51
Noise and leakage currents
3
PRECAUTIONS FOR USE OF THE INVERTER
(3) Selection of rated sensitivity current of earth (ground) leakage breaker
When using the earth (ground) leakage circuit breaker with the inverter circuit, select its rated sensitivity current as
follows, independently of the PWM carrier frequency:
<Example>
z
Inverter leakage current (with and without EMC filter)
Input power conditions
(400V class: 440V/60Hz, power supply unbalance within 3%)
⋅ Breaker designed for harmonic and surge suppression
Rated sensitivity current:
IΔn ≥ 10 × (Ig1 + Ign + Igi + Ig2 + Igm)
⋅ Standard breaker
Rated sensitivity current:
IΔn ≥ 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 (without EMC filter)
Refer to the following table for the leakage
current of the inverter*
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
* Refer to page 13 for the EMC filter.
Voltage
(V)
EMC Filter
ON (mA) OFF (mA)
400
30 1
400
11
CAUTION
⋅ 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.
⋅ The following models are standard breakers....BV-C1, BC-V, NVB, NV-L, NV-G2N, NV-G3NA and 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
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 motorduring 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)
23.5
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
Inverter
ELB
Ig1 Ign
Igi
Ig2 Igm
IM
5.5mm
2
×
5m 5.5mm
2
×
60m
400V
2.2k
3φ
1
3
1
3
Phase
grounding
Earthed-neutral
system
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