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(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, independently of the PWM carrier frequency:
Progressive Super Series
(Type SP, CF, SF, CP)
Rated sensitivity current:
I∆n ≥ 10 × (lg1+Ign+lg2+lgm)
Conventional NV series (Type CA,
CS, SS produced prior to '91)
Rated sensitivity current:
I∆n ≥ 10 × {lg1+lgn+3 × (lg2+lgm)}
lg1, lg2 : 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
0
20
40
60
80
100
120
23.5 814223880
5.5 30 60100
150
1.5
3.7
2.2
7.5 1522
11
37
30
55
45
5.5 18.5
Cable size (mm )
2.0
1.0
0.7
0.5
0.3
0.2
0.1
Motor ca
p
acit
y
(
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)
Leakage current (mA)
Leakage current (mA)
2
Leakage current
example of 3-phase
induction motor
during commercial
power supply
operation
(200V 60Hz)
<Example>
NV
Ig1 Ign Ig2 Igm
2mm ×5m
2mm ×70m
IM
3
200V
1.5kW
(2HP)
Inver-
ter
Noise
filter
22
(16.40feet)
(229.66feet)
CAUTION
• The earth leakage circuit breaker should be installed to the primary (power
supply) side of the inverter.
• 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.
• When the breaker is installed in 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 and
the temperature rises.
* Note the leakage current value of the noise filter installed on the inverter input
side.
Progressive Super Series
(Type SP, CF, SF,CP)
Conventional NV
(Type CA, CS, SS)
5m (16.40feet)
Leakage current (Ig1) (mA)
20
×
1000m
(
3280.80feet
)
= 0.10
Leaka
g
e current
(
I
g
n
)
(
mA
)
0 (without noise filter)
70m (229.66feet)
Leakage current (Ig2) (mA)
20
×
1000m
(
3280.80feet
)
= 1.40
Motor leakage
current (Igm) (mA)
0.14
Total leakage current (mA)
1.66 4.78
Rated sensitivity current
(mA) (
≥
≥≥
≥
Ig
×
××
×
10)
30 100