TM 5-3895-346-14
REGULATOR
ENGINE OVERHAUL
When the dc voltage of the ac - dc system reaches the value for which the voltage regulator is adjusted, the
magnetic field produced by the shunt winding overcomes the armature spring tension and pulls the armature
down, causing the contact points to separate. When the contact points separate, resistance is introduced into
the field circuit. The resistance decreases the field current causing a corresponding decrease in generator
voltage and magnetic pull on the regulator armature. This allows the armature spring tension to reclose the
contact points. When the voltage again reaches the value for which the voltage regulator is adjusted, this cycle
repeats and continues to repeat many times a second, thus limiting the voltage to the value for which the
regulator is set.
With the voltage limited in this manner, the generator supplies varying amounts of current to meet the various
states of battery charge and electrical load.
Voltage regulators are compensated for variations in temperature by means of a bimetal thermostatic hinge on
the armature. The effect of this hinge causes the regulator to adjust at a higher voltage when cold, which partly
compensates for the fact that a high voltage is required to charge a cold battery.
CONTROL RELAY
In addition to a circuit breaker and a voltage regulator, the three-unit regulator has a control relay unit. This
unit has a core with a single shunt winding connected from the SW terminal of the regulator to ground. The
winding and core are assembled into a frame. A flat steel armature supporting the upper one of two relay
contacts is attached to the frame by a hinge and is centered above the core. The lower contact point is
supported by a detachable contact support insulated from the frame. An armature stop is assembled above the
upper contact.
Operation
When the ignition switch is OFF, the contact points are held apart by the tension of a spiral spring acting on the
armature. When the ignition switch is turned ON, battery current flows through the control relay winding to
ground. The magnetic field produced by the winding overcomes the armature spring tension and pulls the
armature down causing the contact points to close. This completes the circuit to ground for the circuit breaker
relay winding so that it can operate when the dc voltage from the power rectifier reaches the value for which the
circuit breaker relay is adjusted. The control relay contact points remain closed until the ignition switch is
turned OFF.
TRANSISTORIZED AND TRANSISTOR REGULATORS
In addition to the standard regulator, there are two other types of regulators being used with the self-rectifying
ac generators in the battery-charging circuit. One is a transistorized regulator which contains a vibrating
voltage regulator unit and a field relay unit. The other is a transistor regulator which contains no moving parts
and is used with a separately mounted field relay.
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