14
Precautions for selecting peripheral devices
1.3.3
Selecting the rated sensitivity current for the earth leakage circuit breaker
When using the earth leakage circuit breaker with the inverter circuit, select its rated sensitivity current as follows.
Breaker for harmonic and surge
Rated sensitivity current l
n
10
(lg1
+
lgn
+
lg2
+
lg3
+
lgm)
Standard breaker
Rated sensitivity current l
n
10
{
lg1
+
lgn
+
lg2
+
3
(lg3
+
lgm)
}
<Example>
NOTE
Install the earth leakage circuit breaker (ELB) on the input side of the converter.
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 with 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.
The following models are the standard breakers
....
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
lg1, lg2, lg3 : leakage current of cable path during
commercial power supply operation
lgn : leakage current of noise filter on the
converter input side
lgm : leakage currents of motor during commercial
power supply operation
(200V 60Hz)
(200V 60Hz)
1. 5 3. 7
2. 2
7. 5 1522
11
37
30
55
45
5.5
18. 5
0. 1
0. 2
0. 3
0. 5
0. 7
1. 0
2. 0
0
2 0
4 0
6 0
8 0
100
120
2 3.5
5.5
8 1422
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
Leakage current example of
three-phase induction motor
during the commercial
power supply operation
Leakage currents (mA)
Leakage currents (mA)
Cable size (mm
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 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
2 0
4 0
6 0
8 0
100
120
leakage currents (mA)
leakage currents (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
lg1
lgn
lg2
lg3
lgm
3
φ
200V 2.2kW
IM
Inverter
ELB
Converter
Noise
filter
5.5mm
2
×
5m
5.5mm
2
×
70m
5.5mm
2
×
5m
Selection Example
(for the diagram shown on the left) (mA)
Breaker for
harmonic
and surge
Standard
breaker
Leakage current lg1 (mA)
33
=0.17
Leakage current lgn (mA)
0 (without noise filter)
Leakage current lg2 (mA)
33
= 0.17
Leakage current lg3 (mA)
33
= 2.31
Leakage current lgm (mA)
0.18
Total leakage current (mA)
2.83
7.81
Rated sensitivity current
(
lg
10)(mA)
30
100
5m
1000m
----------------
5m
1000m
----------------
70m
1000m
----------------
HC2.book 14 ページ ２０１２年１１月１９日 月曜日 午前１０時５２分
