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

Charging System Operation 173
Figure 8-60. A 10-SI series AC generator [Delcotron].
(Delphi Automotive Systems)
Figure 8-59. A 10-SI series AC generator (alternator).
(Delphi Automotive Systems)
provide current output. Field current is drawn from
rectified output and travels through a B-circuit.
The terminals on a 10-DN are labeled BAT, GRD,
R, and F. If the AC generator is used with an external
electromagnetic regulator, the following
applies:
• BAT connects AC generator output to the
insulated terminal of the battery.
• GRD, if used, is an additional ground path.
• R, if used, is connected to a separate field
relay controlling the indicator lamp.
• F connects the rotor winding to the voltage
regulator.
Some 10-DN alternators are used with a
remotely mounted solid-state regulator. The voltage
control level of this unit is usually adjustable.
The terminal connections are the same for electromagnetic
and solid-state regulators.
SI Series
The 10-SI series AC generator uses an internally
mounted voltage regulator and came into use in
the early 1970s. The most common early model
Delcotron alternators are part of the SI series and
include models 10, 12, 15, and 27 as shown in
Figure 8-60. A 14-pole rotor is used in most models.
The 10-SI and 12-SI models have Y-type
stators, and the 15-SI and 27-SI models have
delta-type stators. Two general SI designs have
been used, with major differences appearing in
the rear housing diode installation, regulator
appearance, field circuitry, and ground path.
Most SI models have a rectifier bridge that
contains all six rectifying diodes (Figure 8-61).
The regulator is a fully enclosed unit attached by
screws to the housing. Field current is drawn
from unrectified AC generator output and rectified
by an additional diode trio. All SI models
have A-circuits, their terminals are labeled BAT,
No. 1, and No. 2.
• The BAT terminal connects AC generator
output to the insulated terminal of the battery.
• The No. 1 terminal conducts battery current
to the rotor winding for the excitation circuit
and is connected to the indicator lamp.
• The No. 2 terminal receives battery voltage
so the voltage regulator can react to system
operating conditions.
All SI models have a capacitor installed in the rear
housing to protect the diodes from sudden voltage
surges and to filter out voltage ripples that could
produce EMI. The 27-SI, which is intended
principally for commercial vehicles, has an
adjustable voltage regulator (Figure 8-62). The
voltage is adjusted by removing the adjustment
cap, rotating it until the desired setting of low,