Connection
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22
7-7 Noise
measures
The electrical noise is of two types: One is a noise to invade into the driver from the outside and cause the driver
malfunction, and the other is a noise to emit from the driver and cause peripheral equipments malfunction.
For the noise that is invaded from the outside, take measures to prevent the driver malfunction. It is needed to take
adequate measures because signal lines are very likely to be aff ected by the noise.
For the noise that is emitted from the driver, take measures to suppress it.
Measures against electrical noise
There are the following three methods mainly to take measures against the electrical noise.
Noise suppression
When relays or electromagnetic switches are used together with the system, use noise fi lters and CR circuits to
suppress surges generated by them.
Use an accessory cable when extending a wiring distance between the motor and driver. This is eff ective in
suppressing the electrical noise emitted from the motor.
Cover the driver by a metal plate such as aluminum. This is eff ective in shielding the electrical noise emitted from
the driver.
Prevention of noise propagation
Connect a noise fi lter on the input side of the DC power supply.
Place the power lines, such as the motor and power supply cables, keeping a distance of 200 mm (7.87 in.) or more
from the signal lines, and also do not bundle them or wire them in parallel. If the power cables and signal cables
have to cross, cross them at a right angle.
Use shielded twisted pair cables for power lines and signal lines.
Keep cables as short as possible without coiling and bundling extra lengths.
When grounding PE terminals of multiple drivers to a grounding point, it becomes more eff ective to block the
electrical noise since impedance on the grounding point is decreased. However, ground them so that a potential
diff erence does not occur among the grounding points. An accessory driver cable including with a ground wire is
available.
To ground a shielded cable, use a metal cable clamp that will maintain
contact with the entire circumference of the cable. Ground the cable
clamp near the product.
Cable clamp
Shielded cable
Suppression of eff ect by noise propagation
Loop the noise propagated cable around a ferrite core. Doing so will prevent the propagated noise invades into
the driver or emits from the driver. The frequency band in which an eff ect by the ferrite core can be seen is
generally 1 MHz or more. Check the frequency characteristics of the ferrite core used. To increase the eff ect of noise
attenuation by the ferrite core, loop the cable a lot.
Change the transmission method of the pulse signal to the line driver type in order to prevent noise eff ects. When
the pulse signal of the controller is the open collector type, use an accessory pulse signal converter for noise
immunity.
Noise suppression parts
Noise fi lter
Connect the following noise fi lter (or equivalent) on the input side of the DC power supply. When a power supply
transformer is used, be sure to connect a noise fi lter on the AC input side of the power supply transformer. Doing
so will prevent the propagated noise through the power line. Install the noise fi lter as close to the input terminals
of DC power supply as possible.
Manufacture
Model
SOSHIN ELECTRIC CO.,LTD
HF2010A-UPF
Schaff ner EMC
FN2070-10-06
Use the AWG18 (0.75 mm
2
) or thicker wire for the input and output cables of the noise fi lter, and secure fi rmly
using a cable clamp etc. so that the cable does not come off the enclosure.
Place the input cable as far apart as possible from the output cable, and do not wire the cables in parallel. If the
input and output cable are placed at a close distance or if they are wired in parallel, the noise in the enclosure
aff ects the power cable through stray capacitance, and the noise suppressing eff ect will reduce.
Connect the ground terminal of the noise fi lter to the grounding point, using as thick and short a wire as possible.
When connecting a noise fi lter in an enclosure, wire the input cable of the noise fi lter as short as possible. Wiring in
long distance may reduce the noise suppressing eff ect.
