Mitsubishi Electric 800 Series Instruction Manual page 71

Electro-magnetic interference (EMI) and leakage currents
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.
(a)(b)(c) • 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.
• Inserting a line noise filter into the output suppresses 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
line, inverter-generated noises may flow back through the power supply cables to cause malfunction of the devices
(g)
and the following countermeasures must be taken:
• Install the line noise filter 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
(h) may 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.
EMI countermeasure example
Install filter on inverter
input side.
Inverter
power
supply
Separate inverter and
power line by more than
30 cm (at least 10 cm)
from sensor circuit.
Control
power
supply
Do not earth (ground)
enclosure directly.
Do not earth (ground) control cable.
70
PRECAUTIONS FOR USE OF THE INVERTER
Decrease carrier frequency.
Line
Line
noise Inverter noise
filter filter
Use 4-core cable for motor
power cable and use one cable
as earth (ground) cable.
Use a twisted pair shielded cable.
Power
supply for
sensor
Do not earth (ground) shield but
connect it to signal common cable.
Countermeasure
Install filter on
inverter output side.
M
Motor
Sensor