SkyTrak 6036 Service Manual - Manual (Page 215)

Section 10. Electrical System
Model 6036 S/N 9B0499 and Before 10-21
Fig. 10.25 Typical 12-SI Series Alternator
10.6 CHARGING CIRCUIT
The charging circuit, Fig. 10.26, is described in
paragraph 10.6.1.a.
10.6.1 Alternator
The alternator, Fig. 10.25, has a rotating field
system inside a stationary generating winding.
When the rotor rotates inside the stator, the output
produced is alternating current (ac). This is
unsuitable for charging the battery which requires
direct current (dc), so it is rectified by means of
diodes which convert it to unidirectional flow to the
battery.
“BAT”
TERMINAL NO. 1
TERMINAL
NO. 2
TERMINAL
TEST
HOLE
BEARING
ROTOR
SEAL
BEARING
SLIP
RINGS
SLIP RING
END FRAME
DRIVE
END FRAME
The alternator has a solid state regulator that is
mounted inside the alternator slip ring end frame.
The regulator voltage setting never needs adjust-
ing, and no provision for adjustment is provided.
The alternator rotor bearings contain sufficient
lubricant to eliminate the need for periodic lubrica-
tion. Two brushes carry current through two slip
rings to the field coil mounted on the rotor, and
under normal conditions will provide long periods
of attention-free service.
The stator windings are assembled on the inside
of a laminated core that forms part of the alterna-
tor frame. A rectifier bridge connected to the
stator windings contains six diodes, and electri-
cally changes the stator ac voltages to a dc
voltage which appears at the alternator output
terminal. Alternator field current is supplied
through a diode trio which also is connected to the
stator windings. A capacitor, or condenser,
mounted in the end frame protects the rectifier
bridge and diode trio from high voltages, and
suppresses radio noise.
No periodic adjustments or maintenance of any
kind are required on the entire alternator assem-
bly.
a. Charging Circuit Operating Principles
In Fig. 10.26, TERMINAL NO. 2 of the alternator is
connected to the battery and the base-emitter of
transistors TR3 and TR1 is connected to the
battery through resistor R5, thus turning these
transistors on. Also, resistors R2 and R3 are
connected to the battery through TERMINAL NO.
2, but the discharge current of the battery is very
low because of the resistance values of R2, R3,
R5, TR1 and TR3.
When the ignition switch is closed, current from
the battery flows through the indicator lamp to
alternator TERMINAL NO. 1, through resistor R1,
and transistors TR3 and TR1 to ground, and then
back to the battery. Also, current flows through
the alternator field coil and TR2 back to the
battery. The indicator lamp then turns on. Resis-
tor R6 carries some of the indicator lamp current.
With the alternator operating, ac voltages are
generated in the stator windings, and the stator
supplies dc field current through the diode trio, the
field coil, TR1, and then through the grounded
diodes in the rectifier bridge back to the stator.
Also, the six diodes in the rectifier bridge change
the stator ac voltages to a dc voltage which
appears between ground and the alternator “BAT”
terminal.
STATOR
ASSEMBLY MA1082
MA1081