Mitsubishi Electric 800 Series Instruction Manual page 94

 EMI measures to reduce electromagnetic noises that are radiated by the
inverter to cause the peripheral devices to malfunction
Inverter-generated noises are largely classified into those radiated by the inverter itself and by the I/O cables connected to its
main circuit, those electromagnetically and electrostatically induced to the signal cables of the peripheral devices close to the
power cable connected to the inverter main circuit, and those transmitted through the power cables.
Inverter generated
Air propagated
electromagnetic
noise
noise
Electromagnetic
induction noise
Electrostatic
induction noise
Electrical path
propagated noise
Noise propagation
path
When devices that handle low-level signals and are liable to malfunction due to electromagnetic noises, e.g.
instruments, receivers and sensors, are contained in the enclosure that contains the inverter or when their signal
cables are run near the inverter, the devices may malfunction due to by air-propagated electromagnetic noises. The
following countermeasures must be taken:
• Install easily affected devices as far away as possible from the inverter.
• Run easily affected signal cables as far away as possible from the inverter and its I/O cables.
(a), (b), (c) • Do not run the signal cables and power cables (inverter I/O cables) in parallel with each other and do not bundle
them.
• Install an external EMC filter.
• Install a line noise filter or radio noise filter on the input side and install a line noise filter on the output side to
suppress the radiated noise from the cables.
• Use shielded cables as signal cables and power cables and run them in individual metal conduits to produce further
effects.
When the signal cables are run in parallel with or bundled with the power cables, magnetic and static induction noises
may be propagated to the signal cables to cause malfunction of the devices and the following countermeasures must
be taken:
• Install easily affected devices as far away as possible from the inverter.
(d), (e), (f) • Run easily affected signal cables as far away as possible from the inverter and its I/O cables.
• Do not run the signal cables and power cables (inverter I/O cables) in parallel with each other and do not bundle
them.
• Use shielded cables as signal cables and power cables and run them in individual metal conduits to produce further
effects.
When the power supplies of the peripheral devices are connected to the power supply of the inverter in the same
power system, inverter-generated noises may flow back through the power supply cables to cause malfunction of the
(g) devices and the following countermeasures must be taken:
• Install an external EMC filter.
• Install the line noise filter (FR-BLF/FR-BSF01) to the power cables (output cables) of the inverter.
When a closed loop circuit is formed by connecting the peripheral device wiring to the inverter, leakage currents may
(h) flow through the earthing (grounding) cable of the inverter to cause the device to malfunction. In that case,
disconnecting the earthing (grounding) cable from the device may stop the malfunction of the device.
 Data line filter
Data line filter is effective as an EMI countermeasure. Provide a data line filter for the detector cable, etc.
• Commercially available data line filter: ZCAT3035-1330 (by TDK), ESD-SR-250 (by NEC TOKIN)
Noise directly
Path (a)
radiated from inverter
Noise radiated from
Path (b)
power supply cable
Noise radiated from
Path (c)
motor connection cable
Path (d), (e)
Path (f)
Noise propagated through
Path (g)
power supply cable
Noise from earthing
(grounding) cable due to Path (h)
leakage current
Countermeasure
(e)
(g)
(b)
(a)
(c)
Receiver
Instrument
Motor
3. Precautions for Use of the Inverter
3.1 Electro-magnetic interference (EMI) and leakage currents
Telephone
(g)
Sensor
power supply
Inverter
(f)
(a)
(f)
(d)
(c)
Sensor
M
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