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Phase Sequence Indicators | Up
Construction Electrician Basic - Electricity handbook for electricians | Next
Overcurrent Protection |
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 X1, B to Yl, and C to
Z1, 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
X1, Y to Y1, and Z to Z1.
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 X1 be brought
down to X, the one used on Y1 to Y, and the one used on
Z1 to Z. Reversing any two of the leads will reverse the
direction of rotation of the rotor of the instrument.
INSPECTION OF THE
GENERATOR
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.
3. Fuel.
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.
DISTRIBUTION
PANELBOARDS
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.
In this section, the makeup of panelboards,
connections to them, and the installation of the
advanced-base type of portable panelboards are
presented.
3-14
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