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 TM 55-1905-220-14-5
3-62.2. VOLTAGE REGULATOR-MAINTENANCE INSTRUCTIONS (Cont).
(2) Operation.
(a) When the engine is not running, the armature contact points of the relay are held away from the
stationary points by tension of a leaf spring.
(b) As the engine starts and the generator speed increases, the current flowing through the shunt
winding builds up until it reaches the value for which the relay has been set. At this point, sufficient magnetism
overcomes the armature spring tension, the contact points close and the current flows to the battery. Then the
current which flows through the series winding is in the right direction to add to the magnetic force holding
the armature down and the points closed.
(c) When the engine is slowed down or stopped, the magnetic field is not strong enough to hold the
armature down. The leaf spring pulls the armature away from the core and the points separate,
opening the circuit.
CAUTION
The regulator cutout relay contact points must never be closed by hand with the battery
connected. This would cause a high current flow through the units and damage them.
c. Voltage Regulator.
(1) The voltage regulator has two windings on a single core. One is a shunt winding consisting of
many turns of fine wire which, in series with a resistor, is shunted across the generator at all
times. The second winding is a field current winding which is connected between the generator field circuit
and ground whenever the regulator contact points are closed. In addition to the core
frame, armature and contact points, the unit has a spiral spring which holds the armature away from the
core so the contact points are touching when the voltage regulator is not operating.
(2) Operation.
When the generator voltage reaches the value-for which the voltage regulator is adjusted, the combined
magnetic field produced by the shunt winding and the field current winding overcomes the armature spring
tension, pulls the armature down, and separates the voltage regulator contact points. This introduces
resistance into the generator field circuit so the generator field current and
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