C.E. Niehoff & Co. C709/C725 Troubleshooting Guides - Manual (Page 2)

Page 2
TG64B
Section A: Description and Operation
CEN C709 and C725 Dual Voltage Alternators
Description and Operation
C709 and C725 240 A (28 /14 V) dual voltage alterna-
tors are internally rectified. All windings and current-
conducting components are non-moving, so there are no
brushes or slip rings to wear out. Energize switch (com-
monly an oil pressure switch or ignition switch) acti-
vates regulator. Field coil is then energized when rota-
tion is detected. Upper voltage (28 V) is rectified with
standard diodes. Lower voltage (14 V) circuit output cur-
rent is controlled by SCRs. Alternator output current is
self-limiting and will not exceed rated capacity of alter-
nator.
A2-329 regulator used with these units also
• is flat temperature compensated. Setpoints are 28.0
± 0.2 V and 14.0 ± 0.2 V.
• provides overvoltage cutout (OVCO). Regulator will
trip above 32 V for 28 V system (16 V for 14 V
system) longer than 2 seconds. OVCO feature detects
high voltage and reacts by signaling relay in F–
alternator circuit to open, turning off alternator.
Restarting engine resets OVCO circuit. If vehicle is
run in OVCO mode, OVCO will automatically reset
when system charging voltages drop below 11 V for
both 14 and 28 volt batteries. Regulator
regains control of alternator below output voltage.
• maintains alternator output voltage at regulated
settings as vehicle electrical loads are switched
on and off.
B– terminal
Figure 2 — C709 and C725 Alternators with A2-329 Regulator
Figure 1 — C725 Alternator and
A2-329 Regulator Terminals
14 V B+
terminal
28 V B+
terminal



E terminal
