CD5.121

CD-Series

DC/DC Converter 12V, 8A

20/22

an

r.

n top of the unit).

The DC/DC-converter can be paralleled to increase the output power. There are

no feature included which balances the load current between the DC/DC-

converters. Therefore some restrictions and limitations apply. The DC/DC-

converter with the higher adjusted output voltage draws current until it goes

into current limitation. This means no harm or switch-off to this DC/DC-converter

as long as the ambient temperature stays below 45°C. The CD5.121 can also be

paralleled with power supplies from the QS10.121 from the DIMENSION QS-

series. For other power supplies consult PULS.

The output voltages of all DC/DC-converters shall be adjusted to the same value

(±100mV) at full load. A fuse or diode on the output of each unit is only required

if more than three units are connected in parallel. This avoid that more than 2 times of the nominal output current c

flow backwards into the DC/DC converter in case the output stage of one DC/DC converter has a defect. If a fuse (or

circuit breaker) is used, choose one with approximately 150% of the rated output current of one DC/DC-converte

Keep an installation clearance of 15mm (left / right) between two DC/DC-converters and avoid installing the DC/DC-

converters on top of each other. Do not use DC/DC-converters in parallel in mounting orientations other than the

standard mounting orientation (input terminals on the bottom and output terminals o

Unit A

Input

Output

Unit B

-

+

-

+

+

-

Input

Output

Load

The DC/DC converters can be paralleled for 1+1 redundancy to gain higher system availability. Redundant systems

require a certain amount of extra power to support the load in case one DC/DC converter fails. The simplest way is to

put two DC/DC converters in parallel. This is called a 1+1 redundancy. In case one DC/DC converter 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 an N+1 method. E.g. six DC/DC converters, each rated for 8A are paralleled to build a 40A

redundant system.

Furthermore, 1+1 redundant systems can be built by using a DC/DC converter powered from a battery and a power

supply with AC input.

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 DC/DC-converter. In such a case, the defect unit becomes a load for the other DC/DC-

converters and the output voltage can not be maintained any more. This can only be avoided by utilizing decoupling

diodes which are included in the decoupling module YR2.DIODE.

Recommendations for building redundant power systems:

a)

Use separate input fuses for each DC/DC-converter.

b)

Monitor the individual DC/DC-converter units.

c)

1+1 Redundancy is allowed up to an ambient temperature of 60°C

N+1 Redundancy is allowed up to an ambient temperature of 45°C

d)

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

Mar. 2016 / Rev. 1.5 DS-CD5.121-EN

All parameters are specified at 12V, 8A, 24Vdc input voltage, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.

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Germany