Kussmaul Electronics 091-149-12 - Manual (Page 3)

INTRODUCTION
The Auto Charge 75-BG, Model 091-149 is a compact, high output, completely automatic
battery charger. Available in a wide array of output voltages, it may be specified for operation
from either 120 volts or 230 volts, 50/60 Hz. The specification chart lists the various models
with the output current ratings.
Battery Charger Features:
* Electronic remote sensing of true battery voltage, eliminates the need for remote
sensing wires
* Automatic current limiting
* Battery charge/condition indicator, bottom bar indicates power "ON"
* 0-100 ampere panel meter to indicate charger output current
* A controlled fan operates when the current exceeds 30 amperes and keeps the
charger components cooled.
The charger functions automatically by adjusting its output voltage by varying the triggering
angle of the silicon controlled rectifiers of the full wave rectifier. Output current is detected by
sensing the voltage across a low resistance shunt and modifying the triggering angle to limit the
current. A block diagram appears in figure 1.
Automatic remote sensing measures the true battery voltage, eliminating the need for additional
sensing wires. The output current of the charger is inherently a series of pulses whose frequency
is determined by the power line frequency. Therefore there are brief intervals when no charging
current flows. During this brief interval the battery charger measures and stores the battery volt-
age. The measured voltage is compared to a reference and any error detected is used to control
the charger output.
This charger may remain energized and connected to the battery for extended periods of time
with no danger of overcharging or water boil-off.