Generator Repairs; Checking The Armature With Twin-Contact Tool; Checking The Armature On The Testing Apparatus Using A Blade - Fiat 411 R Service Manual

Generator repairs are to be carried out as foilowsz
a) Brushes.
li broken, chipped, or worn out, replace them with spare parts furnished by the FIAT Company ~ Sezione
Ricambi. Be sure to avoid the installation of other brush makes, as FIAT spares only can ensure a regular
and iong lasting operation ot both commutator and generator.
b) Field-winding. A
Check field coils by circulating test bench current though them (Fig. 133) and measuring the voltage and
the current with the bench instruments, then calculating the coils resistance.
if connections alone are interrupted, repair them carefully; but it the winding is damaged replace the es-
sembly with a new FtAT spare. We do not suggest maicing {laid coils, as a speciai procedure i§'requlred.
Poie-shoe'screws shouicl then be fully tightened to set the air gap at its previous vaiue. Reboring cf
poie~shoes must never be resorted to, if the air gap (see table on page 87] is not obtained; we advise
warning up somewhat the coiis, which are already shaped, to facilitate their installation.
0) Armature.
Commuiator. - li commutator bar surface contacting the brushes is worn or out-of-round, turn down
the commutator. Be careful when fixing the armature in a lathe and centering it, as the instailation
of armature assernbly between centers is not possible. Commuiator centering should be most accurate,
as commutator out-of-round, measured on brush ways should not exceed 0,01 mm {0.0004"). After
commutator turning undercut the mica between bars using a saw blade to a depth of 1 mm (0.0394"}.
Armature winding. —~ If damage is in the armature winding, replace the whole assembly. it is not advisable
to attempt making a new coil, as a special procedure would be required. Armature checks are to be
made with the instruments illustrated in Figs. 134 and 135.
Fig. 135. - Checking the armature on the testing
apparatus using a blade.
(Blade vibrates at short circuiis).
Fig. 134. - Checking the armature with twin-contact tool.
(The interruption is located by the no indication of the
ammeter).
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