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Re: "Thermally protected" motor

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  • John
    Many motors and transformers have a thermal protector embedded in the windings as a safety device. If it goes completely open it can be replaced by
    Message 1 of 4 , Apr 10 6:39 AM
      Many motors and transformers have a "thermal protector" embedded in the windings as a safety device. If it goes completely open it can be replaced by disassembly of the winding. All I have dealt with have been on top of the windings. Since yours is self resetting I guess it is working properly. I would check for too much mechanical load or motor bearing binding. If you choose to bypass the thermal protector you will probably let the magic smoke out!
      de John W8CCW

      --- In Electronics_101@yahoogroups.com, Dave C <davec2468@...> wrote:
      >
      > I have a 10W 100 vac (not 120) induction motor from a Japanese offset printing machine that is intermittent. Regardless the temperature, vibration, coaxing, or pleading, it starts and stops by itself. Correct supply voltage is present at all times. When it fails a resistance check shows an open circuit. When the motor runs I can't connect probes fast enough after turning off power to see resistance.
      >
      > I suspect whatever "thermal protection" is use it is failing.
      >
      > What type of device is typically used in such motors? Are replacements readily available?
      >
      > The reason for all the effort:
      >
      > 1. Replacement motor is more than the worth of the equipment
      >
      > 2. Keep this from the landfill.
      >
      > Thanks,
      > Dave
      >
    • Larry Beaty
      Dave, You should be able to see the thermal limit in the winding, usually at the bottom. But what if this 10W motor does not have such a limiter? In my
      Message 2 of 4 , Apr 10 7:22 AM
        Dave,



        You should be able to see the thermal limit in the winding, usually at the
        bottom. But what if this 10W motor does not have such a limiter? In my
        experience, coils fail at the coil termination. Very carefully expose the
        wires going to the terminations. Some coils I have seen had banjo strings
        (Tight, no loop) to the terminals. They will break. You can remove one
        turn or splice on a wire. Make it slack!



        Best of luck!



        Larry



        From: Electronics_101@yahoogroups.com
        [mailto:Electronics_101@yahoogroups.com] On Behalf Of Dave C
        Sent: Tuesday, April 09, 2013 2:19 PM
        To: Electronics101
        Subject: [Electronics_101] "Thermally protected" motor





        I have a 10W 100 vac (not 120) induction motor from a Japanese offset
        printing machine that is intermittent. Regardless the temperature,
        vibration, coaxing, or pleading, it starts and stops by itself. Correct
        supply voltage is present at all times. When it fails a resistance check
        shows an open circuit. When the motor runs I can't connect probes fast
        enough after turning off power to see resistance.

        I suspect whatever "thermal protection" is use it is failing.

        What type of device is typically used in such motors? Are replacements
        readily available?

        The reason for all the effort:

        1. Replacement motor is more than the worth of the equipment

        2. Keep this from the landfill.

        Thanks,
        Dave





        [Non-text portions of this message have been removed]
      • Dave C
        Thank you Larry & all. It seems to be a matter of a poor solder joint and corrosive substance (it is used in a chemical developer machine) that caused the
        Message 3 of 4 , Apr 10 8:33 AM
          Thank you Larry & all.

          It seems to be a matter of a poor solder joint and corrosive substance (it is used in a chemical developer machine) that caused the intermittent problem.

          There is no sign of the thermal protection per the motor's wiring diagram. Maybe they ran out of that part that day?

          Runs as expected for now...

          Thanks,
          Dave

          Sent from my iPod

          On 10 Apr 2013, at 07:22 AM, "Larry Beaty" <lbeaty@...> wrote:

          In my experience, coils fail at the coil termination


          [Non-text portions of this message have been removed]
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