EM11 User’s Manual 6. EMC(Electromagnetic compatibility)
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6. EMC (Electromagnetic compatibility)
6.1 Definition
Electromagnetic compatibility is the ability of the electric equipment to run in the electromagnetic
interference environment and implement its function stably without interferences on the electromagnetic
environment.
6.2 EMC Standard Description
In accordance with the requirements of the national standard GB/T12668.3, the inverter needs to comply
with electromagnetic interference and anti-electromagnetic interference requirements.
The existing products of our company apply the latest international standard—IEC/EN61800-3: 2004
(Adjustable speed electrical power drive systems part 3: EMC requirements and specific test methods),
which is equivalent to the national standard GB/T12668.3.
IEC/EN61800-3 assesses the inverter in terms of electromagnetic interference and anti-electronic
interference. Electromagnetic interference mainly tests the radiation interference, conduction interference
and harmonics interference on the inverter (required for the inverter for civil use)Anti-electromagnetic
interference mainly tests the conduction interference rejection, radiation interference rejection, surge
interference rejection, fast and mutable pulse group interference rejection, ESD interference rejection and
power low frequency end interference rejection (specific test items including: 1. Interference rejection tests
of input voltage sag, interrupt and change; 2. Phase conversion interference rejection test; 3. Harmonic
input interference rejection test; 4. Input frequency change test; 5. Input voltage unbalance test; 6. input
voltage fluctuation test).
The tests shall be conducted strictly in accordance with the above requirements of IEC/ EN61800-3, and
the products of our company are installed and used according to Section 7.3 and have good electromagnetic
compatibility in general industry environment.
6.3 EMC Guide
6.3.1 Harmonic Effect
Higher harmonics of power supply may damage the inverter. Thus, at some places where mains quality is
rather poor, it is recommended to install AC input reactor.
6.3.2 Electromagnetic Interference and Installation Precautions
There are two kinds of electromagnetic interferences, one is interference of electromagnetic noise in the
surrounding environment on the inverter, and the other is interference of inverter on the surrounding
equipment.
Installation precautions:
1)
The earth wires of the frequency inverter and other electric products shall be well grounded;
2)
The power input and output power cables of the inverter and weak current signal cables (e.g. control
line) shall not be arranged in parallel and vertical arrangement is preferable.
3)
It is recommended that the output power cables of the inverter employ shield cables or steel pipe
shielded cables and that the shielding layer be earthed reliably. The lead cables of the equipment
suffering interferences are recommended to employ twisted-pair shielded control cables, and the
6. EMC(Electromagnetic compatibility) EM11 User’s Manual
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shielding layer shall be earthed reliably.
4)
When the length of motor cable is longer than 100 meters, it needs to install output filter or reactor.
6.3.3 Handling method for the interferences of the surrounding equipment on the
inverter
The electromagnetic interference on the inverter is generated because plenty of relays, contactors and
electromagnetic brakes are installed near the inverter. When the inverter has error action due to the
interferences, the following measures can be taken:
1)
Install surge suppressor on the devices generating interference;
2)
Install filter at the input end of the inverter. Refer to Section 7.3.6 for the specific operations.
3)
The lead cables of the control signal cable of the inverter and the detection line employ shielded cable
and the shielding layer shall be earthed reliably.
6.3.4 Handling method for the interferences of frequency inverter on the surrounding
equipment
These interferences include two types: one is radiation interference of the inverter, and the other is
conduction interference of the inverter. These two types of interferences cause the surrounding electric
equipment to suffer electromagnetic or electrostatic induction. The surrounding equipment hereby produces
error action. For different interferences, it can be handled by referring to the following methods:
1)
For the measuring meters, receivers and sensors, their signals are generally weak. If they are placed
nearby the inverter or together with the inverter in the same control cabinet, they are easy to suffer
interference and thus generate error actions. It is recommended to handle with the following methods:
Put in places far away from the interference source; do not arrange the signal cables with the power
cables in parallel and never bind them together; both the signal cables and power cables employ
shielded cables and are well earthed; install ferrite magnetic ring (with suppressing frequency of 30 to
1,000MHz) at the output side of the inverter and wind it 2 to 3 cycles; install EMC output filter in more
severe conditions.
2)
When the equipment suffering interferences and the inverter use the same power supply, it may cause
conduction interference. If the above methods cannot remove the interference, it shall install EMC filter
between the inverter and the power supply (refer to Section 7.3.6 for the prototyping operation); the
surrounding equipment is separately earthed, which can avoid the interference caused by the leakage
current of the inverter’s earth wire when common earth mode is adopted.
3)
The surrounding equipment is separately earthed, which can avoid the interference caused by the
leakage current of the inverter’s earth wire when common earth mode is adopted.
6.3.5 Leakage current and handling
There are two forms of leakage current when using the inverter. One is leakage current to the earth, and the
other is leakage current between the cables.
1)
Factors influencing the leakage current to the earth and the solutions:
There are distributed capacitance between the lead cables and the earth. The larger the distributed
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
