Introduction to the features of the hottest enviro

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Introduction to the characteristics of environment-friendly green high-voltage inverter

variable frequency speed regulation is an ideal power-saving speed regulation technology recognized by the world at present. However, high voltage variable frequency governors are rarely used. The biggest problem hindering the popularization and application of high-voltage frequency converter is that the traditional high-voltage frequency converter has large harmonic pollution. Harmonic not only consumes reactive power, increases line loss, affects the reliable operation of relay protection, causes additional torque and loss of motor, interferes with weak current system, but also causes serious distortion of electric voltage, and even power system safety accidents. Therefore, high-voltage green frequency converter came into being. With low harmonic pollution and high power factor, this high-voltage inverter is connected in series by multiple low-voltage variable-frequency power units in each phase, and the high-voltage output is realized by superposition. There is a phase difference between the secondary windings supplying power to the power unit to realize the multiple input voltage

take the 6kV green frequency converter as an example. Each phase is connected in series by five power units with a rated voltage of 690V. There are a total of 15 power units in three phases, which are respectively powered by 15 secondary windings of the input isolation transformer. The 15 secondary windings are divided into 5 groups. There is a 12 ° phase difference between each group, which is equivalent to 30 pulse rectification. Since the input is 30 pulses, theoretically all harmonics below 29 times can be offset, and satisfactory sine wave voltage and sine wave current can be obtained in various speed ranges. The total voltage distortion rate is only 1.2%, and the total current distortion rate is only 0.8%. It has the reputation of "perfect harmonic free". Without the use of input filter, it can meet the strict requirements of IEEE that the cost of 3D printing can be greatly reduced

high reliability and easy maintenance

the power unit is a PWM converter with three-phase input and single-phase output. The three-phase bridge rectifier circuit is composed of two-stage tubes. After rectification, four low-voltage IGBTs are reversed to single-phase AC output. Due to the use of conventional low-voltage IGBT, the earliest Japanese technology has simple driving circuit, mature and reliable technology. Due to the modular structure, the power units used in this high-voltage converter are identical and interchangeable. The connection between each power unit and the system is only three AC input terminals, two AC output terminals and one optical fiber plug, which is very convenient for unit maintenance and replacement. Moreover, the power unit bypass technology and power unit redundancy design can also be adopted due to the power unit series structure. For example, the HVF high-voltage green frequency converter developed in China has designed hot backup hot plug protection and main circuit direct connection protection. In addition, the frequency converter has sufficient filter capacitance, so the system can withstand - 30% power supply voltage drop and 5 cycles of power loss

low loss and high efficiency

because this frequency converter has no output transformer, nor does it need power factor compensation device, harmonic filter, etc., and because the harmonic component is very small, the loss from the power transformer to the motor caused by harmonic is greatly reduced. In addition, the IGBT driving power is very small, the peak power is about 5 watts, the average power is less than 1 watt, the switching frequency is low, and there is no need to use voltage sharing circuit and absorption circuit, The efficiency of the frequency conversion part is more than 98%, and the efficiency of the whole frequency conversion system including the input isolation transformer is more than 96%

there is no special restriction on the length of the motor and output cable

the output voltage of this frequency converter jumps from the step to the DC bus voltage of the unit, and the voltage changes 2) sample height: the normal stress at each point of the cross-section of the bending sample is proportional to the vertical distance from the point to the neutral surface, and the rate is very small. At the same time, due to the use of phase-shifting PWM, the equivalent switching frequency of the motor voltage is greatly increased, and the number of output levels is increased. Taking the 6kV frequency converter as an example, the output phase voltage is 11 levels, the line voltage is 21 levels, and the output equivalent switching frequency is 6KHz. With the increase of level number and equivalent switching frequency, the output waveform is greatly improved and the output harmonics are reduced. The motor heating, noise, torque ripple and common mode voltage caused by harmonics are greatly reduced. Therefore, this frequency converter has no special requirements for the motor, so that the oil in the hydraulic cylinder can be drained back to the oil tank. It can be directly used for any ordinary high-voltage motor without reducing the rated capacity. There is no special restriction on the length of the output cable. (end)

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