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Chapter 8 Precautions for Maintenance and Inspection
low-level signals, so it requires the fllowing basic techniques. Also,
since the inverter chops outputs at high carrier frequency, that
could generate noises. If these noises cause peripheral devices to
malfunction, measures should be taken to suppress noises. These
techniques differ slightly depending on noise propagation paths.
①
Basic techniques
• Do not run the power cables (I/O cables) and signal cables of
the inverter in parallel with each other and do not bundle them.
• Use twisted pair shielded cables for the detector connection and
control signal cables, and connect the sheathes of the shield
cables to terminal SC.
• Earth the inverter, motor, etc, at one point.
②
Techniques to reduce noises that enter and malfunction the
inverter
When devices that generate many noises (which use magnetic
contactors, magnetic brakes, many relays, for example) are installed
neat the inverter and the inverter may be malfunctioned by noises,
the following measures must be taken:
• Provide surge suppressors for devices that generate many
noises to suppress noises.
• Fit data line filters to signal cables.
• Earth the shields of the detector connection and control signal
cables with Cable clamp metal.
③
Noise reduction examples
M
Filter
Sensitive electrical
equipment
Steel pipe shielding
Input filter
Input
reactor
Converter
Output
reactor
Output
filter
Steel pipe shielding
Power
supply