DAC-42(A)-x-PN
Page 18
DAC-42(A)-x-PN
Manual
Revision: 1.0
22.01.2024
5.2.3 EMC
Devices DAC-4x(A) series are class “A” equipment and therefore only suitable for industrial surroundings.
The distance between a source of interference (device emitting interference) and an interference sink (a device under the
influence of interference) is very important. The greater the distance between the source of interference and the sink, the
smaller the effects on the equipment will be. In other words, the closer a device is placed to the source of interference, the
greater the interference amplitudes. For this reason, a minimum gap of 0.25 m should be kept between the amplifiers and
strong sources of interference. The following devices are to be regarded as strong sources of interference:
• Switching power supply units
• Frequency converters
• Digital drive modules
• Mains filters with wiring (even if shielded)
• AC/DC commutator motors
• Motor cables (even if shielded)
• Switched inductances, even if anti-interference measures have been taken (solenoid valves, contactors, relays, etc.)
One of the most common input points for interference is wiring. If interfering cables are laid at least 0.25 m away from cables
susceptible to interference, the influence on each other can be minimized. Parts of the amplifier wiring may be susceptible to
interference (analog set point and actual value, solenoid cables). If these cables are laid parallel over a distance longer more
10 m, the necessary distance between them must be increased. Cables susceptible to interference should never be laid
parallel to motor cables. The influence is the least when the cables cross particularly at an angle of 90°.
However, interference can also arise from cables in the amplifier wiring system, in particular solenoid cables.
Examples of devices which are particularly susceptible to interference:
• Office PC’s
• Sensors with small output voltages / currents
• Capacity proximity switches
• Audio equipment (television, hi-fi, radio, etc.)
• Devices which do not meet the EMC guidelines
5.2.4 Specific recommendations for wiring and control cabinets
The following rules and tips are by no means to be complete. Since various electronic components are used in a variety of
different ambient conditions, these guidelines only represent a compromise. The actual design of the wiring also depends
on the interference emission and interference sensitivity of each individual component.
• Use shielded and twisted-pair cables for the solenoid connections. The shield must be grounded (PE Protective
Earth) at both ends. The capacity should be ca. 120 pF/m. If the cables are up 100 m long, their cross-section has to
be 1.5 mm 2 and 2.5 mm 2 for cables longer than 100 m.
• Shields of digital signal lines are to be connected at both ends to a PE, a good conductivity of the connection should
be provided.
• Set point and actual value connections should have shielded and twisted-pair cables. The analog signal line shields
are to be connected, with low impedance, at both ends to PE
• In environments with high interference, use double shielded cables for set point and actual value connections. The
inner shield is only grounded at one end, the outer at both ends.
• In the event of low-frequency interference on the analog signal lines (measured value fluctuations), the shield should
be connected at one end. Preferably, use a corresponding compensation of potential (see also the following point).
• Use only cables with a Cu shielding grid and a covering of > 85 %. Avoid screening films. Metal foils must be avoided.
• The shield should not be interrupted along the entire length of the cable. If contactors, safety switches, chokes, etc.
have to be used in the wiring, the installation of a metallic housing with a high HF shield may be necessary.
• Shield terminals are to be connected over a large area to the shield rail to function well.
• The shield rail must be installed close to the cable duct in the control cabinet.
• The metallic parts of the electrical cabinet are to be connected with low impedance on large areas. Make the desired
connection with mechanical aids such as scratch plates if necessary. Connect the doors of the cabinet with the
shortest possible homogeneous tapes (multiple).
• Solenoid valves, contactors, relays, brakes, etc. must be suppressed directly at the interference source. Suitable
suppression devices are, for example, RC networks, diodes or varistors.
• Analog and digital signal lines should preferably enter the control cabinet from only one side.
• Non-shielded lines of an electric circuit must be twisted.
• Auxiliary wires are to be grounded at both ends.
• Avoid unnecessarily long lines. This keeps the coupling impedance low.
• Wiring should preferably not be freely hanging in the cabinet. Lay cables, including auxiliary cables, as close as
possible to mounting plates and cabinet housing.
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