Electro-magnetic interference (EMI) and leakage currents
PRECAUTIONS FOR USE OF THE INVERTER
83
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
(200 V class: 220 V/60 Hz, 400 V class: 440 V/60 Hz,
power supply unbalance within 3%)
• Breaker designed for harmonic and surge suppression
Rated sensitivity current
In 10 (Ig1 + Ign + Igi + Ig2 + Igm)
• Standard breaker
Rated sensitivity current
In 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
Breaker designed
for harmonic and
surge suppression
Standard breaker
Leakage current Ig1 (mA)
33
5 m
= 0.17
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)
33
50 m
= 1.65
1000 m
Motor leakage current Igm (mA) 0.18
Total leakage current (mA) 3.00 6.66
Rated sensitivity current (mA) ( Ig 10)
30 100
Voltage
(V)
EMC filter
ON (mA) OFF (mA)
200
22 1
400
35 2
400
21
Example of leakage current of
cable path per 1km during the
commercial power supply operation
when the CV cable is routed in
metal conduit
(200V 60Hz)
Leakage current example of
three-phase induction motor
during the commercial
power supply operation
(200V 60Hz)
Motor capacity (kW)
Cable size(mm )
2
1.5 3.7
2.2
7.5 15 22
11
37
30
55
455.5 18.5
0.1
0.2
0.3
0.5
0.7
1.0
2.0
Leakage currents (mA)
0
20
40
60
80
100
120
Leakage currents (mA)
23.5
5.5
81422
30
38
60
80
100
150
Motor capacity (kW)
For " " connection, the amount of leakage current is appox.1/3 of the above value.
(Three-phase three-wire delta
connection 400V60Hz)
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 400V60Hz)
0
20
40
60
80
100
120
leakage currents (mA)
leakage currents (mA)
2 3.5
5.5
81422
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
455.5 18. 5
Noise
filter
Drive
unit
ELB
Ig1 Ign
Igi
Ig2 Igm
M
5.5mm
2
5m 5.5mm
2
50m
200V
2.2kW
3φ
Phase
earthing
(grounding)
Earthed-neutral
system
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