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INSTALLATION AND WIRING
35
#
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# Example of counter measures against noise
FR-
BLF
FR-
BIF
FR-
BLF
Install filter (FR-BLF,FR-
BSF01) to inverter input side.
Control box
Reduce carrier
frequency.
Install filter (FR-BLF,FR-BSF01)
to inverter output side.
Use 4-core cable for motor
power cable and use one
cable as ground cable.
Use twisted pair
shielded cable.
Sensor
Do not ground shield but connect
it to signal common cable.
Do not ground control box directly.
Stop earthing the control cable.
Control power
supply
Separate inverter and power line
30cm (11.81inches) or more
(at least 10cm (3.94inches))
from sensor circuit.
Install filter FR-BIF to
inverter input side.
Inverter power
supply
Power
supply for
sensor
Inverter
Motor
2.3.4 Leakage currents and countermeasures
Due to the static capacitance existing in the inverter I/O wiring and motor, leakage currents flow through
them. Since their values depend on the static capacitance, carrier frequency, etc. take counter measures
using the following methods.
(
1
)
To-ground leakage currents
Leakage currents may flow not only into the inverter's own line but also into the other line through the ground
cable, etc. These leakage currents may operate earth leakage circuit breakers and earth leakage relays
unnecessarily.
#
##
# Countermeasures
•
Decrease the carrier frequency (Pr. 72) of the inverter.
Note that motor noise increases. Selection of Soft-PWM (Pr. 240) will make it unoffending.
•
By using earth leakage circuit breakers designed for harmonics and surge suppression (e.g. Mitsubishi's
Progressive Super Series) in the inverter's own line and other line, operation can be performed with the
carrier frequency kept high (with low noise).
#
##
# To-ground leakage current
•
Note that a long wiring length will increase leakage currents. Decrease the carrier frequency of the
inverter to reduce leakage currents.
•
Higher motor capacity leads to larger leakage currents. Larger leakage currents occur in 400V class than
in 200V class.