Bearing Maintenance; Bearing Insulation And Bearing Insulation Resistance Check; Procedure - ABB AMA Series Manual

7.5.3.6 Bearing maintenance

7.5.4 Bearing insulation and bearing insulation resistance check

7.5.4.1 Procedure

3BFP 000 050 R0101 REV E
Re-greasing intervals for greases fulfilling the required properties other than the ones mentioned
above should be halved.
Rolling bearing grease for extreme temperatures
If the bearing operating temperature is above 100°C (210°F), please consult the manufacturing
ABB factory for suitable greases.
The lifetime of the bearings is likely to be shorter than the lifetime of the electrical machine.
Therefore, the bearings will have to be changed periodically.
The maintenance of rolling bearings requires special care, tools and arrangements as to ensure a
long lifetime of newly fitted bearings.
During bearing maintenance, ensure that:
• No dirt or foreign debris is allowed to enter the bearings at any time during the
maintenance
• The bearings are washed, dried and pre-greased with suitable and high quality rolling
bearing grease before assembly
• The disassembly and mounting of the bearings does not damage the bearings. The bearings
must be removed by using pullers and fitted by heating, or using special tools for the
purpose.
If there is a need to change bearings, please contact ABB After Sales. See After Sales contact
information in Chapter 9.1.5 After Sales contact information.
The bearing insulation resistance check is a maintenance operation made primarily in the
factory during the final assembly and testing. It should also be made during all comprehensive
overhauls of the machine. Good insulation is necessary in order to eliminate the possibility of
circulating bearing currents, which might be induced by shaft voltages. The insulation of the
non-drive end bearing cuts the path of the bearing current and thus eliminates the risk of bearing
damages due to bearing currents.
Both the shaft ends should not be insulated from the frame, as an electrically floating shaft
would have an unknown electrical potential compared to the surroundings and would, therefore,
be a potential source of damage. However, to make the testing of the non-drive end bearing
insulation easier, the drive end bearing is also often insulated. This insulation is short-circuited
by an earthing cable during normal operation; see Figure 7-2 D-end bearing earthing cable.
NOTE: Not all machines are equipped with insulated bearings.
NOTE: Machines with insulated bearings have a sticker indicating the insulated bearing.
For machines with an insulated drive end bearing, the short-circuit earthing cable in the drive
end bearing must be removed prior to commencing the non-drive end bearing insulation
resistance test. If the drive end bearing is not insulated, it is required to perform the non-drive
Manual for Induction Motors and Generators
Maintenance - 75