TCI KRF - Manual (Page 15)

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11. Connect suitable EMC components close to switched inductors (e.g. contactors,
relays, magnetic valves etc.).
12. For control signals in the vicinity of high interference levels, use transmission
techniques such as:
• Differential-mode transmission systems with twisted-pair lines in
conjunction with data line chokes.
• Transmission of digital signals according to the RS-422 standard or in
extreme cases crossing the interference region with fiber-optic cables.
13. Note the mounting position of the filters! The assembly must always take care not
to impair natural convection. This includes the use of ventilation slits in the filter
housing and sufficient spacing to the other components. Over-head mounting is
never permissible. In the event of unusual mounting situations, the thermal
conditions shall be checked after coordination with the factory.
14. Noise minimization
A choke made of highly diverse core materials represents a significant
frequency-dependent filter component. Electro-acoustic effects must inevitably
be expected in AC applications. The materials and processing used generate (for
industrial sector) suitable noise levels by operation in networks with harmonics
complying to EN 50160. However, these can rise significantly in the event of
higher harmonic components. For sensitive applications such as office
installation, therefore, customers should contact factory for advice.
15. Length of motor cables and motor types used
For converter applications, output voltages are generated that typically have
almost rectangular waveforms. These are essentially characterized by the rise
rate expressed as the dv/dt value and the switching frequency of the converter.
The cables and motors present in the output network of the converter with their
inductive and capacitive components significantly determine the EMC properties
of the system. Thus resonances of the cable/motor combination are often
reflected in the resonance of the interference voltage measurement at the
converter input.
The parasitic capacitances of the cable and motor should be treated with special
care. Whereas the parasitic capacitances of the motor depend on its design,
those of the cables depend on the insulation material, cable structure, type of
shielding and especially on their length. A high-frequency current flows through
the grounded parts of the equipment as a function of the switching frequency, the
dv/dt value and the magnitude of the parasitic capacitances.
Here are some of the possible effects: