C.E. Niehoff & Co. N1128 Troubleshooting Guides - Manual (Page 2)

Page 2
TG0027A
Section 1: Component Description and Operation
CEN N1128 Dual Voltage Alternator De-
scription and Operation
N1128 28 V 100 A alternator with 28 V/14 V (60 A
maximum on 14 V) is internally rectified. All wind-
ings and current-transmitting components are non-
moving, so there are no brushes or slip rings to wear
out.
After the
N3212 regulator receives energize signal, it
monitors alternator rotation and provides field
current only when it detects alernator shaft rotating
at suitable speed.
After regulator detects alternator rotation, it gradu-
ally applies field current, preventing an abrupt
mechanical load on accessory drive system. The soft
start may take up to 20 seconds.
N3212 regulator used with these units also
• is negative temperature compensated. Setpoints
are 28.0 ± 0.2 V and 14.0 ± 0.2 V at 75° F.
• provides overvoltage cutout (OVCO). Regulator
will trip OVCO when system voltage rises above
32 V in a 28 V system (16 V in a 14 V system) for
longer than 2 seconds. OVCO feature detects high
voltage and causes alternator field circuit to open,
turning off alternator. Restarting engine resets
OVCO circuit. If vehicle remains operating after
OVCO trip, the OVCO will automatically reset
when system voltage drops to 22 V (11 V on 14 V
side). Regulator then resumes normal operation.
• maintains alternator output voltage at regulated
settings as vehicle electrical loads are switched
on and off.
• allows 28 V only voltage operation if 14 V loads
are not used in the application and 14 V terminal
on regulator is not terminated.
• provides optional 14 V output at the regulator
14 V terminal when phase cable from alternator
is connected to regulator.
• maintains battery equalization between 28 V and
14 V if 14 V output is used.