Description
Power Supply Unit 640 mA
The power supply unit N 125/22 provides the system
power necessary for the instabus KNX. The connection to
the bus line is established by clicking the device onto the
DIN-rail (with a data rail installed) and/or via the bus
connection block located on the front side. If the power
supply N 125/22 is installed the bus connector module
REG 191 is not necessary (also for other DIN-rail devices
connected to the same data rail) because the bus voltage
is carried inside the device from the bus terminal block to
the data rail.
The integrated choke prevents the data telegrams from
short-circuiting on the bus line. When the built-in reset
switch is operated (operation > 20s), the bus devices are
returned to their initial state.
For each bus line, at least one power supply unit
N 125/22 is needed. Up to two power supply units may
be attached to a single bus line. A second unit is not
required unless the supply voltage at a bus device is less
than 21 V.
Note: If two power supply units N 125/22 are operated in
parallel on one bus line and if the overload LED is lit on
one or both power supplies, then the bus configuration
has to be changed until the overload display disappears.
The cable length between the two power supply units
N 125/22 operated in parallel is not prescribed.
When more than 30 bus devices are installed in short bus
cable distance (e.g. 10 m), e.g. in distribution boards, the
power supply unit N 125/22 should be arranged near
these bus devices. The distance between power supply
unit N 125/22 and any of its bus devices must not exceed
350 m.
The power supply unit N 125/22 has a voltage and current
regulation and is therefore short-circuit proof. Short
power failures can be bridged with a backup interval of
approximately 200 ms.
To ensure an uninterrupted power supply a separate
circuit with safety separation should be used for the
power supply unit N 125's power supply line.
The power supply units N 125/22 can supply DC 24 V
power from an additional pair of terminals (yellowwhite).
This DC 24 V output voltage can be used to
power e.g. an additional line via a separate choke N 120.
The power supply units N 125/22 can be powered by
AC 120…230V or by DC 220V.