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Like other electric or electronic devices, inverter is not only an electromagnetic interference
source but also an electromagnetic receiver. The operating principle of inverter determines that it
can produce certain electromagnetic interference noise. And the same time inverter should be
designed with certain anti-jamming ability to ensure the smooth working in certain
electromagnetic environment. The following is its EMC features:
4.7.2.1
Input current is non-sine wave. The input current includes large amount of high-
harmonic waves that can cause electromagnetic interference, decrease the grid power
factor and increase the line loss.
4.7.2.2
Output voltage is high frequency PMW wave, which can increase the temperature rise
and shorten the life of motor. And the leakage current will also increase, which can lead
to the leakage protection device malfunction and generate strong electromagnetic
interference to influence the reliability of other electric devices.
4.7.2.3
As the electromagnetic receiver, too strong interference will damage the inverter and
influence the normal using of customers.
4.7.2.4
In the system, EMS and EMI of inverter coexist. Decrease the EMI of inverter can
increase its EMS ability.
4.7.3 EMC Installation Guideline
In order to ensure all electric devices in the same system to work smoothly, this section,based on
EMC features of inverter, introduces EMC installation process in several aspects of application
(noise control, site wiring, grounding, leakage current and power supply filter). The good effective
of EMC will depend on the good effective of all of these five aspects.
4.7.3.1
Noise control
All the connections to the control terminals must use shielded wire. And the shield layer of the
wire must ground near the wire entrance of inverter. The ground mode is 360 degree annular
connection formed by cable clips. It is strictly prohibitive to connect the twisted shielding layer to
the ground of inverter, which greatly decreases or loses the shielding effect.
Connect inverter and motor with the shielded wire or the separated cable tray. One side of shield
layer of shielded wire or metal cover of separated cable tray should connect to ground, and the
other side should connect to the motor cover. Installing an EMC filter can reduce the
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