GE Pegasus MHV GEEP-427-I Instuctions page 16

Insulation resistance
WARNING:
INSULATION RESISTANCE, THE MACHINE
MUST BE AT
WINDINGS BEING
CONNECTED TO
GROUND FOR A TIME TO REMOVE ALL
RESIDUAL ELECTROSTATIC CHARGE.
GROUND SURGE
FURNISHED, BEFORE DISCONNECTING AND
ISOLATE FROM
MEGGERING.
FAILURE TO OBSERVE THESE PRECAUTIONS
MAY RESULT IN INJURY TO PERSONNEL.
16 GE Energy Motors GEEP-427-I
BEFORE MEASURING
STANDSTILL AND
TESTED MUST
THE FRAME AND TO
CAPACITORS,
LEADS BEFORE
Fig. 1. Temperature correction factor curve
GEEP-427-I Pegasus, Horizontal Induction Motor
Insulation resistance is determined by applying a dc
voltage, typically 500 or 1000 Volts, across insulation,
measuring the current flow after the voltage has been
applied for a specific length of time and then determining
the ratio of voltage to current. Because the current flow
ALL
is low, the value of insulation resistance will be great in
BE
terms of ohms. Accordingly, megohms are used as a
practical unit.
Factors affecting insulation resistance are as
follows:
IF
1. Moisture
2. Surface cleanliness of the insulation
3. Temperature
4. Length of time of applying the dc test voltage
5. Magnitude of the applied dc test voltage
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