PI Manufacturing AC generators - Manual (Page 9)

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 open coupled 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 1000ft.lb. (140 kgm). A flexible coupling,
designed to suit the specific engine/generator combination, is
recommended to minimise torsional effects.
Belt driven applications of two bearing generators require the
pulley diameter and design to be such that the side load or
force applied to the shaft is central to the extension and does
not exceed the values given in the table below : -
Side Load
Frame
kgf N
Shaft
Extension
mm
UC22 408 4000 110
UC27 510 5000 140
In instances where shaft extensions greater than specified in
the table have been supplied reference must be made to the
factory for appropriate loadings.
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
1000ft.lb. (140kgm). A substanial bedplate with
engine/generator mounting pads is required.
It is expected that the generator will be incorporated into a
generating set operating in an environment, where the
maximum shock load experienced by the generator will not
exceed 3g. in any plane. If shock loads in excess of 3g are to
be encountered, anti-vibration mountings must be
incorporated into the generating set to ensure they absorb the
excess.
The maximum bending moment of the engine flange must be
checked with the engine manufacturer.
Generators can be supplied without a foot, providing the
option for customers own arrangement. See SECTION 4.2.1
for assembly procedure.
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 terminal box is constructed with removable panels 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. Additional
earthing points are provided on the generator feet.
The neutral is NOT connected to the frame.
The main stator winding has leads brought out to the
terminals in the terminal box.
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.
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.
Incorrect installation, service or
replacement of parts can result in severe
personal injury or death, and/or
equipment damage. Service personnel
must be qualified to perform electrical
and mechanical service.
Warning !
Warning !