July 2013 3.16 Digital PLC inputs/outputs 269
3.16 Digital PLC inputs/outputs
Input signals and
addresses
Input signals of the switching inputs:
If 24 V DC is present, and therefore a "1" signal is transmitted, the PLC inputs
of the HSCI system consume a current of 5 mA.
Output signals and
addresses
The switching outputs are transistor outputs with current limitation.
Please note:
Permissible load: Resistive load (ohmic load). Inductive loads (e.g. relay,
contactor) with an energy content of up to 100 mJ do not require a
quenching diode. If the energy content exceeds 100 mJ: only with
quenching diode parallel to inductance. Pay attention to the manufacturer's
specification of the energy content when selecting the switching devices.
For the rated operating currents of the PLC outputs, see "Rated operating
current per output" on page 266.
If an output is operated with an inductive load without a quenching diode
and is read back to an input, the input must be protected by varistors or RC
circuits.
PLD-H: The outputs are short-circuit proof.
For component-related reasons, the switching outputs should be loaded
with at least 5 mA in "1" state. They conform to EN 61131-2. If a resistive
load consumes less than 5 mA, it is necessary to either insert a relay or
perform a usability test in accordance with the calculation described in the
following, see "Calculation of the voltage drop in "0" state" on page 270.
For component-related reasons, a current of I
Off
= 500 µA flows through the
switching outputs also in "0" state. If high-impedance loads with a low-level
lower switching threshold are connected directly to the output, the voltage
drop can lead to a "1" state. In such a case, a shunt resistor must be
connected to the output, see "Calculation of the voltage drop in "0" state" on
page 270.
If the holding brakes of motors are not driven exclusively over the inverter
outputs for brakes, a protective circuit in the form of a varistor must be used.
Due to the inductance of the holding brakes and any relays used, a voltage
peak that may exceed 1000 V occurs when the exciting current is switched
off. This may destroy other electronics, such as connected PLC inputs/
outputs.
A protective circuit is not necessary only if the holding brakes are driven
exclusively over the inverter outputs for brakes, because the voltage is
limited internally by electronic switches in the inverters.
Voltage range PLD-H
(with LED)
UEC 11x, X9 of PL 62xx, and
machine operating panel
(without LED)
"1" signal: U
i
11 V to 30.0 V 11 V to 30.0 V
"0" signal: U
i
–3.0 V to 2.2 V –3 V to 2.2 V
Current range PLD-H
(with LED)
UEC 11x, X9 of PL 62xx, and
machine operating panel
(without LED)
"1" signal: I
i
2.0 mA to 6.1 mA 2.1 mA to 6.0 mA
"0" signal: I
i
at
U
i
= 2.2 V
0.3 mA 0.43 mA
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