21 thoughts on “How to Rebuild an Electric AC Motor

  1. Heres a handy tip: Before opening the motor use a marker to make two small lines across the seam where the end plates connect. That will save you lots of time when trying to line up the screw holes when re-assembling. Many older motors ive taken apart have already had this done by the previous owner.

  2. Thanks that is good info, I have a motor that when plugged in, it hums. It works fine but I'm wondering if it is sign of something about to break. Would you know?

  3. Brevity is the soul of wit ~ Shakespeare — Not only have I actually learned a couple of things I didn't know before, I learned how one might explain things efficiently and succinctly. (Brevity is the soul of a great lesson?!) Great job, enjoyed the vid.

  4. Outstanding vid! Had to watch it twice because I only speak American but that's not your fault.
    How did you know when you had gotten the new bearings at just the right position on the shaft to fit properly in the endplate recesses?
    And I just say Molly-be-damned.

  5. Great video but we didn't see you measure the lateral gap (the gap that is to accommodate the expansion of the motor shaft) if before there was 0.000 gap then you should have machined at least 1mm (0.500mm for the washer and 0.500mm for expansion or more) if you just added a washer then the problem will have been worse.

  6. the run capacitor you can replace it with one with a higher voltage for example if u have a 5 MFD or UF 250 VAC you can replace it with a metal oval or round run capacitor a 5MFD 370 VAC or 440VAC as the capacitance has to be the same as you can go up in voltage but not down if u put in a bigger cap it will increase the torque of the motor plus amp draw and noise as will it can overheat. smaller cap it will weaken the torque of the motor and overheat as well too if the motor is thermally protected cheap motors have thermal fuses in them if it blows the motor is toast the ones that reset it can be manual or automatic depending on the motor. the motoy you got has sealed ball bearings they can't be oiled but replaced. sleeve bearings some have to be oiled some are permantly lubricated. cooling for the motors yours is fan cooled as it has an internal fan if its in a machine it will have sufficent cooling other motors that indicate Air Over on the nameplate is the motor has to be mounted in the airstream such as a fan or other air moving appliance.

  7. the motor you have is a PSC Permanent Split Capacitor type meaning a run capacitor is used. A Capacitor start motor has a capacitor in the start windings as that and that and the start windings are taken out of the circuit by a centrifigual switch when the motor reaches 75% of operating speed a capacitor start capacitor run motor has a start cap and a run cap. and has the same centrifigual switch as the capacitor start to take the start windings and start cap out of the circuit. the split phase works in the same way but has no capacitors as the motor is used for pedistal fans, and belted loads such as belt drive fans, blowers and compressors, some can be used in pumps. the smaller motors that has no capacitors is basically a shaded pole type motor. which has low starting torque but are very inefficient. the largest motors are polyphase or 3 phase that only operates on balanced 3 phase power only. some can be star or delta wound. there is no run capacitors on a 3 phase motor. the motor you have is single phase. as nowadays the Shaded pole and PSC motors are rapidly being replaced with ECM or DC Brushless motors for HVAC fans and refrigeration use. if a motor goes out if costs are reasonable with the machine or appliance it came out of the motor if its a shaded pole it can be replaced with a PSC or an ECM motor with the same or close HP ratings rotation and RPM in USA the frequency with electrical power is 60 HZ the rest of the world is 50 HZ as some motors are labled to run on either 50 or 60 HZ. as the RPM and Amp draw of the motor can be different depending on the frequency the motor is operated on.

  8. Good video, thanks for posting it and all the tips.

    You can mark the casing with a felt tip before disassembly so it will align properly on re-assembly with no fiddling about. I'm also looking for a video showing somebody skimming the commutator up on a lathe and changing brushes. I've got a book which I'll work from, but it's always useful to watch somebody with experience doing it. Best wishes.

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