Manual for Induction Motors and Generators
Maintenance -
83
3BFP 000 050 R0101 REV E
Figure 7-7 Connections of the stator windings for insulation resistance measurements
a) Insulation resistance measurement for star connected winding
b) Insulation resistance measurement for delta connected winding
c) Insulation resistance measurement for one phase of the winding. The 'M
Ω
' represents the
insulation resistance meter.
After the insulation resistance measurement the winding phases must be earthed briefly in order
to discharge them.
***Following chapter for rotor type: Slip rings
7.6.4.5 Rotor winding insulation resistance measurement
The insulation resistance of the rotor winding is measured with an insulation resistance meter.
The test voltage of the rotor windings should be 1000 VDC. Required notes and measures:
•
Verify that all power supply cables are disconnected from the main supply
•
Verify the slip ring unit connection cables are disconnected from their supply
•
Verify that the frame of the machine and the stator windings are earthed
•
The shaft is earthed
•
The rotor winding phases not been tested are earthed. The rotor winding can be internally
connected in a delta or star connection. If this is the case, it is not possible to measure the
phases individually
•
The carbon brush connections are checked to be in good order
•
The measurement device is checked
•
The stator winding temperatures are measured, and considered as a reference value for the
rotor winding temperature.
The insulation resistance meter is connected between the whole rotor winding and the shaft of
the machine, see
Figure 7-8 Insulation resistance measurement of the rotor winding
performed rotor winding measurements, the rotor winding phases must be briefly earthed in
order to discharge the windings.
M
Ω
M
Ω
M
Ω
a)
c)
b)
