Mitsubishi Electric MELSERVO-JN Series Instruction Manual page 291

11. OPTIONS AND PERIPHERAL EQUIPMENT
11.9 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 signals, 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 frequencies. 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) Noise reduction techniques
(a) 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 3.12).
(b) 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.
Although a surge absorber is built into the servo amplifier, to protect the servo amplifier and other
equipment against large exogenous noise and lightning surge, attaching a varistor to the power input
section of the equipment is recommended.
(c) Techniques for noises radiated by the servo amplifier that cause peripheral devices to malfunction
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 induced 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
Route 4) and 5)
noise
Static induction
Route 6)
noise
Noises transmitted
through electric
channels
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Noise radiated directly from servo amplifier
Noise radiated from the power supply cable
Noise radiated from servo motor cable
Noise transmitted through power supply cable
Noise sneaking from grounding cable due
to leakage current
Route 1)
Route 2)
Route 3)
Route 7)
Route 8)