THE TRI-CIRCUIT ALTERNATOR
The Tri-Circuit alternator consists of a single ring of
magnets inside the flywheel, which supplies the magnetic
field for a stator having one output lead which produces
AC voltage. The output lead connects to a charge lead
that contains one diode which rectifies minus -12 volts
DC (5 amps at 3600 RPM) for lights. This same charge
lead contains a second diode that rectifies plus +12 volts
DC (5 amps at 3600 RPM) for battery charging and
external loads. See Fig. 205. The alternator uses less
than 0.2 horsepower.
Fig. 205 - Tri-Circuit Alternator
If an accessory such as an electric clutch is used on the
equipment, 3.5 amps powers the clutch, and up to 1.5
amps charges the battery, thus not over-charging the
battery. A two-pole clutch switch is used on the vehicle
when an electric clutch is an accessory. When the clutch
is switched on, one circuit is used to engage the clutch,
and the other circuit bypasses the resistor, thus allowing
full alternator output to be applied to the battery and
clutch. Fig. 206 and 207.
Fig. 206 - Typical Wiring Diagram
Fig. 207 - Typical Wiring Diagram (Contd.)
If the clutch is not engaged, a resistor is placed in series
with the alternator charge lead, thereby limiting the
charge current to about 3 amps. See Fig. 207. The
resistor (20 watts), becomes hot and must be mounted
somewhere on the vehicle by the manufacturer.
The battery is not used for the lights, so lights are
available even if the battery is disconnected or removed.
Current for the lights is available as long as the engine is
running. 12 volt lights with a total rating of 60 to 100
watts may be used. With lights rated at 70 watts, the
voltage rises from 8 volts at 2400 RPM to 12 volts at
3600 RPM, so the brightness of the light changes with
the engine speed.
TESTING ALTERNATOR STATOR OUTPUT
Connect load lamp to AC (green connector) output plug
and ground as shown in Figure 208. Load lamp should
light to full brilliance at medium engine speed. If lamp
does not light, or is very dim at medium speeds, remove
blower housing and flywheel. Disconnect the ground
terminal end of AC coil, which is attached to the stator
laminations with screw.
Fig. 208 - Testing Stator Output