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13. OPTIONS AND AUXILIARY EQUIPMENT
13.2.7 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 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 (11.8 in)) to minimize leakage currents.
Rated sensitivity current
10 {Ig1 Ign Iga K (Ig2 Igm)} [mA] ..........(13.2)
K: Constant considering the harmonic contents
Leakage current breaker
Type
Mitsubishi
products
K
Models provided with
harmonic and surge
reduction techniques
NV-SF
NV-CF
1
General models
NV-CA
NV-CS
NV-SS
3
SM
Servo
amplifier
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 servo amplifier (Found from Fig. 13.1.)
Ig2: Leakage current on the electric channel from the output terminals of the servo amplifier to the
servo motor (Found from Fig. 13.1.)
Ign: Leakage current when a filter is connected to the input side (4.4mA per one FR-BIF)
Iga: Leakage current of the servo amplifier (Found from Table 13.6.)
Igm: Leakage current of the servo motor (Found from Table 13.5.)
Table 13.5 Servo motor's
leakage current
example (Igm)
Table 13.6 Servo amplifier's
leakage current
example (Iga)
Servo motor
output [kW]
Leakage
current [mA]
Servo amplifier
capacity [kW]
Leakage
current [mA]
0.05 to 0.5 0.1 0.1 to 0.6 0.1
0.6 to 1.0 0.1 0.7 to 3.5 0.15
1.2 to 2.2 0.2 5 72
3 to 3.5 0.3
50.5
70.7
Table 13.7 Leakage circuit breaker selection example
Servo amplifier
Rated sensitivity
current of leakage
circuit breaker [mA]
MR-J2S-10A to MR-J2S-350A
MR-J2S-10A1 to MR-J2S-40A1
15
MR-J2S-500A 30
120
100
80
60
40
20
0
23.5
5.5
81422388015
0
30 60 100
Fig. 13.1 Leakage current example
(Ig1, Ig2) for CV cable run
in metal conduit
Cable size[mm
2
]
[mA]
Leakage current
MR-J2S-700A 50