Mitsubishi Electric FR-A820-00046 Instruction Manual page 146

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