Rockwell Automation System Design for the Control of Electrical Noise - Manual (Page 12)

Publication GMC-RM001A-EN-P — July 2001
1-2 Electrical Noise Control Overview
In both cases, equipment must be installed to manufacturers
recommendations to achieve compliance. The frequency range
covered is 150kHz to 1GHz, though the upper limit is likely to be
raised as operation frequencies increase.
Despite this, a CE compliant industrial drive system may still suffer
functional failures due to electrical noise. Additional measures are
often necessary to prevent noise from being coupled between source
and victim. The frequency range involved in system failures is
generally confined between 200kHz and 10MHz.
Best Practices
Most industrial control products do not utilize high frequencies
directly, but they can generate them in the form of noise. Logic
circuits are affected by this noise, so you need to be able to control it.
Because it is far less expensive to apply noise control measures during
system installation than it is to redesign and fix a malfunctioning
system, we recommend you implement the best-practice procedures
described in this document.
If basic measures are implemented rigorously, a reliable system
should result. However, if just one wire is routed incorrectly or a filter
is missed, it may be enough to cause problems. Experience shows that
it is very difficult to ensure that these measures are applied 100% of
the time. If all possible measures are taken (incorporating
redundancy), the system is likely to be more tolerant of minor
mistakes in implementation.
Noise Control Basics A typical industrial control system will contain a mixture of noise
sources and potential victims. Problems are caused when a coupling
mechanism is introduced.
Noise Sources
Typical noise sources include:
• Mechanically switched inductive loads create intense intermittent
noise.
• PWM drive power outputs create intense continuous noise.
• Switch-mode DC power supplies can create continuous noise.