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6 Specifications of Peripheral Devices
MITSUBISHI CNC
6-3 Selection of earth leakage breaker
When installing an earth leakage breaker, select the breaker on the following basis to prevent the breaker from
malfunctioning by the higher frequency earth leakage current generated in the servo or spindle drive unit.
(1) Selection
Obtaining the earth leakage current for all drive units referring to the following table, select an earth leakage
breaker within the "rated non-operation sensitivity current".
Usually use an earth leakage breaker for inverter products that function at a leakage current within the
commercial frequency range (50 to 60Hz).
If a product sensitive to higher frequencies is used, the breaker could malfunction at a level less than the
maximum earth leakage current value.
Earth leakage current for each drive unit
(Note) Maximum earth leakage current: Value that considers wiring length and grounding,
etc.(Commercial frequency 50/60Hz)
(2) Measurement of earth leakage current
When actually measuring the earth leakage current, use a product that is not easily affected by the higher
frequency earth leakage current. The measurement range should be 50 to 60Hz.
Unit Earth leakage current Maximum earth leakage current
MDS-D-SPJ3-075NA to 110NA 6mA 15mA
MDS-D-SVJ3-03NA to 35NA 1mA 2mA
1. The earth leakage current tends to increase as the motor capacity increases.
2. A higher frequency earth leakage current will always be generated because the inverter circuit in
the drive unit switches the transistor at high speed. Always ground to reduce the higher frequency
earth leakage current as much as possible.
3. An earth leakage current containing higher frequency may reach approx. several hundreds of mA.
According to IEC479-2, this level is not hazardous to the human body.
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