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INSTALLATION AND WIRING
32
2.3.3 Inverter-generated noises and reduction techniques
Some noises enter the inverter causing it to misoperate and others are radiated by the inverter causing
misoperation of peripheral devices. Though the inverter is designed to be insusceptible to noise, it handles
low-level signals, so it requires the following basic measures to be taken. Also, since the inverter chops the
output at a high carrier frequency, it could generate noise. If these noises cause peripheral devices to
misoperate, measures should be taken to suppress the noise. The measures differ slightly depending on
noise propagation paths.
1) Basic measures
•
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 shielded cables for the detector connection and control signal cables and connect the
sheathes of the shielded cables to terminal SD.
•
Ground the inverter, motor, etc. at one point.
2) Measures against noises which enter and cause misoperation of the inverter
When devices which generate many noises (which use magnetic contactors, magnetic brakes, many
relays, for example) are installed near the inverter and the inverter may be effected by noise, the following
measures must be taken:
•
Provide surge suppressors for devices that generate noise to suppress noise.
•
Fit data line filters (refer to page 33) to signal cables.
•
Ground the shields of the detector connection and control signal cables with cable clamp metal.
3) Measures against noise, which is radiated by the inverter causing misoperation of peripheral devices.
Inverter-generated noise is largely classified into those radiated by the cables connected to the inverter and
inverter main circuit (I/O), those electromagnetically and electrostatically inducted to the signal cables of
the peripheral devices close to the main circuit power supply, and those transmitted through the power
supply cables.
Air-propagated
noise
Magnetic induction
noise
Static induction
noise
Cable-propagated
noise
Noise directly radi-
ated by inverter
Noise radiated by
power cables
Noise radiated by
motor cables
Noise propagated
through power
cables
Noise from ground
cable due to
leakage current
Path 4),5)
Path 6)
Path 1)
Path 2)
Path 3)
Path 7)
Path 8)
Inverter-generated
noise
2