Installation and wiring
INVERTER INTRODUCTION 35
3.5.4 EMC installation instructions
Just as other electrical and electronic equipment, an inverter is the source of electromagnetic interference and an
electromagnetic receiver when working with a power system. The amount of electromagnetic interference and noise is
determined by the working principles of an inverter. In order to guarantee the inverter working reliably in the
electromagnetic environment, it must have a certain ability of anti-electromagnetic interference in design. In order to
make the drive system work normally, please meet the following requirements in different aspects when installing:
Field wiring
Power line supply electricity independently from power transformer, five or four core line are commonly used, do
not share a single line with common line and ground.
Generally signal wire (weak current) and power wire (heavy current) are in control cabinet, for the inverter, power
wire is divided into input line and output line. Signal wire can be easily interfered by power wire, causing the device
malfunction. When wiring, signal wire and power wire should be wired in different areas, do not parallel or interlace
them at close range(within 20cm), and especially don’t bundle up the two. If the signal cables must pass the power
lines, the two should keep in 90 degree angle. Do not interlace or band together the input and output power wire,
especially if noise filter is installed. It will cause electromagnetic noise coupling while going through input and
output power line’s capacitance, thus the noise filter will not work.
Generally a control cabinet contains different electric equipment such as inverters, filters, PLCs, measuring
devices, their ability of emitting and bearing electromagnetic noise are diverse from each other, and so it requires
classifying them. The classification can be divided into strong noise equipment and noise sensitive equipment,
Install the similar equipment in the same area and, and keep a distance more than 20cm among different
equipment.
Input noise filter, input and output magnet ring (Zero phase reactor)
By adding noise filter to the input terminal, the inverter will be isolated from the other equipment, and its ability to
conduct and radiate will be reduced effectively. By adding ferrite ring to the input and output terminal and
coordinating with internal filter, the inverters will perform even better.
Shielding
Good shielding and grounding can greatly reduce the interference of the inverter, and can improve the
anti-interference ability of the inverter. Sealing the inverter with conductive metal sheet(case) and connecting the
metal sheet to ground, the radiation interference will be reduced effectively. To reduce the interference of inverter
and improve the anti-interference ability, cable with shielding layers should be used in input and output line and the
both ends of the layer should be connected to ground. Under electromagnetic interfered environment, shielding
cable is suggested to be used in control terminal wiring and communication terminal wiring. Generally, the both
ends of shielding layer should be connected to the control /communication ground, and they can also be
connected to earth ground.
Grounding
Inverter must be connected to the ground safely and reliably. Grounding is not only for equipment and personal
safety, but also the simplest, the most efficient and the lowest cost method to solve the EMC problem, so it should
be prioritized. Please refer to section3.7" Terminal wiring".
Carrier wave
The leakage current contains the leakage from line to line or line to ground. The amount of it depends on the size
of the distributed capacitance when wiring and the carrier frequency of the inverter. The higher the carrier
frequency, the longer the motor cable, and the larger the cable cross-sectional area is, the larger the leakage
current is. Reducing the carrier frequency can effectively reduce the leakage current. When the motor line is long
(50m above), the output side should be installed with ac reactor or sine wave filter, when the motor line is longer, a
reactor should be installed every fixed distance. At the same time, reducing carrier frequency can effectively
reduce the conduction and radiation interference of the inverter.
