Line-to-line leakage currents
Harmonics of leakage currents flowing in static capacitances between the inverter output cables may operate the external
thermal relay unnecessarily. When the wiring length is long (50m or more) for the 400V class small-capacity model (7.5kW or
less), the external thermal relay is likely to operate unnecessarily because the ratio of the leakage current to the rated motor
Line-to-line leakage current data example (400V class)
Use Pr. 9 Electronic thermal O/L relay.
If the carrier frequency setting is high, decrease the Pr. 72 PWM frequency selection setting.
Note that motor noise increases. Selecting Pr. 240 Soft-PWM operation selection makes the sound inoffensive.
To ensure that the motor is protected against line-to-line leakage currents, it is recommended to use a temperature
sensor to directly detect motor temperature.
Installation and selection of moulded case circuit breaker
Install a moulded case circuit breaker (MCCB) on the power receiving side to protect the wiring of the inverter input side.
Select the MCCB according to the inverter input side power factor (which depends on the power supply voltage, output
frequency and load). Especially for a completely electromagnetic MCCB, one of a slightly large capacity must be selected
since its operation characteristic varies with harmonic currents. (Check it in the data of the corresponding breaker.) As an
earth leakage current breaker, use the Mitsubishi earth leakage current breaker designed for harmonics and surge
Leakage Current (mA) *
Wiring length 50m
Wiring length 100m
*The leakage current of the 200V class is about a half.
Line-to-line leakage currents path
EMC and leakage currents
Motor: SF-JR 4P
Carrier frequency: 14.5kHz
Used wire: 2mm
, 4 cores