6
The main vibration frequencies produced by the generator
are as follows:-
4 pole
1500 rpm
25 Hz
4 pole
1800 rpm
30 Hz
However, vibrations induced by the engine are complex and
contain frequencies of 1.5, 3, 5 or more times the
fundamental frequency of vibration. These induced vibrations
can result in generator vibration levels higher than those
derived from the generator itself. It is the responsibility of the
generating set designer to ensure that the alignment and
stiffness of the bedplate and mountings are such that the
vibration limits of B.S. 5000 Part 3 are not exceeded.
In standby applications where the running time is limited and
reduced life expectancy is accepted, higher levels than
specified in BS5000 can be tolerated, up to a maximum of
18mm/sec.
Two bearing generators require a substantial bedplate with
engine/generator mounting pads to ensure a good base for
accurate alignment. Close coupling of engine to generator
can increase the overall rigidity of the set. For the purposes
of establishing set design the bending moment at the engine
flywheel housing to generator adaptor interface should not
exceed 275 kgm (2000 ft lbs) . A flexible coupling, designed
to suit the specific engine/generator combination, is
recommended to minimise torsional effects.
Alignment of single bearing generators is critical and
vibration can occur due to the flexing of the flanges between
the engine and generator. As far as the generator is
concerned the maximum bending moment at this
point must not exceed 275 kgm
(2000 ft lbs).
Single bearing generators require a substantial bedplate with
engine/generator mounting pads to ensure a good base for
accurate alignment.
The maximum bending moment of the engine flange must be
checked with the engine manufacturer.
Torsional vibrations occur in all engine-driven shaft systems
and may be of a magnitude to cause damage at certain
critical speeds. It is therefore necessary to consider the
torsional vibration effect on the generator shaft and
couplings.
It is the responsibility of the generator set manufacturer to
ensure compatibility, and for this purpose drawings showing
the shaft dimensions and rotor inertias are available for
customers to forward to the engine supplier. In the case of
single bearing generators coupling details are included.
Important !
Torsional incompatibility and/or
excessive vibration levels can cause
damage or failure of generator and/or
engine components.
The standard build terminal box arrangement is for cable
entry into the right hand side of the terminal box when
viewed from generator N. D. E.
Cable entry from the left hand side is possible if specified at
time of order.
The terminal box is constructed with a removable panel for
easy adaptation to suit specific glanding requirements.
Within the terminal box there are insulated terminals for line
and neutral connections and provision for earthing.
The neutral is NOT connected to the frame.
Caution!
No earth connections are made on
the generator and reference to site
regulations for earthing must be
made. Incorrect earthing or
protection arrangements can result
in personal injury or death.
The main stator winding has six leads brought out to
terminals in the terminal box. The three leads brought to the
neutral terminal have been arranged to allow for the
provision of differential protection with the option of clamps
and mounting plates for specific current transformers
supplied by Newage International.
If it becomes necessary for customers to use current
transformers not of Newage supply, these should be fitted
by competent technicians with particular care being taken to
ensure the cables are positioned centrally within the current
transformer opening.
The generator AVR incorporates protection circuits which
operate on overload or fault conditions.
If a detected abnormal condition still exists after 8 seconds
the AVR de-excites the generator causing a collapse in
output voltage. This de-excitation may be as a result of an
electronic solid state protection circuit, or the AVR tripping
the excitation circuit breaker, if fitted, which would be
located adjacent to the AVR.
To reset the AVR trip circuits it is necessary to stop the
engine - generator. The AVR solid state trip circuits will
automatically reset after the generator has been stationary
for 3 seconds. The excitation trip circuit breaker needs to be
manually reset if fitted.
The system designer should ensure that these AVR
functions are compatible with the overall system protection.
Fault current curves (decrement curves), together with
generator reactance data, are available on request to assist
the system designer to select circuit breakers, calculate fault
currents and ensure discrimination within the load network.
This instruction book must be read before incorporation of
the generator into a generating set. Maintenance must be
carried out with the generating set out of service and
precautions taken to avoid accidental starting of the
generator set.
Warning !
Incorrect installation, service or
replacement of parts can result in
severe personal injury or death,
and/orequipment damage. Service
personnel must be qualified to
perform electrical and mechanical
service.
