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Hard-wired 2oo3 Relay Logic

Hard-wired 2oo3 Relay Logic

Hard-wired 2oo3 Relay Logic

I am looking to implement 2oo3 relay logic to shutdown process equipment. It will tie into an existing hard-wired master control circuit that is normally energized, de-energize to trip.

Three output channels from an existing PLC, through interposing relays that are hardwired in 2oo3 configuration will be connected into the existing master control relay coil circuit.
Is there a manufacturer who makes pre-configured plug-in relay modules with 2oo3 logic already configured?

RE: Hard-wired 2oo3 Relay Logic

A-B,... other companies offering these are Banner, Schmersal, Pilz, Norstadt, STI. You can't just use any "highly reliable" relay, the relay also must have guided contacts. This means that on a 4-pole NO & NC relay, if any one NO contact welds, then none of the 4 NC contacts will be allowed to make when the coil is de-energized.

RE: Hard-wired 2oo3 Relay Logic

It sounds like you are talking about using three single relays, wired in 2oo3 configuration. I was questioning if there was a pre-configured module or board, three plug-ins, 3 coils, and outputs already factory-configured for 2 oo3 logic. I don't think there is, that i have found.

RE: Hard-wired 2oo3 Relay Logic

I doubt it as well. In fact I'd never heard of 2oo3 before this question. It reminds me of an aerospace project I did in the 70's with 96 hogh power relays in a box controlled by custom SCADA solution I designed for pre-launch used to charge batteries etc. I ordered sense contacts on each relay and checked by remote after every toggle command. During my R&D tests the relays were found to be flakely. Then I discovered the facts about 10% wetting current and used an RC capacitor discharge to make the contacts relaible to signal TTL logic levels.

My way of thinking about MTBF is not just 2oo3 but make 1 better by not degrading the MTBF from 10^7 mechanical contacts to 10^3 from over stress and improper derating or insufficient arc suppression but I don't know the application. Elevator? Aerosapce?

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