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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. |
The "Excitation Field Regulator (EFR) Test" can be activated using the Cat® Electronic Technician (Cat® ET). The test can be used as an aide in troubleshooting the following:
- The enable circuits.
- The current command circuits from the Drivetrain ECM.
- The operation of the EFR.
- The current feedback circuits.
This test can be performed when an EFR-related diagnostic code has been activated by the Drivetrain ECM. The test can be performed anytime that the operation of the EFR and the associated circuits requires verification.
The test can be a troubleshooting aid when any of the following Drivetrain ECM diagnostic codes are activated.
- MID 081, CID 3425 FMI 03, 04, 08 (Generator Excitation Field Regulator Enable Line)
- MID 081, CID 3460 FMI 08 (Generator Excitation Field Regulator Command Line)
- MID 081, CID 3500 FMI 03, 04, 08 (Generator Excitation Field Regulator Current Feedback Line)
The following figure represents the location for the Excitation Field Regulator.
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| Illustration 1 | g03674372 |
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Excitation Field Regulator harness connectors (view: under the Generator looking from the left side of the cooling air duct). (1) 14 contact control circuit harness connector (2) 4 contact exciter circuit harness connector | |
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| Illustration 2 | g01957338 |
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Contacts for 14 contact EFR control circuit harness connector (1) ( A) Current Feedback (B) Current Feedback Return (C) Diagnostic Feedback Return (D) Battery Control (-) (E) Battery Control (+) (F) Reserved (G) Reserved (H) Current Command Sink (I) Shield (K) Shield (L) Diagnostic Feedback (M) Enable Return (N) Current Command Power | |
When a machine area that contains high-voltage components must be entered, the "Power Train Electrical System Service Shutdown" procedure must be performed. The procedure must be performed before the cover for the compartment is removed.
Reference: Refer to Troubleshooting, UENR3890, "Cat 794 AC Off-Highway Truck/Tractor". Perform the "Power Train Electrical System Service Shutdown" procedure to verify that the voltage in the drive train system has been discharged. After the voltage of the DC bus in the "Inverter Retarding Contactor" compartment is verified as discharged, and a jumper wire is in place, return to this point in this procedure and continue.
For an explanation of how the Drivetrain ECM uses the EFR to control the output of the Generator, refer to the System Operation, "Electric Power Generation".
- Turn the "Battery Disconnect Switch" to the ON position. Turn the "Key Start Switch" to the ON position.
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Illustration 3 g06356180 View of available ECM's - Connect and start Cat® ET. Select "Diagnostics" , then select "Diagnostic Tests", and then select the "Drivetrain ECM".
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Illustration 4 g06356184 Selection of the "Generator Excitation Field Regulator Output Test" in Cat® ET. - Select "Generator Excitation Field Regulator Output Test".
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Illustration 5 g06356202 "Generator Excitation Field Regulator Output Test" screen - Follow the instructions presented on the screen to satisfy the preconditions for the test. As the conditions are satisfied, the condition will be GRAYED OUT. The ECM will not allow the test to proceed until all preconditions are satisfied.
- Once the preconditions and the setup conditions are satisfied, the user will be given the option of turning ON the ECM command to the EFR. Turn ON the command.
- The "Drivetrain ECM" will send an approximate 30 percent duty cycle command to the EFR. The EFR will respond with a 4 amp current output to the generator exciter winding.
- Use Cat® ET to monitor the current sent to the generator exciter winding.
The current being sent to the generator exciter winding in the range of 3.8 amps to 4.2 amps.
The exciter winding current is in the range of 3.8 amps to 4.2 amps.
The current value indicates that the operation of the EFR is correct. The test has confirmed that the EFR enable circuits, the command circuits, the current feedback circuits, are operating correctly.
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The exciter winding current is not in the range of 3.8 amps to 4.2 amps.
There is a problem with the EFR or with one of the related EFR circuits.
Refer to the active procedure for the active EFR-related diagnostic code. Perform the troubleshooting procedure for the active diagnostic code to determine the cause of the problem.
Note: Refer to Troubleshooting, UENR3890, "Cat 794 AC Off-Highway Truck/Tractor" for troubleshooting information.