Relay Cycle Life

What do you guys think the number of cycles to failure are on relay switching a 120VAC capacitive load. I am guessing 1 million cycles.

The contacts are rated at 10 amps. The motor FLA is 65MA. The relay coil is 24VDC. It is cycling .175 seconds on and .175 seconds off. I am again guessing , but I think the actuation time of the coil is about .007 seconds.

The relay manufacturer may be able to help you determine the MTBF for the particular relay under those conditions. At such a rapid cycle rate, your application may be better served by a solid state relay.

I would think you would get close to the statistical rated life. The short duty cycle shouldn't hurt a DC coil relay like it will an AC coil relay. You are also so far below the contact rating that I don't think that will be an issue.

This reminds me of a funny story. An experienced engineer I know had a salesman hand him an AC-coil form C socketed relay and proclaimed it indestructible. The engineer said "We'll see" and went to test it. He tested it by wiring the coil excitation through the relay's own normally closed contact, basically making a buzzer. The relay made it 5 minutes before it let out the magic smoke. The next day he handed the burnt out husk of a relay to the salesman and said "It didn't fair so well".

Keith

OkiePC said:

The relay manufacturer may be able to help you determine the MTBF for the particular relay under those conditions. At such a rapid cycle rate, your application may be better served by a solid state relay.

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Exactly....that is what I am trying to convince my boss of