GE Industrial Control Systems GEEP-124-I Copyright 1997,1998 The General Electric Company, USA
14
GEEP-124-I Horizontal Induction Motor
WPI, Antifriction Bearing
Insulation resistance
WARNING:
BEFORE MEASURING
INSULATION RESISTANCE, THE MACHINE
MUST BE AT STANDSTILL AND ALL
WINDINGS BEING TESTED MUST BE
CONNECTED TO THE FRAME AND TO
GROUND FOR A TIME TO REMOVE ALL
RESIDUAL ELECTROSTATIC CHARGE.
GROUND SURGE CAPACITORS, IF
FURNISHED, BEFORE DISCONNECTING AND
ISOLATE FROM LEADS BEFORE
MEGGERING.
FAILURE TO OBSERVE THESE
PRECAUTIONS MAY RESULT IN INJURY TO
PERSONNEL.
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 is low, the value of insulation resistance
will be great in terms of ohms. Accordingly, megohms
are used as a practical unit.
Factors affecting insulation resistance are as
follows:
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
Fig. 1. Temperature correction factor curve
DLCGEEP-124-I/000, Approved, 2016-11-11, CampinasDM