ARE Series Chargers
RS-759, Rev. 11
5-7
5.8.1.2
Load Sharing
Load sharing allows two or more power supplies connected in parallel to share the load in proportion to their
ratings. The power supplies will share the load within 5% of the rating of the largest unit between 10% and 100%
of their ratings. The load sharing is connected through the no charge alarm, which disconnects the load sharing
should one charger shut off.
5.8.2
Connections
A.
The No Charge Alarm form C contact is terminated at TS7-2, 3, 4. The common (4) and normally closed (2)
contact is closed during a low current condition.
B.
For load sharing connect all units which are to share the load to the system bus using equal lengths of
properly sized cables from output of each power supply. Connect #18 AWG insulated wire from TS7-1(LS)
of charger A to TS7-1(LS) of charger B.
5.8.3
Adjustment
A.
The No Charge Alarm is set by potentiometer P2 on the printed circuit board. Turning P2 clockwise
increases the current at which the alarm activates. To check the alarm setting, slowly reduce the power
supply output current by reducing the load or the output voltage until the alarm activates. To set the alarm,
turn P2 counterclockwise. Adjust the output current to the desired alarm setting. Turn P2 clockwise until the
alarm activates. In order for the load sharing to operate properly, the No Charge Alarm must be set close to
zero current.
B.
Load Sharing:Turn on only one unit at a time and adjust the output voltage to the desired level using a digital
voltmeter. Connect a digital voltmeter positive lead to the power supply positive output and the negative lead
to TS7-1(LS). Adjust potentiometer P1 on the alarm board for 5.0VDC at zero output current.
5.8.4
For Two Power Supplies
Turn on both units. Add some load to the system and adjust P1 on the unit with lower output to match the output
of the other unit. For best results the load should be between 50% and 100% of the combined rating of the
equipment.
5.8.5
For More Than Two Power Supplies
Start by adjusting two of the units then add the rest of the units one at a time, adjusting P1 on each added unit
until all units are sharing the load.
5.8.6
Operational Notes
1.
Load sharing is not intended to be effective below 10% of rated output. Operation below 10% may result in
unequal outputs or loss of output current form one of the units. It is recommended that where paralleled units
are being used to float a battery before the system load is installed, only one unit be left operating.
2.
Occasional minor movements in the panel ammeter pointer may occur when paralleled units are operated at
light loads. This is an indication of the transfer of small currents between units and does not show up at the
load.
3.
It is possible for hunting to occur if the output voltages are mis-adjusted. Repeat Step B under “Adjustment”.
5.8.7
Specifications
A.
No Charge Alarm
Contact Ratings
1 Ampere at 28 Volts DC or 120 Volts AC
Pickup/Dropout Differential
3%
