SHAFT-BALANCE 4N7976 - Caterpillar

Except for the oilfield generators, all Cat SR500 generators are provided with voltage regulators. The voltage regulator controls the generator output voltage. The voltage regulators are listed in table 1.
Table 1
Voltage Regulator Availability
VR3 N/A
VR3F Option
VR4 N/A
DVR Standard
Illustration 1 g00626331
Adjustment Controls of the VR3F Regulator
(1) Voltage droop potentiometer
(2) Voltage level potentiometer
(4) FusesThe VR3F regulator has voltage droop capability (1). The VR3F regulator has the voltage level control (2). However, the VR3F regulator does not have voltage gain capability.Voltage droop and voltage level are controlled by multiturn potentiometers. The adjusting screws on the potentiometers do not have a fixed stop. When the potentiometer reaches the end of adjustment, a ratchet action begins. The beginning of a ratchet action can be felt with the adjusting tool. The adjusting screw can be turned past the potentiometer stop (ratchet action) without further changing the potentiometer setting.
Illustration 2 g00626333
Digital Voltage Regulator (DVR)
(5) Display
(6) Function key
(7) Scroll down key
(8) Scroll up key
(9) Keypad
(10) J1 connector
(11) Screw terminalsThe digital voltage regulator (DVR) is a microprocessor-based voltage regulator. The parameters are preset at the factory or the parameters can be modified to meet the specific requirements on the site. Certain system parameters can also be monitored on the display (5) of the DVR. Keypad (9) is used to change the information that is shown on the display (5). J1 connector (10) is used to join the DVR to a personal computer. Screw terminals (11) are used to join the DVR to the generator and various customer options.Adjustment Procedure for the Voltage Regulators
VR3F Regulator
Note: The VR3F regulator is protected by a fuse. The VR3F regulator also has a solid-state overcurrent protection. If a fuse becomes open, contact a Cat dealer.
Remove the access panel of the generator.
Loosen the locknut on the voltage droop potentiometer (1). Remove the protective screw from the voltage level potentiometer (2).
Turn voltage droop potentiometer (1) counterclockwise to zero droop. Tighten the locknut. Voltage droop potentiometer (1) is located next to the regulator.
Perform required maintenance on the engine before you start the engine.
Start the engine. Allow the engine to warmup. Refer to the Safety Section, "Engine Starting".
Increase engine speed to full governed rated speed (high idle).
Observe the voltmeter reading. If the desired voltage is not indicated, set the no-load voltage with the voltage level potentiometer (2) or the voltage adjust rheostat. The voltage adjust rheostat is on the control panel.
Close the load circuit breaker. Apply full load gradually. Adjust the governor control until the nameplate frequency is on the frequency meter or until the rated speed is displayed on the tachometer. The unit of measurement for frequency is Hertz. The unit of measurement for the rated speed is RPM.
Remove the load. If necessary, adjust the voltage level potentiometer (2) to obtain the desired voltage.
Apply the load. Observe the voltmeter reading. Repeat Steps 8 and 9 until the voltage at no load equals the voltage at full load.
Tighten the locknuts. Install the protective screws on the respective potentiometers. Install the access panel of the generator. STOP.Digital Voltage Regulator (DVR)
Refer