Power Tech Generators PT-10KW, Operator'S Manual

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GENERATOR ASSEMBLY INFORMATION
BRUSH and EXCITER TYPE GENERATOR
BRUSH TYPE
Brush Type generators use a set of carbon or graphite brushes that are set into a spring loaded brush
holder, which house and support the brushes. This brush holder is mounted in such a way as to allow the
brushes to maintain a sliding electrical contact between the stationary and rotating components of the
generator. This connection enables DC current to flow from the Voltage Regulator through the Brushes
and into the Rotor assembly.
EXCITER TYPE
The exciter pole pieces contain residual magnetism, which sets up lines of force across the air
gap to the exciter armature. When the exciter begins to rotate a voltage is induced and current flow is
initiated in the exciter armature AC windings. This voltage is fed to the rotating rectifier assembly,
rectified and fed to the alternator field, which sets up lines of force across the air gap to the alternator
stator windings and to the output circuit.
A static voltage regulator is connected to the generator output. The regulator will rectify part of
the output voltage to provide a DC voltage to the exciter field coils. This will increase the density of the
lines of force in the exciter, increasing the voltage induced into the exciter armature windings, and
therefore, to the rotating rectifiers. The rotating rectifier output will increase which will increase the
alternator field strength and generator output will build up its rated voltage. Adjustment of the generator
output to the rated voltage level is accomplished by controlling the current fed to the exciter field coils.
Regulation is automatic with the static type voltage regulator. An additional voltage adjustment range is
provided if desired by turning the Voltage Adjust Rheostat.
ELECTRONIC VOLTAGE REGULATION
Electronic Voltage Regulator (EVR) also referred to, as an Automatic Voltage Regulator (AVR)
is a very reliable device, which uses solid-state electronics to maintain voltage accuracy at ±2% of the
regulated voltage. The Voltage Regulator is designed to automatically regulate and maintain the
generated AC voltage through out the load range that is from no load to full load.
VOLTAGE CONNECTION
The generator may be connected at the terminal board to deliver 120/240 volts to a 3 wire
grounded neutral system, or 120-volts only to a 2 wire distribution system. If any equipment requires
240-volts, then the 120/240-volt connection must be used. If all equipment requires 120-volts then
the 120-volt connection is preferred, even if two lines leave the same switch box. The two lines at
the inputs to the switch box are both connected to the un-grounded 120-volt lines from the generator.
The 120-volt connection enables the Electronic Voltage Regulator (EVR) to hold the voltage very
close to the 115 or 120 volts, as initially adjusted, regardless of the power distribution amount the
different distribution lines. The 120-volt connection is recommended if the entire electrical load
requires only 115 or 120 volts.
Although the 120/240-volt connection may also be used when all loads requires only 110 volts, it
should be pointed out that this connection, the 240-volts, is regulated and the lightly loaded phase, or
line, will deliver a high line to neutral voltage and the heavily loaded phase will deliver a low line to
neutral voltage. The heavily loaded line may have such a low voltage that air conditioning will have
more difficulty in starting, and long starting lines may overload generator and trip circuit breakers.
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