Both the interior and exterior of the motor should be free of spilled oil, water, dust, and dirt. The exterior should be wiped and the interior blown out with compressed air at a reduced pressure.
CAUTION
Moisture.
Can damage windings.
Protect motor from moisture.
Wipe off removable rust preventatives with a clean cloth soaked in petroleum solvent.
WARNING
Solvent may explode.
Have no flames or spark.
Dispose of rags in special container.
Make sure that the bearings and lubricant cavities are free of dust and dirt and that the (oil) plugs in the cavity are sealed and tight. Scratches or rust on the shaft journals must be carefully removed.
Relubricate BearingsUse the specified or compatible grease or the specified viscosity turbine oil as applicable. Refer to lubrication plates on the motor and to the instruction book.
Remove DesiccantCheck Winding Insulation ResistanceRegardless of the method or location of storage, the winding insulation should be measured prior to placing the motor in service. A low winding insulation resistance is an indication of excessive moisture in the winding and it should be dried before being energized.
Check the insulation resistance using a hand cranked or solid state insulation resistance tester and test with at least 500 volts but not greater than machine rated voltage. Use 500 volts on motors rated 600 volts or lower.
For machines with newer insulation systems, such as MiCLAD VPI, the insulation resistance after one (1) minute should be greater than 1000 megohms. (Values in excess of 5000 megohms are common.) Refer to the instruction book.
If the insulation resistance is less than satisfactory and the cause is excessive moisture in the winding, dry the windings by applying heat from:
1.A warm air oven.
2.Electric strip heaters.
3.Circulating currents through the coils.
Do not use radiant type heaters.
The heat should be applied slowly so the desired temperature will not be obtained in less than eight (8) hours. Heating faster may damage the winding. The insulation resistance should be measured before the heat is applied and every six to eight hours thereafter. For newer Class F insulation systems, such as MiCLAD VPI, a temperature of 245°F (118° C) is commonly used for this drying procedure.
Insulation resistance will decrease as the machine warms up but will begin to increase shortly as the dryout continues.
A uniform temperature must be maintained in the machine to obtain meaningful readings. When the insulation readings stop changing, the drying process is complete and may be discontinued. If the insulation resistance is still low, check for other causes.
To prevent damage to the bearings, the bearings and the bearing housings should be removed before starting any of the heating methods. The rotor should also be removed to allow more uniform heating of the winding. Temperature indicators or detectors should be connected to the winding and monitored to see that the recommended temperature is not exceeded. A fan can be helpful in getting more uniform winding temperatures and in carrying away the moisture when strip heaters are used as the heat source.
MiCLAD is a Siemens trademark.
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