Automation Devices 6472.3 Handbuch - Seite 10

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Good wiring practices for
avoiding electrical noise
problems.
Automation Devices controls have been
designed with a high degree of immunity to
electrical noise; however, depending on the
control installation, electrical noise can cause
problems. These problems occur in less than
1% of the product installations. Most
electrical noise problems can be avoided by
following some simple guidelines. Good
wiring practices need to be used to prevent
electrical noise from interfering with your
control's
operation.
Another
electrical
noise
is
Electro-Magnetic
Interference (EMI).
Symptoms of Electrical Noise
The symptoms of electrical noise would
appear as follows: a brief pause or a brief
"bump" in the vibratory feeder's output that
the control automatically recovers from. In
rare cases the control will either stop
operating or run continuously at full power in
120 pulse (AC) mode until the power switch is
slowly cycled OFF and ON.
Sources of Electrical Noise
Electrical noise is generated by devices like
relay coils, solenoid valves, contactors, servo
motors, and (variable frequency inverter)
motor drives. The electrical noise is then
transferred to another device by one of three
ways. The noise could be conducted through
the power wires, or capacitively coupled from
wire to adjacent wire, or it is transmitted from
the wires of a nearby noise source.
Solutions for Electrical Noise
1. Use shielded wires for all I/O (Input /
Output) signals. The I/O signals may include: 4-
20mA input, Run input, Sensor input, 0-
5VDC input, Interlock input or AUX output.
The shield "drain" wire should be tied to the
chassis in the feeder control. The drain wire
should be kept shorter than 2". Please see
the enclosed picture.
name
for
Example of a "drain" wire termination
2. Never run I/O signal wires in the same
conduit or raceway as AC power lines such
as wires to motors, solenoids, heaters,
welders and vibratory feeder controls, etc.
3.
I/O wires within an enclosure should
be routed as far away as possible from relays,
solenoids, transformers, power wiring and
other noisy equipment. Keep the I/O signal
wires separate from the control's input and
output power wiring. Secure the wires in
place.
4.
Whenever relays or solenoid valves
are used, install a Snubber on them to reduce
electrical noise. Use a diode on a DC coil.
Use a RC Snubber on an AC coil.
+
RECTIFIER
DIODE
VDC
1N4006
-
QUENCH-ARC
VAC
SNUBBER
104M06QC47
5.
In extremely high EMI environments,
Power Line Filters and ferrite beads can be
effective. Install ferrite beads on I/O signal
wires as close as possible to the circuit board
terminal strip. Loop the wire through the bead
several times or use several beads on each
wire for additional protection.
In USA: Automation Devices, Inc.
7050 West Ridge Road
Fairview, PA 16415-2099
Phone: 814-474-5561
FAX: 814-474-2131
Web Site:
WWW.AUTODEV.COM
E-mail:
Good Wiring ADI GP.doc
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RELAY
COIL
RELAY
COIL