Caterpillar SR4 Generator Set

⚠ kW load sharing is a function of the engine governor only

⚠ Adjust governor setting for proper kW balance before adjusting reactive kVAR unbalance

1. Adjust governor setting for proper kW balance before attempting to adjust reactive kVAR unbalance (kW load sharing is a function of the engine governor only).
2. Turn the gain potentiometer to the full CCW position.
3. Turn the droop potentiometer to the full CCW position.
4. On each generator, adjust the voltage level potentiometer to the rated no load voltage.
5. Apply full rated load with 0.8 pf to the individual generator.
6. Adjust the gain potentiometer to compensate for voltage drop due to governor speed droop at rated load, if the governor is not isochronous.
7. Adjust the droop potentiometer to obtain 5% droop when operating as a single unit at full load 0.8 pf.
8. Remove the load.
9. Parallel the generators at no load and adjust for minimum circulating current, if any, using the voltage level potentiometer.
10. Apply full rated resistive and reactive loads.
11. Adjust to minimum circulating current using the droop potentiometer.

1. Allow each electric set to run under load (about 30 minutes).
2. Adjust the governor control to give rated frequency at full load.
3. Remove the load and check the high idle speed; it should be approximately 2 to 5% above full load speed (for governors equipped with droop).
4. For the most consistent results, repeat steps 2 and 3 until condition 2 of Initial Start-up has been met.

⚠ Damage to the generator is possible. Do NOT exceed rated ampere load on any single generator.

Tools: Voltmeter

1. Adjust voltage as described for Single Unit Operation, Initial Start-Up.
2. With the engine running at rated speed, turn the voltage droop clockwise about 1/2 of full range.
3. Readjust the voltage level control until the voltage is about 5% above desired voltage.
4. Apply full load.
5. Readjust the voltage droop control to obtain desired voltage with full load at 0.8 power factor.
6. Repeat Steps 3, 4 and 5 for each generator to be paralleled until line voltage is equal to desired level at full load and no load voltage is approximately 5% above rated voltage.
7. Parallel generators and apply the driven load; adjust voltage droop controls to share current proportionally.
8. Make final adjustments after paralleled generators have been running at full load for one hour or more; tighten locknuts and install the access cover.

Tools: Adjusting tool

1. Remove the left side access panel of the generator.
2. VR1 and VR2 regulators - Loosen the locknuts on the voltage droop, voltage level and voltage gain potentiometers.
3. VR3 and VR3F regulators - Loosen the locknut on the voltage droop potentiometer and remove the protective screw from the voltage level potentiometer.
4. Turn voltage droop potentiometer counterclockwise to zero droop and tighten the locknut (VR1, VR2, VR3 and VR3F regulators only).
5. Turn voltage gain potentiometer counterclockwise to zero, then to about 1/4 of full range of clockwise travel (VR1, VR2, VR3, and VR4).
6. Perform required maintenance on engine before starting.
7. Start the engine and allow it to warm.
8. Increase engine speed to full governed rated speed (high idle).
9. Observe the voltmeter reading; if desired voltage is not indicated, set no load voltage with voltage level potentiometer.
10. Close the load circuit breaker and apply full load gradually; adjust governor control until nameplate rated frequency is on the frequency meter.
11. If voltmeter reading increases with full load, turn gain potentiometer slightly counterclockwise; if it decreases, turn it clockwise.
12. Remove load, adjust voltage level potentiometer if necessary to obtain desired voltage.
13. Apply the load, observe voltmeter reading; repeat steps 9 thru 11 until no load voltage equals full load voltage.
14. Tighten locknuts, install protective screws on the respective potentiometers and install the generator access panel.

⚠ Never attempt to work on electrically hot wiring. Stop the electric set before rewiring generator leads. Open circuit breakers or remove fuses before working on the equipment which they control.

Tools: Three light bulbs

1. Connect the light bulbs, with rated voltage, between the generator leads and the corresponding line phase, across the open circuit breaker.
2. Start the units to be paralleled and bring them up to speed; as they approach the same speed the lights will start to blink.
3. If the lights blink in sequence one of the units is connected backward; remove generator leads 1 and 3 at the circuit breaker and exchange them.
4. If lights blink in unison the phase rotation of both generators is the same.

⚠ ct = Center Tap - Do Not Use - Tape Loose End

⚠ Transformers must be identical (same stock number) and polarized

Tools: Voltmeter, AC 115 V supply

1. Select a transformer and call it Trans #1.
2. Identify the primary winding (115 V).
3. Arbitrarily select one primary winding lead and mark it H1; mark the other primary lead H2.
4. Arbitrarily select one secondary lead and mark it X1; mark the other X2; if a center tap exists, tape the end.
5. Make the connections for the polarity test.
6. Apply 115 V AC across H1 and H2 and measure this applied voltage.
7. Measure voltage of Trans #1 from X1 to X2; this will be approximately 12 V AC.
8. Measure voltage from H2 to X1; if equal to the sum of H1-H2 and X1-X2 voltages, polarity is correct; if the difference, reverse X1 and X2 markings.
9. Select a second transformer, Trans #2, with the same stock number, and repeat Steps 2, 3 and 4.
10. Connect the H1 leads together and the H2 leads together; connect the X2 lead of Trans #1 to the X1 lead of Trans #2.
11. Apply 115 V AC across H1 and H2; measure voltage of Trans #2 from X1 to X2 (approximately 12 V AC).
12. Measure voltage from Trans #1, X1 to Trans #2, X2; 0 V AC means incorrect polarity marking, 24 V AC means polarity is correct.

⚠ If an oven is used for drying, use a forced air type rather than a radiant type. Radiant ovens can cause localized overheating.

Tools: Megohmmeter (megger)

1. Perform an insulation resistance check of the main stator windings using a megohmmeter (megger).
2. Energize space heaters in generator, if so equipped.
3. Put the generator in an oven at a temperature of not more than 85°C (185°F) for four hours.
4. Install space heaters of the same type used in marine applications to heat the windings and remove moisture.
5. Use a canvas enclosure around the generator and heating lamps to increase the temperature; make an opening in the top for release of moisture.
6. Send a low voltage current through the windings to increase the temperature of the windings; do not exceed 85°C (185°F).

⚠ Bearings being removed for failure analysis should not be cut off with a torch.

⚠ DO NOT MIX GREASES

1. Remove bearing bracket; inspect the bracket bore and bearing outer race and rolling elements.
2. Inspect the bearing bracket bore for out of roundness, excessive wear, and a bracket step less than 0.0762 mm (.003 in).
3. Spherical Roller Bearing should be cleaned and re-packed with 108-8611 Grease; pack the bearing and cavity to one-third to one-half of cavity volume.
4. All ball bearings should be cleaned and the bracket cavity re-packed with 2S-3230 Grease to one-third to one-half of the cavity volume.
5. Make sure the grease supply tube to the bearing is filled with grease.
6. Remove the bracket drain plug and operate generator for one hour to force excess grease out of the cavity.
7. Stop the engine, install the bracket drain plug and wipe off excess grease.
8. For future greasing intervals follow the recommendation on the lubrication plate or the Maintenance Schedule; repeat Step 5 each time the bearings are greased.

⚠ DO NOT MIX GREASES

Tools: Grease fitting

1. Remove the louver assembly or rear plate from the rear of the generator housing.
2. Remove the top and lower grease pipe plugs.
3. Install a grease fitting in the top, threaded grease pipe.
4. Grease shielded ball bearings with 1.8 to 2.0 oz of 2S-3230 Grease at an interval of every 2000 hours.
5. Grease spherical roller bearings with 1 oz of 108-8611 Grease at an interval of every 1000 hours. DO NOT MIX GREASES.
6. Wipe off excess grease, remove the top grease fitting and install plug.
7. Operate generator for one hour to allow grease to expand and force excess grease out of the cavity.
8. Stop the engine, install the plug in the bottom grease pipe and wipe off excess grease.
9. Install the louver assembly or rear plate.

1. Start the unit to be parallel according to the procedure in the Engine Operation section.
2. Turn the synchronizing lights on.
3. After the engine has run a few minutes, bring it up to synchronous speed (the same frequency as the unit on the line); the synchronizing lights will begin to blink.
4. Using the governor control, adjust the engine speed until the lights blink very slowly.
5. The lights are off when the voltages of the two units are in phase; at this point very quickly close the breaker while the lights are out.
6. Use governor controls to share kW load between engines.
7. After generator temperature has stabilized (approximately one hour), adjust the droop control of each generator to share the reactive load and limit the circulating currents.

⚠ Accidental starting of the engine can cause personal injury. To prevent accidental starting, disconnect the batteries before performing maintenance or repair work.

1. Turn the Engine Control Switch to Stop position.
2. Correct the fault condition that caused the shutdown.
3. Rotate the Engine Control Switch to the Off-Reset position.
4. Make sure that the Emergency Stop buttons on the generator set control panel and the engine junction box are reset.
5. Make sure that the Air Shutoff Lever located at the top of the air inlet housing is reset (if equipped).
6. Turn the Engine Control Switch to Manual or Automatic to start the system.

1. Perform all before-starting inspections.
2. Turn Engine Control Switch to the engine Start position.
3. Hold switch in start position until oil pressure is sufficient to deactivate (de-arm) the oil pressure failure circuit.
4. When engine starts, the engine fault circuits are now functional (armed).
5. After the engine starts and its systems have stabilized, apply the load.
6. Regulate the frequency of the generator with the Governor Motor Control Switch or Manual Governor Control Lever.