Circuit Description; Figure 5-1 Block Diagram, Typical Are-S Float Charger - Unipower ARE–S Series Product Manual

ARE-S Series Chargers, Single Phase

5. CIRCUIT DESCRIPTION

Figure 5-1 is a functional block diagram of a ARE-S series float charger. AC input power is applied through the
input circuit breaker to the power transformer. The circuit breaker provides over-current and fault protection in
case of malfunction or a short circuit in the input side of the equipment.
Single-Phase
AC Input
AC
Circuit
Breaker
Power Transformer
SCR Rectifiers

FIGURE 5-1 BLOCK DIAGRAM, TYPICAL ARE-S FLOAT CHARGER

The output voltage regulation against changes in load, line input levels, and frequency changes is provided by a
half-controlled SCR bridge rectifier, which controls the voltage output to the DC filter.
The electronic voltage/current control senses the start of the AC cycle. It also senses the output voltage level,
which it compares with a reference setpoint. The error signal that results determines the instant to fire the SCRs
during the AC cycle and maintain the DC output level.
The output current sensing and current limit operation is located on the Interface and Control/Display boards.
The output current is sensed by measuring the voltage across a resistive shunt. The Interface and Control/Display
boards convert the shunt signal into an output current value. When the output current exceeds the preset level, the
current limit control overrides the voltage control to reduce the output current to the preset value.
Over-voltage protection is located on the Interface and Control/Display boards. If a fault occurs that result in the
charger output going to an excessively high output voltage for more than 15 seconds, a "primary" high voltage
shutdown is initiated. The high voltage shutdown mode will cease firing the SCRs, which will turn off the output
to the charger. The charger will attempt to restart up to 3 times if the output falls below a safe level. If the
excessive high voltage condition persists the charger will shutdown until the AC breaker is toggled. If the high
voltage persists above a safe level for more than ~20 seconds, a second protection circuit, independent from the
first, operates to remove triggering of the SCRs turning off the charger. To reset this "secondary HVSD" the DC
breaker must be opened and the internal DC bus must fall below 10Vdc. The user must then restart the charger
using the SEL key on the front panel.
The SCR rectifiers convert the AC voltage from the transformer into a DC voltage. The output of the rectifiers is
filtered and supplied to the battery and the load through the DC circuit breaker.
Optional Relay Board
OPT Alarm Relays
Trigger
Circuitry
DC Filter
5-1
Alarms LEDs
High Voltage
Shutdown
Electronic
Voltage & Current
Control
DC Circuit Breaker
Circuit Description
Control and Display Board
Operator Panel
STD Alarm Relays
Interface Board
Battery and Load
PM990.1090.XX, Rev. 10