Mitsubishi Electric FR-A820-00046 (0.4K), Instruction Manual

Page: 146 / 1218

Electro-magnetic interference (EMI) and leakage currents Precautions for use of the inverter
3 - 2
The leakage currents of the 400 V class are about twice as large.
●
Countermeasures
– 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 the molded case circuit breaker
Install a molded case circuit breaker (MCCB) on the power receiving side to protect the wiring at
the inverter input side. Select an 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, 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 suppression.
Example Line-to-line leakage current example (200 V class)
Motor: SF-JR 4P
Carrier frequency: 14.5 kHz
Cable: 2 mm
2
, 4 cores
Cabtyre cable
Motor capacity [kW] Rated motor current [A]
Leakage current [mA]
Wiring length 50 m Wiring length 100 m
0.4 1.8 310 500
0.75 3.2 340 530
1.5 5.8 370 560
2.2 8.1 400 590
3.7 12.8 440 630
5.5 19.4 490 680
7.5 25.6 535 725
Tab. 3-1: Line-to-line leakage current data example
I001043E
Fig. 3-1: Line-to-line leakage currents
Power
supply
Inverter/
converter
Thermal
relay
M
3~
Line-to-line static
capacitances