SEAL 2720390 - Caterpillar

Initial Start-up
Preparing a generator for parallel operation requires special attention. Before attempting to parallel units for the first time, all units must be checked to be sure the following three conditions are met:1. Same phase rotation2. Same alternating current frequency3. Same voltage adjustmentPhase Rotation
The phase rotation must be the same. A set of three light bulbs can be used to determine whether the phase rotation of the incoming unit and the phase rotation of the on line unit(s) are the same.To Determine Proper Phase Rotation (Using Three Light Bulbs)
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.
1. Connect the light bulbs, with rated voltage, between the generator leads and the corresponding line phase, i.e., terminal 1 to line 1 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.a. If the lights blink in sequence one of the units is connected backward. To correct, remove generator leads 1 and 3 at the circuit breaker and exchange them. This reverses the direction of phase rotation. Line 2 should always be connected to line 2.b. If lights blink in unison the phase rotation of both generators is the same, and condition 1 of "Initial Start-up" has been met. The Synchronizing Lights Module (with reverse power relay) will provide additional protection to the system. If the engine should lose power, the other units in parallel will attempt to motorize the engine and generator. Instead of power going out, power flows into the failing generator, making it a motor. When this occurs, the reverse power relay will activate to shutdown the failing engine and generator.For more information, including wiring information, refer to the Service Manual module, Form SENR4027.Frequency Adjustment
The speed of units to be paralleled must be the same. Speed is proportional to the alternating current frequency.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). If these speeds can not be obtained, contact your Caterpillar dealer.4. For the most consistent results, repeat steps 2 and 3 until condition 2 of "Initial Start-up" has been met.Voltage Adjustment
The following voltage adjustment is for individual compensation, also known as reactive droop correction. There is another method called differential compensation, also known as crosscurrent compensation, where the regulator is biased by the difference in reactive current outputs of the paralleled generators. Make reference to Engine Data Sheet, Zero Droop Voltage For Parallel Operation LEKX8142 for adjustment procedure.The voltage level and voltage droop adjustments determine the amount of circulating currents between generators. Carefully matched voltage regulator adjustments will reduce the circulating currents. Loads of 0.8 power factor (primarily