to be monitored by the safety relay to ensure they are responding in time and properly resetting. CAUTION: If the contactors are opened while the servo is still enabled or if the motor is in servo-controlled motion, damage may occur to the drive. It may occur on the first instance or the 100th instance, but it is not good for the output stage of the servo (or VFD for that matter) to open the circuit under load. You MUST make sure that your decel rates are set up properly. The contactors allow the drive to do the work to decel the load and should only open under load if the drive has malfunctioned. A-B had an example on their Knowledge Base several years ago for this setup. It is probably still there, but I am sorry I cannot point you to a specific article.

[Tim Williams 1]

I am not an expert nor do I play one on TV. I don't think what you propose is acceptable for Category 3. The enable input is a solid state device which is not safety-rated. I believe drforsythe has the correct implementation. That is redundant contactors on the output of the drive. I believe I found the document he was thinking of. In any case it shows Category 3 implementation of both controlled and uncontrolled stops.