2 Safety precautions
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7
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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 affected by the noise.
For the noise that is emitted from the driver, take measures to suppress it.
Refer to p.15 for "Installing and wiring in compliance with EMC directive."
Measures against electrical noise
There are the following three methods mainly to take measures against the electrical
noise.
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Noise suppression
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When relays or electromagnetic switches are used together with the system, use
noise filters and CR circuits to suppress surges generated by them.
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Use an accessory cable when extending a wiring distance between the motor and
driver. This is effective in suppressing the electrical noise emitted from the motor.
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Cover the driver by a metal plate such as aluminum. This is effective in shielding
the electrical noise emitted from the driver.
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Prevention of noise propagation
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Place the power lines, such as the motor and power supply cables, keeping a
distance of 100 mm (3.94 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.
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For more effective elimination of noise, use a shielded I/O signal cable or attach
ferrite cores if a non-shielded cable is used.
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Keep cables as short as possible without coiling and bundling extra lengths.
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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
Braided screen
cable
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When grounding PE terminals of multiple drivers to a grounding point, it becomes
more effective to block the electrical noise since impedance on the grounding
point is decreased. However, ground them so that a potential difference does not
occur among the grounding points.
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Suppression of effect by noise propagation
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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 effect 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 effect
of noise attenuation by the ferrite core, loop the cable a lot.
