Saab 95 1967, Руководство по обслуживанию

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Testing 2/3 of maximum output current
Switch on battery and load the alternator. Adjust the
speed to exactly 2 000 r/min. The alternator output must
now be 2/3 of maximum current = 23 A.
Testing the RPM at maximum output
Leave the battery switched on. Increase the load on alter-
nator and let it warm up. Increase speed. Max. output
(35 A—14 V) must be achieved at 2 700—3 700 r/min
(warm).
Testing the alternator components
Testing of diodes
Use only a test lamp not exceeding 24 V or an Ohmmeter.
Always disconnect the diodes from the stator windings
before individual testing commences. Due to the 3-phase
bridge connection of the rectifier, a faulty diode could
otherwise not be detected. The positive diodes connected
between 8+ and phase are conducting from supply wire
to the housing and insulate in the reverse direction. The
diodes between phase and B- (reversed polarity) are con-
ducting from housing to supply and insulate from supply
to housing.
Connect the test lamp (up to 24 V) in series to the diode
to be tested. On diodes of normal polarity, the test lamp
will light up if 3+ is connected to the anode. The lamp
must not light up if 8+ is applied to the housing (cathode).
On diodes of reversed polarity, the bulb must light up if
3+ is connected to the supply (cathode) but not if the di-
rection of current is reversed. Faults of diodes can be open
circuit in the conducting direction due to excessive cur-
rent and too much heat or conducting in both directions,
in most cases due to excessive voltages during operation.
f diodes with OHM-meter
Mn an Ohmmeter.
. . . be
Similarly, diodes can . . .
resistance of a good diode is very small In the conducting
direction (e g a few Ohms), whereas the resistance in the
insulating direction is very much higher (e.g. a few K Ohms)_
w
Short Circuit to Ground (diodes unsoldered).
Short circuit to ground of stators can be tested as usual
with a test lamp up to 40 V. . ‘
With diodes connected, short Circmt to ground can be
tested if their insulating direction is considered. The posi-
tive terminal of the tester must be applied to the stator
winding and the negative to the housing.
Note the test voltage: Not more than 24 V.
Short circuit of windings (diodes unsoldered)
As for D.C. generators a short circuit tester can be used
to test the stator. However, this test is only possible if the
alternator is dismantled, i.e. the stator must be removed.
Furthermore, short circuit of windings can also be ascer-
tained with an Ohm-meter. Three measurements must be
taken, one each on every two-phase wires: U — V, U — W
and V — W.
The resistance value of each measurement must be the
same, 0.26 ohm + 10 % (at 68°F = 20°C).
The Testers (test voltage 40 V) are suitable to test the in-
sulation of exciter winding and slip rings.
Check the exciter winding resistance from slip ring to slip
ring. The resistance value must be 4.0—4.4 Ohms.
Supply Su
pplv
(Anwe) (Cathode)
Conducting Dir.
Insulating Dir. Conducting Dir
Hill In (Hill ‘lllllllll I ll
Housin f "Ill
+Diod 9 D' d Homing
— io
321—6