Inovance MD280NT2.2GB - Page 157

EMC
MD280 User Manual
- 156 -
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2. When the equipment suffering interference and the AC drive use the same power
supply, it may cause conduction interference. If the above handling cannot eliminate the
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3. Grounding the surrounding equipment separately can avoid the interference
caused by the leakage current of the AC drive’s grounding cable when common grounding
mode is adopted.
7.3.5 Leakage Current and Handling
There are two forms of leakage current when the AC drive is used. One is leakage current to
ground, and the other is leakage current between cables.
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 There are distributed capacitance between lead cables and the ground. The larger the
distributed capacitance is, the larger the leakage current is. The distributed capacitance
can be reduced by effectively shortening the distance between the AC drive 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 increase of motor noise.
 To install a reactor is also an effective method to remove the leakage current.
 The leakage current may increase following increase of the circuit current. Therefore,
when the motor power is high, the corresponding leakage current is large.
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Factors of producing Leakage Current Between Cables and Solutions
There is distributed capacitance between the output cables of the AC drive. If the current
passing the cables contains higher harmonic, it may cause resonance and thus result in
leakage current. If a thermal relay is used in this case, error actions may result.
The solution is to reduce the carrier frequency or install an output reactor. It is recommended
that a thermal relay not be installed before the motor when using the AC drive, and that
electronic overcurrent protection function of the AC drive be used instead.
7.3.6 Precautions for Installing the EMC Input Filter at Input Side of Power Supply
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appliances, and the metal enclosure ground of the filter must be reliably connected
to the metal ground of the installing cabinet and have good conduction continuity.
Otherwise electric shock may result and the EMC effect may be greatly affected.
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same common ground. Otherwise, the EMC effect may be greatly affected.
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as possible.
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