Isulation Resistance

First of all if you can clean it periodically the insulation and apply spray varnish over the insulation if you find any minor damages,secondly you have to monitor its temp during running if its constantly running above previious records then you have to inspect it throughly...increase its cooling by external fan etc...drop its load if possible so its current increases...Meggering above 1000V is damaging for insulation in the long run for motors upto 2500V...

What voltage R U talking about?Any motor can be wound with different CLASS of insulation.In the USA a is low class and k is high class.If we have two each 10 hp 480 volt 3 phase motors with same frame number but run in 2 different applications then we have choices. One is in a dry 20 deg C location.We use class c wire and "bearings " with C3 class or 3 thousand ball bearing clearance.The second motor is run in a 40 deg C aplication with 85 % humidity.We use class K insulation 4 the stator wire and bearing with 0.010 clearance.Works GREAT.In a dusty place all bearing end in a "R" class sealed bearing class." Z" shields distroy the bearings in the dust.

Dry the damn thing out.<wheeze>

if its a small motor u can remove the rotor and heat with bulbs to improve IR value .larger machines cirulate a low current applying a low voltage.

You can improve insulation resistanace of the motor in the following ways.

1. Dismantel the motor carefully and separated from stator.

2. Before that you can take cold resistance of the winding ( shows low resistance) and Insulation resistance of the winding with respect to body (earth) and winding to winding.( Shows very high resistance)

3. Preliminary heating will be done in the oven in lower temperature (i.e<100 deg C) for 2 to 3 hours.So moisture in the winding is go off.

4. Pour the insulation warnish slowly so that all windig slots get weted with the warnish.

5. Agaain in the same oven keep the winding few more hours say 10-12 hours.

6. You measure the Insulation resistance of the winding with respect to body (earth) and winding to winding. and compare with earlier values. Diffinetly you will notice better values.

This process is called baking process.

In conentinal the heating process are done by putting incandicent lamp or by keeping the winding in sun heat to the power.