S.B.C. Elettronica S.p.A. - Engineering Division
HPDxxN – High Power User’s Manual
12
Additional measures
- With the exception of mains cables to the filter, all power and control wiring must be shielded
and, wherever possible, kept segregated (minimum distance 20 cm). If control and power cables
must cross, the intersection must be at a right angle.
- Shielded cables must be installed on a copper bar by means of a high conductivity wire clamp.
The area of contact must be as large as possible and the shield must be unbroken. In general the
shield should be connected at each extremity. In certain circumstances, however, control cable
shields may be connected only at one end to eliminate mains hum that could interfere with the control
signal. Decide case by case as numerous factors must be considered. Adopt the following general
approach: if the shield is solely for shielding, connect at both ends. If current flowing in the shield
interferes with the shielded signals, connect at one end only.
- The incoming cable must be connected to an earth terminal by means of a screw to ensure
proper contact between shield and earth.
- RF interference suppression filters must be installed as close as possible to the drive and must
have a large area of contact with the power panel or the baseplate. Remove all paint. The filter earth
terminal must be connected to the earth bar along the shortest possible route.
- As far as possible keep the power side (drive) and control side (PLC or NC) physically
separated by separating the metal mounting plates. Do not route any cables through the mounting
plates.
Protective measures for drives with > 3.5mA dispersion current per phase
Interference currents dispersed through the earth system may be considerable in certain
conditions. Therefore, make sure all suppression filters are properly earthed before they are
connected. Cable sizes must be in line with the requirements of safety standards.
If a suppression filter is permanently connected and current dispersion during normal operation is
greater than 3.5mA (which would be expected with most drives) adopt one of the following
measures additionally:
a) Increase shield size to at least 10 mm².
b) Install a detection system to monitor the shield and automatically disconnect the drive in the
presence of faults.
c) Install a second conductor in parallel (electrically) with the shield using separate terminals.
