John Deere stx38 - Manual (Page 128)

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3/21/97
CIRCUIT OPERATION AND DIAGNOSIS ELECTRICAL
CHARGING CIRCUIT OPERATION
STX30 & STX38 (SN —210000)
Function:
To maintain battery voltage between 11.8 and 13.2.
Operating Conditions:
The key switch must be in the run position with the
engine running for the charging system to operate.
Theory of Operation:
The charging system is a permanent magnet and stator
design. Charging output is controlled by a regulator-
rectifier (N1).
As the flywheel turns, a permanent magnet located in
the flywheel induces AC current in the stator (G2)
windings. The AC current flows to the regulator-rectifier
(N1). The regulator-rectifier (N1) converts AC current to
DC current needed to charge the battery.
The voltage sensing circuit (210 red wire) allows the
regulator-rectifier (N1) to monitor battery voltage. If
battery voltage is low, the regulator-rectifier (N1) allows
DC current to flow to the regulator to charge it. When
the battery is fully charged, the regulator stops current
flow to the battery.