User manual

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5.15 PARALLEL OPERATION
Up to four units of the same VOLTAGE and CURRENT rating can be connected in parallel to provide
up to four times the output current capability. One of the units operates as a master and the
remaining units are slaves. The slave units are analog programmed by the master unit.
In remote digital operation, only the master unit can be programmed by the computer while the slave
units may be connected to the computer for voltage, current and status readback only.
There are two methods, basic and advanced, to configure multiple supplies for parallel operation.
Refer to Sec. 5.15.1 and to Sec. 5.15.2 for detailed explanation.
In this method, setting the units as Master and Slaves is made by the rear panel J1 connections and
the setup switch SW1. Each unit displays its own output current and voltage. To program the load
current, the Master unit should be programmed to the total load current divided by the number of
units in the system. Refer to the following procedure to configure multiple supplies for simple parallel
operation.
5.15.1 Basic parallel operation
5.15.2 Advanced parallel operation
In this method, multiple supplies can be configured to parallel operation as a single power supply.
The total load current and output voltage are displayed by the Master unit and can be readback
from the Master unit. The Slave units display only their operating status (On, Off or Fault
condition).
Refer to the following procedure to configure multiple supplies for Advanced parallel operation.
1. Basic configuration
Repeat steps 1 to 5 in Sec. 5.15.1 (Basic parallel operation).
1. Setting up the Master unit
2. Setting up the slave units
3. Setting Over Voltage protection
4. Setting Foldback protection
5. Connection to the load
Set the master unit output voltage to the desired voltage. Program the current limit to the
desired load current limit divided by the number of parallel units. During operation, the master
unit operates in CV mode, regulating the load voltage at the programmed output voltage.
Connect the sensing circuit to local or remote sensing as shown in Fig.5-4 or Fig.5-5.
-1.The output voltage of the slave units should be programmed 2%~5% higher than the output
voltage of the master unit to prevent interference with the master unit's control.
The current limit of each unit should be programmed to the desired load current limit
divided by the number of parallel units.
-2.Set the rear panel setup switch SW1 position 2 to it's up position.
-3.Set the rear panel setup switch SW1 position 3 in the same position as
SW1 position 4 of the master.
-4.Connect short between J1-8 and J1-12 (refer to Table 4-4.)
-5. Connect J1 terminal 10(IPGM) of the slave unit to J1 terminal 25(P) of the master unit.
-6. Connect J1 terminal 23(IPGM_RTN) of the slave unit to J1 terminal 12(COM) of the master
unit.
During operation the slave units operate as a controlled current source following the master
output current. It is recommended that the power system is designed so that each unit supplies
up to 95% of its current rating because of the imbalance which may be caused by cabling and
connections voltage drop.
The master unit OVP should be programmed to the desired OVP level. The OVP of the slave
units should be programmed to a higher value than the master OVP. When the master unit
shuts down, it programs the slave unit to zero output voltage. If a slave unit shuts down
(when its OVP is set lower than the master output voltage), only that unit would shut down
and the remaining slave units would supply all the load current.
Foldback protection if desired, may only be used with the master unit. When the master unit
shuts down it programs the slave units to zero output voltage.
In parallel operation, power supplies can be connected in local or remote sensing. Refer to
Fig.5-4 and 5-5 for typical connections of parallel power supplies. The figures show
connection of two units, however the same connection method applies up to 4 units.