Solid State Relay Differences?

Aug 26, 2005 5 Replies

The project I am working on will need a relay for a 1/3 to 1/2 hp 240V pump motor.



Have been trying to do my homework concerning possible solid state relays to use.



So far the Teledyne S24A25 (zero crossing turn on) and the Crydom A2425-10 (random turn on) seem quite similar except for the difference in turn on.



Am wondering how much difference this actually makes?



Welcome any suggestions for these or other suitable solid state relays.



Thanks



Ken



I was trying too use some zero crosing models for controlling a solenoid. It became unstable at times with the inductance, and randomly pulsed when it was not supposed to. I would recommend the standard type.

greg

The principal difference is the amount of RF noise that is generated.

And for an inductive load like a motor it's a particularly good idea to use one with zero crossing.

Use the Zero Crossover one...I have been using them on 1/2hp motors for 8 years with no failure and they are outside where the temps are +30c in the summer to -20c in the winter.

kip

On 26 Aug 2005 11:49:39 -0700, snipped-for-privacy@yahoo.com put finger to keyboard and composed:

I'd concur with those who recommend the zero crossing types. For an inductive load ...

V = L dI/dt + IR

... so if V=0 at t=0, then I=0 and dI/dt = 0.

This ensures the softest start.

A capacitive load (eg main filter caps in PSUs) will also benefit from zero-voltage startup as I = C dV/dt.

- Franc Zabkar

Please remove one 's' from my address when replying by email.

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