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Thread: Using VFD on single phase source

  1. #1
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    Using VFD on single phase source

    I have a situation where we ended up not using a 480V 1.5HP in line fan and it's ABB VFD during construction of one of our buildings. Now I am going to donate the fan and drive to a good friend who is remodeling a local tavern he just purchased, issue is he only has 240V single phase power available (this will be kicked up to 480V 1Ph). I don't run into situations where I am using freak drives to run a 3 phase load from a single phase source, and that is where my question lies.

    I know normally in this situation, you would double the size of the drive to handle the extra power needed to run the fan. The plan is to install differential pressure sensors in the smoking room and one in the bar area. We'll then be exhausting enough to meet minimum ventilation needed to keep the room smoke free plus keeping the room negative so the smoking room doesn't draft into the bar area. Mostly the fan will be running at minimum levels but may have times especially when doors open where it needs to ramp up to keep the negative state. Seeing as it will 95% of the time be running at far less than 50% of it's full load, any opinions on if the drive will work and if not how long it'll last?

    Thank You

  2. #2
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    Quote Originally Posted by WiscElectrician View Post
    I have a situation where we ended up not using a 480V 1.5HP in line fan and it's ABB VFD during construction of one of our buildings. Now I am going to donate the fan and drive to a good friend who is remodeling a local tavern he just purchased, issue is he only has 240V single phase power available (this will be kicked up to 480V 1Ph). I don't run into situations where I am using freak drives to run a 3 phase load from a single phase source, and that is where my question lies.

    I know normally in this situation, you would double the size of the drive to handle the extra power needed to run the fan. The plan is to install differential pressure sensors in the smoking room and one in the bar area. We'll then be exhausting enough to meet minimum ventilation needed to keep the room smoke free plus keeping the room negative so the smoking room doesn't draft into the bar area. Mostly the fan will be running at minimum levels but may have times especially when doors open where it needs to ramp up to keep the negative state. Seeing as it will 95% of the time be running at far less than 50% of it's full load, any opinions on if the drive will work and if not how long it'll last?

    Thank You
    What does ABB say about this long term use? We have done the transformer thing but just for temporary to program and test the drive controls in the shop.
    Tom
    TBLO

  3. #3
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    There are two issues: the current flowing through the diodes in the bridge rectifier will pull 1.732x more current and the DC bus ripple is going to be much worse without the added capacitance afforded by de-rating the drive by 50%. The DC bus ripple is generally the worse of the two, and it is related to load. So at lower load there will be less ripple, but at full load (presuming the full 1HP of the motor), the ripple may cause damage to the drive. More likely however is that the drive will simply detect it and shut down.

    One thing you could try (if your drive offers this option) is to program in a 50% current limit on the drive. How a VFD responds to that is (typically) that the PWM is folded back, despite the commanded speed; i.e. the commanded speed is overridden by the current limit function, because speed = current. That way whenever someone did open a door or something, the drive will simply go to it's maximum current limit setting and stay there. It may result in some loss of function in your smoke deterrence system, but only temporarily from the sounds of it.
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  4. #4
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    Are you going to be powering a 1.5 HP motor?

    That said many standard sizes for 480 volt drives I have come across we would be purchasing a drive rated for 2.0 HP to drive a 1.5 HP motor, so you possibly have some extra capacity from the drive if it was originally selected to drive a 1.5.

  5. #5
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    Wouldn't it be a lot easier, and more maintainable, to replace the motor (if possible) and let it run full-speed? Seems like a lot of work to re-use the fan & drive.

  6. #6
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    Quote Originally Posted by zbang View Post
    Wouldn't it be a lot easier, and more maintainable, to replace the motor (if possible) and let it run full-speed? Seems like a lot of work to re-use the fan & drive.
    He wants to modulate using the onboard pid to maintain a differential static pressure in the space

    I doubt the spaces will be tight enough to do it
    might be easier to put a small control damper on the fan inlet
    get a small actuator/controller, may be able to get one with the dp sensor built in (used on a vav box) and just run sensing tubes
    need a very small range <0.10" wc

    probably run full speed or damper 100% anyways
    the power saving nil
    Last edited by Ingenieur; 05-08-17 at 09:33 PM.



  7. #7
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    Quote Originally Posted by kwired View Post
    Are you going to be powering a 1.5 HP motor?

    That said many standard sizes for 480 volt drives I have come across we would be purchasing a drive rated for 2.0 HP to drive a 1.5 HP motor, so you possibly have some extra capacity from the drive if it was originally selected to drive a 1.5.
    Never mind about the motor, I first thought you had a left over drive after reading OP again you have a left over fan/motor assembly and the drive for it. Still could be a 2 hp rated drive though.

  8. #8
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    There's a state that still allows smoking in a bar?

  9. #9
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    Quote Originally Posted by Open Neutral View Post
    There's a state that still allows smoking in a bar?
    That entered my mind but I think I've been in area that still have two sections. Last summer in central Missouri, MDSW informs me.
    Tom
    TBLO

  10. #10
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    Quote Originally Posted by Open Neutral View Post
    There's a state that still allows smoking in a bar?
    Yep - Mizzourah

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