The supplier of Inverter Brake Unit reminds you: in the industrial production and daily use of inverter, because of the obvious energy-saving effect of inverter, convenient adjustment, simple maintenance, networking and other advantages, more and more widely used inverter driven motor system, but the interference caused by the special working mode of inverter can not be ignored.
In order to prevent interference, hardware anti-interference and software anti-interference can be used. Among them, hardware anti-interference is the most basic and important anti-interference measures, generally we are to suppress and eliminate the interference source, cut off the coupling channel of the interference to the system, and reduce the sensitivity of the system interference signal. Specific measures in the project can be used isolation, filtering, shielding, grounding and other methods.
Isolation can be used to isolate the easily interfered part from the interference source, cut off the interference coupling channel, so that the signal between them can not be transmitted normally. Isolation transformer, photoelectric isolation and relay isolation can also be used to block DC interference in AC signal and suppress the intensity of low-frequency interference signal, so as to isolate various analog loads and digital signal sources, that is, to disconnect analog signal and digital signal, so as to avoid the conduction of interference signal. Isolate the interference signal on the frequency converter, reduce the harm of the interference signal to the equipment, or reduce the interference, reduce the harm to the frequency converter, and ensure the healthy operation of the equipment.
In order to prevent the interference from affecting the normal operation of the inverter, passive filtering technology and active filtering technology should be used in the harmonic processing, which can effectively eliminate the impact of harmonics on the power grid. Passive filter device has simple structure, low cost and mature technology, but it also has some defects that are difficult to overcome. Source filtering technology is a new harmonic control technology, which consists of two main parts: instruction current operation circuit and compensation current generation circuit. Dynamic compensation is realized, which can compensate the reactive power whose frequency and size change. It has a very fast response speed to the change of compensation object, but its cost is high. Due to the low power factor of the power grid, the high-power inverter is more likely to have a greater impact. In order to resist the interference generated in the operation process of the inverter, these two filtering technologies can be used to prevent interference.
Inverter is composed of very fine microprocessor and other integrated circuits, which is sensitive to the electromagnetic interference produced by other components, so it is easy to cause serious errors. The electromagnetic interference of other components enters from the control cable of frequency converter, so strong anti-interference measures should be taken for the cable. The side close to the frequency converter should be connected to the common end of the control circuit, but not to the grounding end of the frequency converter or directly grounded. The other end of the shielding layer can be suspended. The signal line adopts double core shielding and is completely separated from the main circuit and control circuit. It cannot be placed in the same piping or trunking. The surrounding electronic sensitive equipment lines also require shielding. In order to make the shielding effective, the shielding cover must be reliably grounded.
The correct grounding mode is very important for the normal operation of the inverter. The correct grounding can not only effectively suppress the external interference of the system, but also reduce the interference of the equipment itself to the outside world. To a great extent, it can suppress the internal noise, prevent the invasion of external interference, and improve the anti-interference ability of the system. When the frequency converter and other equipment or multiple frequency converters need to be grounded at the same time, all equipment should be grounded separately, instead of connecting the grounding terminal of one or more equipment. It should be adopted according to the specific situation, and attention should be paid not to interfere with the equipment due to poor grounding. Reduce the mutual interference between the inverter and other equipment, so that the inverter and other equipment can work normally and play a better role.
Installation of reactor
The reactor can mainly control the interference of high-order harmonics. The inverter itself is a high-order harmonic generator, and the reactor can block the external transmission of harmonics, and at the same time avoid the external harmonics into the inverter. In order to improve the output current of frequency converter and reduce motor noise, AC reactor can be installed at the output end of frequency converter. In order to suppress the harmonic current at the input side of frequency converter and improve power factor, AC reactor can be installed at the input end of frequency converter. Reactor can not only reduce the harmonic output and input, but also change the overvoltage protection of line power supply.
The interference signal transmitted by induction can be weakened by reasonable wiring. The specific methods are as follows:
(1) The power line and signal line of the equipment should be far away from the input and output lines of the inverter;
(2) The power line and signal line of other equipment shall not be parallel to the input and output lines of frequency converter.
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