Shaded Pole AC motor/motion sensor power question

Discussion in 'General Electronics Chat' started by Valence, Aug 30, 2013.

  1. Valence

    Thread Starter New Member

    Aug 30, 2013
    3
    0
    Hello all,

    Have a newbie question for you. I'm trying to get a small shaded pole motor hooked up to a motion sensor, with no success. Here are links to the components involved:

    Motor: http://www.mcmaster.com/#6142k54/=oajcig
    115/60 v/hz 1amp @ full load

    Sensor: http://heath-zenith.hcents.com/data/manuals/595-5109-13.pdf
    120/60 v/hz---- 4.2 amp / max 500 watt across white pole. I'm assuming that means it's max load.

    So here is whats happening, when the motor is plugged straight into the wall socket it operates fine. However when I hook it up, roughly following the schematics on the heath-zenith pdf, adding only a switch on the hot leg as it comes from power, the motor spins extremely slowly, if at all. And also begins to heat up rapidly. Small incandesent light bulbs work fine as well as another 1/60 hp .8 amp motor (works mostly fine, different style motor altogether however).

    I know there are obviously power compatibility issues between the sensor and motor at fault here but I'm having trouble reasoning them out. If the sensor can produce a 500 watt switch, while the motor only needs roughly 1amp x 115v = 115watts at full load to operate normally, why is it acting like its getting more than it can handle? Conversely when hooked directly up to building power, when it's getting like 15+amps or 1800watts why does it act correctly? Seems like in the second scenario it would be worse.

    Anyways I'm obviously new at this and could use some clarification on the circuit, the power going in and out of the sensor, and what it all means. I'm not sure if I need to research a relay or some type of resistor to control the power into the motor. And where/what that component would be. Rationalizing it out after writing this, it seems like a 1 amp resister on the hot leg as it leaves the sensor would bring the line amp down to the motors max load rating, not sure that would help though. IDK.

    Any help would be appreciated.

    best
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You need to know the controlling element of the motion sensor, if it it is designed for a resistive lighting load, I suspect there is a miss match to the inductive motor load, if it was a simple relay control it should be no problem.
    Max.
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
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    +1
    The motion sensor doc mentions a half-bright dimming function, which leads me to believe that it probably uses a phase angle firing triac or something to switch power to the LIGHTS. Since it's designed for resistive lighting, it probably doesn't have any snubber circuit to prevent it misfiring when switching an inductive load.

    You could try using the motion sensor to switch an SSR, and use the SSR to switch the motor. But don't forget the snubber for the SSR, lest you have the same problem. Or you could try soldering a snubber onto whatever is inside the motion sensor if you're comfortable with that.
     
  4. #12

    Expert

    Nov 30, 2010
    16,252
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    Aha, a motor that strantor understands.:D
     
    strantor likes this.
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    2,367
    Ok in that case then either it could be used on full and pick up a relay to switch the motor, but if the intent was to get variable speed instead of incandescent dimming, it is not going to work.
    Max.
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
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    Relay would make it easier, but that's also an inductive load. I recommended the SSR because of the inductive relay coil. But I have no idea how much inductance a relay coil has compared to a shaded pole motor, or to what degree the significantly decreased load of the relay vs. the motor would make things better. If you think that the relay would work just fine, then I'll leave that call up to you; you know more than I do.
     
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