Digital Voltage Regulator Caterpillar

Troubleshooting

Usage:

SR4B 1BN

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Table 1
Common Troubleshooting Procedures⁽¹⁾⁽²⁾
Problem	Troubleshooting Procedure
Reverse Power Shutdown	Check CT polarity. Check connections to the digital voltage regulator terminals 5 and 6.
No Voltage (50 ACV or Less)	Check for the fault codes. Correct the fault codes. Determine if DC voltage is properly connected ("B+"/"B-"). Check for loose sensing or PM wires. Check for blown PM fuses. Determine if underfrequency setpoint (parameter :10) is too high. Temporarily disconnect battery from the digital voltage regulator. Then, connect battery to the regulator. Restart the regulator. Check terminal 42. Battery voltage (24 VDC) should not be present. (Excitation disable circuit) Check rotating diodes on the generator.
Low Voltage (Residual to Less Than Rated Output Voltage)	Check for the fault codes. Correct the fault codes. Determine if generator output voltage setpoint (parameter :01) is set too low. Determine if droop setpoint (parameter :30) is set to zero. Droop setpoint should be 0. Check parameter :03 for correct generator type. Determine if parameter :06 is less than the expected generator operating frequency. Check parameter :02 for the correct PT ratio. Check that parameter :02 is not doubled. Check that one PM fuse is not blown. Check rotating diodes on the generator.
High Voltage (Voltage Higher Than Range Allows)	Check for the fault codes. Correct the fault codes. Check parameter :02 for the correct PT ratio. Check that parameter :02 is not too low. Check that parameter :15 (IR Compensation) is set to zero. Determine if the generator output voltage setpoint (parameter :01) is set too high. Determine if the minimum voltage setpoint (parameter :09) is set too high.
Unstable Voltage (Voltage Fluctuation Greater Than 0.25%)	Check for the fault codes. Correct the fault codes. Remove the remote voltage adjust rheostat. Disconnect droop current transformer. Check for loose wiring. Check rotating diodes on the generator.
Initial Voltage Overshoot	Check parameter :03 for correct generator type.

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⁽¹⁾	A regulator may fail to perform correctly if it is not properly connected. A regulator may also fail if there is a failure of downstream equipment, such as diodes.
⁽²⁾	It is possible to get an unexplained reverse VAR fault if the CT is connected backward. Check the CT connection if this fault occurs.

This section provides troubleshooting procedures for generator voltage problems that are related to the digital voltage regulator.

Note: Before starting to troubleshoot, check the part number to determine if the digital voltage regulator being used is proper for the application. The part number label on the digital voltage regulator indicates the sensing voltage range and whether or not the regulator is the optional KVAR/PF model. Refer to the following chart.

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Table 2
Digital Voltage Regulator Application Chart
Regulator Version	Voltage Range	Early Part Number	Former Part Number	Current Part Number
Basic	79 to 124 Volt 3 phase sensing	116-7480	130-3471	155-3831
Basic	125 to 249 Volt 3 phase sensing	116-7481	130-3472	155-3832
Basic	250 to 600 Volt 3 phase sensing	116-7482	130-3473	155-3833
KVAR/PF Optional Version	79 to 124 Volt 3 phase sensing	116-7483	130-3474	155-3834
KVAR/PF Optional Version	125 to 249 Volt 3 phase sensing	116-7484	130-3475	155-3835
KVAR/PF Optional Version	250 to 600 Volt 3 phase sensing	116-7485	130-3476	155-3836