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Variable 100-350VAC output controlled by PLC?

  1. Mar 10, 2017 #1
    Hello, I have a strange request from a client.

    He has a "burn-off" which is used to burn bits of labels that are stuck onto his products, that's a bit vague, but it's all the info I have.

    The request is that he wants to be able to change the voltage going through the burn-off anywhere between 100-350VAC, presumably to burn things quicker/slower depending on the product and label.

    He wants the voltage to be selectable via his HMI, but I'm not quite sure how to go about it.

    A variable transformer makes sense, you can even get motorised ones. However, they don't have a feedback from what I can tell. I've found a 0-580VAC motorised Variac.
    My idea is that I can use 2 digital outputs for forward and reverse on the motor, then, for feedback I can somehow convert the voltage to 0-10VDC or 4-20mA (the AI card has both). I say "somehow convert" because I know it can be done with simple electrical components, but I dare say my company would prefer an "off the shelf" solution.

    Or am I going about it all the wrong way?

    Thanks for any help you can provide!
  2. jcsd
  3. Mar 10, 2017 #2
    If they are ready to buy it, then 'off the shelf' sell them a frequency converter with variable voltage output.

    Ps.: for myself I too would go for the transformer... But for a company it's different. Don't forget to make a big, demonstrative box for that few component in the voltage feedback.
  4. Mar 10, 2017 #3
    I suppose the thing that bumps the cost up is he wants it selectable from the HMI.
    So then it needs to go through the PLC and all that jazz.
    We could just put a non motorised Variac next to the HMI. Much cheaper, only one component needed and he only needs to twiddle a knob.
  5. Mar 10, 2017 #4


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  6. Mar 10, 2017 #5
    You beautiful person!
    Well done, that's the hardest part out of the way, helps me immensely!
    Thank you!
  7. Mar 10, 2017 #6
    Is this a radiant (resistive) heater element? Then a basic electric heat controller should work, feed back would be some type of a thermal sensor.
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