Troubleshooting GP Repair
wc_tx000548gb.fm 80
6.10 Checking Main and Rotor Windings
See Graphic: wc_gr003123
To check the resistance of the windings, carry out the following
procedures:
6.10.1 Stop the engine.
6.10.2 Remove the two screws which secure the end cover to the generator
and remove the end cover.
6.10.3 Disconnect the Automatic Voltage Regulator (AVR) (a).
6.10.4 Remove the screw (b) that secures the brushes and remove the
brushes.
6.10.5 Disconnect the yellow-, red-, black-, and green-marked wires (f) from
the terminal strip. On GP 2500A models, disconnect the voltage plug
(g).
6.10.6 Using the Ohms setting on the multimeter, measure the resistance of
main winding 2 by measuring across the upper two terminals (c)
(yellow and red). On GP 2500A models, measure across the red and
white wires. Also check the resistance of main winding 1 by measuring
across the two lower terminals (d) (black and green). On GP 2500A
models, measure across the brown and blue wires. Each generator
size will have a different value. Check the chart in the graphic for the
correct values; use a tolerance of +0.5/-0.0 Ohm.
• If the correct resistance is not measured, the main windings are
bad; replace the stator.
• If the correct resistance is measured, the main windings are OK,
continue.
6.10.7 Using the Ohms setting on the multimeter, measure the resistance of
the rotor winding by measuring across the slip rings (e). Each
generator size will have a different value. Check the chart in the
graphic for the correct values; use a tolerance of +1.0/-0.0 Ohm.
• If the correct resistance is not measured, the rotor winding is bad;
replace the rotor.
• If the correct resistance is measured, the rotor winding is OK.
6.10.8 If possible, the resistance of the insulation should also be checked
using a 500V megger or similar instrument. When using a megger, a
resistance value of at least 1 megohm should be obtained. Measure
between each winding group and the generator frame. If 1 megohm is
not measured, dry out the windings in a warm atmosphere and recheck
every 30 minutes until 1 megohm is obtained.
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