Note
Comment to IEEE 43
According to IEEE 43, also for winding temperatures < 40 °C, R
i
must be converted over to the
reference temperature of 40 °C.
As the minimum values for R
i
apply at 40 °C, the required R
i
values are somewhat higher for
winding temperatures below 40 °C.
Measuring the polarization index
1. To determine the polarization index, measure the insulation resistances after 1 and
10 minutes.
2. Express the measured values as a ratio:
Polarization index = R
i
10 min
/ R
i
1 min
Many measuring devices display these values automatically following the measurement.
Measuring the polarization index is not helpful for insulation resistances > 5000 MΩ, and is
therefore not included in the assessment.
R
i
10 min
/ R
i 1 min
Assessment
≥ 2
Insulation in good condition
< 2
Dependent on the complete diagnosis of the insulation
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.
• If the measured value is close to the critical value, you must subsequently check the
insulation resistance at shorter intervals.
See also
Insulation resistance and polarization index (Page 51)
Limit values of the anti-condensation heating insulation resistance
The insulation resistance of the anti-condensation heating with respect to the machine housing
must not be lower than 1 MΩ when measured at 500 V DC.
Assembly
5.2 Preparing for installation
1LE5, 1PC4 shaft heights 280 ... 355
54
Operating Instructions, 11/2022, A5E41454666A
