Functions 3. Installation
RC700 Series Rev.3 109
3.5 Noise Countermeasures
In the explanation of this section, the controller also means the drive unit.
To minimize electrical noise conditions, the following items must be observed in the system’s
cable wiring:
To minimize electrical noise condition, be sure of followings for wiring.
- The earth wire of the power supply should be grounded. (Ground resistance: 100 Ω or
less) It is important to ground the frame of Controller not only for prevention from
electric shock, but also for reducing the influence of electric noise around the Controller.
Therefore, be sure to connect the earth wire (yellow/green) of the Controller’s power
cable to the ground terminal of the factory power supply. For details about the plug
and AC power cable, refer to the 3.3 Power Supply.
- Do not tap power from a power line that connects to any equipment which may cause
noise.
- When you tap power for the Controller and the single-phase AC motor from the same
power line, change the phase of one or the other. Ensure that they will not be the same
phase.
- Use a twisted pair motor power line.
- Do not run AC power lines and DC power lines in the same wiring duct, and separate
them as far as possible. For example, separate the AC motor power line and the
Controller power line as far as possible from the sensor or valve I/O lines; and do not
bundle both sets of wiring with the same cable tie. If more than one duct/cable must
cross each other, they should cross perpendicularly. The preferable example is shown
in the right figure.
- Wire as short as possible to the I/O connector and EMERGENCY connector. Use a
shielded cable and clamp the shield to the attached connector interior. Make sure to
keep away from the peripheral noise source as far as possible.
- Make sure that the induction elements used to connect to the Controller’s I/O (such as
relays and solenoid valves) are noise suppression parts. If an induction element without
protection against noise is used, make sure to connect a noise suppression part such as a
diode located at the induction element in parallel with it. In selecting noise suppression
parts, make sure that they can handle the voltage and current incurred by the induction
load.
- To start and change revolutions of the conveyer’s (or the like’s) AC motor (ex: an
induction motor or three-phase induction motor) regularly or abruptly, make sure to
install a spark suppressor between the wires. The spark suppressor is more effective
when placed closer to the motor.
- As they are easily influenced by noise, keep cable such as USB, Ethernet, RS-232C, or
fieldbus away from peripheral noise sources.
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