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

Charging System Operation 163
AC generators are double-contact units (Figure 8-40).
When the first set of contacts opens at lower rotor
speeds, current passes through a resistor wired in
series with the field circuit. These contacts are
called the series contacts. The value of the regulating
resistor is kept very low to permit high field
current when needed. At higher rotor speeds, the
coil further attracts the armature and a second set
of contacts is closed. This grounds the field circuit,
stopping the field current. These contacts are called
the shorting contacts because they short-circuit the
field to ground. The double-contact design offers
consistent regulation over a broad range of AC
generator speeds.
Figure 8-40. The circuit diagram of a double-contact
regulator. (Delphi Automotive Systems)
SOLID-STATE
REGULATORS
Solid-state regulators completely replaced the
older electromagnetic design on late-model vehicles.
They are compact, have no moving parts,
and are not seriously affected by temperature
changes. The early solid-state designs combine
transistors with the electromagnetic field relay.
The latest and most compact is the integrated circuit
(IC) regulator (Figure 8-41). This combines
all control circuitry and components on a single
Figure 8-41. An example of the latest integrated circuit regulator design, a Ford IAR
regulator and brush holder.