7
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Remark
General preventive measures against noise
There are two kinds of noises: Radiated noise that is transmitted into the air and
Conductive noise that is directly transmitted along connected lines.
Countermeasures must be taken considering both kinds of noises and referring to
the following 3 points.
(1) Protecting against noise
(a) Keep signal lines away from noise sources such as a power cable or a high-
power drive circuit.
(b) Shield the signal lines.
(2) Reducing generated noise
(a) Use a noise filter, etc. to reduce the level of the noise generated due to a
source such as a high-power motor drive circuit.
(b) Attach a surge suppressor on the terminal of the molded case circuit breaker
(MCCB), electromagnetic contactor, relay, solenoid valve, or induction motor
to supress the noise.
(3) Releasing noise to the ground
(a) Make sure to connect the ground cable to the ground.
(b) Use a short and thick cable to lower its ground resistance.
(c) Ground the power system and the control system separately.
