Mitsubishi Electric FR-CV-7.5K Instruction Manual page 32

(2) Selection 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,
independent of the carrier frequency setting:
Breaker for harmonic and surge
Rated sensitivity current:
lΔn ≥ 10 × (lg
1 + lgn + lg
Standard breaker
Rated sensitivity current:
lΔn ≥ 10 × {lg
+ lgn + 3 × (lg
1
lg , lg : leakage currents of cable path during
1 2
commercial power supply operation
lgn* : leakage current of noise filter on power
regeneration common converter input
side
lgm : leakage current of motor during
commercial power supply operation
<Example>
2
22mm ×5m
(16.40 feet)
NV Noise
Power regeneration
filter
common converter
+
Inverter 15K
Ig1 Ign
Leakage current Ig1 (mA)
Leakage current Ign (mA)
Leakage current Ig2 (mA)
Motor leakage current Igm (mA)
Total leakage current (mA)
Rated sensitivity current (mA) ( ≥Ig × 10)
Note: 1. The NV should be installed to the primary (power supply) side of the power regeneration common
converter.
2. 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 grounded system, the sensitivity current becomes worse for ground
faults in the inverter secondary side. Hence, the protective grounding of the load equipment should be
10Ω or less.
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 it since the eddy current
and hysteresis loss increase and the 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), AA neutral wire, NV with 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 power regeneration common
converter input side.
2 + lgm)
+lgm)}
2
2
×30m
22mm
(98.43 feet)
3φ
IM
200V
15kW (20HP)
Ig2 Igm
Breaker for
Harmonic and Surge
5m (16.40 feet)
50 ×
1000m (3280.80 feet)
0 (without noise filter)
30m (98.43 feet)
50 ×
1000m (3280.80 feet)
2.32
30
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)
120
100
80
60
40
20
0
2 3.5 8 14 22 38 80 150
5.5 30 60 100
2
Cable size (mm )
Standard Breaker
=0.25
=1.50
0.57
6.46
100
27
Other wiring
Leakage current example
of 3-phase induction motor
during commercial power
supply operation
(200V 60Hz)
2.0
1.0
0.7
0.5
0.3
0.2
0.1
1.5 3.7 7.5 15 22 37 55
2.2 5.5 11 18.5 30 45
Motor capacity (kW)
2