Yanmar 4LHA-HTP Operation Manual page 645

Chapter 9 Electrical System
4. Alternator
4-5 Alternator functioning
(1) IC regulator
The IC regulator is the transistor (Tr,) which is series-
connected with the rotor. The IC regulator controls the
output voltage of the generator by breaking or conduc-
ting the rotor coil (exciting) current.
When the output voltage of the generator is within the
standard value, the transistor (Tr,) turns on. When the
voltage exceeds the standard value, the Zener diode
goes on and the transistor (Tr,) turns off.
With the repeated turning on and off of the transistor,
the output voltage is kept at the standard value.- (Refer
to the circuit diagram below.)
(2) Charge lamp
When the transistor (Tr,) is on, the charge lamp key
switch is turned to ON, and current flows to R„ R* and
to Tr, to light the lamp. When the engine starts to run
and output voltage is generated in the stator coil, the
current stops flowing to this circuit, turning off the
charge lamp.
(3) Circuit diagram
4-6 Handling precautions
(1) Be careful of the battery's polarity (+, - terminals), and
do not connect the wrong terminals to the wrong
cables, or the battery will be short-circuited by the
generator diode.
In this case too much current will flow, the IC regulator
and diodes burn out, and the wire harness will burn.
(2) Make sure of the correct connection of each terminal.
(3) When quick-charging, etc., disconnect either the bat-
tery terminal on the AC generator or the terminal on the
battery.
(4) Do not short-circuit the terminals.
(5) Do not conduct any tests using high tension insulation
resistance. (The diodes and IC regulator will bum out.)
BAT: Generator output terminal
D,.: IC protecting diode
L: Charge lamp terminal
ZD: Zener diode
E: Earth
Tr„ Tr,: Transistor
9 - i a
4LHA Seriei
\ Battery switch
| Battery
D,—D. Output commutation diode
Resistor
R,—R,
D,—D, Charging lamp switching diode
To supply current to rotor coil
F:
Thermistor
Rn:
(Temperature gradient resistance)