Electrical Heater

If my memory is correct, an SCR-type heat controller combines both of the concepts you mention: Phase-angle switching and PID (proportional-integral-derivative) control. You may be able to find catalog and technical info by searching "heater controller" or "solid-state heater controller" or the like. This will also give you a few manufacturers, and you can then consult with them or their distributors. There are also programmable "ramp-and-soak" controllers that can bring your temperature up at any desired speed, maintain the temperature for the proper time, and then cool down at a desired speed, such as used in heat treating metals. You should be able so succeed rather easily in this.

What type and size of heaters banks are you using?

You could replace the contactors with Solid State Relays SSR and a temperature controller that has SSR output for better temperature control.

For even better control, split heater bank into smaller zones, if possible. You will then need to add more controllers, but your control will be much better and the size of the SSRs can be reduced.

Just ensure you have adequate ventilation and heat sinks for the SSRs.

Most of the time, phase angle control is used for quartz or IR heaters.

Greenja.

first of all thanks for your cooperation and opinions

and for more information the heater consist of 9 zones, and each zone has two

opposite sub heaters, and if i use on/off control i can made use of plc to monitor the

value of volt and calculate the time in heater automatically instead of putting it

manually, but i still need the heat equation of the electrical heater considering

the contribution factor between zones

(we use nickle crom wirs for heating) each zone has 3phase power = 21.66 k.w