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Advice re inductor on motor neutral

Discussion in 'Sensors and Actuators' started by Bluejets, Apr 7, 2019.

  1. Bluejets

    Bluejets

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    Oct 5, 2014
    Have a small induction motor on sliding gate I just finished building.
    Motor unit is a commercially built unit and during the initial start it fair clunks into operation.
    After that it it relatively smooth.
    Motor is similar in arrangement to that show in the diagram. (500w AC 220v)
    Just found the sketch on the internet to save my having to draw it up so don't take any notice of the "earth/ground" symbol.
    Thought perhaps I might be able to wind my own inductor up on a ferrite torroid and fit to the neutral to reduce this rather annoying tendancy.
    Idea being to reduce the inrush current at startup.

    Any thoughts...??

    GateMotor.jpg
     
  2. Alec_t

    Alec_t

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    Jul 7, 2015
    Have you considered using an NTC surge-limiter thermistor?
     
  3. Bluejets

    Bluejets

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    Oct 5, 2014
    No you misunderstand.
    The proposed (series) inductor is to try to limit the motor inrush current at startup allowing a smoother runup to the design speed.
     
  4. Alec_t

    Alec_t

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    Jul 7, 2015
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    I'm not looking for mains surge/overvoltage protection.
    And I am aware of the device you refer to when used in projector bulb circuits but this is a motor (bit different kettle of fish)
    What I am after is similar to motor start voltage reduction.
     
    Last edited: Apr 8, 2019
  6. Martaine2005

    Martaine2005

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    May 12, 2015
    Perhaps you could try a ‘start capacitor’. Borrow it from your compressor or washing machine to see if it helps. That is what they are for. They help starting and eliminate the in rush.

    Martin
     
  7. Ylli

    Ylli

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    Jun 19, 2018
    To quote Alec_t..... which is precisely what an NTC thermistor, such as one of these, would do.

    High resistance when cold, and the peak current draw for the motor would be reduced. As it gets hot, it's resistance decreases allowing the motor to deliver rated torque.
     
  8. Minder

    Minder

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    Apr 24, 2015
    The motor is a PSC type and already has the capacitor, which incidentally is used for a 90deg phase shift, otherwise no start.

    The problem is these motors do not control well at lower voltage, although if under 1/2hp, a ramped Triac start might be used.
    M.
     
  9. Bluejets

    Bluejets

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    Oct 5, 2014
    Forgive the french, but the motor would blow the crap out of those things in the first few milliseconds which is why I objected in the first instance.

    Thanks M...I'll look into it a bit further along those lines...much appreciated.
     
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