1 Introduction Frequency Manage is a control technology, microelectronics, power electronics, and communications technologies in a single higher-tech technology. It is in quite very good speed, energy-saving performance, in all walks of life to get a wide variety of applications. Since its soft launch, can lessen the influence of equipment and electrical machinery, gear and motor life extension. With the rapid improvement of science and technologies, with its energy-saving frequency converter, power saving, reputable and efficient characteristics applied to all places of industrial handle, such as frequency control in water supply, air conditioning, method manage, elevators, machine tools and so on. The application of the regulation to make sure accuracy, decreasing labor intensity and increase financial efficiency, but also brought along some of the interference issue. Energy supply and electrical equipment on internet site will impact the inverter, inverter run-time generated higher harmonics can interfere with the operation of surrounding gear. Inverter generated disturbances are mainly three types: interference with electronic equipment, jamming and communications gear, such as production of radio interference. Automatic handle devices on the personal computer and electronic equipment generated interference is primarily induced interference on communications equipment and radio interference generated by such as radioactive interference. If the frequency converter to resolve the interference difficulty is not very good, not only the method can not reliably, but also impact other electrical and electronic equipment to work properly. So it is necessary inverter applications, the interference problems discussed in order to market its further expand the applications. The following focuses on the interference frequency converter and its Suppression. Frequency Handle Program
2 main sources of electromagnetic interference, and way
2.1 Major sources of electromagnetic interference
Electromagnetic interference, also known as electromagnetic interference (EMI), is the external noise and unwanted signals at the receiver brought on by electromagnetic interference, is normally carried out through the circuit and in the type of field communication. Rectifier bridge inverter is non-linear load on the grid, it will generate the exact same power harmonics and other electrical and electronic gear generates harmonic interference. In addition, most of the frequency converter using PWM inverter technologies, as its work in switching mode and for high-speed switching, making a large number of coupling noise. As a result, the inverter of the method to other electrical and electronic equipment is a source of electromagnetic interference. On the other hand, the harmonic interference in energy inverter power provide, mostly through interference with frequency converter. There are a lot harmonic energy source, such as a variety of rectifier gear, exchange equipment, AC and DC electronic voltage regulation gear, non-linear loads and lighting gear. These loads have to make the grid voltage and existing waveform distortion produced, so the other devices on the network harm interference. Inverter from the power provide be contaminated after the exchange of power interference, if not dealt with will power noise interference via the energy inverter power provide circuit. Power supply interference on the inverter primary overvoltage, undervoltage, instantaneous energy-down surge, fall peak voltage pulse RF interference. Second, the common mode interference by the inverter handle signal line may interfere with the typical work of inverter.
two.two channels of electromagnetic interference
The power inverter can generate big harmonics interfere with other devices on the method is strong. The interference indicates electromagnetic interference with the common method is consistent with the primary points of electromagnetic radiation, conduction, inductive coupling. Especially as follows: the surrounding electronics, electrical gear produces electromagnetic radiation direct drive motor with electromagnetic noise, makes the motor iron loss and copper consumption to enhance, and carried out interference to the power transmission to the program by means of the distribution network of other equipment Inverter other lines of adjacent coupling is induced, induced the interference voltage or current. Similarly, the interference signals within the method the identical way interfere with the normal operation of inverter. The following had been analyzed.
(1) electromagnetic radiation Inverter if it is not in a completely enclosed metal casing, it can radiate electromagnetic waves via space. The radiation field strength depends on the interference of the current intensity, the device of equivalent radiation resistance and firing frequency interference sources. Rectifier bridge inverter is non-linear load on the grid, it generates harmonics on the identical network access to other electronic, electrical gear generates harmonic interference. Most inverter bridge inverter employing PWM method, when the frequency and amplitude according to the offered instructions and repeat the anticipated switch mode, its output voltage and the existing power spectrum is discrete, and corresponding with and switching frequency The high-order harmonic group. Higher carrier frequency and field handle of high-speed switching devices switch (dv / dt up to 1kV/ s above) interference brought on by radiation has been outstanding.
When the frequency converter with cracks or holes in metal case, the radiation intensity and the interference signal wavelength, when the size of the pores and close to the wavelength of electromagnetic wave, it will interfere with the surrounding radiation sources. The radiation field in the metal object could also be formed secondary radiation. Similarly, inverter converter outdoors the radiation can interfere with typical function.
(two) conduction The addition of electromagnetic interference with its wires connected to the external launch, can also be coupled, or ground loop impedance coupled to interference into other circuits. Compared with the radiation interference, its spread can be quite far away. The typical signifies of transmission is: low-voltage network access from the industrial inverter interference signal will be generated along the medium voltage distribution transformers into the network, and along the other finish of distribution transformer entered civil low voltage distribution network to access Given that the civil power distribution bus of the electrical equipment into remote victims.
(three) inductively coupled Induction coupling amongst radiation and conduction amongst the third route of transmission. When the low frequency interference, electromagnetic interference radiation is quite restricted, and the interference supply not straight connected with the other conductor, but this time the power of electromagnetic interference by the inverter input and output wires and other adjacent wire or conductor create inductive coupling, in the neighboring wire or conductor induces a existing or voltage interference. Inductive coupling can be capacitive coupling among conductors kind can also kind or by inductive coupling capacitors, inductors mixed kind, which is the source of interference in the frequency and the distance amongst the adjacent conductors and other elements.
3 measures against electromagnetic interference
According to the standard principles of electromagnetic kind of electromagnetic interference (EMI) must have sources of electromagnetic interference, electromagnetic interference means electromagnetic interference-sensitive systems on the three components. To stop interference, hardware and software program can be utilized anti-interference measures. Among them, the hardware is the most basic and anti-jamming