891736T Mercruiser MOTOR ASSEMBLY, Complete

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. a. 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.Frequency Adjustment
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 and3. 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. 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. Use the same voltmeter to make adjustments on each unit to be paralleled.1. Adjust voltage as described for Single Unit Operation, Initial Start-Up.2. With the engine running at high idle, turn the voltage droop clockwise about 1/2 of full range.If driven load is to be unity power factor, set the voltage droop control on all generators at 1/2 of full range and proceed to Step 7. If driven load is to be normal (0.8 power factor) proceed to Step 3.3. Readjust the voltage level control until the voltage is about 5% above desired voltage.4. Apply full load at .8 power factor.If a generator is to be paralleled with other generators, the voltage droop of each generator must be the same to satisfactorily divide reactive load.5. Readjust the voltage droop control to obtain desired voltage with full load at .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 .8 power factor and no load voltage is approximately 5% above rated voltage.7. Parallel generators and apply the driven load (see the topic Operation/Paralleling). If the sum of the amps of the individual generator amperes exceeds the total amps going to the load by 10% at full load, adjust voltage droop controls to share current proportionally between generators.
Do NOT exceed rated ampere load on any single generator.
8. Tighten the locknuts on all controls and install the access cover. Condition 3 has been met.Starting Multiple Units
Starting-Units are started the same as single units.Paralleling
Units may be paralleled at no load or paralleled with units under load. To parallel two or more units the following conditions must be met:1. Same phase rotation.2. Same voltage level.3. Same voltage droop.4. Same frequency.5. Voltages must be in phase.The first three conditions have been met in the initial start-up for parallel operation.1. Start the unit to be paralleled according to the procedure in the engine operation section.2. Turn the synchronizer lights on.3. After the engine has run long enough to warm up, 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 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 engines7. After generator temperature has stabilized (1 hr.), adjust the droop control of each generator so as to share the reactive load and to limit the circulating currents. Less droop (moving control CCW) increases the reactive current carried by the generator.The frequency of the incoming unit should be slightly greater than the line frequency. This will allow the incoming unit to assume some of the load rather than add to the system load.Load Division-(Speed Droop)
Once two units have been paralleled their share of the load is determined by the governor control setting. If two units of the same capacity and the same governor characteristics have the same governor control settings they will share the load equally.To transfer the load from one engine to the other follow this procedure:The total load must not exceed the capacity of the engine.1. Increase the governor speed control of one unit to increase the load.2. Reduce the governor speed control of the other unit to decrease the load on that unit.3. Raise or lower the governor speed control of both units to change system frequency.Circulating Currents
When two units are paralleled there will be circulating currents. These currents are not doing useful work, but are flowing between the generators. By determining the total generator amperage and subtracting the amperage going to the load, the amount of circulating current can be determined.Circulating currents are caused by voltage differences between the two units.With cold generator sets, circulating current may be as high as 25% of rated amperes, without being considered harmful. Circulating current is part of the total generator current and this total must not exceed