Motor DE Side Bearing Temperature

Did you test run the motor off load before fitting?

GA from me.

I will add to the logic: Since it is taking an hour of running (as said by OP!) before the temperature starts to creep up, then it might be logical to assume that the heat IS MIGRATING from another source than the bearing (the winding?) to the bearing area.

Thanks Mr. snakers

Coil resistance is u1-u2=0.033ohms, v1-v2=0.032ohms and w1-w2=0.033ohms

Insulation resistance between body to winding is greater than 2gigaohms at 500volts so we can clearly say that No problem in armature winding from the above readings.

As per you stated we also have doubt on rotor only(we measured the temperature by used IR sensor on DE side of the motor from that we felt shaft temperature more than the bearing temperature, differenance around 3 degree celius).

Lets reason this out. If the shaft temperature is higher than the bearing temperature the heat is likely coming from the rotor. If it is a wound stator and a squirrel cage rotor (no windings), The stator winding resistance has little meaning. Heat in the rotor section can only come from a broken or cracked shorting bar.

Basically these are short circuited turns that have high current flows. If each of the short circuited turns resistances on the rotor are low, the I ² R losses are low, hence little heat.

If you have a broken (or cracked) shorting bar, the R values increase as does the heat. This is a common problem with motors this size. I have seen where re-brazed bars have re-cracked a year later.

The rotor needs to be examined very closely. Use of temperature sensitive paint requires reassembly, running, disassembly and examination of paint temperature indicators. More likely a close examination with magnifying glass will identify the problem area(s). I sugest that you take a very close look.

Please let me know what you find.

Check the alignment and how much thrust load the DE bearing is getting.

Is this on a VFD? You could be inducing eddy current losses. Was the bearing originally an insulated bearing?

Have you checked that proper fan of is mounted on the motor.

The possible causes will depend on the type of motor and coupling.

• Is the motor mounted horizontally or vertically?
• Are the bearings ball, roller or journal (sleeve) type?
• Are the bearings grease or oil lubricated?
• Are the bearings externally cooled (for example, with a water jacket)?
• Is the coupling bolted or flexible?
• Was any machining done on the rotor shaft, bearing housing or frame feet of the motor?

One problem I've sometimes found in rewound motors is that the electrical center has moved so far that the shoulder of the rotor shaft rubs on the side of the bearing.

In vertical motors, the most common problem I've seen is installing the thrust bearing upside down so it doesn't provide support.

Oil lubricated bearings can have a blockage in the oil flow path.

Greased bearings sometimes get over-packed with grease, which increases friction.

For externally cooled bearings, the water flow path could be blocked, the temperature of the cooling water may have changed, the water jacket could be clogged with corrosion, or a layer of rust may be inhibiting heat transfer.

If you can give us additional information on the motor, some of these can be eliminated and more detailed suggestions provided.