CPS20.481

C-Series

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CPS20.481 power supplies can be paralleled to increase the output power. The

output voltage of all power supplies shall be adjusted to the same value

(±100mV) in “Single use” mode with the same load conditions on all units, or

the units can be left with the factory settings. After the adjustments, the

jumper on the front of the unit shall be moved from “Single use” to “Parallel

use”, in order to achieve load sharing. The “Parallel use” mode regulates the

output voltage in such a manner that the voltage at no load is approx. 4%

higher than at nominal load. See also chapter 6. If no jumper is plugged in, the

unit is in “Single use” mode. Factory setting is “Single use” mode.

If more than three units are connected in parallel, a fuse or circuit breaker

with a rating of 15A or 16A is required on each output. Alternatively, a diode or redundancy module can also be

utilized.

Unit A

AC

DC

Unit B

AC

DC

-

+

-

+

Load

+

-

required output current is higher than the current of one unit.

Keep an installation clearance of 15mm (left / right) between two power supplies and avoid installing the power

supplies on top of each other. Do not use power supplies in parallel in mounting orientations other than the standard

mounting orientation (terminals on bottom of the unit) or in any other condition where a derating of the output

current is required (e.g. altitude, above 60°C, …).

Pay attention that leakage current, EMI, inrush current, harmonics will increase when using multiple power supplies.

Power supplies can be paralleled for redundancy to gain higher system availability. Redundant systems require a

certain amount of extra power to support the load in case one power supply unit fails. The simplest way is to put two

power supplies in parallel. This is called a 1+1 redundancy. In case one power supply unit fails, the other one is

automatically able to support the load current without any interruption. Redundant systems for a higher power

demand are usually built in a N+1 method. E.g. five power supplies, each rated for 10A are paralleled to build a 40A

redundant system. For N+1 redundancy the same restrictions apply as for increasing the output power, see also section

22.5.

Please note: This simple way to build a redundant system does not cover failures such as an internal short circuit in

the secondary side of the power supply. In such a case, the defective unit becomes a load for the other power supplies

and the output voltage can not be maintained any more. This can be avoided by utilizing redundancy modules, which

have decoupling devices (diodes or mosfets) included. Further information and wiring configurations can be found in

chapter 21.3.

Recommendations for building redundant power systems:

a)

Use separate input fuses for each power supply.

b)

Set the power supply into “Parallel use” mode.

c)

Monitor the individual power supply units. Therefore, use the DC-OK relay contact of the CPS20 power supply.

d)

It is desirable to set the output voltages of all units to the same value (± 100mV) or leave it at the factory setting.

Apr. 2014 / Rev. 1.5 DS-CPS20.481-EN

All parameters are specified at 48V, 10A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.

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