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  • Dearest engineers – Induction motors
  • eth3er
    Free Member

    I have a 400v/1.5kw/3.45A 3phase induction motor being used for an extractor fan, I need to slow it down to quieten it down (neighbours complaints). Inverter it is but anyone know where I might get such an inverter?

    molgrips
    Free Member

    Is it a bare fan or ducted? If so best way to quieten it down is to remove sources of turbulence from the airflow. Our cooker hood makes tons of noise, but if you disconnect the tube it makes none at all.

    eth3er
    Free Member

    It is ducted, huge hotel kitchen type deal.

    RustyNissanPrairie
    Full Member
    wolvesdug
    Free Member

    You can get inverters from most electrical wholesalers.You could also try the extractor manufacturer as they will do a inverter that will have a wall mounted control unit away from the inverter itself. Handy when you have crap on your hands!!
    Ever thought about a silencer. We used to fit them to fans to quieten down.They were a much bigger scale (fan rating was 110KW+)so you should have no probs. This way you will not lose the level of extraction you have now.

    molgrips
    Free Member

    Won’t there be a requirement for it to move a certain volume per hour?

    stcolin
    Free Member

    An inverter/variable speed drive will work perfectly. Usually for a fan application, step it down a frame size kW wise, as an inverter will ‘boost’ to get a fan going but wont require much to keep it spinning.

    IanMunro
    Free Member

    I bought a 2.2kW 240V jobbie from this lot recently
    http://www.inverterdrive.com/

    Quick turn around and have shed loads of inverters that meet your needs.

    MrOvershoot
    Full Member

    wolvesdug – Member
    You can get inverters from most electrical wholesalers.You could also try the extractor manufacturer as they will do a inverter that will have a wall mounted control unit away from the inverter itself. Handy when you have crap on your hands!!
    Ever thought about a silencer. We used to fit them to fans to quieten down.They were a much bigger scale (fan rating was 110KW+)so you should have no probs. This way you will not lose the level of extraction you have now.

    That would be my option, having spent the last 15 years dealing with extraction/aspiration sytems.
    Unless your looking for energy savings you are going to loose some airflow capacity even if you only drop it 5Hz (10%)
    Have a look somewhere like here http://www.industrialacoustics.com/uk/building_services/duct_silencers.asp

    funkynick
    Full Member

    st colin – Member
    An inverter/variable speed drive will work perfectly. Usually for a fan application, step it down a frame size kW wise, as an inverter will ‘boost’ to get a fan going but wont require much to keep it spinning.

    Eh?

    Surely that will depend on whether the motor is overspec’d for the application or not…

    The fan loading on a motor will be proportional to the square of the fan speed, so if the current motor is overspec’d and is essentially running at or near it’s synchronous speed, then underspecing the inverter will be fine.

    But, if the motor is the correct size for the application then an underspec’d inverter will will allow the motor to run at slower speeds, however you will then not be able to run at full fan speed if you ever needed to.

    Whatever, the inverter needs to be rated for the power required to drive the fan at the maximum speed required…

    However, as stated above, does reducing the fan speed still give the required extraction rate for the application?

    You might be better off looking for a more efficient fan/motor setup rather than installing an inverter.

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