EARTHING ARRANGEMENT
On all star connected machines a substantial neutral terminal is provided for connection to the distribution network.
This is not connected to the frame of the machine. The a.c. generator frame should, however, be solidly earthed to the
generating set bedplate and connected to the common system earth. On generating sets used for mains failure standby
special earthing arrangements may be necessary and the local area Electricity Authority or Company should be
consulted.
DIRECTION OF ROTATION
All machines are fitted with a radial bladed fan and are suitable for running in either direction of rotation. The standard
machine is supplied to give a phase sequence U.V.W. with the machine running clockwise looking at the drive end
unless otherwise specified at the time of ordering. If machine rotation is reversed after the machine has been
dispatched apply to factory for appropriate instructions and wiring diagrams.
MAIN TERMINAL ARRANGEMENT
The main output terminals have been designed to accept cables rated in accordance with normal standard
specifications for single or multicore cables, and are based on the use of crimped-type cable terminations.
Frame PC1 - The terminal arrangement consists of 4, M6 dia. stud terminals
SC1 - The terminal arrangement consists of 4, M6 dia. stud terminals
SC2 - The terminal arrangement consists of 4, M10 dia. stud terminals
SC3 - The terminal arrangement consists of 4, M12 dia. stud terminals
In all cases the 4 output terminals are marked U.V.W. and N.
A.C. GENERATOR TO ENGINE ASSEMBLY
Torsional Vibration
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 a.c. generator shaft and
couplings. It is the responsibility of the generator set manufacturer to ensure comparability, and for this purpose
drawings showing the shaft dimensions, coupling details and rotor inertias are available for customers to forward to the
engine supplier.
Two Bearing Machines
It is beyond the scope of this publication to give guidance on ways and means of a.c. generator installation in great
depth due to the many different designs of generating sets and engine configurations. However, it is recommended that
the engine/a.c. generator is mounted on a substantial steel bedplate with machined cads to ensure accurate
engine/a.c. generator alignment. Where machine faces cannot be accurately achieved, it is necessary to fit shims
under the engine/a.c. generator feet to ensure alignment and avoid vibration.
If flexible mountings are used under the bedplate and their position is far removed from the corresponding engine/ a.c.
generator feet, a rigid bedplate becomes essential otherwise distortion during running will disturb the alignment or
possibly create vibration.
Couplings
A good quality flexible coupling should be fitted and alignment carefully checked, preferably in accordance with the
coupling manufacturers' recommendation, to avoid excessive shaft and bearing stresses. In addition a flexible coupling
will ensure that in the majority of cases torsional vibration problems will not arise.
Normally machines of this size are flexibly coupled. However, if belt drives are required full details of the drive, belt size
and pulley dimensions should be forwarded to ensure bearing loadings and shaft stresses are not excessive.
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