Chapter 6 Troubleshooting
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Ch
ap
ter 6
6-3-5.
Remedies for leakage current
There are two forms of leakage current when using the inverter. One is leakage current to the
earth, and the other is leakage current between the cables.
1) Factors of affecting leakage current to the earth and its solutions:
There are the distributed capacitance between the lead cables and the earth. The larger the
distributed capacitance, the larger the leakage current; the distributed capacitance can be reduced by
effectively reducing the distance
between the inverter and the motor. The higher the carrier frequency, the larger the leakage
current. The leakage current can be reduced by reducing the carrier frequency. However, the carrier
frequency reduced may result in
the increase of motor noise.Please note that additional installation of reactor is also an effective
method to solve leakage current problem.
The leakage current may increase with the increase of circuit current. Therefore, when the motor
power is higher, the corresponding leakage current will be higher too.
2) Factors of producing leakage current between the cables and its solutions:
There is the distributed capacitance between the output cables of the inverter. If the current
passing lines has higher harmonic, it may cause resonance and thus result in leakage current. If the
thermal relay is used, it may generate error action.
The solution is to reduce the carrier frequency or install output reactor. It is recommended that
the thermal relay shall not be installed in the front of the motor when using the inverter, and that
electronic over current protection function of the inverter shall be used instead.
6-3-6.
Precautions on installing EMC input filter at the input end of
power supply
1) Note: when using the inverter, please follow its rated values strictly. Since the filter belongs to
Classification I electric appliances, the metal enclosure of the filter and the metal ground of the
installing cabinet shall be well earthed in a large area, and have good conduction continuity, otherwise
there may be danger of electric shock and the EMC effect may be greatly affected. Through the EMC
test, it is found that the filter ground end and the PE end of the inverter must be connected to the same
public earth end, otherwise the EMC effect may be greatly affected.
2) The filter shall be installed at a place close to the input end of the power supply as much as
possible.
