Inverter-Generated Noises And Their Reduction Techniques - Mitsubishi Electric FR-A740-00023 Instruction Manual

Noise and leakage currents
3.1.2

Inverter-generated noises and their reduction techniques

Some noises enter the inverter to malfunction it and others are radiated by the inverter to malfunction peripheral
devices. Though the inverter is designed to be insusceptible to noises, 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 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 SD.
⋅ Earth (Ground) 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 near 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 (page 53 ) to signal cables.
⋅ Earth (Ground) the shields of the detector connection and control signal cables with cable clamp metal.
3) Techniques to reduce noises that are radiated by the inverter to malfunction peripheral devices
Inverter-generated 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.
Inverter
Air propagated
generated noise
noise
Electromagnetic
induction noise
Electrostatic
induction noise
Electrical path
propagated noise
52
Noise directly
Path 1)
radiated from inverter
Noise radiated from
Path 2)
power supply cable
Noise radiated from
Path 3)
motor connection cable
Path 4), 5)
Path 6)
Noise propagated through
Path 7)
power supply cable
Noise from earth (ground)
Path 8)
cable due to leakage
current
7)
2)
1)
3)
Instrument Receiver
Motor
5)
Telephone
7)
Sensor
power supply
Inverter
8)
1)
6)
4)
3)
Sensor
IM