Analysis on Working Principle and Function of Inverter by Inverter Controller Manufacturers

Release Time:

2022-05-06 09:14

Inverter is a power control equipment that uses frequency conversion technology and microelectronics technology to control AC motors by changing the frequency of the motor's working power supply. The frequency converter is mainly composed of filter, rectifier, inverter, drive unit, brake unit, detection unit and microprocessor unit. The voltage and frequency of the output power supply are adjusted by opening and closing of the IGBT inside the inverter, and the required power supply voltage is provided according to the actual needs of the motor, so as to achieve the purpose of energy saving and speed regulation. In addition, the inverter also has overvoltage, overcurrent, overload protection and other protection functions. With the continuous improvement of industrial automation, frequency converter has been widely used.

The basic composition of the inverter: The inverter is usually divided into four parts: rectifier unit, large-capacity capacitor, inverter and controller. Rectifier unit: convert AC power with fixed working frequency into DC power; large-capacity capacitor: store the converted electric energy; inverter: an electronic switch composed of a high-power switching transistor array to convert DC into square waves with different frequencies, widths and amplitudes; Controller: work according to the set program, control the amplitude and pulse width of the output square wave, so that the AC power superimposed into an approximate sine wave drives the AC motor.

The structure and principle of the inverter: The development of the inverter also has to go through a gradual process. The frequency converter produced by the initial frequency conversion controller manufacturer did not adopt the topology of AC-DC: AC-DC and then AC, but directly AC-DC without intermediate DC link. This frequency converter is called AC-AC frequency converter. At present, this kind of inverter has applications in both high power and low speed regulation. Its output frequency range is 0-17 (1/2-1/3 input voltage frequency), so it cannot meet the requirements of many applications. And there was no IGBT at that time, only SCR, so the scope of application was limited. The working principle of the inverter is to control the three-phase power frequency power supply through multiple sets of phase-controlled switches to directly generate the required variable-voltage variable-frequency power supply. Its advantages are high efficiency and energy can be easily returned to the grid. Its disadvantage is that the output frequency must be less than 1/3 or 1/2 of the input power frequency, otherwise the output waveform will be too bad, the motor will jitter and cannot work. Therefore, the AC-AC converter has been limited to low-speed speed occasions, which greatly limits its scope of application.

The role of the inverter: The energy saving of the inverter is mainly manifested in the application of fans and pumps. In order to ensure the reliability of production, variable frequency controller manufacturers have a certain margin when designed as power drive. When the motor can not run at full load, the excess torque not only meets the requirements of power drive, but also increases the consumption of active power, resulting in a waste of electric energy. The traditional speed control method of fans, pumps and other equipment is to adjust the air supply and water supply by adjusting the opening of the inlet or outlet baffle and valve. The input power is large, and a large amount of energy is consumed in the process of intercepting the baffle and the valve. When using frequency conversion speed regulation, if the flow requirement is reduced, the requirement can be met by reducing the speed of the pump or fan.