Heater controlling using ssr ?

[jit_singh_tara]

Dear Friends ,

I need to drive 3000 watt heater for maintaining a temperature of 190 deg. I want to know which method would be best for reaching the desired temperature without overshoot .

1. Running the heater constant ON for certain temp like 100 deg , then start switching the heater on /off , decreasing the on time as the temp approaches set temp.

I tried the above method but got an overshoot of 10 deg and undershoot of 15 deg in first run ,
What is the best method to do such thing .

Can we reach the desired temperature like this in first run , though it can take some more time by lowering the constant on point from 100 to say 80 or so and then switch on /off.


Please suggest the best method to do so .

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One more thing i would like to know how would be the response of heater ,ssr with pwm of a fixed frequency . Will ssr be able to deliver the current at high speed say 1/50 of a sec .

Will HEATER(3000 W) , SSR , PWM be a good driving technique so as to have minimum overshoot and undershoot.

Please share some ideas regarding PID algorithm and auto tuning or manual tuning and its advantages over other driving techniques ?

 

[milan.rajik]

SSR switching AC load ? I think PWM cannot be used. If it is an optically isolated, triac based SSR then I think you can use phase angle control to control the power to the heater. It will be just a dimmer. Instead of connecting a light you will be connecting a heater. You have to do some plotting like what will be the temperature at what wattage. Like what will be the temperature when heater is provided 1000W, 1200W, etc... Does the temperature rise linearly with power to heater ?

Even I asked a question whether SSR can be used for dimming or not but nobody answered. But I think as the SSR has a non ZC optical isolator inside you don't need a MOC3012. As SSR contains a triac so I think it can work as a dimmer. Just write a phase angle control code and interface a ZC detection circuit to MCU and try to control the power to Load through SSR. See if it works.

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For testing purpose see if you can use one of these SSRs.

https://www.banggood.com/buy/Solid-State-Relay.html

They are cheaper but I don't know about the quality. Crydom relays are good but the price is high. See if above mentioned relays can be used for heater control. You can easily provide 5 to 12V for activating the SSR using a transistor.

 

[milan.rajik]

Additionally fix a LM35 to SSR or its heatsink and a Cooler fan controlled through PWM to SSR heatsink. Monitor the temperature of SSR and if it increases then turn ON the fan and cool it. This will give your SSR a long life.