11. OPTIONS AND PERIPHERAL EQUIPMENT
11 - 28
11.9 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 driver,
servo motor, etc. securely.
To minimize leakage currents, make the input and output cables as short as possible, and make the
grounding cable longer than 30 cm.
Rated sensitivity current ≥ 10 • {Ig1 + Ign + Iga + K • (Ig2 + Igm)} [mA] ····································· (11.1)
Ig1: Leakage current on the electric channel from the earth-leakage current breaker to the input terminals
of the driver (Found from Fig. 11.5.)
Ig2: Leakage current on the electric channel from the output terminals of the driver to the servo motor
(Found from Fig. 11.5.)
Ign: Leakage current when a filter is connected to the input side (4.4 mA per one FR-BIF)
Iga: Leakage current of the driver (Found from table 11.3.)
Igm: Leakage current of the servo motor (Found from table 11.2.)
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