Harmonic Wave Inverter - HC net electrical industry - Video Encoder/Decoder Manufacturer

This article explains the mechanism of harmonic generation, transmission and effective way to suppress interference. Inverter for high power diode to rectifier, power transistor inverter, the result is generated in the input and output circuit current of high harmonics, interference power system, load and other nearby electrical equipment. In actual use, the inverter harmonic interference problems often encountered, the following brief harmonic generation mechanism of transmission and effective way to suppress interference.

1, inverter-harmonic generation mechanism Inverter main circuit generally AC - DC - AC component, the external input 380V/50Hz three-phase industrial frequency power by the uncontrolled rectifier bridge into DC voltage signal by the filter capacitor filter and high-power transistors inverter switching devices for the exchange of variable frequency signal. In the rectifier circuit, the input current waveform is irregular rectangular wave, wave by Fourier series decomposition for the fundamental and harmonics, which would interfere with high harmonic input power supply system. In the inverter output circuit, the output current signal is modulated by the PWM carrier signal pulse, high-power inverter device for GTR, the PWM carrier frequency is 2 ~ 3kHz, while the high-power IGBT PWM inverter device of the highest carrier frequency up to 15kHz. Similarly, the output loop current signals are decomposed into only with sine wave of the fundamental and other harmonics, and high harmonic currents on the load direct interference. Another high harmonic currents through Cable To space radiation, interference with nearby electrical equipment.

2, common method of harmonic interference suppression Harmonic means of transmission is conduction and radiation, conduction disturbances resolve mainly conducted in the circuit to filter out or isolate the high frequency current; solve radiated interference is interference on the line sources or shielding. Specific common methods:

(1) variable frequency power supply system and other equipment, power supply independent of each other, or in the inverter and other Electricity The input side of the installed equipment transformer isolation, cut off the harmonic current.

(2) at the converter input side and output side of the series with a suitable reactor, or installation of harmonic filters, filter component must be the LC-type, absorption of harmonics and increased power or load impedance, to achieve the purpose of harmonic suppression.

(3) Electric motor And transducer cables between the laying of pipe should be wearing or armored cable, and with other weak Telecommunications Numbers were in a different trench laying cables to avoid radiation interference.

(4) signal line with shielded cable, and Wiring With the inverter main circuit control line stagger distance (at least 20cm or more), cut off radiation interference.

(5) converter using a dedicated grounding wire, and ground with a thick short-term, close to other electrical equipment ground wiring must be separated from inverter, using short-term. This can inhibit the current harmonic radiation interference to nearby equipment.

3, examples of harmonic interference suppression Example 1, a frequency switching control system, inverter starts operating normally, while neighboring high level gauge readings, the first table input 4mA when the display was not the lower limit level; level not reached cap value, the upper limit level gauge is shown, resulting in down converter to receive instructions, to force converter stops running.

This is clearly a high frequency converter harmonic interference level gauge, level gauge interference of transmission is the power circuit or the signal line. The solution: the level gauge of the power supply from another power supply transformer, harmonic interference weakened, then the signal line penetration pipe laying, and with the inverter main circuit line, separated by a distance, through such treatment, the fundamental harmonic interference suppression, level gauge work back to normal.

Example 2, a liquid display system frequency control, level gauge and transducer installed in the same cabinet, inverter works properly, and level meter display are not allowed and unstable, at first we Huai Ning a table, second table, the signal lines and fluid medium in question, replace all of these Meter , Signal cable, and to improve the fluid properties, fault still exists, and this failure is the inverter's high harmonic current through the output loop cable out radiation, delivered to the signal cable, causing interference.

Solution: liquid level signal lines and control lines and the inverter control line and separated from the main back road some distance, and the extracellular signal-line penetration steel cabinet laid a good ground cover, troubleshooting.

Example 3, a frequency control system, formed by the two transducer and the body in the same cabinet, inverter frequency adjustment means are potentiometers hand, running an inverter and when working properly, both at the same time run-time, frequency interference, which adjust a potentiometer on the inverter frequency inverter affect another, and vice versa. The beginning we thought potentiometer and control line failure, exclude this possibility, the determination is caused by harmonic interference.

Solution: to which a potentiometer fixed to another cabinet, and the lead shielding signal line with the results less interference. In order to completely suppress interference and re-processing of a cabinet, and placed a certain distance from the original cabinet, to which a converter to move the cabinet, the appropriate wiring and lead to make the necessary changes, so that after treatment, interference basically eliminated, troubleshooting. Example 4, a frequency control system, switch the two sets of pumps, the original pump is started by auto-frequency step-down operating normally, are replaced by variable frequency operation, although slow to realize FM function, but the converter output to motor between serious heat output line, motor shell temperature increase, often tripping protection. This is because the inverter output voltage and current signals Package With PWM high harmonics, and harmonic current in the output and the motor winding wire to form an additional power loss.

Solution: the converter input line and output line to separate each go their own cable channel, use a bigger section of the cable for the original cable, between the output and the motor cable length as short as possible. Such treatment, heat troubleshooting. On the scene of various inverter high harmonic interference, basically according to the above described method can be successfully inhibited, but the magnitude of harmonic components and the equipment is very strict, radical interference high harmonics is very difficult to be further research to solve. Comment Large   In   Small

I am an expert from fiber-optic-multiplexer.com, while we provides the quality product, such as Video Encoder/Decoder Manufacturer , Optical Ethernet Switch, pdh multiplexer,and more.

Comment on "Harmonic Wave Inverter - HC net electrical industry - Video Encoder/Decoder Manufacturer"