Electro-magnetic interference (EMI) and leakage currents
PRECAUTIONS FOR USE OF THE INVERTER
69
3
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.
Selecting the rated sensitivity current for the earth leakage circuit breaker
When using an earth leakage circuit breaker with the inverter circuit, select its rated sensitivity current as follows,
independently of the PWM carrier frequency.
<Example>
• Inverter leakage current (with and without EMC filter)
Input power conditions (400 V class: 440 V/60 Hz, power supply unbalance within 3%)
Do not change the initially set ON (enabled) position of the EMC filter ON/OFF connector in the case of the inverter. The Class C2 compatibility
condition is not satisfied with the EMC filter OFF. The FR-F846-00250(11K)-L2 to FR-F846-00470(22K)-L2 are not provided with the EMC filter
ON/OFF connector. The EMC filter is always ON.
The inverter must be used in the earthed-neutral system.
• Breaker designed for harmonic and surge suppression
Rated sensitivity current
I
n
≥
10
(Ig1 + Ign + Igi + Ig2 + Igm)
• Standard breaker
Rated sensitivity current
I
n
≥
10
{Ig1 + Ign + Igi + 3
(Ig2 + Igm)}
Ig1, Ig2: Leakage currents in wire path during commercial power
supply operation
Ign: Leakage current of inverter input side noise filter
Igm: Leakage current of motor during commercial power supply
operation
Igi: Leakage current of inverter unit
Item
Breaker designed
for harmonic and
surge suppression
Standard breaker
Leakage current Ig1 (mA)
1
66
5 m
= 0.11
3
1000 m
Leakage current Ign (mA)
0 (without noise filter)
Leakage current Igi (mA)
1 (without EMC filter)
For the leakage current of the inverter, refer to
the following table.
Leakage current Ig2 (mA)
1
66
60 m
= 1.32
3
1000 m
Motor leakage current Igm (mA)
0.36
Total leakage current (mA)
2.79
6.15
Rated sensitivity current (mA) (
≥
Ig
10) 30
100
Voltage
(V)
EMC filter
ON (mA)
400
400
2
Motor capacity (kW)
For " " connection, the amount of leakage current is appox.1/3 of the above value.
(Three-phase three-wire delta
connection 400
V60 Hz)
Example of leakage current per 1km during
the commercial power supply operation
when the CV cable is routed in metal conduit
Leakage current example of three-
phase induction motor during the
commercial power supply operation
(Totally-enclosed fan-cooled
type motor 400 V60 Hz)
0
2 0
4 0
6 0
8 0
100
120
Leakage current (mA)
Leakage current (mA)
2 3.5
5.5
8 1422
30
38
60
80
100
150
Cable size (mm
2
)
0. 1
0. 2
0. 3
0. 5
0. 7
1. 0
2. 0
1. 5 3. 7
2. 2
7. 5 1522
11
37
30
55
45
5.5
18. 5
Noise
filter
Inverter
ELB
Ig1
Ign
Igi
Ig2
Igm
M
5.5 mm
2
5 m
5.5 mm
2
60 m
400 V
2.2 kW
3
φ
Phase
earthing
(grounding)
Earthed-neutral
system
