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  1. #1
    Join Date
    May 2013
    Location
    Auckland, New Zealand
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    997

    Default changing the motor on the extractor

    I have a bag house extractor. The motor is 4kw, the fan is roughly 500mm dia.

    photo 3.jpgphoto 2.jpg

    I am wondering, by changing the motor to 7.5kw, will this increase the performance of the extractor?


    1.JPG

    thanks guys.
    SCM L'Invincibile si X, SCM L'Invincibile S7, SCM TI 145EP, SCM Sandya Win 630, Masterwood OMB1V, Meber 600, Delta RJ42, Nederman S750, Chicago Pneumatics CPRS10500, Ceccato CDX12



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  3. #2
    Join Date
    Jun 2013
    Location
    Geelong
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    423

    Default

    It won’t if the motor spins at the same rpm, check the motor label.
    cheers

  4. #3
    Join Date
    Feb 2006
    Location
    Perth
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    27,756

    Default

    To increase flow you'll need to spin the impeller faster.
    The easiest way this can be dome is using a VFD.

    If your 4kW motor is already near its max current draw, running it at a higher speed may result in the motor drawing too much current.
    If the DC was only used intermittently ie 30s at a time, that might be OK but any longer will in the long run probably cause motor failure.

    Going to a bigger motor that can handle higher currents is where a more powerful motor makes sense.

    My DC had a 3HP Single Phase motor (SP) and I wanted more speed so I replaced the SP motor with a 3P motor and a VFD.
    The current draw was fine 50Hz (9.4A) but at 60Hz the current draw was 13.7A this cause the motor to get too hot after about 5 minutes of use.
    I then switched to a 4HP (3kW) motor and it can run all day at 13.7A.

    If your current motor is RUNNING nowhere near its rated current you may not need to change the motor when a VFD is added.

    NB spinning impeller faster will also make a LOT more noise.

  5. #4
    Join Date
    Oct 2009
    Location
    South Africa
    Posts
    950

    Default

    That impeller looks fairly rustic to my eye, you might get better airflow if you can find a more modern design impeller that fits. Finding something that fits is going to be the tricky bit though.

  6. #5
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,756

    Default

    Quote Originally Posted by Colin62 View Post
    That impeller looks fairly rustic to my eye, you might get better airflow if you can find a more modern design impeller that fits. Finding something that fits is going to be the tricky bit though.
    It's not that unusual for large impellers to use straight vanes. If they're made big enough and spun fast enough they can still move lots of air

  7. #6
    Join Date
    Aug 2007
    Location
    Saskatoon, SK, Canada.
    Posts
    1,436

    Default

    Pretty rustic looking though with it being welded up from angle iron and flat pieces added to the outer tips with more welding. Upside is that it is a backward inclined impeller.

    Pete

  8. #7
    Join Date
    May 2013
    Location
    Auckland, New Zealand
    Posts
    997

    Default

    Quote Originally Posted by BobL View Post
    To increase flow you'll need to spin the impeller faster.
    The easiest way this can be dome is using a VFD.

    If your 4kW motor is already near its max current draw, running it at a higher speed may result in the motor drawing too much current.
    If the DC was only used intermittently ie 30s at a time, that might be OK but any longer will in the long run probably cause motor failure.

    Going to a bigger motor that can handle higher currents is where a more powerful motor makes sense.

    My DC had a 3HP Single Phase motor (SP) and I wanted more speed so I replaced the SP motor with a 3P motor and a VFD.
    The current draw was fine 50Hz (9.4A) but at 60Hz the current draw was 13.7A this cause the motor to get too hot after about 5 minutes of use.
    I then switched to a 4HP (3kW) motor and it can run all day at 13.7A.

    If your current motor is RUNNING nowhere near its rated current you may not need to change the motor when a VFD is added.

    NB spinning impeller faster will also make a LOT more noise.
    Thanks BobL, kind of inline with my thought to date...
    SCM L'Invincibile si X, SCM L'Invincibile S7, SCM TI 145EP, SCM Sandya Win 630, Masterwood OMB1V, Meber 600, Delta RJ42, Nederman S750, Chicago Pneumatics CPRS10500, Ceccato CDX12



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