VOLTAGE REGULATOR
DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulat-
ing circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
OPERATION
The amount of DC current produced by the gener-
ator is controlled by EVR circuitry contained within
the PCM. This circuitry is connected in series with
the generators second rotor field terminal and its
ground.
Voltage is regulated within the PCM on the NGC
vehicles, to control the strength of the rotor magnetic
field. The EVR circuitry monitors system line voltage
at the PDC and calculated battery temperature or
inlet air temperature sensor (refer to Inlet Air Tem-
perature Sensor, if equipped, for more information ).
It then determines a target charging voltage. If
sensed battery voltage is lower than the target volt-
age, the PCM feeds the field winding until sensed
battery voltage is at the target voltage. A circuit in
the PCM cycles the feed side of the generator field at
250 times per second (250Hz), but has the capability
to feed the field control wire 100% of the time (full
field) to achieve the target voltage. If the charging
rate cannot be monitored (limp-in), a duty cycle of
20% is used by the PCM in order to have some gen-
erator output. Also refer to Charging System Opera-
tion for additional information.
JR
CHARGING
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