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Guide to Wiring for Master-Slave Parallel Operation

DC Power Supply: Basic Wiring to Load and Action against Unstable Output

Many of our DC power supply products are equipped with a parallel operation function that allows the output capacity to easily increase by connecting DC power supply units of the same model in parallel. Master-slave parallel operation is highly rated and the front panel of the master unit displays the settings and output level of all the power supply units in parallel connection. In this mode, operability is comparable with single-unit operation.

Users are asked to carry out wiring (for signal systems and to the load) to enable parallel operation, which is very useful as explained above. Operation Manuals refer to the steps for the wiring; however there are surprisingly many cases where the wiring is not completed as instructed. In particular, improper wiring to the load causes abnormal oscillation, which users may regard as a fault and contact us with inquiries. There is little difference in the steps for wiring to the load for parallel operation between the product series. The following explains the basic steps for wiring and actions to correct instability. (Note: These steps and actions are not applicable to the PBZ Series high speed bipolar power supply.)

1. Basic Wiring

(1) Make sure that the lines from the power supply units to the load are an identical short length. As illustrated in Fig. 1, confirm that the L1, L2 and L3 wires are the same length and make them as short as possible.

(2) If long wires to a load are required, connect the power supply to a relay using the shortest possible line and put a long line between the relay and the load. In this event, twist the line (L4) if possible.

Fig. 1 provides an example.

Figure 1

Make sure that the L4 wire is a sufficient diameter to safely pass the total current of three power supply units. In this fundamental wiring configuration, hunting may occur or the output may be unstable. In this event, take the actions explained below. While observing the status, try any or all of the actions.

2. Action when Unstable Output still occurs

Figure 2

(1) Connect the negative or positive side of the output terminal to ground it. In Fig. 2, the green lines represent ground wires.

If the input terminal of the DUT is not grounded, either the negative or positive side may be grounded. If the DUT is grounded, attach the grounding to the side of the output terminal identical to the side on which the DUT is grounded.

(2) Lay transition wiring, represented by yellow lines in Fig. 2, between the output terminal on the side serving as the control common.

If the negative terminal is the control common, interconnect the negative terminals. If the positive terminal is the control common, interconnect the positive terminals.

Control Common


Control Common


Positive terminal


Positive terminal


Negative terminal


Negative terminal


Negative terminal


Negative terminal


Negative terminal


Negative terminal


Negative terminal

(3) Connect a large capacity capacitor, represented in pink in Fig. 2, to the relay.

Note: No such capacitor may be connected to the PBZ Series high speed bipolar power supply.

These actions will address most of the problems arising from the load wiring.

Nobuo Kanzaki
SE Section, Solution Business Promotion Department

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The PAD-L, PMC and PAN Series DC stabilized power supplies and special order items
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