HUB 2P9039 - Caterpillar

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 rotation.2. Same speed capabilities.3. Same voltage characteristics.These three conditions may be compared to similar conditions required for engagement of two gears. To mesh as smoothly as possible, two gears must meet the following three conditions:1. Same direction of rotation.2. Same rotation speed.3. The tooth of one segment must fit the root of the engaging segment.Phase Rotation
The phase rotation must be the same. A set of three light bulbs is used to determine whether the phase rotation of the incoming unit and the phase rotation of the line are the same.1. Connect the light bulbs 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.
SYNCHRONIZING LIGHTSa. If the lights blink in sequence one of the units is connected backward. To correct this 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.
Never attempt to work on electrically hot wiring. Stop the electric set before rewiring generator leads. Open circuit breakers before working on the equipment which they control.
b. If lights blink in unison the phase rotation of both engines is the same, and condition 1 has been met.Engine Speed
The speed of units to be paralleled must be the same. Speed refers to the alternating current frequency.1. Allow each electric set to run under load long enough for the internal temperatures to stabilize (about one hour).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 3% above full load speed. If these speeds can not be obtained, contact your Caterpillar dealer.4. For the most consistent results repeat steps 2 and 3. Condition 2 has been met.Voltage Adjustment
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. Adjustments to the voltage droop control should be made to give a 2% droop for load of unity power factor (load composed primarily of lighting). Loads of .8 power factor (primarily motors) require a generator voltage droop of about 5%. Voltage droop is expressed as the percentage of voltage change from no load to full load.1. Remove the exciter-regulator access cover and loosen the locknuts of the voltage level and droop controls and