44
INSTALLATION AND WIRING
(2) Selection of the rated sensitivity current for the earth (ground) leakage circuit
breaker
When using the earth (ground) leakage circuit breaker with the inverter circuit, select its rated sensitivity
current as follows, independent of the carrier frequency setting:
<Example>
• Breaker for harmonic and surge:
Rated sensitivity current:
l∆n ≥ 10 × (lg
1
+ lgn + lg
2
+ lgm)
• Standard breakers:
Rated sensitivity current:
l∆n ≥ 10 × {lg
1
+ lgn + 3 ( (lg
2
+lgm)}
lg
1
, lg
2
:leakage currents of cable path
during commercial power supply operation
lgn*: leakage current of noise filter on
inverter input side
lgm: leakage current of motor during
commercial power supply operation
Note: 1. The NV should be installed to the
primary (power supply) side of the
inverter.
2. Earth (Ground) fault in the secondary
side of the inverter can be detected at
the running frequency of 120Hz or
lower.
3. In the connection neutral point
earthing (grounding) system, the
sensitivity current is purified against an
earth (ground) fault on the inverter
secondary side. Earthing (grounding)
must be conform to the requirements
of national and local safety regulations
and electrical code. (JIS, NEC section
250, IEC 536 class 1 and other
applicable standards)
Breaker for
harmonic and surge
Standard breakers
Leakage current Ig1 (mA) 33 ×
5m
= 0.17
1000m
Leakage current Ign (mA) 0 (without noise filter)
Leakage current Ig2 (mA) 33 ×
70m
= 2.31
1000m
Motor leakage current Igm
(mA)
0.18
Total leakage current (mA) 2.66 7.64
Reted sensitivity current (mA)
(
≥
Ig × 10)
30 100
4. When the breaker is installed on the secondary side of the inverter, it may be unnecessarily operated by
harmonics if the effective value is less than the rating. In this case, do not install the breaker since the
eddy current and hysteresis loss increase, leading to temperature rises.
5. The following models are standard breakers. . . . . . . . . . . . . . . . . .BV-C1, BC-V, NVB, NV-L, NV-G2N, NV-
G3NA, and NV-2F type, leakage current
relays (except for NV-ZHA), NV with AA
neutral wire open-phase protection
The following models are breakers for harmonic and surge. . . . . .NV-C/NV-S/MN series, NV30-FA, NV50-
FA, BV-C2, leakage current alarm
breaker (NF-Z), NV-ZHA, NV-H
* Be careful of the leakage current value of the noise filter installed on the inverter input side.
(Refer to the FR-A500 catalog for details of Mitsubishi inverter dedicated filter.)
0
20
40
60
80
100
120
23.5
5.5
81422
30
38
60
80
100
150
0.1
1.5 3.7
2.2
7.5 1522
11
37
30
55
45
0.2
0.3
0.5
0.7
1.0
2.0
5.5 18.5
Leakage current example
of 3-phase induction motor
during commercial power
supply operation
(200V 60Hz)
Leakage current (mA)
Leakage current (mA)
Cable size (mm )
2
Motor capacity (kW)
Example of leakage current
per 1km in cable path during
commercial power supply
operation when the CV
cable is routed in metal
conduit (200V 60Hz)
NV
Ig1
Ign
Ig2 Igm
IM
Inverter
Noise
filter
5.5mm
2
×
5m
5.5mm
2
×
70m
3
φ
200V 2.2kW
