KE300A Inverter EMC (Electromagnetic Compatibility)
166
capacitance is, the larger the leakage current will be. The distributed capacitance can be reduced by
effectively reducing the distance between the inverter and the motor. The higher the carrier frequency is,
the larger the leakage current will be. The leakage current can be reduced by reducing the carrier
frequency. However, reducing the carrier frequency may result in addition of motor noise. Note that
additional installation of reactor is also an effective method to remove the leakage current.
The leakage current may increase following the addition of circuit current. Therefore, when the motor
power is high, the corresponding leakage current will be high too.
2) Factors of producing leakage current between the cables and solutions:
There is distributed capacitance between the output cables of the inverter. If the current passing the lines
has higher harmonic, it may cause resonance and thus result in leakage current. If 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 thermal
relay not be installed before the motor when using the inverter, and that electronic over current protection
function of the inverter be used instead.
7.3.6 Precautions for Installing EMC input filter at the input end of power supply
1) 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 should be large and the metal ground of the installing
cabinet should be well earthed and have good conduction continuity. Otherwise there may be danger of
electric shock and the EMC effect may be greatly affected.
2) Through the EMC test, it is found that the filter ground must be connected with the PE end of the
inverter at the same public earth. Otherwise the EMC effect may be greatly affected.
3)
The filter should be installed at a place close to the input end of the power supply as much as
possible.
