Leakage Currents And Countermeasures - Mitsubishi Electric FR-F500 Series Instruction Manual

# # # # Example of counter measures against noise
Install filter (FR-BLF,FR-
BSF01) to inverter input side.
Inverter power
supply
Install filter FR-BIF to
inverter input side.
Separate inverter and power line
30cm (11.81inches) or more
(at least 10cm (3.94inches))
from sensor circuit.
Control power
supply
Do not earth (ground) control box directly.
Stop earthing (grounding) the control cable.

2.3.4 Leakage currents and countermeasures

Leakage currents flow through static capacitances existing in the inverter I/O wiring and motor. Since their
values depend on the static capacitances, carrier frequency, etc., take the following measures.
( 1 ) To-earth (ground) leakage currents
Leakage currents may flow not only into the inverter's own line but also into the other line through the earth
(ground) cable, etc. These leakage currents may operate earth (ground) leakage circuit breakers and earth
(ground) 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 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.
Reduce carrier
frequency.
Control box
FR-
Inverter
BLF
FR-
BIF
Power
supply for
sensor
Do not earth (ground) shield but connect
it to signal common cable.
37
INSTALLATION AND WIRING
Install filter (FR-BLF,FR-BSF01)
to inverter output side.
FR-
BLF
Use 4-core cable for motor
power cable and use one
cable as earth (ground) cable.
Use twisted pair
shielded cable.
Sensor
Motor