Noise Reduction Techniques - Mitsubishi Electric MR-J4-10B(-RJ) Instruction Manual

11. OPTIONS AND PERIPHERAL EQUIPMENT

11.14 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 equipment 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 equipment malfunctions 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 bundling power lines (input/output) and signal cables together or running them in parallel to
each other. Separate the power lines from the signal cables.
Use a shielded twisted pair cable for connection with the encoder and for control signal
transmission, and connect the external conductor of the cable to the SD terminal.
Ground the servo amplifier, servo motor, etc. together at one point. (Refer to section 3.11.)
(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 equipment 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 equipment 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
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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)