Figure 13-36. Transistorized Voltage Regulator
alternator output. The solid-state regulator virtually has
(1) It can be used to isolate the field circuit from
replaced the mechanical units in all currently produced
the battery whenever the ignition switch is turned off (fig.
equipment due to the extreme reliability and low
13-39). In this application, the magnetic coil is energized
manufacturing costs of solid-state components. Another
with the ignition switch. The contact points then pull
desirable feature of a solid-state regulator is that it can
together, completing the field circuit.
be made small enough to be built into the alternator.
(2) It also can be used to operate an alternator
no-charge warning light (fig. 13-39). In this application,
13-30. Accessory Items.
the magnetic coil is energized by one of the stator
windings. This will cause the contact points to be pulled
a. Fuel Pressure Field Switch (Fig. 13-38). The
together whenever the alternator produces sufficient
fuel pressure field switch is a device that is used on high
current to sustain operational voltage. When the contact
output alternators to prevent the alternator from placing a
points are open (alternator not operating), the field circuit
load on the engine until it is running by opening the
receives current from a lead that passes in series
alternator field circuit until the fuel pressure reaches the
through an indicator lamp that is in parallel with a
normal operational range.
resistor. The field current will cause the lamp to light. As
the alternator begins to produce, the field relay contact
b. Field Relay. The field relay is used in two basic
points will close, shunting the field circuit directly to
battery voltage, causing the indicator lamp to go out.