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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 operate as
Slaves. The Slave units are analog programmed by the Master unit. In remote digital operation (RS-232/RS-485,
etc.), only the Master unit can be programmed by the controller while the Slave units may be connected to the
controller for voltage, current and status readback only.
There are two parallel operating methods, Basic and Advanced, to configure multiple power supplies for
parallel operation. With both parallel operating methods, power supplies should be connected in a Daisy-Chain
configuration. Refer to Sections 5.15.1, to Section 5.15.2, and to Section 5.16 for additional details.
5.15.1
Basic Parallel Operation
In this method, setting the units as Master and Slaves is made by the rear panel J1 connections and the setup
DIP-switch SW1. Each unit displays its own Output current and Output 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 Basic parallel operation.
5.15.1.1 Setting up the Master Unit
Set the Master unit Output voltage to the desired voltage. Program the Output 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 to the programmed Output voltage. Connect the sensing circuit to local or remote
sensing as shown in Figure 5-4 or Figure 5-5.
5.15.1.2 Setting up the Slave Units
1. The Output voltage of all 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 Output current limit of each unit
should be programmed to the desired load current limit divided by the number of paralleled units.
2. Set the rear panel setup DIP-switch SW1-2 to the UP position.
3. Set the rear panel setup DIP-switch SW1-3 to the same position as SW1-4 of the Master unit.
4. Connect a wire jumper between J1-8 and J1-12 (refer to Table 4-4).
5. Connect J1-10 (IPGM) of the Slave unit to J1-25 (P) of the Master unit.
6. Connect J1-23 (IPGM_RTN) of the Slave unit to J1-12 (COM) of the Master unit.
During operation, the Slave units operate as a controlled current source that follows the Master unit Output
current. It is recommended that the power system be designed so that each unit supplies up to 95% of its Output
current rating because of the imbalance which may be caused by cabling and connection voltage drop.
5.15.1.3 Setting Over-Voltage Protection
The Master unit OVP setting should be programmed to the desired OVP level. The OVP setting of the Slave
units should be programmed to a higher value than that of the Master unit OVP setting. 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 unit Output voltage), only that Slave unit would shut down, and the remaining
Master/Slave units would supply all the load current.
5.15.1.4 Setting Foldback Protection
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.
5.15.1.5 Connection to the Load
In parallel operation, power supplies can be connected with local or remote sensing. Refer to Figure 5-4 and 5-5
for typical connections of parallel power supplies. The figures show the connection of two (2) units, however the
same connection method applies for up to four (4) units.
5.15.2
Advanced Parallel Operation
In this method, multiple power supplies can be configured to parallel operation as a single power supply. The
total calculated load current and Output voltage are displayed by the Master unit and can be read back 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 power supplies for Advanced parallel operation.
5.15.2.1 Basic Configuration
Repeat Steps 1 to 5 in Section 5.15.1 (Basic parallel operation).
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83-517-000 Rev. A
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