MOV

[ILCML]

Hello, I would like to implement an MOV on the input of a PLC. Can anyone provide me with links to good information on how to specify one? I want to protect the PLC from line voltage (120vac) transients.

thanks

 

[SteveFehr]

Your best bet is to put a TVSS as close to the service entrance (and grounding electrode) as possible. If you're concerned about transients originating within the facility, place another TVSS on the panel that it's fed from.

 

[ausgen]

SteveFehr is correct in that there's no substitute for primary and secondary protection in your boards. Best practice these days is for diverters at your MSB and multistage filters at your DBs. I look after a lot of mountaintop sites in high GFD areas so my critical controls items are all 24 V DC fed and where this isn't possible (like mains monitoring inputs on a generator controller) I add tertiary filtering or diverting. I use a lot of Novaris gear but the PRD40 range from Schneider are a decent plug-in DIN option also. Most of the larger manufacturers offer a good range of products in this area so have a look around. Just to emphasise though, typical surge energy from a ground flash will blow the DIN units off the panel unless you have something more capable sitting in your board(s) upstream.