Joined: 02 November 2006
I am looking for some help/guidance.
I am currently designing a module (fancy ISO container with electrical equipment inside) that is fed by two separate 3 phase supplies (Essential & non-essential). The supplies are terminated into Schneider 100A NSX100 MCCBs. My client has asked for an emergency stop system (2 buttons required) to shut down both supplies and supply a volt free relay output to their UPS.
My initial thought was to install an 'Undervoltage Release' on the MCCB with an emergency stop circuit on N/C contacts. This was refused by the client as the module is to be located in a remote area with 'posible dodgy' supply's.
My next thought was to use a shunt release powered from upstream of the MCCB however this would then require the emergency stop circuit to be N/O which is not good practice. I then considered using a change-over contact/contactor to allow the emergency stop circuit to be N/C, this was also rejected by the client as they dont want to rely on a contactor.
The client has requested we use a safety relay to power the shunt trip coil on de-energisation of the emergency stop circuit. I have spoken to Schneider Technical who have informed me these relays are used for industrial machines and as such a contactor would have to be used as well as. Schneider have advised I use a system as described in their FAQ website section (FA141719) which uses a self-latching circuit and a contactor down stream of the MCCB to isolate the supply. This looks fine for a single incoming supply but I cant work out how to connect it with 2 separate supply's from 2 common emergency stops. I also wondered if I could use the under voltage release from the NSX100 for this rather then a separate contactor?
Any help or ideas gratefully received as I feel I have been going round in circles with this!
Joined: 04 April 2006
Simon, I think one of the first things to do, is have a look at the safety reference material of some of the big safety relay manufacturers. pilz, Jakob, omron, guardmaster, amoungst others.
Then look at a risk analysis of the install, to determine the required safety level.
Energise your safety relay panel, from the essential supply, with a possible battery backup?
The double pole e-stops wire in series to the safety relay inputs.
They also can monitor the status of contactors on the load side of the breakers. As these are often alot easier to monitor than breakers for safety, they are also alot cheaper, as an addin. For simplicity visualize as 2 motor ccts, protected by the same relay.
By going to contactors it becomes a fail safe install, shunt trips are an energise to trip function, normally only done on HV or high power schemes through special protective relays.
I hope this helps.