Inverter-Generated Noises And Their Reduction Techniques - Mitsubishi Electric FR-F500 Series Instruction Manual

2.3.3 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 noise, it handles low-level signals,
so it requires the following basic measures to be taken. Also, since the inverter chops the outputs at high
carrier frequency, that could generate noise. If these noises cause peripheral devices to malfunction,
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 pair shielded cables for the detector connection and control signal cables and connect the
sheathes of the shielded cables to terminal SD.
• Earth (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 noises, the following
measures must be taken:
• Provide surge suppressors for devices that generate many noises to suppress noises.
• Fit data line filters (refer to page 35) 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 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.
Inverter-generated
noise
INSTALLATION AND WIRING
Noise directly radi-
Air-propagated
ated by inverter
noise
Noise radiated by
power cables
Noise radiated by
motor cables
Magnetic induction
Path 4),5)
noise
Static induction
Path 6)
noise
Noise propagated
Cable-propagated
through power
noise
cables
Noise from earth
(ground) cable due
to leakage current
34
Path 1)
Path 2)
Path 3)
Path 7)
Path 8)
2