Figure 3-11 shows the leads of two generators to be parallel. The proper procedure for ensuring phase sequence with a phase sequence indicator is as follows: Connect indicator terminals A to X
1 , B to Y
l , and C to Z
1 , press the contact switch, and note the direction of rotation of the rotor.
Now move the A terminal to X, the B to Y, and the C to Z, and again press the switch. If the rotor turns in the same direction as before, the phase rotation is the same for the alternators, and the connection can be made X to X
1 , Y to Y
1 , and Z to Z
1 . If the rotor turns in the opposite direction, transpose the connections of any two of the incoming alternator leads before making the connection.
It is not absolutely necessary that A be connected to the left-hand terminal, B to the center terminal, and C to the right-hand terminal. This is a practical method, however, used to avoid the danger of confusing the leads. The important thing is to ensure that the phase sequence indicator that was used on X
1 be brought down to X, the one used on Y
1 to Y, and the one used on Z
1 to Z. Reversing any two of the leads will reverse the direction of rotation of the rotor of the instrument.
Open all access doors of the generator set and make a thorough visual inspection of the generator for loose or missing mounting hardware and damaged or missing
parts (look for broken or loose electrical and hose
Figure 3-11. - Diagram for checking phase sequence of alternators.
connections, for example, and for loose bolts and cap screws). Also, check the fault indicator panel and control cubicle for broken or missing bulbs and fuses.
WARNING While performing your visual inspection, look for service tags. If service tags are present, do not attempt to start or run the generator.
Check the wiring diagrams in the instruction manual furnished with the generator to see whether any wire is connected improperly. If you find faults, correct them immediately.
Be sure to check the levels of the following:
1. Crankcase lubricant.
2. Radiator coolant.
4. Electrolyte in the batteries. After donning the proper personnel protective equipment (chemical gloves, goggles, and face shield), add to the actual level to bring it up to the required level, if necessary.
On large generators you should check the area ventilation; the fan cover must be opened and latched in that position. There must be no cover or obstructions over the radiator section. The bypass shutters or doors may be closed to shorten the warming-up period, and roof hatches and side louvers may be opened for additional ventilation, if required.
Power from the generator set must be delivered to various connected loads safely and efficiently. The relatively large cables connected to the load terminal board of the generator, if sized properly, can conduct all the power the generator can produce. This power has to get to the different connected load equipment without overloading the conductors or overheating conductor insulations.Continue Reading