Sự tiến hóa và tương lai của công nghệ cung cấp năng lượng lò cảm ứng

Là cốt lõi của hệ thống sưởi công nghiệp hiện đại, the development of induction heating power supply technology profoundly reflects the progress of power electronics. From early thyristor (Scr) power supplies to today’s mainstream Insulated Gate Bipolar Transistor (IGBT) power supplies, the circuit topology has also evolved from series resonance to parallel resonance. This article reviews the development of IGBT power supply technology, compares the advantages and disadvantages of different circuit topologies, and looks ahead to the application prospects of next-generation Silicon Carbide (SiC) power devices.

The Rise of IGBT Technology: A Revolution in Induction Heating Power Supplies

Before the maturation of IGBT technology, induction heating power supplies primarily used thyristor-based medium-frequency power supplies. While this technology was mature and low-cost, it suffered from low operating frequencies, inefficient performance, and significant harmonic pollution to the power grid.

In the late 1980s and early 1990s, the IGBT—a fully-controlled power device combining the high input impedance of a MOSFET and the low on-state voltage drop of a GTR—began to emerge in the induction heating field. The advent of IGBTs brought revolutionary changes to induction heating power supplies:

• Higher Switching Frequencies: The switching speed of IGBTs is far superior to thyristors, allowing the power supply’s operating frequency to increase from a few kilohertz to tens or even hundreds of kilohertz. This enabled a wider range of heating applications, such as surface hardening and through-heating of small-diameter bars.
• Higher Efficiency: The relatively low conduction and switching losses of IGBTs significantly improved the overall efficiency of the power supply, giảm tiêu thụ năng lượng.
• Superior Control Performance: As fully-controlled devices, IGBTs can achieve precise and rapid regulation of output power through techniques like Pulse Width Modulation (PWM), enhancing the control accuracy and flexibility of the heating process.
• Smaller Size and Weight: The increase in operating frequency allowed for a substantial reduction in the size and weight of passive components like transformers, inductors, and capacitors, making the equipment more compact.

From Series to Parallel: The Evolution of Circuit Topologies

To achieve efficient energy transfer in induction heating power supplies, resonance technology is commonly used. Trong số đó, series resonance and parallel resonance are the two primary circuit topologies.

The Early Mainstream: Series Resonance

Early IGBT induction heating power supplies often adopted a series resonant topology. Its main characteristic is that the induction coil and the compensation capacitor are connected in series to form a series resonant circuit.

Thuận lợi

• Simple Startup: The series resonant circuit is relatively easy to start, making it suitable for applications requiring frequent starts and stops.
• Low Voltage Stress on Devices: In a resonant state, the load appears purely resistive, and the inverter output voltage is consistent with the load voltage, placing lower voltage requirements on the IGBTs.
• Natural Constant-Current Characteristics: When the operating frequency deviates from the resonant point, the circuit impedance increases rapidly, providing a current-limiting effect that helps protect power devices during a load short-circuit.

Nhược điểm

• Difficult Load Matching: The equivalent resistance of a series resonant load is very low, requiring a matching transformer to match the impedance between the inverter and the load. This adds complexity, trị giá, and losses to the system.
• Limited High-Frequency Application: Trong các ứng dụng tần số cao, the leakage inductance and distributed capacitance of the matching transformer severely affect its performance.
• Overcurrent Protection Challenges: Despite its natural current-limiting properties, if a short-circuit occurs near the resonant point, the current can rise sharply, posing a significant threat to the IGBTs and making protection difficult.

The Modern Mainstream: Parallel Resonance

With technological advancements, the parallel resonant topology has gradually become the mainstream choice for medium and large-power induction furnace power supplies. Its characteristic is that the induction coil and the compensation capacitor are connected in parallel, forming a parallel resonant circuit.

Thuận lợi

• Strong Load Adaptability: The equivalent impedance of a parallel resonant load is high, allowing it to be directly connected to the inverter’s output terminals without a matching transformer. This simplifies the circuit structure, improving efficiency and reliability.
• Wide Power Regulation Range: A wide range of power regulation can be easily achieved by adjusting the inverter’s output voltage or frequency.
• Natural Overvoltage Protection: The voltage across the parallel resonant circuit is highest at resonance. When the load changes or becomes an open circuit, the voltage decreases, providing a degree of protection for devices like IGBTs.
• Suitable for High-Power Applications: The absence of an output transformer makes it particularly advantageous in high-power applications, resulting in a more compact structure and lower cost.

Nhược điểm

• Relatively Complex Startup: Parallel resonance requires a specific startup circuit and control strategy.
• High Current Stress on Components: At resonance, the current flowing through the induction coil and capacitor is much larger than the current output by the inverter. This places high demands on the current-carrying capacity of the compensation capacitors.

Driving Force of Evolution: As the demand for higher power, hiệu quả, and reliability in induction furnaces grew, the parallel resonant topology, with its advantages of eliminating the matching transformer, simple structure, and ease of achieving high power, gradually replaced series resonance to become the preferred solution for medium-to-high frequency, high-power induction furnace power supplies.

Looking to the Future: Application Prospects of Silicon Carbide (SiC) Power Devices

Although IGBT technology is very mature, its performance is approaching the physical limits of silicon material. To further enhance the performance of induction heating power supplies, the industry has turned its attention to third-generation wide-bandgap semiconductor materials, represented by Silicon Carbide (SiC).

Compared to traditional silicon-based IGBTs, SiC MOSFETs offer the following significant advantages.

The Transformation Brought by SiC Technology

• Ultimate Performance Improvement: Induction heating power supplies using SiC devices are expected to see efficiency improvements from the current ~95% with IGBTs to over 98%. Meanwhile, the substantial increase in operating frequency will open up new applications for ultra-high-frequency induction heating (ví dụ., semiconductor material growth, precision medical device welding).
• System Miniaturization and Lighter Weight: Due to higher switching frequencies and lower losses, the size of magnetic components (inductors, máy biến áp) and heat sinks can be significantly reduced, achieving higher power density.
• Greater Reliability: The excellent high-temperature resistance and lower operating temperature rise of SiC devices translate to a longer service life and higher system reliability.

Challenges and Outlook

Currently, the main challenges for SiC devices are their relatively high cost and the complexity of their driver circuit design. Tuy nhiên, as manufacturing processes mature and market scale expands, the cost of SiC devices is rapidly decreasing. It is foreseeable that in the near future, as cost issues are resolved, wide-bandgap semiconductor devices represented by SiC will gradually replace IGBTs to become the core of the next generation of high-efficiency, high-frequency, high-power-density induction furnace power supplies, leading induction heating technology to a new level.

Phần kết luận

From series to parallel, from thyristors to IGBTs, the development of induction furnace power supply technology has consistently pursued higher efficiency, stronger reliability, and better control performance. Each technological iteration has brought profound changes to the industrial heating sector. Hôm nay, we stand on the threshold of a new technological revolution. The next generation of power devices, centered on Silicon Carbide (SiC), will reshape the future of induction heating power supplies with their unparalleled performance advantages, injecting powerful new momentum into energy conservation, emission reduction, and the transformation of the manufacturing industry.