In the core technology system of frequency converters, IGBT (Insulated Gate Bipolar Transistor) and PWM (Pulse Width Modulation) technologies are like two brilliant pearls, each shining with its unique light, yet closely collaborating to lay a solid foundation for the efficient operation of frequency converters. The continuous development and innovation of these two technologies have driven the ongoing improvement of frequency converter performance, making their applications in the industrial field more extensive and in-depth.

  • IGBT Technology: IGBT is a new type of composite power semiconductor device that combines the advantages of BJT (Bipolar Junction Transistor) and MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). It plays a crucial role as the core execution unit in frequency converters and is often referred to as the “power heart” of the converter. The working principle of IGBT is based on its unique structure and electrical characteristics. It consists of three electrodes: the gate (G), emitter (E), and collector (C). By applying an appropriate voltage signal to the gate, the conduction and blocking states of the IGBT can be controlled. When a positive voltage is applied to the gate, a conductive channel is formed inside the IGBT, allowing current to flow between the collector and emitter, enabling energy transmission. Conversely, when a reverse voltage or zero voltage is applied to the gate, the conductive channel disappears, the IGBT turns off, and the current is blocked. In the inverter stage of the frequency converter, the rapid switching action of the IGBT is key to converting direct current (DC) to alternating current (AC). By controlling the orderly conduction and blocking of multiple IGBTs according to specific timing sequences and patterns, the DC power supply is “cut” into a series of AC voltage waveforms with variable pulse widths and frequencies. This provides the motor with the required variable frequency and voltage AC power, enabling precise control of the motor’s speed and torque. IGBT has many excellent performance characteristics that make it an ideal choice for frequency converters. It can withstand high voltage and large currents, meeting the needs of frequency converters at different power levels; it has fast switching speed, allowing it to complete conduction and blocking actions in a short time, significantly improving the efficiency and dynamic response performance of the frequency converter; at the same time, IGBT has low conduction resistance and switching losses, reducing energy loss during transmission and conversion, and improving the energy utilization efficiency of the system. Additionally, IGBT is relatively simple to drive, highly reliable, and easy to control precisely, which has led to its widespread application and high recognition in the field of frequency converters.

  • PWM Technology: PWM technology, or Pulse Width Modulation, is the core algorithm and key means for achieving precise control in frequency converters. It acts like a precise “signal commander,” finely adjusting the pulse width of signals to achieve precise control of output voltage and current. The basic principle of PWM technology is to control the duty cycle of pulse signals (i.e., the proportion of high-level time to the total cycle time) to equivalently simulate voltage or current signals of different amplitudes and frequencies. In frequency converters, PWM technology is mainly applied in the inverter circuit to convert DC power into AC power with variable frequency and voltage. Specifically, the PWM controller generates a series of pulse signals with specific duty cycles and frequencies based on preset control strategies and the motor’s operational requirements. These pulse signals are used to control the conduction and blocking times of power switching devices such as IGBTs. When the pulse signal is at a high level, the IGBT conducts, allowing current to pass; when the pulse signal is at a low level, the IGBT blocks, and the current is cut off. By continuously adjusting the duty cycle and frequency of the pulse signals, equivalent AC signals with variable frequency and voltage can be obtained across the motor windings, thereby achieving precise control of the motor’s speed and torque. PWM technology has many significant advantages that make it the core of frequency converter control technology. It enables efficient power conversion, reducing energy loss between the power supply and the motor by optimizing PWM waveforms, thereby improving the overall efficiency of the system; the harmonic content of the output voltage is low, and by reasonably designing the PWM modulation strategy, the harmonic components in the output voltage can be effectively reduced, minimizing electromagnetic interference with the grid and other equipment, and enhancing the stability and reliability of the system; PWM technology also features fast response and precise control, allowing it to quickly adjust the output voltage and frequency in real-time based on the motor’s operating status and load changes, ensuring good dynamic performance during motor start-up, speed regulation, and braking. Furthermore, PWM technology is easy to digitize, and when combined with modern digital signal processors (DSPs) and microcontrollers (MCUs), it can implement complex control algorithms and functions, further enhancing the intelligence and automation levels of frequency converters.