Key Points for Noise Reduction

Pay attention to the following points when wiring to minimize the effect of noise.

• The power supply must be grounded to a class D ground (grounding resistance of 100 Ω or less).
  Grounding of the Controller frame is important not only for the purpose of preventing electric shock, but also to reduce the effects of electrical disturbances from the surrounding area. The ground wire (green/yellow) of the Controller power cable must be connected to the ground terminal of the power distribution system.
  For details on the plug and the AC power cable of the Controller, refer to the following section.
  Power Supply

• Power should be supplied as far as possible away from power lines connected to equipment which may be a source of noise.

• If the Controller and single-phase AC motor are powered from the same power line, change the phase.

• Power lines should be twisted pair.

• AC and DC lines should be housed in different ducts and as far apart as possible.
  For example, AC motor power lines and Controller power lines should be as far away as possible from I/O lines for devices such as sensors and valves, and both should not be bundled together with cable ties.
  If the lines are crossed, they should be crossed perpendicularly.
  

  Symbol	Description
  a	Dedicated AC line duct
  b	As far apart as possible
  c	Dedicated DC line duct

• Keep wiring to I/O connectors and safety I/O connectors as short as possible. Be sure to use shielded wires, and clamp the shield inside the connector. Also, keep as far away as possible from noise sources in the surrounding area.

• When using inductive load components such as relays and solenoid valves for Controller I/O, use components that have noise protection.
  If the component is not protected from noise, be sure to attach a diode or other noise-protection component immediately before the inductive load. Select noise protection components that match the withstand voltage and current according to the inductive load.

• For AC motors such as conveyors (induction motors, 3-phase induction motors, etc.), be sure to insert a spark suppressor between the wires when starting, switching forward/reverse rotation, and so on.
  Putting it between the lines and as close as possible to the motor will also increase its effectiveness.

• Communication cables such as USB, Ethernet, RS-232C, and fieldbus are susceptible to noise, and so keep them as far away as possible from noise sources in the surrounding area.

• The following EMC measures should be implemented for the Fieldbus I/O cables as needed.

  • Ground the cable shield section.
    

    Symbol	Description
    a	Remove outer sheath and secure with FG clamp
    b	Secure to the Controller with a screw to provide grounding

  • Attach ferrite core to cable.
    

    Symbol	Description
    a	Ferrite core