Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

Charging System Operation 165
Figure 8-43. Field current in a typical solid-state regulator
during starting. (Delphi Automotive Systems)
Figure 8-44. Field current drawn from AC generator
(alternator) output. (Delphi Automotive Systems)
stable voltage across resistor R3. Resistor R4 prevents
excessive current through TR1 at high temperatures.
To prevent circuit damage, diode D3
bypasses high voltages induced in the field windings
when TR1 turns off. Resistor R2 is a thermistor,
which causes the regulated voltage to vary
with temperature. R5 allows the indicator lamp to
turn off if the field circuit is open.
For more information about voltage regulators,
see the “Voltage Regulator Service Section” in
Chapter 8 of the Shop Manual.
Specific Solid-State Regulator
Designs
GM Delco-Remy (Delphi)
The Delco-Remy solid-state automotive regulator
is used in Figures 8-43 to 8-46 to explain the basic
operation of these units. This is the integral regulator
unit of the SI series AC generators. The 1 and
2 terminals on the housing connect directly to the
regulator. The 1 terminal conducts field current
from the battery or the AC Generator (alternator)
and controls the indicator lamp. The 2 terminal
receives battery voltage and allows the Zener
diode to react to it.
Unlike other voltage regulators, the multifunction
IC regulator used with Delco-Remy CS-series
AC generators (Figure 8-46) switches the field
current on and off at a fixed frequency of 400 Hz
(400 times per second). The regulator varies the
duty cycle, or percentage of on time to total cycle
time, to control the average field current and to
regulate voltage. At high speeds, the on time might
be 10 percent with the off time 90 percent. At low
speeds with high electrical loads, this ratio could
be reversed: 90 percent on time and 10 percent off
time. Unlike the SI series, CS AC generators have