Sensor systems 2 AS-Interface

Issue date 2004-11-19 - Catalogue AS-Interface 2004/2005
Gateway
AS-Interface
power supply
AS-Interface - Power Supplies, Power Extenders and Repeaters
AS-Interface
3 Power Supplies, Power Extenders
and Repeaters
On the AS-lnterface data and power supply are transferred on only
2 conductors. Data communication is based on an AC current supply, while
the power supply is DC (29.5 ... 31.6 V). In this respect a power pack with
a decoupling network is required for the AS-Interface power supply. All power
packs satisfy the PELV (Protective Extra Low Voltage) requirements of
EN 50178 and EN 60204, so that a protective conductor (PE) is not required
for the AS-Interface circuit. Since the AS-Interface has a symmetrical
design, the system ground should be connected to the shield terminal on
the power pack.
To increase system safety an earth fault monitor function is integrated in
some power packs. This reliably signals any irregularity in the contact between
the AS-Interface cable and the earth potential. Whilst on the one
hand such a fault can lead to a breakdown of AS-Interface communication,
two earth faults can lead to the uncommanded operation of a plant item,
which can then no longer be switched off by the system. This must be prevented
in accordance with EN 60204. A method, which can be employed
here, is to arrange for the AS-Interface network to be switched off on detection
of an earth fault.
Depending on the size of the system, power packs providing between 2.4 A
and 8 A can be inserted at any point in the AS-Interface network. For dual
masters, there are also corresponding dual power supplies available. If particularly
large consumers are present, the power supplies should be placed
in their vicinity.
Repeater
Segment 1
Segment 2
AS-Interface
power supply
Switch cabinet In field
If this is not possible, for example due to the protection class required, then
the master can be used as a field device, together with a series-connected
power extender. By this means the length of cable between the power
pack and the power extender does not count as part of the AS-Interface network
length and in this way a number of AS-Interface networks, each with
a master and series-connected power extender, can be supplied by a single
power pack.
At least 28 V must be applied to the power extender to ensure that it functions.
The sum of the input currents to the AS-Interface stations must be
less than the maximum output current of the power pack. In the case of the
modules the current consumption comprises the following: Operating current,
current consumption of the sensors supplied by the AS-Interface, plus
the current needed to drive the outputs, if these are not externally supplied.
Subject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
Pepperl+Fuchs Group Tel.: Germany +49 621 776-0 USA +1 330 4253555 Singapore +65 67799091 Internet http://www.pepperl-fuchs.com
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Masters and
Gateways
Power Supplies,
Extender, Repeaters
Safety at work
I/O Modules - Control
cabinet
I/O Modules - Field
application
Analogue modules
Other modules
Inductive sensors
Photoelectric
sensors
Rotary encoders
Accessories