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Preparing The Mating Faces - Siemens 1LA8 Operating & Installation Instructions Manual

Low-voltage motor simotics tn series n-compact.
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Measuring the polarization index
1. To determine the polarization index, measure the insulation resistances after one minute
2. Express the measured values as a ratio:
For insulation resistances > 5000 MΩ, the measurement of the PI is no longer meaningful and
consequently not included in the assessment.
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 149).
● If the measured value is close to the critical value, you must subsequently check the
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.

Preparing the mating faces

Prepare the foundation faces dependent on the machine type:
● Mounting on a foundation
● Flange connection
● Wall mounting
SIMOTICS TN Series N-compact 1LA8
Operating Instructions 08/2017
and ten minutes.
PI = R
/ R
insul 10 min
insul 1 min
Many measuring devices display these values automatically following the measurement.
/ R
(10 min)
(1 min)
≥ 2
< 2
insulation resistance at shorter intervals.
– Ensure that the foundation faces are flat and free of contaminations.
– Check the dimensions of the mounting-foot holes.
– Clean the flange before installation. Ensure that the flange surfaces are flat and perfectly
– Check the geometry of the flange.
– Ensure that the wall faces are flat and free of contaminations.
– Check the dimensions of the mounting-foot holes.
– Support the machine from below, e.g. using a wall bracket or by bolting it.
Insulation in good condition
Dependent on the complete diagnosis of the insulation
5.1 Preparations for installation


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