Temp Control in Heater Cloth Element

S

Thread Starter

sunil

Hallo. We have a requirement for temperature control of the heater cloth element which is used to heat mold for Resin Transfer Machining process.

I have 8 inputs coming from thermocouples and would like to use plc for that reason as the cost for individual temperature controller is more. There are 10 bands which have power requirements.

My question is how can I integrate a power control unit in this. Can anyone suggest please.
 
First of all could you be a bit more specific - you have 8 thermocouples and you need to control 10 bands.

1. What is the relation between them, i.e. is 1 thermocouple related to one band, do you have 8 thermocouples per band, or 8 thermocouples to 10 bands?

2. What accuracy do you need in the temperature control, i.e. will an on-off heater control suffice, or do you need variable power to heater for more accurate temperature control?

3. Do the heater bands require seperate power control units or will one common power control unit suffice?

I would recommend the following (adapted to your specific requirements):

Get hold of a PLC that accepts thermocouple inputs and produces 4-20mA output signal. Program a PI loop(s) in the PLC to obtain an output signal proportional to the power required. Obtain an SCR Power controller (SCR19 from Omega or equivalent). Send the output signal from the PLC to the Power Controller, and you should have your system up and running. Obviously size your components to your requirements.
 
D

Dick Compton

Depends.

Simple = TC input, PID, PLC output, solid state contactor.

Zoned? If thermocouples are between areas, ~40% of TC1 + ~60% of TC2 = temperature PV. PID, PLC output, solid state contactor.

Anticipation? Have PLC have 2 groups of setpoints -- when mold is closed = setpoints #1. When mold is open = setpoints #2. This is because the thermal characteristics are dramatically different in these two conditions.
 
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