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ATTENTION
In order to change the operating frequency
of the voltage regulator, refer to its manual.
4.9.1.4
Terminal identification
The identification of the alternator and accessory
terminals is provided in the specific wiring diagram of
each alternator.
4.9.1.5
Electrical connection of the voltage
regulator
In order to perform correctly the electrical connections
of the alternator to the voltage regulator, refer to the
manual of the voltage regulator.
The model of the used voltage regulator depends on
the characteristics of the alternator and the desired
application. Therefore, the electrical connections to the
alternator and the identification of the terminals may
differ from one model to another.
4.9.2
Accessories
4.9.2.1
Excitation and sensing
The auxiliary exciter (PMG) provides AC voltage to
supply the power circuit of the voltage regulator, which
is responsible for rectifying and controlling the
excitation of the alternator.
The voltage regulator responds to the voltage signal of
the sensing transformer, connected to the stator
terminals of the alternator by controlling the excitation
voltage and keeping constant the alternator voltage.
4.9.2.2
Parallel operation
For two or more alternators operate in parallel, the
voltage regulator should be able to control or allow the
reactive control (VAR) during operation.
Is necessary a current transformer (paralleling CT) for
the voltage regulator control the reactive power. This
paralleling circuit is necessary to control the reactive
power flow between the alternators connected in
parallel.
4.9.2.3
Differential protection
Current transformers (CTs) for differential protection
(when supplied) are installed in the neutral of the
alternator. The signal from the secondary of these
transformers must feeding the differential protection
relay, comparing with the CTs installed on phases of
the alternator or on the control panel and protection of
the generation system.
The secondary of these CTs must have the same
characteristics.
24
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Installation, operation and maintenance manual
ATTENTION
Should ensure that all CTs are correctly
connected to the system or with the
secondary short-circuited when the
alternator go into operation.
4.10 MECHANICAL ASPECTS
4.10.1 Bases and foundations
The dimensioning of the bases must be performed to
confer rigidity to the structure, avoiding amplification of
the vibration levels of the set. The base must have a
flat surface against the feet of the alternator in order to
prevent deformations on the frame.
The base must always be leveled in relation to the
ground (floor). The leveling is obtained by placing
shims between the base and the floor.
The shims for leveling must cover at least 80% of the
surface area of contact with the feet.
The material of the leveling shims must provide the
same rigidity of the basis.
4.10.2 Alignment and leveling
The alternator must be perfectly aligned with the driving
machine, especially in cases of direct coupling
ATTENTION
An incorrect alignment may damage the
bearings, cause vibration and break the
shaft.
The alternator must be correctly aligned with the driving,
especially in cases of direct coupling.
The alignment must be done according to the
recommendations of the coupling manufacturer.
It is necessary to make the parallel and angular alignment
of the alternator, as shown in Figure 4.8 and Figure 4.9.
Parallel misalignment
Figure 4.8: Parallel alignment
Figure 4.8 shows the parallel misalignment of the two
shaft ends and the practical way to measure it by using
suitable dial gauges.
The measurement is made in four points at 90º, with the
two half-couplings rotating together so as to eliminate the
effects of surface irregularities on the dial gauge contact
surface. Choosing the upper vertical point 0º, half the
difference of the dial gauge measurement in points 0º
and 180 represents the vertical coaxial error. This must
be properly corrected by adding or removing shims. Half
the difference of the dial gauge measurement in points
90° and 270° represents the horizontal coaxial error.
Radial measurement
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