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6. OPTIONS AND AUXILIARY EQUIPMENT
6-2-6 Noise reduction techniques
Noises are classified into external noises which enter the servo
amplifier to cause it to malfunction and those radiated by the servo amplifier to cause peripheral
devices to malfunction. Since the servo amplifier is an electronic device which handles small sig-
nals, the following general noise reduction techniques are required.
Also, the servo amplifier can be a source of noise as its outputs are chopped by high carrier fre-
quencies. If peripheral devices malfunction due to noises produced by the servo amplifier, noise
suppression measures must be taken. The measures will vary slightly with the routes of noise
transmission.
1) General reduction techniques
• Avoid laying power lines (input and output cables) and signal cables side by side or do not
bundle them together. Separate power lines from signal cables.
• Use shielded, twisted pair cables for connection with the encoder and for control signal
transmission, and connect the shield to the SD terminal.
• Ground the servo amplifier, servo motor, etc. together at one point (refer to Section 3-4).
2) Reduction techniques for external noises that cause the servo amplifier to malfunction
If there are noise sources (such as a magnetic contactor, an electromagnetic brake, and
many relays which make a large amount of noise) near the servo amplifier and the servo
amplifier may malfunction, the following countermeasures are required.
• Provide surge absorbers on the noise sources to suppress noises.
• Attach data line filters to the signal cables.
• Ground the shields of the encoder connecting cable and the control signal cables with
cable clamp fittings.
3) Techniques for noises radiated by the servo amplifier that cause peripheral devices to mal-
function
Noises produced by the servo amplifier are classified into those radiated from the cables
connected to the servo amplifier and its main circuits (input and output circuits), those in-
duced electromagnetically or statically by the signal cables of the peripheral devices located
near the main circuit cables, and those transmitted through the power supply cables.
Noises produced
by servo amplifier
Noises transmitted
in the air
Magnetic induction
... Routes 4) and 5)
noise
Static induction
... Route 6)
noise
Noises transmitted
through electric
channels
6– 20
Noise radiated directly
... Route 1)
from servo amplifier
Noise radiated from the
... Route 2)
power supply cable
Noise radiated from
... Route 3)
servo motor cable
Noise transmitted through
... Route 7)
power supply cable
Noise sneaking from
grounding cable due to
... Route 8)
leakage current
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