Best method of controlling a resistive heater - Engineering Discussions - IET EngX - IET EngX
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Best method of controlling a resistive heater

Hey all, 

I'm creating a resistive heating system (I don't have a choice on that, the resistors are already provided), and I'm looking for the best method of being able to control this. 

Resistors are 50W 4 Ohm Panel Mount Units, of which I've got about 32, but I'll likely need more going forward. 

Currently it uses 4 zones, each of which use a custom MOSFET PCB which is PWM pulsed by an Arduino which is all fed from 4 24V DC power supplies. 

This has worked OK thus far, but it's not the most reliable and I was wondering if there's something COTS which would suit this better that provides a better method of control to be able to vary the temperature of the panel, as the current ones have no sense feedback, so they're unable to temperature compensate. 

I was wondering if an inverter could sort something like this? 

I know I'm limited by the supply of the room (which is just 230V, there's no 415V supply etc.), but I'm curious to see what people recommend in terms of whether to look at motor controllers as off the shelf PWM units, current stabilised sources etc. 

  • I would suggest a commercial temperature controller/programmer. This allows you to programme the required ramp rates dwell times etc.

    3500 Advanced Temperature Controller and Programmer | Eurotherm by Schneider Electric  is an example.

    Do you know from previous work approximately what power you need? Being in a vacuum chamber should reduce heat losses (or have I missunderstood?) This should give you some idea of voltage and current requirements.

    Eurotherm also supply matching power controllers which can include load monitoring and alarming.

    An otherwise unloaded ring will supply 30A, although to get this from one socket you will need a plug with two neutral pins (tounge in cheek).

  • Thanks Roger for the info, I'll check out the controller now. 

    Unfortunately no, my predecessor never bothered within defining that. 

    Yeah the vacuum should reduce heat loss. 

    I just recall that the last time we had this working, it required someone to go and manually program each of the 4 panels with a specific PWM, which then made it a bit of a dumb system, as it wouldn't temperature compensate or go to a setpoint, it was just at that frequency until switched off. 

    I want to do this properly and have it setpoint controlled, with the ability to customise the ramp, hold and fall times, and ideally be able to monitor it remotely as we're looking to have this all eventually output into a digital dashboard of the area. 

    I wanted to initially do this all via PLC but it seems getting hold of PLC components at present are challenging, with extensive lead times. 

  • The Eurotherm controllers have a communication option, It was RS232 last time I worked with them I guess it will be ethernet now.

    Lots of components are a problem at the moment. We have two machine projects with 6 month delays waiting for Siemens inverters Frowning2

  • Yeah it's really bad at the minute supply wise! Will look into the eurotherm! 

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