DETROIT DIESEL 53
Battery-Charging Generator Regulator 7.1.1
acts to prevent oxidation of the voltage regulator contacts. Regulators incorporating the choke coil are identified by a
spot of green paint on the regulator base, next to the single mounting bolt hole.
CAUTION: A capacitor must not be installed unless the transistorized regulator incorporates the choke coil.
When the engine starting switch is closed, the field relay winding is energized and causes the contacts to close. Current
then flows from the battery through the relay contacts to the regulator "F2" terminal. From this point, the current flows
through the generator field winding and then through the transistor and voltage contact points to ground.
As the generator speed increases, the increased voltage from the generator "BAT" terminal is impressed through the field
relay contacts across the regulator shunt winding. The magnetism created in the winding causes the voltage contacts to
open, thus causing the transistor to shut off the field current. The generator voltage then decreases and the voltage
contacts reclose. This cycle repeats many times per second, thereby limiting the generator voltage to the value for which
the regulator is set.
The magnetism produced in an accelerator winding, when the voltage contacts are closed, aids the shunt winding in
opening the contacts. When the contacts are open, the absence of the magnetism in the accelerator winding allows the
spring to immediately re-close the contacts. This action speeds up the vibration of the contacts.
CAUTION: Do not short across or ground any of the terminals on the regulator or the generator and do not attempt
to polarize the generator.
The transistor regulator is composed principally of transistors, diodes, capacitors and resistors to form a completely static
electrical unit containing no moving parts.
The transistor is an electrical device which limits the generator voltage to a pre-set value by controlling the generator
field current. The diodes, capacitors and resistors act together to aid the transistor in performing this function, which
is the only function that the regulator performs in the charging circuit.
The voltage at which the generator operates is determined by the regulator adjustment. Once adjusted, the generator
voltage remains almost constant, since the regulator is unaffected by length of service, changes in temperature or
changes in generator output and speed.
A separately mounted field relay connects the regulator "POS" terminal and the generator field windings to the battery
when the engine starting switch is closed.
Fig. 4 - Transistor Regulator (Negative Ground Circuits Only)
May, 1971 SEC. 7.1.1 Page 5