Shaft Grounding Brushes (Optional) - Siemens 1LA8 Operating Instructions Manual

8.8.3

Shaft grounding brushes (optional)

With non-encapsulated and non-sealed shaft grounding brushes, rust may form on the
brushes' running surface on the shaft after extended breaks in operation.
Live parts
If the shaft grounding does not function correctly, the shaft can carry high voltages which do
not dissipate quickly enough when the machine comes to a standstill. This can lead to death
or serious injury as a result of electric shock, or bearing damage caused by current flowing
through the bearing.
● Regularly inspect the shaft grounding brushes and replace them if necessary.
● Keep the brushes' running surface clean: Regularly inspect the brushes' running surface
8.8.4 Measurement of the insulation resistance after an extended stoppage
Measuring the insulation resistance and polarization index (PI) provides information on the
condition of the machine. It is therefore important to check the insulation resistance and the
polarization index at the following times:
● Before starting up a machine for the first time
● After an extended period in storage or downtime
● Within the scope of maintenance work
The following information is provided regarding the state of the winding insulation:
● Is the winding head insulation conductively contaminated?
● Has the winding insulation absorbed moisture?
As such, you can determine whether the machine needs commissioning or any necessary
measures such as cleaning and/or drying the winding:
● Can the machine be put into operation?
● Must the windings be cleaned or dried?
Detailed information on testing and the limit values can be found here:
"Testing the insulation resistance and polarization index" (Page 45)
SIMOTICS TN Series N-compact 1LA8
Operating Instructions 05/2014
WARNING
and remove any rust before starting the machine up.
Operation
8.8 Stoppages
95