Relays and Solenoids

We have a hydraulic press that is controlled with a PLC. There are five 120V solenoids on the press that control the movement of the Ram. Between the PLC and the Solenoids are Relays, Omron G2R-2-SN relays to be exact, which are rated for 5 amps. The solenoids don't ever pull 5 amps but I am getting a lot of arcing on the contacts and eventually they fail. I have used these before on solenoids and not had a problem but there is a first time for everything. I suspect that it is do to inductance and that I need some snubbers in the circuit. I have never used these before and was wondering if someone could point me in the right direction for finding some for this application. Do they make relays with them built into the contacts? I have never seen them if they do.

Just looking for some suggestions.

Thanks.

Do the valve coils have surge suppressors on them?

solenoid relays and arcing contacts

I'm pretty certain that Phoenix Contacts makes terminal blocks for din rail that include surge protection components. I know that I have seen such in their CLIPLine Catalog, pg 204. This way you won't need to find relays with them or attach separately. They are built right in.

ndzied1 said:

Do the valve coils have surge suppressors on them?

Click to expand...

No they don't.

Would a Solid State relay be better to use in a case like this?

Here is a link with some info on snubbers.

http://www.filmcapacitors.com/RC1313.htm

I used "Quencharcs" from Newark InOne, formerly Newark Electronics.
The application was almost identical to yours with the exception of being relay logic. I also used them across the contacts of the temperature controllers that pulled large contactors.

Personally I think solid state relays are great

Most provide for zero-crossover switching which eliminates a multitude of issues with AC devices, they are excellent when used to directly control things like heat/cut wires.

Remember my sealer project that used heat to cut plastic wrap? I used a solid state relay on that to ACTUALLY control the power to the heat wire. I used a Crydom SSR rated for 240vac @ 40 amps with control voltage from 3-32vdc. They make them up to 125amp and can work with milliamp currents. The zero-crossover switching allowed me to be able to "pulse" the wires in milliseconds to maintain a "warm" wire

NOTE: I doubt it could "pulse" a solenoid but may eliminate issues..of course the cost is higher.

This may help explain what I mean about zero-crossover switching...it may also be called zero-swtiching or zero-volt switching

Solenoid coils are inductive loads, as the coil is switched off, and the current value drops, the voltage peaks. This is what is causing the arcing of you relay contacts. An R/C snubber will eliminate this on an AC driven coil. A Diode across the coil with the cathode (band) to the DC+ terminal, will eliminate this because the polarity of the collapsing voltage changes. Newark, Allied, Digi-key.....

Thanks for the replies guys, I like the zero crossing Solid State Relays Ron mentioned. I think I'll be checking those out.