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4.2 Other precautions
Leakage current
EMC filter reduces conductive interference to the power supply when it is inserted to
the power line of the inverter. The internal circuit of the EMC filter consists of coils,
capacitors and resistors, and these reduce conductive interference to the power
supply. In this circuit, the capacitors, which are inserted between the power supply
line and the ground (earth), reduce the interference but increase leakage current to
the ground (earth).
● Influence of leakage current
Possible effects of leakage current are as follows.
(a) If the EMC filter is not properly grounded (earthed), there is a chance of an
electric shock.
(b) An earth leakage circuit breaker (earth leakage circuit relay) installed on top of
the EMC filter may operate unnecessarily.
● Countermeasures to the above
Take the following countermeasures to the above effects.
(a) Connect the EMC filter to the ground (earth) before connecting the power
supply. Confirm that the grounding (earthing) is securely performed through the
ground (earth) of the enclosure.
(b) Select an earth leakage circuit breaker or an earth leakage circuit relay
according to the leakage current of the EMC filter. (Refer to the following for the
selection method. Calculate by applying the leakage current from the EMC filter
to "Ign".)
Because the leakage current of the high power filters is so large, the earth
leakage circuit breaker may not be available. In that case, use a higher rated
earth leakage circuit relay. If it is not possible to use either of an earth leakage
circuit breaker or an earth leakage circuit relay, perform grounding (earthing)
securely as shown in (a).
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