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11. OPTIONS AND PERIPHERAL EQUIPMENT
11.10 Earth-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 an earth-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 {Igl Ign Iga K (Ig2 Igm)} [mA] ................... (11.1)
Ign
Noise filter
Cable
Cable
Ig1 Iga Ig2 Igm
M
Servo
amplifier
NV
Earth-leakage current breaker
K
Type
Mitsubishi
Electric
products
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
Ig1: Leakage current on the electric channel from the earth-leakage current breaker to the input terminals
of the servo amplifier (Found from Fig. 11.1.)
Ig2: Leakage current on the electric channel from the output terminals of the servo amplifier to the servo
motor (Found from Fig. 11.1.)
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 Fig. 11.5.)
Igm: Leakage current of the servo motor (Found from Fig. 11.4.)
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]
Leakage current
Fig. 11.1 Leakage current example (Ig1, Ig2) for CV cable run in metal conduit
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