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12. OPTIONS AND AUXILIARY EQUIPMENT
12.2.7 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 base unit, 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 (11.8 in)) to minimize leakage currents.
Rated sensitivity current
10 {Ig1 Ign Iga K (Ig2 Igm)} [mA] ..........(12.1)
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-HW
1
General models
BV-C1
NFB
NV-L
3
M
MELSERVO
-J2M
Noise
filter
NV
Ig1 Ign Iga Ig2 Igm
Cable
Cable
Ig1: Leakage current on the electric channel from the leakage current breaker to the input terminals
of the base unit (Found from Fig. 12.1.)
Ig2: Leakage current on the electric channel from the output terminals of the drive unit to the
servo motor (Found from Fig. 12.1.)
Ign: Leakage current when a filter is connected to the input side (4.4mA per one FR-BIF)
Iga: Leakage current of the drive unit (Found from Table 12.4.)
Igm: Leakage current of the servo motor (Found from Table 12.3.)
Table 12.3 Servo motor's
leakage current
example (Igm)
Table 12.4 Drive unit's
leakage current
example (Iga)
Servo motor
output [kW]
Leakage
current [mA]
Drive unit
capacity [kW]
Leakage current
[mA]
0.05 to 0.4 0.1 0.1 to 0.4 0.3
0.75 0.6
120
100
80
60
40
20
0
23.5
5.5
814223880150
3060 100
Fig. 12.1 Leakage current example
(Ig1, Ig2) for CV cable run
in metal conduit
Cable size[mm
2
]
[mA]
L
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a
k
a
g
e
c
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r
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