ker88839_ch08.qxd
1/9/06
11:28 AM
Page 163
Charging System Operation
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
163
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.
SOLID-STATE REGULATORS
Figure 8-40. The circuit diagram of a double-contact regulator. (Delphi Automotive Systems)
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.
