user manual

- 12 -
Preparation For Service
Cleaning
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 Bearings
Use 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 Desiccant
Check Winding Insulation Resistance
Regardless 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.