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Commissioning
7.1 Measures before commissioning
For a winding temperature of approx. 25° C, the minimum insulation resistances are 20 MΩ
(U ≤ 1000 V) or 300 MΩ (U > 1000 V). The values apply for the complete winding to ground.
Twice the minimum values apply to the measurement of individual assemblies.
● Dry, new windings have an insulation resistance of between 100 and 2000 MΩ, or possibly
even higher values. An insulation resistance value close to the minimum value could be due
to moisture and/or dirt accumulation. The size of the winding, the rated voltage and other
characteristics affect the insulation resistance and may need to be taken into account when
determining measures.
● Over its operating lifetime, the motor winding insulation resistance can drop due to ambient
and operational influences. Calculate the critical insulation resistance value depending on
the rated voltage by multiplying the rated voltage (kV) by the specific critical resistance
value. Convert the value for the current winding temperature at the time of measurement,
see above table.
Measuring the polarization index
1. To determine the polarization index, measure the insulation resistances after one minute
and ten minutes.
2. Express the measured values as a ratio:
PI =
Many measuring devices display these values automatically following the measurement.
For insulation resistances > 5000 MΩ, the measurement of the PI is no longer meaningful and
consequently not included in the assessment.
NOTICE
Damage to insulation
If the critical insulation resistance is reached or undershot, this can damage the insulation and
cause voltage flashovers.
● Contact the service center (Page 109).
● If the measured value is close to the critical value, you must subsequently check the
See also
Insulation resistance and polarization index (Page 63)
Limit values of the anti-condensation heating insulation resistance
The insulation resistance of the anti-condensation heating with respect to the machine housing
should not be lower than 1 MΩ when measured at 500 V DC.
66
R
R
/
insul 10 min
insul 1 min
R
/ R
(10 min)
(1 min)
≥ 2
< 2
insulation resistance at shorter intervals.
Assessment
Insulation in good condition
Dependent on the complete diagnosis of the insulation
1PC134, 1PC136 crane motors SH 132 ... 315
Operating Instructions, 02/2019, A5E43212221A
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