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Copyright 2017 Cummins Inc.
ALIGNING ALTERNATOR WITH ENGINE
Proper alignment of the alternator and engine as-
semblies is necessary to avoid premature wear and
improper operation of the generator set. Review the
following alignment conditions and procedures for
aligning the alternator assembly to engine flywheel
housing.
Angular Misalignment: Is the result of the alterna-
tor bearing center axis not aligning with axis of the
engine crankshaft. This condition creates an angle
between the alternator shaft axis and the crankshaft
axis. The cause of this type of misalignment is usu-
ally shimming error.
Axial Misalignment: Is the result of the alternator
shaft axis not aligning with engine crankshaft axis.
The tolerances in the bolted flywheel and drive disc
connection may add up to displace the alternator
axially relative to the crankshaft axis.
Misalignment Symptoms: If the assembly is al-
lowed to run under these conditions, the discs must
flex in alternate directions twice for each engine rev-
olution. It is important to minimize the amount of
disc flexing since, if it is excessive, the drive disc will
crack. Although perfect bearing alignment is desir-
able, it is more important to keep disc deflection to
the minimum possible. This procedure assumes
that the pilot bore of the drive discs are in the exact
center and the flywheel counterbore (pilot) has no
practical runout. Under these conditions, perfect
Angular alignment will be attained when no deflec-
tion of the disks is measured.
Excessive Axial misalignment will cause more alter-
nator vibration than Angular misalignment.
Axial misalignment needs to be checked only when
an objectionable vibration is present.
Either type of misalignment may be present in a
generator set assembly, with angular misalignment
being the most common problem. Angular align-
ment may also be effected by set installation condi-
tions and/or mishandling during shipping of the gen-
erator set.
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