BUSHING 9M4823 - Caterpillar

Discrete Diode Test
Check the Bridge Diodes for the 1400 Frame and 1600 Frame Generator
Illustration 1 g01327476
To perform this diode check, the diodes must be isolated. Refer to Illustration 1.
Illustration 2 g01327478
Attach a battery and a light to each diode in both directions to test the diode. Refer to Illustration 2.
Replace the diodes that illuminate the light bulb when wired in both directions.Check the Windings and Rotating Diodes by use of Separate Excitation
Ensure that the generator is disconnected from any external load and inspect the terminal box to check that the connections are fully tightened.
Stop the unit, disconnect, and isolate the CDVR wires.
Illustration 3 g01327528
Illustration 4 g01327530
There are two ways of creating an assembly with separate excitation. Assemble one of the following test circuits.Note: The voltage from a 12 V or a 24 V battery is too high regarding the required excitation voltage when running at rated engine speed. A rheostat must be used to adjust the required excitation current for the nominal voltage at no load. Refer to Illustration 3. Refer also to Illustration 4.As an alternative, a 12 V battery that is directly connected may be used if running the engine at low idle speed. Refer to "Dynamic" flashing.Both these systems should have characteristics which are compatible with the machine field excitation power. Refer to the nameplate.
Run the generator at the recommended speed that is used during normal operations.
Gradually increase the exciter field current by adjusting the rheostat and measure the output voltages on "L1- L2 - L3". Checking the excitation voltage and current at no load and on load. Refer to the machine nameplate or ask for the factory test report.When the output voltage is at rated value and is balanced within 1% for the rated excitation level, the machine is in working order. The fault therefore comes from the CDVR or associated wiring (that is sensing or auxiliary windings).
Rectifier Assembly Troubleshooting Checklist
Table 1
Package S/N:
Factory Claim Number
DSN
Dealer Contact - Name and Phone
External varistor check Installed (Y / N) -
Megohmmeter measurement (VDC) -
Condition (Good/Bad) -
Internal varistor check Megohmmeter measurement (VDC) -
Condition (Good/Bad) -
Diode check AC1 AC2 AC3
Forward Biased Check - Pos. (VDC) -
Forward Biased Check - Neg. (VDC) -
Reverse Biased Check - Pos. (VDC) -
Reverse Biased Check - Neg. (VDC) -
Exciter Rotor check Insulation test results (Megohms) -
Winding test results (Ohms) -
Main Rotor check Insulation test results (Megohms) -
Winding test results (Ohms) -
Other Failed Parts (Regulator, Exciter Stator, Exciter Rotor)
Failure Analysis Root Cause/Time Line of event