8000m Series
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1. Signals of instruments, receiver and sensors for measuring are fairly weak to be
interfered easily if they are close to the VFD or in the same control cabinet. It is
recommended to solve the problem: Keep away from VFD as far as possible; Do
not arrange signal cables running close and parallel to power cables, especially
never bundle them up; It is recommended to use shield cable for signal and power
transfer, and must be grounded correctly; To the output of VFD, add ferrite beads
and make 2~3 coils each (Select the models for suppressing scope of
30~1000MHz); To some worse cases, install an EMC output filter.
2. If the device which is interfered shares the same power source with VFD and
results in conducting interference, and the methods above cannot eliminate the
interference, an EMC filter should be installed to the power input of VFD (For
details refers to 7.3.6).
3. Grounding peripheral devices separately can avoid the interference caused by
VFD ground leakage current through common ground.
7.3.5 Leakage Current Handling
There are two types of leakage current in VFD application: one is ground leakage
current, and the other is line-to-line leakage current.
1. Factors of ground leakage current
There is distributed capacitance between line conductor and earth ground. The
larger the distributed capacitance, the larger ground leakage current is. For
reducing the distributed capacitance, it is effective shortening the distance from
VFD to motor. The higher the Carrier frequency is, the larger the ground leakage
current is. It is effective to reduce ground leakage current by lowering the carrier
frequency, but will result in increasing of motor noise. Note: Installing an electric
reactor is also an effective method for lowering ground leakage current.
Ground leakage current will increase as the main circuit current increasing, i.e. the
larger power the motor, the larger ground leakage current is.
2. Factors of line-to-line leakage current
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