SEAL 1887122 - Caterpillar

All Caterpillar SR4 generators, except oil field generators, are provided with voltage regulators for control of the generator output voltage. The voltage regulator types are shown as follows:
VR1 Epoxy Module (A1) - (A2) Type Regulator Voltage Adjustment Controls(1) Voltage droop potentiometer.(2) Voltage level potentiometer.(3) Voltage gain potentiometer.(4) Thermal protector.
VR2 Card Cage Type Regulator Voltage Adjustment Controls(1) Voltage droop potentiometer.(2) Voltage level potentiometer.(3) Voltage gain potentiometer.(4) Thermal protector.(5) Magnetic breaker.
VR3 Regulator Voltage Adjustment Controls(1) Voltage droop potentiometer.(2) Voltage level potentiometer.(3) Voltage gain potentiometer.(6) Fuse(s).
VR3F Regulator Voltage Adjustment Controls(1) Voltage droop potentiometer.(2) Voltage level potentiometer.(6) Fuses. The VR3, VR3F and VR4 regulators have multi-turn potentiometers for voltage level and voltage gain control. The adjusting screw on the potentiometers do not have a fixed stop. When the potentiometer reaches the end of adjustment, a ratchet action begins; this 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. The VR4 regulator does not have voltage droop capability. The VR3F regulator does not have voltage gain capability.
VR4 Regulator Voltage Adjustment Controls(2) Voltage level potentiometer.(3) Voltage gain potentiometer.(6) Fuse. To Adjust The Voltage Regulator:1. Remove the left side access panel of the generator.2. VR1 and VR2 regulators - Loosen the locknuts on the voltage droop (1), voltage level (2) and voltage gain (3) potentiometers. VR3 and VR3F regulators - Loosen the locknut on the voltage droop (1) potentiometer and remove the protective screw from the voltage level (2) potentiometer. VR3 regulators only - Remove the protective screw from the voltage gain (3) potentiometer. The VR3F regulator does not have a voltage gain control.3. Turn voltage droop potentiometer (1) counterclockwise to zero droop and tighten the locknut (VR1, VR2, VR3 and VR3F regulators only). Voltage droop potentiometer (1), for the VR3 and VR3F regulators, is located on a mounting bracket below the regulator, (some generators are not provided with voltage droop).4. Turn voltage gain potentiometer (3) counterclockwise to zero, then turn voltage gain potentiometer (3) to about 1/4 of full range of clockwise travel (VR1, VR2, VR3, and VR4).5. Perform required maintenance on engine before starting.6. Start the engine and allow it to warm (refer to "Starting").7. Increase engine speed to full governed rated speed (high idle).8. Observe the voltmeter reading. If desired voltage is not indicated, set no load voltage with voltage level potentiometer (2).9. Close the load circuit breaker and apply full load gradually. Adjust governor control until nameplate rated frequency is on the Hertz (frequency) meter.10. If voltmeter reading increases with full load applied, turn gain potentiometer (3) slightly in counterclockwise direction. Or, if voltmeter reading decreases with full load applied, turn gain potentiometer (3) slightly in clockwise direction (VR1, VR2, VR3, and VR4).11. Remove load, adjust voltage level potentiometer (2) if necessary to obtain desired voltage.12. Apply the load, observe voltmeter reading. Repeat steps 9 thru 11 until no load voltage equals full load voltage.13. Tighten locknuts and install the protective screws on