Solid state relay for PWM kiln control

Hi guys,

Am looking at methods of controlling a 120v kiln using a PID Ramp/Soak temperature controller. The recommended cycle time is 2 seconds so any relay (solid state or electromechanical) will be functioning rapidly. Is this going to be a problem with a solid state relay with a typical number of operations before failure rate? The cycle time of 2 seconds means tht the ssr will lat about a week, with a MTBF of 100k operations.

Thoughts/advice
Nitrous

Are you sure your SSR has a MBTF of only 100K cycles? If so, you are looking at the wrong SSR/.

Post a link to the data sheet of your proposed SSR.

IMHO, use the SSR , they switch on, I think, and off as the voltage passes through 0 volts probably have a MBTF (Mean time between failures) closer to infinity,

A solid state relay should provide many more operations than 100K cycles as you mention. Since there are no mechanical contacts to wear out it should be ideal for your application.

I just want to mention these gusy because they are a one shop stop for some: **broken link removed**

The SCR's do require a heatsink nd some thermal grease to mount and have various control inputs.

You should be aware that there are in general 3 modes of control for an AC line:
1) Slow cycle Triac/relay which is basically what you have (SST)
2) ZCP or Zero Crossing Pulse - This SCR control mode ensures that crossing occur at zero and thus uses a multiple of half cycles/ One half cycle is the minimum amount of power, other than zero.
3) PAP or Phase Angle Fired. In some cases you can get better heater lifetime, but line turn-on can occur anywhere. This allow a much finer control of power.

Furthermore, you can find a lot more varieties of AC line controllers. Some with current feedback, some with heater open detection, some with power measurement.

You might also consider a separate alarm module. I only had to do that twice in a system I put together. I really like Eurotherm, but their stuff is pricy.

Thanks for your replies, gentlemen.
Nitrous