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EMC and leakage currents
3.1.2 EMC measures
Some electromagnetic noises enter the inverter to malfunction it and others are radiated by the inverter to malfunction
peripheral devices. Though the inverter is designed to have high immunity performance, it handles low-level signals, so it
requires the following basic techniques. Also, since the inverter chops outputs at high carrier frequency, that could generate
electromagnetic noises. If these electromagnetic noises cause peripheral devices to malfunction, EMI measures should be
taken to suppress noises. These techniques differ slightly depending on EMI 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 SD.
⋅ Ground the inverter, motor, etc. at one point.
2)Techniques to reduce electromagnetic noises that enter and malfunction the inverter (Immunity measures)
When devices that generate many electromagnetic noises (which use magnetic contactors, magnetic brakes, many
relays, for example) are installed near the inverter and the inverter may be malfunctioned by electromagnetic noises,
the following measures must be taken:
⋅ Provide surge suppressors for devices that generate many electromagnetic noises to suppress electromagnetic
noises.
⋅ Fit data line filters to signal cables.
⋅ Ground the shields of the detector connection and control signal cables with cable clamp metal.
3)Techniques to reduce electromagnetic noises that are radiated by the inverter to malfunction peripheral devices (EMI
measures)
Inverter-generated electromagnetic noises are largely classified into those radiated by the cables connected to the
inverter and inverter main circuits (I/O), those electromagnetically and electrostatically induced to the signal cables of
the peripheral devices close to the main circuit power supply, and those transmitted through the power supply cables.
Noise propagated through
power supply cable
Path 3)
Path 2)
Path 1)
Noise directly
radiated from inverter
Path 4), 5)
Air propagated
noise
Path 6)
Electrical path
propagated noise
Path 8)
Path 7)
Inverter generated
electromagnetic
noise
Electromagnetic
induction noise
Electrostatic
induction noise
Noise radiated from
power supply cable
Noise radiated from
motor connection cable
Noise from ground
cable due to leakage
current
Instrument Receiver
IM
Motor
Telephone
Sensor
1)
2)
3)
3)
8)
7)
5)
7)
4)
6)
Inverter
1)
Sensor
power supply