4 May 01 17:02
I am in the midst of a redesign and am coming up against some problems with management regarding E-stop (emergency stop) implementation in a motor drive amplifier. Could someone who has experience with this particular facet of the UL 508/508 comment? Here are the details:
We manufacture both a controller and amplifier designed to drive three-phase brushless motors. Our amplifier runs off of 120VAC (3 ph) and provides a bus voltage of 140DC at 20 A cont. (40A pk).
Our existing E-stop circuitry involves connecting the E-stop button to a AC Contactor that supplies the drive power (120VAC) to the amplifier. If the but ton is pushed, the contactor opens, the drive power is removed and the motors will coast to a stop ( I believe this is a Category 0 stop).
There is a push to integrate this E-stop circuitry into the amplifier itself, thus making it Plug-n-play, so to speak. However, the physical size of a force guided contactor designed to carry the 40A makes it impossible to integrate into the unit.
So, the big question is, are there alternative methods available that would meet the safety standard, but would allow for smaller components or implentation at a different point?
Management is not willing to give up the idea unless I can provide some sort of documentation that specifically states it must be done externally and in a specific way.
I apologize for being so long winded, but I felt it was necessary to provide as much information as possible.
Thanks for any assistance