Note: If you are not familiar with the components and the operation of the Electric Drive System, refer to the Systems Operation, "Electric Drive System" section of this manual before performing this procedure. A knowledge of the components in the system and how the components are connected in the system can aid in determining the location of a fault to ground.
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| Illustration 1 | g06375618 |
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Ground fault detection system schematic | |
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| Illustration 2 | g03866092 |
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Ground fault detection components (1) Ground fault detection sensor - location: crowbar compartment (2) Shunt resistor - location: crowbar compartment | |
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| Illustration 3 | g03866090 |
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Ground fault detection components (3) Discharge resistor assembly - location: upper rear left-hand cabinet compartment | |
Insulation of the system electrical conductors provide the isolation between the conductors and frame ground. A ground fault in a power system occurs when the insulation deteriorates to a condition where a detectable amount of electrical current is “leaked” to frame ground. The greater the degree of breakdown in the insulation or the isolation, the greater the amount of current leakage to ground.
A small amount of ground fault leakage is normally present in a power system and is expected in the system. A small amount usually does not result in a problem in the system until the amount of leaked current to ground approaches a level where damage to system components can occur.
An EID 1184 "AC Ground Fault Event" is activated when the ground fault detection system has detected a ground fault in the AC section of the drive train system. The EID 1184 event code can be activated by either the "Motor 1" ECM or the "Motor 2" ECM as a "Level 2 Ground Fault Event" or a "Level 3 Ground Fault Event".
The "Discharge Resistor Assembly" that is connected between the DC positive bus and the DC negative bus is used in the ground fault detection system. For actual ground fault detection, the ground fault detection sensor is connected between the resistor common connected center point of the voltage divider circuit and the intentional frame ground 1 connection in the crowbar compartment. This configuration effectively connects the voltage sensor to the frame ground reference center point or “neutral point” of the "DC Power Bus".
Note: In the high-voltage section of the "Inverter Cabinet", the "Intentional Frame Ground 1" connection is the only ground connection (through resistors) between the DC Power Bus and frame ground . This ground connection must be disconnected before any insulation testing is performed for components in the "Inverter Cabinet".
When a ground fault occurs, the leakage of AC current to frame ground will cause an AC frequency on the ground reference center point. This AC frequency is detected by the voltage sensor and the ECMs as a deviation from the normal frame ground reference point. The amplitude of the frequency will be displayed on the "Advisor" or in Cat® ET as a ground fault percentage. The detected amount of ground fault leakage will determine if the event is activated as a "Level 2" event or a "Level 3" event.
The percentage range that can be displayed for an AC ground fault is 0 percent to 100.0 percent.
The following AC ground fault percentage values and the indications are:
- 0 to 49.9 percent - The amount of detected AC ground fault leakage is in the acceptable range. No Events will be activated. Normal machine operation can continue.
- 50.0 percent to 99.9 percent - The amount of AC ground fault leakage is elevated. The ECM will activate a "Level 2 AC Ground Fault Event". Machine operation can continue. If the "Level 2 AC Ground Fault Event" remains active for more than 2 hours, action should be taken to determine the cause of the problem.
- 100.0 percent or greater - A high level of AC ground fault leakage has been detected. An immediate safe shutdown of machine operation is required. At the detected level of ground fault leakage, system components can be damaged if machine operation continues.
The components in the electric drive train system that could be involved when an E1184 "AC Ground Fault Event" is active are:
- The generator or the high-voltage three-phase generator cables.
- The traction motors or the high-voltage three-phase motor cables.
- The grid blower motor or the three-phase cables between the grid blower motor and the "Retarding Grid Blower Inverter".
- The internal AC section of the "Retarding Grid Blower Inverter".
Points to consider before performing these procedures:
- The truck operating conditions at the time of AC ground fault activation can provide a good indication of what part of the system the ground fault is located. For example, when the truck is traveling, the generator and the drive motors are active. When the truck is in the "Retarding" mode, the generator, the drive motors and the grid blower motor are active. When the truck is in the "Engine Performance Test" mode, the generator and the grid blower motor are active. If the AC ground fault is only active when in the "Retarding" mode or in the "Engine Performance Test" mode, the indication is that grid blower motor and the cables should be tested first. This type of testing will be conducted in one of the first steps of the procedure.
- While not as likely to cause an AC ground fault, moisture in the "Retarding Grid Assembly" can be a common cause of ground faults. If the machine has recently been washed or has been parked in a wet environment before the ground fault event has been activated, use the "Advisor" to run the "Grid Dry Mode" before other causes are investigated.
- Moisture at a connection point or in a component can be a common cause of faults to frame ground. If the machine has recently been washed or has been operated in a wet environment before this ground fault event has been activated, check the condition of the connectors and the seals. Ensure that moisture has not entered any of the AC components including the generator, the drive motors, or the grid blower motor. If moisture is detected in any of the AC components, thoroughly clean and dry the wet components.
- Excessive dirt or contamination around connectors or components can cause a fault to frame ground. If a maintenance procedure has recently been performed involving electrical components or conductors and the ground fault event was activated, check for dirt or contamination at the connections. Connectors and connector enclosures must be free of dirt, dust, and other forms of contamination. If any of the high-voltage connections in the "Inverter Cabinet" or in the drive train system components require cleaning, do not use solvents or detergents. Use clean air to remove dry contaminants. Use isopropyl alcohol or a solution that contains at least 90 percent isopropyl alcohol to clean the contacts.
- A "Level 3" ground fault may leave visual evidence of a short circuit in the area of the fault. A thorough visual check of the areas where the fault could possibly occur if the first action that is taken after the DC voltage is verified as discharged in the Inverter Cabinet. Look for damaged insulation, damage at the connection points or discoloration on the component frame.
- A resistance of 2 mega ohms is the low threshold that is considered to be an acceptable level of insulation resistance for wire insulation, bus bar isolation, motor windings, or generator windings. When these components are in good condition, the insulation resistance to ground will be much greater than 2 mega ohms. When the insulation of a conductor or a component winding measures above 2 mega ohms by a small margin, the indication is that the insulation has deteriorated to a level that is adequate, but is not considered to be in good condition. Consideration should be given to replacement or repair of a conductor or a component that tests at greater than 2 mega ohms of insulation resistance by a small margin.
- The ground fault detection sensor provides a signal to each motor control ECM. Both of the ECMs should activate the same ground fault event. If only one ECM has activated the ground fault event, refer to the Troubleshooting, "MID 169/170 - CID 3047 - FMI 03" procedure in this manual for the ECM that has not activated the ground fault event.
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| Illustration 4 | g01975173 |
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5K V Insulation Tester (Megohmmeter or "megger") | |
Note: When troubleshooting a suspected fault to ground in the system, a 5K V Insulation Tester, also called a Megohmmeter or "megger", will be used to check the integrity of the insulation for the conductors and components in the system. The insulation tester can test the components at a maximum of 5000 V. Do not test the insulation resistance of any of the conductors or components at greater than 2500 V. Some components can only be tested at a lower voltage. Follow the instructions for the test voltage to use when testing the insulation. Damage to the components can result if the insulation is tested at too high of a voltage.
The user must read the operating instructions for the 5K V Insulation Tester and become familiar with the operation of the "megger" before using the tool. The 5K V Insulation Tester will be referred to as the "megger" in the following procedures.
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| Illustration 5 | g03855047 |
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| Illustration 6 | g03855099 |
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Inverter Cabinet high-voltage compartments that may require opening for the AC ground fault troubleshooting procedures. (4) "Retarding" contactor compartment (high voltage) (5) "Retarding" grid system cable connection compartment (high voltage) (6) High-voltage cable entry compartment (high voltage) (7) Generator and traction motor cable connection compartment (high voltage) (8) "Retarding Grid Blower Inverter" compartment | |
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The Power Train Electric Drive System will contain hazardous voltage levels during machine operation and for a short period of time after engine shutdown. Do not remove any covers that will expose energized high voltage electrical components while the engine is operating. Any type of maintenance on the following components can only be performed after the Power Train Electrical System Service Shutdown procedure has been followed:
Failure to follow these instructions could result in personal injury or death. |
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In order to avoid the buildup of hazardous live voltages on the exposed surfaces, all grounding wires and grounding straps must be properly connected at all times during engine operation. Any disconnected grounding wires, including the grounding wires for all high voltage components and the grounding strap for the inverter cabinet must be properly reconnected before the engine is started. Failure to follow these instructions could result in personal injury or death. |
Note: Use the systems schematics pages in this manual for a reference to identify the high-voltage connections for the AC components in the system.
Test Step 1. LEVEL 2 AC GROUND FAULT PROCEDURE
If the "Level 2", E1184, "AC Ground Fault Event" is active or if moisture has entered the grid blower motor, the generator, or the traction drive motors, follow these steps to try to resolve the problem:
The key start switch and the disconnect must be in the OFF position to begin these procedures.
If the "Level 2", E1184, "AC Ground Fault Event" is active or if moisture has entered the grid blower motor, the generator, or the traction drive motors, follow these steps to try to resolve the problem:
The key start switch and the disconnect must be in the OFF position to begin these procedures.
Note: If required to open a high-voltage compartment or enclosure for this procedure, use the high-voltage meter to verify that the voltage between the DC bus connections or the AC connections is less than 50.0 V before any other action is taken.
A. First visually inspect the high-voltage cables from the generator to the "Inverter Cabinet". Repetitive AC ground faults from these cables touching frame/tubes/hoses will cause main rectifier failures.
B. Stop machine operation and run the "Grid Dry Mode". Check the status of the ground fault event.
C. Determine if any type of moisture or contamination may have entered the grid blower motor, the generator, or the traction motors. This condition could be caused by washing, operating in the rain, snow, or other means. If contamination or moisture in these components is suspected, check all high-voltage connections for moisture, dirt, or other forms of contamination. Clean any contaminated areas or dry any wet areas. All connections must be clean, dry, and tight. Install the covers and check the status of the ground fault event.
D. If the Engine has not recently been in operation, operate the engine at high-idle for 5 minutes. Check the status of the ground fault event.
Expected Result:
The "Level 2", E1184, "AC Ground Fault Event" is no longer active.
Results:
OK -The "Level 2", E1184, "AC Ground Fault Event" is no longer active. The ground fault was probably caused by a temporary condition that is no longer present.STOP
NOT OK -The "Level 2", E1184, "AC Ground Fault Event" is still active. The condition that is causing the ground fault to be activated is still present. Proceed to Test Step 2.
Test Step 2. DETERMINE THE LOCATION OF THE LEVEL 3 AC GROUND FAULT
A. First visually inspect the high-voltage cables from the generator to the inverter cabinet. Repetitive AC ground faults from these cables touching frame/tubes/hoses will cause main rectifier failures.
B. Attempt to operate the truck in the travel mode in the forward direction or the reverse direction. Check and record the status of the "Level 3", E1184, "AC Ground Fault Event".
C. Attempt to operate the truck in a slow travel mode with the "Retarding" mode active. Check and record the status of the "Level 3", E1184 AC Ground Fault Event.
D. Stop the truck. Run the Cat® ET "Engine Performance Test". Check and record the status of the "Level 3", E1184, "AC Ground Fault Event".
E. Use Limp Mode to disable one motor at a time and check the status of the AC ground fault.
Expected Result:
Results:
OK - The status of the "Level 3", E1184, "AC Ground Fault Event" has been recorded during the listed machine operating conditions.
Repair: Check the following conditions and indications to determine what section of the AC system to test first.
- If the "Level 3", E1184, "AC Ground Fault Event" is active during machine travel AND when the "Retarding" mode is active, the indication is that the traction drive motors or the three-phase motor cables are the most likely locations of the fault to ground. Start the procedure at the "INSULATION TESTING OF THE TRACTION DRIVE MOTORS AND THE CABLES" Test Step.
- If the "Level 3", E1184, "AC Ground Fault Event" is active when the machine is in the "Retarding" mode AND when the engine Performance Test is run, the indication is that the grid blower motor or the three-phase blower motor cables are the most likely locations of the fault to ground. Start the procedure at the "INSULATION TESTING OF THE GRID BLOWER MOTOR AND CABLES" Test Step.
- If the "Level 3", E1184, "AC Ground Fault Event" is active always during machine operation regardless of the mode that the truck is operated in, the generator or the three-phase generator cables are the most likely locations of the fault to ground. Start the procedure at the "INSULATION TESTING OF THE GENERATOR AND THE CABLES" Test Step.
STOP
Test Step 3. PERFORM THE POWER TRAIN ELECTRIC DRIVE SYSTEM SERVICE SHUTDOWN PROCEDURE
This procedure will require entries into compartments that contain high-voltage components.
When an area that contains high-voltage components must be entered, the "Power Train Electrical System Service Shutdown" procedure must be performed before the cover for the compartment or housing is removed.
Results:
OK -The "Power Train Electrical System Service Shutdown" procedure has been performed, the voltage is verified as discharged, and the jumper wire is in place.
Test Step 4. INSULATION TESTING OF THE TRACTION DRIVE MOTORS AND THE CABLES
A. Turn the key start switch and the battery disconnect switch to the OFF position.
B. At the "Inverter Cabinet", remove the cover for the generator and traction motor cable connection compartment. Use the high-voltage meter to measure for any voltage between the DC positive and negative bus connections or the AC connections in these compartments.
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| Illustration 7 | g03855379 |
C. Insure all voltages are 50 V or less.
D. Conduct a thorough visual check of the AC three phase cables that are connected between the traction drive motors and the "Inverter Cabinet". Check for insulation that is thin or worn through due to abrasion with another machine component. Look for areas where the insulation may be faulty due to other forms of damage. Look for areas where there may be a visual indication of arcing or discoloration on the machine or component frame.
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| Illustration 8 | g03855559 |
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Using the "megger" to test one of the three "Traction Drive Motor 1" phases (9) Red positive clip connected to one of the three phase cables (10) Black negative clip connected to the "Ground 1" lug at the front of the crowbar compartment | |
E. Connect the "megger" for testing the insulation of the "Traction Motor 1" and the cables. Connect the red positive clip to one of the motor's three phase cables. Connect the black negative clip to the ground lug on the side of the compartment. This test will check the insulation resistance of the motor cable and the motor winding.
F. Ensure that all personnel are not in contact with any of the AC conductors. Ensure that no one is in the rear axle housing and the housing cover is closed. Ensure that all disconnected motor cables are not in contact with any of the bus conductors.
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| Illustration 9 | g01980735 |
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Testing the insulation of the drive motor cables and windings at 2500 V. This test detected a resistance of 303.1 mega ohms to frame ground | |
Note: In the next step, the insulation resistance of the motor cable and the motor windings will be tested. A test on one of the motor cables and windings will effectively test all three phases of the motor cables and windings. The windings are internally connected in the motor.
G. Set the dial on the "megger" to 2500 V. Press the “START/STOP” button on the "megger" to start the test. Test the motor cable and the motor winding at 2500 V. Continue the test until the test voltage has stabilized for 10 seconds. Press the “START/STOP” button to stop the test. The "megger" will discharge the system. Wait until the voltage readout on the "megger" display is 0 V.
H. To repeat the insulation test for "Motor 2", repeat steps “D”, “E”, “F” and “G”. Once the insulation test for "Motor 2" has been completed, proceed to the "Expected Results".
Expected Results: The insulation test for one or both of the traction drive motors and cables has indicated a resistance to ground of less than 2 mega ohms.
Results:
YES -The insulation test is indicating that there is a fault to ground. The fault is in either a motor cable or in a motor winding in at least one of the drive motors that was tested. Less than 2 mega ohms of resistance is not an acceptable insulation resistance for drive motor operation.
Repair -
The location of the ground fault has been isolated to either a motor cable or to a motor winding.
Both of the traction drive motors and both sets of three-phase cables should be tested individually. Individual tests will determine the condition of the insulation for each component that is tested. The threshold of 2 mega ohms of resistance to ground is what is considered sufficient for continued machine operation. An insulation resistance that is at this low threshold or just above this threshold is an indication that the insulation has deteriorated to a level that is adequate, but is not in good condition.
To determine if the cable is causing the problem or the motor winding is grounded, disconnect the three-phase cable connections from the involved motor in the rear axle housing. Position the three cable ends in a position where contact with the axle housing or any other surface in the housing cannot occur. The cable ends must be isolated.
Ensure that the other end connections for the cables in the "Inverter Cabinet" remain isolated from the cabinet frame and from each other.
In the rear axle housing, test each cable individually. Connect the red (positive) clip to a cable end and the black (negative) clip to a good axle housing ground. Ensure that no one is near the cable ends in the cabinet or in the axle housing.
Test each cable individually at 2500 V. Press the "START/STOP" button on the "megger" to start the test. Continue the test until the test voltage has stabilized for 10 seconds. Press the "START/STOP" button to stop the test. The "megger" will discharge the cable. Wait until the voltage readout on the "megger" display is 0 V.
The resistance between the cable and ground must be greater than 2 mega ohms for the cable to pass the test. Replace any cable that does not pass the test.
Regardless of whether any cables are faulty, an insulation test of both of the drive motors must be done. This test will check the integrity of the winding insulation.
At the motor that has the cables disconnected, connect the "megger" red positive clip to one of the winding connections on the back of the motor. Connect the black (negative) clip to a good frame ground on the axle housing or on the motor housing.
Test the motor windings at 2500 V.
The resistance between the motor windings and ground must be greater than 2 mega ohms for the motor to pass the test. If a drive motor does not pass the test, call the "Dealer Solutions Network" (DSN). Report the findings of this insulation test. The DSN personnel will provide instructions on the action that must be taken to resolve this problem.
Test the other drive motor and cables in the same manner to determine the integrity of the insulation.
If the insulation test of a traction motor winding registers a marginal resistance above 2 mega ohms, the insulation is adequate for machine operation, but is not in good condition. Call the DSN to report the results of this test and to discuss any further action that should be taken.
STOP
NO -The insulation tests of the traction drive motors and the cables are not indicating a fault to ground. The tests measured a resistance of much greater than 2 mega ohms. There is no indication of a ground fault in the drive motors section of the AC system.
Repair: The insulation test of the traction drive motors and the cables has not indicated a fault to ground in this system. The "Generator" system and the grid blower motor system will need to be tested.
Proceed to Test Step 5.
Test Step 5. INSULATION TESTING OF THE GENERATOR AND THE CABLES
At the "Inverter Cabinet" cable connection compartment, the three-phase cable connections for the "Traction Motor 1" and "Traction Motor 2" cable connections remain disconnected.
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| Illustration 10 | g03855379 |
Note: "Insure Frame Ground 1" remains disconnected / isolated.
A. In the cable connection compartment, disconnect the generator three-phase cable connections from the bus bars. Place a non-conductive material between the cables ends to prevent contact with the bus bars and the cabinet frame.
B. Conduct a thorough visual check of the AC three-phase generator cables that are in the cabinet. Check for insulation that is thin or worn through due to abrasion with another machine component. Look for areas where the insulation may be faulty due to other forms of damage. Look for areas where there may be a visual indication of arcing or discoloration on the machine or component frame.
C. Connect the "megger" for testing the insulation of the generator cables and the generator stator windings. Connect the red (positive) clip to one of the three-phase cables for the generator. Connect the black (negative) clip to a good frame ground point.
D. Ensure that all personnel are not in contact with any of the AC conductors. Ensure that no one is in the area of the generator. Ensure that all disconnected generator cables are not in contact with any of the bus conductors.
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| Illustration 11 | g01981773 |
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Testing the isolation of the generator system at 2500 V - This test detected a resistance of 364.9 mega ohms to frame ground | |
E. Set the dial on the "megger" to 2500 V. Press the "START/STOP" button on the "megger" to start the test. Test the generator cable and the generator windings at 2500 V. Continue the test until the test voltage has stabilized for 10 seconds. Press the "START/STOP" button to stop the test. The "megger" will discharge the system. Wait until the voltage readout on the "megger" display is 0 V.
Test Results:
1. If the test of the generator windings and cables indicated a resistance that is much greater than 2 mega ohms, proceed to the "NO" result.
2. If the insulation test of the generator windings and cables indicated a resistance to ground close to or below 2 mega ohms, each of the three-phase cables will need to be tested individually. Determine if one of the cables is faulted to ground or if a generator winding is faulted to ground. Proceed to Step “F”.
F. Open the high-voltage enclosure on the top of the generator. Disconnect the three-phase cable connections from the generator connections. Use a non-conductive material to isolate the three cable ends to prevent contact with the generator connections.
G. At the front of the "Inverter Cabinet", repeat Steps “C”, “D ”, and “E” to test the now disconnected cables. Test each of the three cables individually. Regardless of whether a cable is found to have faulty insulation, continue to the next step. Test the condition of the generator winding insulation.
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| Illustration 12 | g03855572 |
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Insulation testing the generator windings (11) Red (positive) clip of the insulation tester connected to a generator winding connection plate (12) Black (negative) clip of the insulation tester connected to a generator ground point (bolt) (13) The three-phase cables disconnected from the connection plates and insulated with rubber to isolate the cable ends from the generator contacts. | |
At the generator high-voltage enclosure, connect the "megger" red (positive) clip to one of the generator winding connection plates. Connect the black (negative) clip to a good frame ground on the generator housing.
Expected Result:
At least one of the insulation tests has indicated a resistance to ground of less than 2 mega ohms. The measurement was registered during a cable test or during the testing of the generator windings.
Results:
The insulation test is indicating that there is a fault to ground in either a generator cable or in a generator winding. Less than 2 mega ohms of resistance is not an acceptable insulation resistance for generator operation or cable operation.
Repair:
The location of the ground fault has been isolated. Either the generator cable or a generator winding registered the low resistance to ground.
The threshold of 2 mega ohms of resistance to ground is considered sufficient for cable insulation or for generator winding insulation. An insulation resistance at or just above this low threshold indicates that the insulation has deteriorated to an adequate level, but is not in good condition.
If one or more of the cables registered a resistance close to or less than 2 mega ohms to ground, the cable must be replaced.
If the insulation test of the generator windings registers a resistance a small margin above or below 2 mega ohms, call your dealer "Technical Communicator". Report the findings of these insulation tests. The "Technical Communicator" will provide instructions on the action that must be taken to resolve this problem.
STOP
NO -The insulation tests of the generator and the cables are not indicating a fault to ground. Each of the insulation tests measured a resistance of much greater than 2 mega ohms. There is no indication of a ground fault in the generator section of the AC system.
Repair: The insulation test has not indicated a fault to ground in this system. The grid blower motor system will need to be tested.
Proceed to Test Step 6.
Test Step 6. INSULATION TESTING OF THE GRID BLOWER MOTOR AND CABLES
At the "Inverter Cabinet", the three-phase cable connections for the "Motor 1", "Motor 2", and the generator cable connections, remain disconnected.
A. At the rear of the "Inverter Cabinet", remove the cover for the "Retarding Grid Blower Inverter" compartment. Use the high-voltage meter to measure for any voltage between the DC positive and negative bus connections or the AC connections in the compartment.
B. Conduct a thorough visual check of the AC three-phase grid blower motor cables that are connected to the "Retarding Grid Blower Inverter". Check for insulation that is thin or worn through due to abrasion with another machine component. Look for areas where the insulation may be faulty due to other forms of damage. Look for areas where there may be a visual indication of arcing or discoloration on the machine or component frame.
Note: ( 360-2920 Converter As) The converter assembly is also called a "Retarder Grid Blower Inverter". A resistance of 500,000 ohms to ground is the low threshold for the "Retarder Grid Blower Inverter". If any tests are getting down close to 500,000 ohms of resistance to ground, there is a problem. The test should show 500,000 ohms or greater resistance to ground.
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| Illustration 13 | g03855576 |
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"Retarding Grid Blower Inverter" connections (14) Three-phase cables that are used to supply AC power to the grid blower motor | |
C. At the "Retarding Grid Blower Inverter", disconnect the "BM-A", "BM-B", and "BM-C" three-phase cables that supply the AC power to the "Grid Blower Motor". Position the cable ends where contact with each other, the housing "Retarding Grid Blower Inverter", or with the cabinet frame cannot occur.
D. Use a multimeter to measure the resistance between each of the "Retarding Grid Blower Inverter" phase lugs and the "Retarding Grid Blower Inverter" housing:
1. If all three resistance measurements are high - greater than 2 mega ohms or “infinite”, the "Retarding Grid Blower Inverter" is most likely not causing the problem. Proceed to the next Test Step “E”.
2. If any of the three resistance measurements is less than 2 mega ohms, there is a problem inside the "Retarding Grid Blower Inverter". Stop the procedure and contact your dealer "Technical Communicator" for possible consultation with Caterpillar. Indicate the steps that have been taken to find the cause of this problem and the findings that have been discovered.
E. Connect the "megger" for testing the insulation of the blower motor cables and the grid blower motor stator windings. Connect the red (positive) clip to one of the disconnected blower motor cables. Connect the black (negative) clip to a good cabinet frame ground point.
F. Ensure that all personnel are not in contact with any of the AC conductors. Ensure that no one is in the area of the grid blower motor or the motor connection in the front of the cabinet.
G. Set the dial on the "megger" to 1000 V. Do not test the insulation of the grid blower motor and cables at greater than 1000 V. Press the "START/STOP" button on the "megger" to start the test. Test the motor cable and the grid blower motor windings at 1000 V. Continue the test until the test voltage has stabilized for 10 seconds. Press the "START/STOP" button to stop the test. The "megger" will discharge the system. Wait until the voltage readout on the "megger" display is 0 V.
Test Results:
A. If the insulation test of the "Grid Blower Motor" and cables indicated a resistance to ground much greater than 2 mega ohms, proceed to the “NO” result.
B. A resistance to ground, very close to 2 mega ohms or below 2 mega ohms, indicates each of the three-phase cables needs to be tested individually. The tests will determine if one of the cables is faulted to ground or if a blower motor winding is faulted to ground. Proceed to Step “G”.
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| Illustration 14 | g03855577 |
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Grid blower motor connection enclosure (15) Three-phase cables that are used to supply AC power to the grid blower motor from the "Retarding Grid Blower Inverter" (16) Three-phase cables that go out to the grid blower motor | |
H. Remove the cover from lower connection enclosure on the front of the grid assembly. Disconnect the three phase cables (15) that are used to supply AC power to the grid blower motor from the "Retarding Grid Blower Inverter". Position the cable ends where contact with each other or with the frame cannot occur. If necessary, insulate the cable ends to avoid contact with any other surface. Ensure that the other end connections for the cables in the "Rear Inverter Cabinet" compartment are still isolated from the cabinet frame and from each other.
I. At either end of the disconnected cables, connect the "megger" for testing the insulation of one of the blower motor cables. Connect the red (positive) clip to one of the disconnected "Blower Motor" cables. Connect the black (negative) clip to a good frame ground point.
J. Ensure that all personnel are not in contact with any of the AC conductors. Ensure that no one is in the area of the "Grid Blower Motor" or the "Retarding Grid Blower Inverter" in the rear of the cabinet. Set the dial on the "megger" to 1000 V. Do not test the insulation of the cable at greater than 1000 V. Test the insulation of each individual cable.
K. After testing the insulation of each of the blower motor cables, test the insulation of the grid blower motor windings. At the lower connection enclosure on the grid assembly, connect the red (positive) clip to one of the phase connections plates or to the cable end. Connect the black (negative) clip to a good frame ground point.
L. Set the dial on the "megger" to 1000 V. Do not test the insulation of the grid blower motor at greater than 1000 V. Test the motor winding insulation.
Expected Result:
At least one insulation test indicates a resistance to ground of less than 2 mega ohms during a cable test or blower motor windings test.
Results:
YES - The insulation test is indicating that there is a fault to ground in either a motor cable or in a "Grid Blower" motor winding. Less than 2 mega ohms of resistance is not an acceptable insulation resistance for "Grid Blower" motor operation or cable operation.
Repair:
The location of the ground fault has been isolated to either a blower motor cable or to a blower motor winding.
The threshold of 2 mega ohms of resistance to ground is what is considered sufficient for cable insulation or for grid blower motor winding insulation. An insulation resistance at, or just above, this low threshold indicates that the insulation has deteriorated to an adequate level, but is not in good condition.
If one or more of the blower motor cables has registered a low resistance to ground, the cable must be replaced. The cables can be disconnected in the "Retarding Grid" system cable connection compartment on the front of the "Inverter Cabinet". Each section of the cable can be tested at this location to determine the section of cable with the faulty insulation.
If the insulation test of the grid blower motor windings registers a small margin below or above 2 mega ohms, contact your dealer "Technical Communicator". Report the findings of these insulation tests. The "Technical Communicator" personnel will provide instructions on the action required to resolve this problem.
STOP
NO - The insulation tests of the "Grid Blower" motor and the cables are not indicating a fault to ground. The tests measured a resistance of much greater than 2 mega ohms. There is no indication of a ground fault in the "Grid Blower" motor section of the AC system.
Repair: The "Grid Blower" motor system does not appear to be the location of the AC ground fault. The insulation test has not indicated a fault to ground in this system.
Proceed to Test Step 7.
Test Step 7. CHECK THE STATUS OF THE GROUND FAULT EVENT
A. Reconnect all the bus bars, connections, and components disconnected during the steps of this procedure. Tighten all connections to the proper torque.
B. Verify that the three phase cables for the generator system, the traction motor system, and the grid blower motor system are properly connected and torqued.
C. No instruction was given to disconnect any ground wires or ground straps. Verify that no ground wires or ground straps are disconnected. Do not start the engine with any ground wires or ground straps disconnected.
D. Verify that any jumper wires that were connected have been removed.
E. Install all compartment covers, protective covers, or enclosure covers that are removed. Check all the "Inverter Cabinet" compartment cover seals. The seals should be intact and in good condition. Verify that all the "Inverter Cabinet" compartment covers are installed and the bolts are properly tightened.
F. Turn the battery disconnect switch to the ON position. Start the engine and run the engine at low idle.
G. Determine if the E1184, "AC Ground Fault Event", is active.
Expected Result:
The E1184, "AC Ground Fault Event", is not active.
Results:
OK -The E1184, "AC Ground Fault Event", is not active. The problem does not exist currently.
Repair:
The initial ground fault could have been caused by a temporary problem that is no longer present. The problem could have been caused by a problem at one of the connections that was disconnected and reconnected.
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NOT OK -The E1184, "AC Ground Fault Event", is still active. The problem has not been corrected.
Repair:
Verify that all the steps that were outlined in this procedure were followed. Verify that all the sections of the system that could be checked for a ground fault were checked. If all these steps have been followed an ECM is still activating the ground fault event, contact your "Dealer Technical Communicator" for possible consultation with Caterpillar. Indicate the machine conditions that were present when the event was activated. Indicate the steps that have been taken to try to find the cause of this problem. Indicate findings that have been discovered during the testing procedures. The "Technical Communicator" personnel will provide instruction on the actions that must be taken to resolve this problem.
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