Can you describe the procedure for overhauling a three phase induction motor?

Answer 1

The only preventive maintenance that can be done to electric motors by maintenance personnel is to disassemble the motor. The motors bearings can be cleaned and re greased or if sealed bearings that can be changed out for new ones. Remove any grease or dust build up from the stator with compressed air. The stator then should be washed out with a solvent that is specifically made for cleaning electrical equipment. Dry the stator making sure that the motor coils have room around them for air to flow. Dirt accumulations around coil wiring insulation is the biggest cause of motor failure. The coil wires need cooling air moving across them. With totally enclosed motors the cooling vanes on the outside of the motor need to be kept clean as they are the only means of removing the heat from the motor.

Answer 2

The only preventive maintenance that can be done to electric induction motors by trained maintenance personnel is first to dis-assemble the motor. The motor's bearings can then be cleaned and re-greased or, if sealed bearings, they can be changed out for new ones.

Dirt accumulations around coil wiring insulation are the biggest cause of motor failure so a main task is to remove any dust build-up from the rotor - and any fan blades which are fitted to it - and the stator by using compressed air. Then, to remove any grease build-up, the stator and the rotor should be washed with a solvent that is specifically made for cleaning electrical equipment.

Then the stator and rotor must be thoroughly dried, making sure that their coils have room around them for air to flow. The motor can then be re-assembled and tested.

When the motor is in use, the rotor and the stator's coil wires need cooling air moving across them, both to conduct away heat and to remove any dust that may get drawn inside so, with both open and totally enclosed motors, the cooling vanes on the outside of the motor - and any fan blades fitted to the rotor - need to be kept clean as they are one of the main means of removing heat from the motor. The other means of removing heat is by heat conduction: from the coils through the stator frame to the base plate of the motor and from there to whatever massive structure - concrete or metal usually - the motor is mounted onto.

Answer 3

To disassemble a three phase motor first remove the cooling fan shroud. Next remove the fan from the rotor shaft. Next remove the four long bolts that hold the end bells on to the stator. Next center punch the fan end end bell with one dot on both the bell and the stator. Do the same with the other end bell and stator using two center punch dots. This is for reassembly purposed. Separate the end bells from the stator on both ends. Now slide the rotor out of the stator from either end. To reassemble work in reverse making sure to get the end bells on the right ends. This is where the punch marks come into play. Align the marks up and install the through bolts. Tighten up the bolts. Tap the end bells lightly with a hammer in the area of the bearings. This will properly seat the bearings in the end bells. Reinstall the fan and fan shroud. Done.