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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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| Illustration 1 | g06424030 |
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View of the rear of the inverter cabinet (A) Ground Fault Voltage Sensor (B) DC Bus Voltage 1 Sensor (DVC1) (C) DC Bus Voltage 2 Sensor (DVC2) | |
This procedure checks the operation of the system voltage sensors. There are three sensors in the system: "DC Power Bus Voltage Sensor #1 (DVC1)", "DC Power Bus Voltage Sensor #2 (DVC2)", and the "Ground Fault Voltage Sensor".
Three identical voltage sensors are used in the "Inverter Cabinet". The "DC Bus Voltage Sensor #1 (DVC1)" and the "DC Bus Voltage Sensor #2 (DVC2)" determine the voltage of the DC Bus. The "Ground Fault Detection Sensor" detects system ground faults.
The DC Bus Voltage Sensors #1 and #2 each create an electrical current output proportional to the voltage of the DC Bus. The output current circuits are connected to a 150 ohm burden resistor at the terminal blocks. The voltage drop across those resistors, from each voltage sensor, is monitored by both "Motor Control 1 ECM" and "Motor Control 2 ECM". Each ECM uses this voltage input to determine the voltage of the DC Bus.
Perform this procedure if the DC Bus Voltage Sensors #1 or #2, or the Ground Fault Detection Sensor, are suspected of a fault. Faulty voltage sensor operation is indicated by the following:
- A motor ECM activated a diagnostic code for a specific voltage sensor circuit. The troubleshooting procedure for the specific diagnostic code is performed before this procedure is performed. The diagnostic code procedure will refer to this procedure, when the voltage sensor is the suspected cause of the active fault.
- A motor ECM activated an event code that could be caused by a malfunctioning voltage sensor. The event could be a high, or a low "DC Power Bus Voltage" Event. The event code procedure will refer to this procedure, when an event is activated that could be caused by a faulty voltage sensor.
Note: A 243-3141 (5-KV) Insulation Tester is required for this procedure.
Before the test procedure can begin, the Power Train Electrical System Service Shutdown procedure must be performed. Verify that the voltage in the power train system components is discharged.
Refer to the Troubleshooting, "Electrical Shutdown and Voltage Discharge" section of this manual in order to perform the Power Train Electrical System Service Shutdown procedure.
Before performing this procedure, ensure that the Battery Disconnect Switch is in the OFF position. Lock and Tag-Out the Battery Disconnect Switch.
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| Illustration 2 | g01392482 |
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This Electrocution Hazard safety message is posted on every compartment and component cover where High Voltage could be present. A Power Train Electrical System Service Shutdown procedure must be performed before any cover is removed from any components or compartments bearing this Electrocution Hazard safety message. | |
Testing the DC Power Bus Voltage Sensor #1 (DVC1)
- Verify that the key start switch and the battery disconnect switch are in the OFF position.
- Remove the compartment cover and identify the DVC1 Sensor (B).
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Illustration 3 g06424034 View of the rear of the inverter cabinet
(B) DC Bus Voltage 1 Sensor (DVC1)
(1) DC positive connection (DCP)
(2) DC negative connection (DCN) - Use a high-voltage meter to measure the voltage between the two DC Bus bars located in the compartment. Check for voltage between the voltage sensor high-voltage connections. Verify less than 50.0 VDC exists between the DC connections before continuing to the next step.
- Examine the low voltage circuit wires connected. Ensure that the wires are in good condition and the end connections for the power, ground, and signal wires are clean and securely connected.
- Disconnect the DCP (1) and the DCN (2) connections from the DC Power Bus Voltage 1 Sensor (B)
- Connect the positive lead from the "Insulation Tester" to the positive terminal (1) on the voltage sensor.
- Connect the negative lead from the "Insulation Tester" to the negative terminal (2) on the voltage sensor.
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Illustration 4 g06424041 DC Power Bus Voltage 1 Sensor (DVC1) connections Note: In the next step, when the "Battery Disconnect" is ON, and the engine "Lockout Control" switch is moved to the ON position: The 24 V control system voltage will energize regardless of the status of the key start switch.
- Energize the 24 V control system by moving the battery disconnect to the ON position and the engine "Lockout Control" switch to the ON position.
- Use the "Insulation Tester" to supply 500.0 VDC to the voltage sensor. Use the "Advisor" or Cat® ET to monitor the "DC Power Bus Voltage 1" status.
- Use the "Insulation Tester" to supply 1000.0 VDC to the voltage sensor. Use the "Advisor" or Cat® ET to monitor the "DC Power Bus Voltage 1" status.
Expected Result:
When voltages are applied to the sensor, status of the "DC Power Bus Voltage 1" is approximately the voltage being supplied by the insulation tester.
Result: - OK
The "DC Power Bus Voltage 1" status displayed approximately 500.0 VDC and approximately 1000.0 VDC when the voltages were applied to the voltage sensor. The voltage sensor is working correctly.
Repair:
The voltage sensor is not causing the active condition. Return to the troubleshooting procedure for the DC Power Bus Voltage 1 Sensor (CID 2934) and perform the troubleshooting procedure again. Verify that there is not a problem with a connection, the burden resister, or the DC Power Bus Voltage 1 Sensor circuits.
STOP.
Result: - NOT OK
The "DC Power Bus Voltage 1" status did not properly display either the 500.0 VDC or the 1000.0 VDC or both voltages when the voltages were applied to the voltage sensor. The operation of the voltage sensor is not correct.
Repair:
The voltage sensor has failed. Replace the DC Power Bus Voltage 1 Sensor. To verify that the voltage sensor has failed: The "DC Power Bus Voltage 1 Sensor" can be switched with the "DC Power Bus Voltage 2 Sensor". Switching the sensors should cause an Event or a diagnostic code for the DC Power Bus Voltage 2 Sensor to activate.
Do not switch the "DC Power Bus Voltage 1 Sensor" or the "DC Power Bus Voltage 2 Sensor" with the "Ground Fault Detection Sensor".
STOP.
Testing the DC Power Bus Voltage Sensor #2 (DVC2)
When the "Power Train Electrical System Service Shutdown" procedure has been performed and the voltage in the "Inverter Cabinet" is verified as discharged: Proceed with this test.
Note: In this test step, the "Insulation Tester" will supply a known voltage to the voltage sensor. That voltage will be used to check the operation of the voltage sensor.
- Verify that the key start switch and the battery disconnect switch are in the OFF position.
- At the "Inverter Cabinet", remove the rear compartment cover for DVC2 (C).
- Use the high-voltage meter to measure voltage between the DC Bus bars located in this compartment. Check for voltage between the voltage sensor high-voltage connections.
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Illustration 6 g01867073 Typical view
Insulation tester cables connected to the DC Power Bus Voltage 2 Sensor DC input connections (sensor location may not match in the cabinet) - Verify less than 50.0 VDC between the DC connections before continuing to the next step.
- Disconnect the DCP connection (3) and the DCN connection (4) from the voltage sensor.
- Connect the positive lead from the "Insulation Tester" to the positive terminal (3) on the voltage sensor.
- Connect the negative lead from the "Insulation Tester" to the negative terminal (4) on the voltage sensor.
- Energize the 24 V control system by moving the battery disconnect to the ON position and the "Engine Lockout Control" switch to the ON position.
- Use the Insulation Tester to supply 500.0 VDC to the voltage sensor. Use the "Advisor" or Cat® ET to monitor the "DC Power Bus Voltage 2" status.
- Use the insulation Tester to supply 1000.0 VDC to the voltage sensor. Use the "Advisor" or Cat® ET to monitor the "DC Power Bus Voltage 2" status.
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| Illustration 5 | g06424036 |
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View of the rear of the inverter cabinet (C) DC Bus Voltage 2 Sensor (DVC2) (3) DC positive connection (DCP) (4) DC negative connection (DCN) | |
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| Illustration 7 | g01865805 |
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"DC Power Bus Voltage Sensor #2 (DVC2)" connections | |
Expected Result:
When voltages are applied to the sensor, status of the "DC Power Bus Voltage 2" is approximately the voltage being supplied by the "Insulation Tester".
Result: - OK
The "DC Power Bus Voltage 2" status displayed approximately 500.0 VDC and approximately 1000.0 VDC when the voltages were applied to the voltage sensor. The voltage sensor is working correctly.
Repair:
The voltage sensor is not causing the active condition. Return to the troubleshooting procedure for the "DC Power Bus Voltage 2 Sensor" (CID 2935) and perform the troubleshooting procedure again. Verify that there is not a problem with a connection or the burden resister. Verify that the circuits that are used for the operation of the "DC Power Bus Voltage 2 Sensor" are correct.
STOP.
Result: - NOT OK
The "DC Power Bus Voltage 2" status did not properly display either the 500.0 VDC, the 1000.0 VDC or both, when applied to the voltage sensor. The operation of the voltage sensor is not correct.
Repair:
The voltage sensor has failed. Replace the "DC Power Bus Voltage 2 Sensor" (DVC2). If further verification that the voltage sensor has failed is required, the voltage sensor can be switched with the "DC Power Bus Voltage 1 Sensor (DVC1)". Switching the sensors should cause an event or a diagnostic code for the "DC Power Bus Voltage 1" to activate.
Do not switch the "DC Power Bus Voltage 2 Sensor" or the "DC Power Bus Voltage 1 Sensor" with the "Ground Fault Detection Sensor".
STOP.
Testing the Ground Fault Detection Sensor
Before the test procedure can begin, the "Power Train Electrical System Service Shutdown" procedure must be performed. Verify that the voltage in the power train system components is discharged.
Refer to the Troubleshooting, "Electrical Shutdown and Voltage Discharge" section of this manual to perform the "Power Train Electrical System Service Shutdown" procedure.
Before performing this procedure, ensure that the "Battery Disconnect Switch" is in the OFF position. Lock and tag the disconnect.
Note: This procedure will require the use of the 243-3141 Insulation Tester Gp.
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| Illustration 8 | g06424045 |
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Ground Fault Detection Sensor connections | |
- Verify that the key start switch and the battery disconnect switch are in the OFF position.
- At the front panel for the "Inverter Cabinet", remove the "Motor Control 2 ECM" .
- Identify the Ground Fault Detection Sensor (A).
- Use the high-voltage meter to measure for voltage between the voltage sensor high-voltage connections. Verify that there is less than 50.0 VDC between the DC connections before continuing to the next step.
- Examine the low voltage circuit wires connected. Ensure that the wires are in good condition and the end connections for the power, ground, and signal wires are clean and securely connected.
- Disconnect the DCP connection (5) and the DCN connection (6) from the Ground Fault Detection Sensor (A).
- Connect the positive lead from the "Insulation Tester" to the positive terminal (5) on the sensor.
- Connect the negative lead from the "Insulation Tester" to the negative terminal (6) on the sensor.
Note: In the next step, when the battery disconnect is in the ON position and the engine lockout control switch is moved to the ON position: The 24 V control system voltage will be energized regardless of the status of the key start switch.
- Energize the 24 V control system by moving the battery disconnect to the ON position and the engine lockout control switch to the ON position.
- At the "Motor Control 2 ECM", use the 7X-1710 "spoon" type multimeter probes to monitor the sensor power supply. Insert the positive multimeter probe along the +15 V supply contact J2-49 (wire PWR2P-BK(Black)). Insert the negative multimeter probe along the -15 V supply contact J2-41 (wire PWR2N-BK(Black)). When the ECM is powered, the voltage measurement should be approximately 30 VDC.
- Use the Insulation Tester to supply 250.0 VDC to the voltage sensor. The output of the voltage sensor will be checked at the motor control ECM.
- At the "Motor Control 2 ECM", use the 7X-1710 "spoon" type multimeter probes to monitor the voltage sensor signal circuits. Insert the positive multimeter probe along the signal plus (+) contact J2-58 (wire VDC2-BK(Black)). Insert the negative multimeter probe along the signal minus (-) contact J2-66 (wire PWR2N-BK(Black)). With 250 VDC applied to the voltage sensor, the voltage measurement should be approximately 1.73 VDC.
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| Illustration 9 | g06424038 |
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View of the rear of the inverter cabinet (A) Ground Fault Voltage Sensor (5) DC positive connection (DCP) (6) DC negative connection (DCN) | |
Expected Result:
With the power applied to the ECM, the sensor power supply at the ECM is correct. With 250 VDC applied to the voltage sensor, the voltage measurement is approximately 1.73 VDC.
Result: - OK
The Ground Fault Detection Sensor output is correct when 250 VDC is applied to the voltage sensor.
Repair:
The operation of the voltage sensor is correct. If a problem is still occurring with the "Ground Fault Detection Sensor" circuits: Investigate the circuits and connections that are used in the ground fault circuits. The circuits are illustrated in the system schematic diagrams in the back of this manual.
STOP.
Result: - NOT OK
Either the sensor power supply is not correct or the sensor output signal at the ECM is not correct.
Repair:
If the correct sensor power supply is not present at the ECM contacts: Refer troubleshooting procedure for "DC Power Bus Voltage 1 Sensor (DVC1)" (CID 2934), or the "DC Power Bus Voltage 2 Sensor (DVC2)" (CID 2935). Perform the "Check the Operation of the ECM" test step.
If the voltage sensor signal is not correct at the ECM contacts when 250 VDC is applied to the sensor: Verify that the ECM sensor supply power is present at the voltage sensor contacts. If the power is not present at the sensor contacts, check the connections in the circuits at the TB2 terminal connections.
If the power supply is present at the voltage sensor, and the voltage sensor signal is not correct at the ECM contacts: Check the signal circuit connections at the TB4 terminal connections.
Verify that the resistance of the RVDC2 circuit resistor is correct and the resistor connections are secure.
If a problem cannot be found in the voltage sensor circuits, replace the Ground Fault Detection Sensor to resolve the problem.
STOP.