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Thread: Question for an Electrical Engineer

  1. #1
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    Question Question for an Electrical Engineer

    I have a small electric induction motor which is suddenly not spinning up to it's normal speed - I reckon maybe half power. Power supply would appear to be fine, bearings are free and the motor is capable of spinning freely. There is what I would describe as a lack of torque in the motor, but this is a perception rather than anything with any real substance behind it.

    Any ideas - is this the brushes in the motor worn out or similar? Sound familiar - terminal or fixable? Any info much appreciated.
    Nooooooooooooobody expects the Spanish Inquisition!! Our main weapon is.........

  2. #2
    Firstly, you won't have brushes in an induction motor as power between the rotor and stator is induced by electro magnetism. Is the motor 3phase or single phase? What is the application of the motor?

    regards

  3. #3
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    Quote Originally Posted by Chasser View Post
    Firstly, you won't have brushes in an induction motor as power between the rotor and stator is induced by electro magnetism. Is the motor 3phase or single phase? What is the application of the motor?

    regards
    shows what I know huh...!! Best I check my terminology more carefully on all counts.

    It is a very small single phase motor - runs off 6V, spinning a small mirror at about 4 cycles a second (guess) - so 240 rpm - when working. Diameter of the disc is about 70mm.
    Nooooooooooooobody expects the Spanish Inquisition!! Our main weapon is.........

  4. #4
    Sounds as if it would be DC? In which case it would have brushes, usually you will get s kind of pulsing or complete failure if the brushes have worn, I should imagine the cost of a small 6v motor will be a couple of quid, it may be easier to find a new one on RS or Maplins, the Google the part number to find who has it cheapest. Sorry I can't be of more use its quite hard diagnosing these faults without seeing it.

    regards

  5. #5
    What are you running it off, IS it measuring 6 volts while spinning, what current is it drawing. If you don't have a multi meter, Try an alternative 6volt supply to rule out any issues with power. More than likely the motor is at fault. deerwarden

  6. #6
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    Quote Originally Posted by deerwarden View Post
    What are you running it off, IS it measuring 6 volts while spinning, what current is it drawing. If you don't have a multi meter, Try an alternative 6volt supply to rule out any issues with power. More than likely the motor is at fault. deerwarden
    I will need to be a little more scientific on this, clearly. I was quoting the mfr voltage - it'll be drawing less than an amp I reckon.
    Nooooooooooooobody expects the Spanish Inquisition!! Our main weapon is.........

  7. #7
    Without any more details, it sounds like a single phase AC motor with a set of starter windings and a capacitor for starting. I would check the capacity. Be careful not to get shocked by any charge it is holding.

  8. #8
    I have a faulty motor which answers your various descriptions; 6 volt DC, mirror, hardly any torque...It is the rotary part of a rotating laser level. The motor itself is mechanically and electrically okay...it is the electronic control panel which is at fault.

    For anybody to diagnose your fault you will need to furnish all the details of the device and symptoms...

    Alan

  9. #9
    CPC would also be an alternative to RS or Maplins.
    Having said that a local to you motor rewind service would be a good start.....

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