Hitachi WJ200 Series Instruction Manual page 414

3. As user you must ensure that the HF (high frequency) impedance between
adjustable frequency inverter, filter, and ground is as small as possible.
• Ensure that the connections are metallic and have the largest possible contact
areas (zinc-plated mounting plates).
4. Avoid conductor loops that act like antennas, especially loops that encompass large
areas.
• Avoid unnecessary conductor loops.
• Avoid parallel arrangement of low-level signal wiring and power-carrying or
noise-prone conductors.
5. Use shielded wiring for the motor cable and all analog and digital control lines.
• Allow the effective shield area of these lines to remain as large as possible; i.e.,
do not strip away the shield (screen) further away from the cable end than
absolutely necessary.
• With integrated systems (for example, when the adjustable frequency inverter
is communicating with some type of supervisory controller or host computer in
the same control cabinet and they are connected at the same ground +
PE-potential), connect the shields of the control lines to ground + PE (protective
earth) at both ends. With distributed systems (for example the communicating
supervisory controller or host computer is not in the same control cabinet and
there is a distance between the systems), we recommend connecting the shield
of the control lines only at the end connecting to the adjustable frequency
inverter. If possible, route the other end of the control lines directly to the cable
entry section of the supervisory controller or host computer. The shield
conductor of the motor cables always must connected to ground + PE at both
ends.
• To achieve a large area contact between shield and ground + PE-potential, use
a PG screw with a metallic shell, or use a metallic mounting clip.
• Use only cable with braided, tinned copper mesh shield (type "CY") with 85%
coverage.
• The shielding continuity should not be broken at any point in the cable. If the
use of reactors, contactors, terminals, or safety switches in the motor output is
necessary, the unshielded section should be kept as short as possible.
• Some motors have a rubber gasket between terminal box and motor housing.
Very often, the terminal boxes, and particularly the threads for the metal PG
screw connections, are painted. Make sure there is always a good metallic
connection between the shielding of the motor cable, the metal PG screw
connection, the terminal box, and the motor housing. If necessary, carefully
remove paint between conducting surfaces.
6. Take measures to minimize interference that is frequently coupled in through
installation cables.
• Separate interfering cables with 0.25m minimum from cables susceptible to
interference. A particularly critical point is laying parallel cables over longer
distances. If two cables intersect (one crosses over the other), the interference is
smallest if they intersect at an angle of 90°. Cables susceptible to interference
should therefore only intersect motor cables, intermediate circuit cables, or the
wiring of a rheostat at right angles and never be laid parallel to them over
longer distances.
7. Minimize the distance between an interference source and an interference sink
(interference- threatened device), thereby decreasing the effect of the emitted
interference on the interference sink.
• You should use only interference-free devices and maintain a minimum
distance of 0.25 m from the adjustable frequency inverter.
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