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Insulation resistance
The minimum insulation resistance between new, cleaned or repaired windings with reference to
ground is 10 M .
The critical insulation resistance (Recruit) is calculated by multiplying the rated voltage, e.g. 0.69 kV
AC, with the constant factor (0.5M
Recruit = 0.69 kV×0.5 M /kV = 0.345 M
Measurement
The minimum insulation resistance between the windings and ground measurement is taken at
500 V DC and at a winding temperature of 25 ºC ± 15 ºC.
The measurement of the critical insulation resistance: it should be measured with 500 V DC with
the winding at operating temperature.
Normal failure and corrective measures on insulation resistance
Cause: Might be due to high humidity. Correction: Windings must be dried.
Cause: After extended periods of operation, the minimum insulation resistance may decrease.
However as long as the measured value is not less than the Recruit values the motor will
continue to operate.
Correction: If the measured value is less than the Recruit value then the motor must be replaced
or repaired.
3.6 Temperature measurement
Temperature is an important reference index of motor running, the important parts for motor real-
time temperature, the operation state, effective prevention of master motor fault, to ensure reliable
operation is very important.
The motor temperature is influenced by cooling medium and environmental temperature.
Measurement of motor winding temperature rise, usually embedded temperature measuring
device (such as PT100), temperature measuring element through the lead wire connection
control system, the motor temperature, or using the high precision of resistance method is
founded. For measuring surface temperature of motor, should use special instruments such as
infrared thermometer to measure, measure position generally in the middle position of the motor
or eyebolt position.
Warning
when Motor is running, the surface temperature will gradually rise,
Please do not directly touch by hand, in order to avoid scald.
3.7 Converter application
/ kV):
In applications when motor torque is variable (piston-type compressor,
load for example), the inevitable result is a non-sinusoidal motor current,
whose harmonics can lead to excessive system perturbation or excessive
electromagnetic interference.
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