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11. OPTIONS AND AUXILIARY EQUIPMENT
11.18 Leakage current breaker
(1) Selection method
High-frequency chopper currents controlled by pulse width modulation flow in the AC servo circuits.
Leakage currents containing harmonic contents are larger than those of the motor which is run with a
commercial power supply.
Select a leakage current breaker according to the following formula, and ground the servo amplifier, servo
motor, etc. securely.
Make the input and output cables as short as possible, and also make the grounding cable as long as
possible (about 30cm) to minimize leakage currents.
Rated sensitivity current
10 {Ig1 Ign Iga K (Ig2 Igm)} [mA] (11.1)
K: Constant considering the harmonic contents
Leakage current breaker
Type
Mitsubishi
products
K
Models provided with
harmonic and surge
reduction techniques
NV-SP
NV-SW
NV-CP
NV-CW
NV-L
1
M
Servo
amplifier
Noise
filter
NV
I
g
1I
g
nI
g
aI
g
2I
g
m
Cable
Cable
General models
BV-C1
NFB
NV-L
3
Ig1: Leakage current on the electric channel from the leakage current breaker to the input terminals of the
servo amplifier (Found from Fig. 11.3.)
Ig2: Leakage current on the electric channel from the output terminals of the servo amplifier to the
servo motor (Found from Fig. 11.3.)
Ign: Leakage current when a filter is connected to the input side (4.4mA per one FR-BIF(-H))
Iga: Leakage current of the servo amplifier (Found from Table 11.5.)
Igm: Leakage current of the servo motor (Found from Table 11.4.)
120
100
80
60
40
20
0
23.5
5.5
8 1422 38 80 150
3060 100
Cable size[mm
2
]
[mA]
L
e
a
k
a
g
e
c
u
r
r
e
n
t
120
100
80
60
40
20
0
2
3.5
5.5
8
14
22
38
80
150
30
60
100
Cable size[mm
2
]
[mA]
L
e
a
k
a
g
e
c
u
r
r
e
n
t
a. 200V class
b. 400V class
Fig. 11.3 Leakage current example (lg1, lg2) for CV cable run in metal conduit