CORE AS-OIL COOLER 3354190 - Caterpillar

Illustration 10 g03866027
Inverter Cabinet rear view
(22) Resister Assembly Compartments
(23) Retarding Grid Blower Inverter (RGBI) compartment
(24) Rectifier Assembly Compartment
Remove the covers on the rear of the Inverter Cabinet.
Many of the system components in the rear cabinet compartments are connected by wire conductors to the DC bus. Visually check the wiring, the connections, the bus bars, and the components for signs of a short to frame. Look for areas where a wire could be in contact with the cabinet frame. Look for signs of moisture or contamination in the compartments.
If signs of a short circuit are not observed, refer to the high voltage connection diagram in the back of this manual. Start disconnecting components that are connected to the DC Power Bus one at a time. Each time that a component is disconnected, use the megger to test the DC system from the contactor compartment at 2500 V. Determine if the disconnection of a specific component enabled an acceptable higher resistance between the DC bus and ground. Replace any components that are determined to be causing the problem.
If a cause is not found, methodically check the components in the front of the cabinet. Individually check all of the components that are connected to the DC Power Bus. The components mainly consist of phase modules. Visually check the connections, the bus bars, and the components for signs of a short to frame. Look for areas where a wire could be in contact with the cabinet frame. Look for signs of moisture or contamination in the compartments. Replace any components that are determined to be causing the problem. Expected Result:A cause of the ground fault condition has been found and the component that is causing the problem has been replaced. The ground fault condition is no longer present. Results:
OK - The cause of the ground fault condition has been resolved. Proceed to Test Step 5.
NOT OK - There are no obvious signs of a short to ground. All sections of the DC system have been checked and a cause of the ground fault condition has not been identified. All of the DC connected components have been checked and eliminated as a cause of the condition. Repair: Ensure that all of the DC connected components that are connected to the DC Power Bus have been checked and are OK. Ensure that the circuits in the grid system have been checked and are OK. Check the bus bars that are in the Inverter Cabinet. When the components are disconnected and the insulation test is still indicating a short to ground, a possible short circuit between the positive and the negative bus bars should be investigated. Start disconnecting section of the bus bars and recheck the status of the resistance to ground. The megger connections can be moved in order to check different sections of the bus bars.Replace any sections of the bus that are found to be faulty. If all of these steps have been followed and the insulation test is still registering a low