Hitachi WJ Series User Manual page 33

Chapter 1
Precautions for installation and wiring
!
1. Input-side AC reactor or other equipment is required if necessary to comply with EMC directive
from the harmonic distortion point of view (IEC 61000-3-2 and 4).
2. If the motor cable length exceeds 20 m, use output-side AC reactor to avoid unexpected
problem due to the leakage current from the motor cable (such as malfunction of the thermal
relay, vibration of the motor, etc.).
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 be 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 0.25 m 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°.
7. 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. 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.
8. Follow safety measures in the filter installation.
 If using external EMC filter, ensure that the ground terminal (PE) of the filter is properly
connected to the ground terminal of the adjustable frequency inverter. An HF ground
connection via metal contact between the housings of the filter and the adjustable frequency
inverter, or solely via cable shield, is not permitted as a protective conductor connection.
The filter must be solidly and permanently connected with the ground potential so as to
preclude the danger of electric shock upon touching the filter if a fault occurs.
To achieve a protective ground connection for the filter:
 Ground the filter with a conductor of at least 10 mm2 cross-sectional area.
 Connect a second grounding conductor, using a separate grounding terminal parallel to the
protective conductor. (The cross section of each single protective conductor terminal must
be sized for the required nominal load.)
1-3-3
Safety Instructions/Risks