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3
PRECAUTIONS FOR USE OF THE INVERTER
EMC and leakage currents
(3) Selection of rated sensitivity current of earth (ground) leakage current breaker
When using the earth leakage current breaker with the inverter circuit, select its rated sensitivity current as follows,
independently of the PWM carrier frequency.
<Example>
Selection example (in the case of the left figure (400V class connection))
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
Breaker Designed for
Harmonic and Surge
Suppression
Standard Breaker
Leakage current Ig1 (mA)
×
66 ×
5m
= 0.11
1000m
Leakage current Ign (mA) 0 (without noise filter)
Leakage current Igi (mA) 1
Leakage current Ig2 (mA)
×
66 ×
60m
= 1.32
1000m
Motor leakage current Igm (mA) 0.36
Total leakage current (mA) 2.79 6.15
Rated sensitivity current (mA) (≥ Ig × 10) 30 100
NOTE
Install the earth leakage breaker (ELB) on the input side of the inverter.
In the connection earthed-neutral system, the sensitivity current is blunt against an earth (ground) fault in the
inverter output side. Earthing (Grounding) must conform to the requirements of national and local safety regulations
and electrical codes. (NEC section 250, IEC 536 class 1 and other applicable standards)
When the breaker is installed on the output side of the inverter, it may be unnecessarily operated by harmonics even
if the effective value is less than the rating.
In this case, do not install the breaker since the eddy current and hysteresis loss will increase, leading to temperature
rise.
General products indicate the following models. ...... BV-C1, BC-V, NVB, NV-L, NV-G2N, NV-G3NA, NV-2F earth leakage
relay (except NV-ZHA), NV with AA neutral wire open-phase protection
The other models are designed for harmonic and surge suppression ....NV-C/NV-S/MN series, NV30-FA, NV50-FA, BV-
C2, earth leakage alarm breaker (NF-Z), NV-ZHA, NV-H
(200V 60Hz)
(200V 60Hz)
0
20
40
60
80
100
120
23.5
5.5
81422
30
38
60
80
100
150
Motor capacity (kW)
Example of leakage current of
cable path per 1km during the
commercial power supply operation
when the CV cable is routed in
metal conduit
Example of leakage current
of three-phase induction motor
during the commercial
power supply operation
Leakage currents (mA)
Leakage currents (mA)
Cable size (mm
2
)
0.1 0.2
0.4
0.75
1.5
2.2
3.7
5.5 11
7.5
20
15
0.02
0.03
0.05
0.07
0.1
0.2
0.3
0.5
0.7
1.0
0
20
40
60
80
100
120
23.5
5.5
81422
30
38
60
80
100
150
0. 1
0. 2
0. 3
0. 5
0. 7
1. 0
2. 0
1.5 3.7
2.2
7.5 15
11 205.5
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
Example of leakage current of three
-
phase induction motor during the
commercial power supply operation
(Totally-enclosed fan-cooled
type motor 400V60Hz)
leakage currents (mA)
leakage currents (mA)
Cable
size (mm
2
)
Noise
filter
Inverter
ELB
Ig1 Ign
Igi
Ig2 Igm
IM
5.5mm
2
×
5m 5.5mm
2
×
60m
400V
2.2k
W
3φ
1
3
1
3