Driving a 3 phase compressor with PWM

Discussion in 'General Electronics Chat' started by R!f@@, Mar 26, 2010.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    I would say not to grin at what I am about to discuss.

    As you know nowadays Inverter air con is doing big.
    And I thought of practical application on doing this.

    Say you have a three phase 440V / 220V compressor. Would it be ideal for any one like us to try and built DC PWM driver for this compressor.
    What are the limitation that we would face in doing this.
    Can't we cook up a circuit and built it.
    We are building boards and it works pretty well.

    The thing is when I think of the high voltage DC involved and the type of power switches that have to be used to accomplish this makes me wonder that this is out of my league.

    It's not that I cannot get the components, and I can pretty much place an order on eBay to have the board fabricated.

    What do you guys think, Is this a capable thing to do if I try.
    What do I have to face if I set out on this journey.

    This is an Idea and I think I can make big business out of this and pretty much I think I will try this no matter what.

    Just like to know from you what are the things that have to be taken into account when designing something big like this.
     
  2. SgtWookie

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    Jul 17, 2007
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    Well, it will certainly be challenging. ;)

    Probably use something like three H-bridges constructed using IGBT's with opto drivers to power three broadband isolation transformers, using 30kHz to perhaps 70kHz as a base PWM frequency.

    To make it decently efficient would require a lot of effort.
     
  3. R!f@@

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    I like that, positive attitude.
    Challenging.... definitely for me. I never backed out from a challenge.

    Have you seen any of those circuits. Since I have yet to get my hands on one of 'em.
    But I think I will get one.

    IGBT's > this I know and opto's can Isolate, but why transformers.

    Second Q? Isn't PWM efficient. It can soft start, eliminating surges, Power can be adjusted to the requirement's of the environment.
    What more is there?
     
  4. SgtWookie

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    Do some research on Class D amplifiers to get you headed in the right direction.

    Then imagine three Class D amplifiers producing a 3-phase output.
     
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  5. shortbus

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    Sep 30, 2009
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    This would be like a VFD (variable frequency drive) They take AC and convert it to DC then convert back to AC. The main use though is to allow you to run 3phase motors on single phase. But they were originally made to control motor speed.

    But remember- every time you convert you lose a certain amount of power. There is no free lunch.
     
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  6. rjenkins

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  7. R!f@@

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    Hey !! I did buy these vector inverters to repair a huge ironing machine in our Hospital.

    But I never thought that these could handle such huge heavy duty compressors. If they can what is stopping most guys from re making their AC's into an inverter type, it would definitely cut the cost.
    And is it possible to find a powerful one to PWM a single face compressor motor.
    If so, throw me a suggestions and I will rip open my room Air con. Bet on it.
     
  8. rjenkins

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    The example I found was rated at 2.2KW, I'd guess that's in the power range of an aircon compressor.

    I've used various sizes over the years, from around 100W to over 30KW in machine tool applications.

    In your original post, you mention a Three Phase motor - you can certainly control the speed of a three phase motor.

    Your last post says 'single face' - single Phase? You can't easily speed control that.
     
  9. R!f@@

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    Single phase came suddenly as I thought of my AC :).
    I suppose this is a no no.
    Sow we cannot cut down the cost of single phase huh!

    3 phase once I am talking about are 43KW once
     
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