DETROIT DIESEL 53
Battery-Charging Generator Regulator 7.1.1
Fig. 5 - Transistor Regulator with Plug-In Connections
The voltage regulator illustrated in Fig. 4 is designed for negative ground battery-charging circuits only. It has two
exposed terminals. The voltage setting may be adjusted by relocating a screw in the base of the regulator.
The voltage regulator shown in Fig. 5 has shielded plug-in connections and requires a cable and plug assembly to
connect the regulator into the battery-charging circuit. This type of regulator may be used in negative ground, positive
ground and insulated charging circuits. The voltage setting may be adjusted by removing a plug in the cover and
turning a slotted adjusting button inside the regulator.
Operation
When the engine starting switch is closed, the field relay winding is energized, which causes the relay contacts to close.
In the negative ground circuit with the field relay contacts closed and the engine not running, generator field current can
be traced from the battery through the relay contacts to the regulator "POS" terminal. Current then continues through the
back-bias diode (D-1) and power transistor (TR-1) to the regulator "FLD" terminal, and then through the generator field
winding to ground, completing the circuit back to the battery.
When the generator begins to operate, A.C. voltages are induced in the stator windings. These voltages are changed, or
rectified, to a D.C. voltage which appears at the output, or "BAT", terminal on the generator. The generator then
supplies current to charge the battery and operate vehicle accessories.
As generator speed increases, the voltage reaches the pre-set value and the components in the regulator cause
transistor TR-I to alternately "turn off" and "turn on" the generator field voltage. The regulator thus operates to limit the
generator output voltage to the pre-set value.
In the positive ground circuit, when the switch is closed and the engine is not running, the field current can be traced from
the battery positive ground to generator ground, and then to the regulator "POS" terminal. The current continues through
diode D-l and transistor TR-1 to the regulator "FLD" terminal, and then through the field winding and field relay contacts
back to the battery, thus completing the circuit. Except for this primary difference, this circuit operates in the same
manner as that described for the negative ground circuit.
REGULATOR PRECAUTIONS
Never short or ground the regulator terminals: do not attempt to polarize the circuit.
Make sure all connections in the charging circuit are tight to minimize resistance.
Refer to "A.C. Generator Precautions" in Section 7.1.
Page 6
