The advantages of electron beam welding, such as its electrode-free nature, resistance to oxidation, reliable process repeatability, and minimal thermal deformation, have made it a widely used technique in various industries. These industries include aerospace, atomic energy, national defense, military, automotive, and electrical instrument sectors. The fundamental principle underlying electron beam welding involves the emission of electrons from the cathode in the electron gun. These electrons, generated through either direct or indirect heating, are accelerated by a high-voltage electrostatic field. With the assistance of the electromagnetic field's focusing effects, the accelerated electrons come together to form an electron beam with an extremely high energy density. This intense beam of electrons is then employed to bombard the workpiece. As a result, the tremendous kinetic energy carried by the electrons is converted into heat, causing the workpiece to melt at the targeted welding area and form a molten pool. Consequently, the electron beam welding technique successfully achieves the joining of workpiece materials.
The high-voltage power supply plays a crucial role in electron beam equipment as it provides the necessary acceleration voltage for the electron gun. Its performance directly affects the electron beam welding process and the quality of the welds. The high-voltage power supply used in electron beam welding machines is different from other types of power supplies, as it has specific technical characteristics.
The key technical requirements for high-voltage power supplies in electron beam welding machines are related to ripple coefficient and stability. The ripple coefficient should be kept below 1%, ensuring minimal variation in the voltage output. Additionally, stability is a crucial factor, with a tolerance of ±1%. To further ensure stable power output, the wave coefficient should be less than 0.5%, and stability should be maintained within ±0.5%. Moreover, the repeatability requirement should be kept below 0.5%, as it directly impacts the welding process and the electron beam spot.
Considering the specific characteristics of electron beam welding, the high-voltage power supply needs to be properly integrated with various interlocking systems. These interlocks include vacuum interlocking, cathode interlocking, gate valve interlocking, and focusing interlocking. Their purpose is to ensure the safety of the equipment and personnel involved in the welding process. By synchronizing the operation of the high-voltage power supply with these interlocking systems, potential hazards can be prevented.
Furthermore, the high-voltage power supply must comply with EMC (Electromagnetic Compatibility) standards to avoid any interference issues with other equipment. It should also have a soft-start function to mitigate the impact of sudden power supply closure, thus ensuring a smooth and controlled operation.
Overall, the high-voltage power supply used in electron beam welding machines is a critical technology that directly influences the welding process and the quality of welds. By meeting specific technical requirements and being integrated with interlocking systems, as well as complying with EMC standards, it ensures reliable and safe operation.
To meet the demands of the high power output (up to 30kW), high output voltage (150kV) and high operating frequency (20kHz), this power supply has stringent requirements for stability accuracy, ripple and voltage regulation rate. Advanced three-phase fully-controlled controllable rectification technology has been employed, along with a high-power high-frequency inverter and a new power device - IGBT, as the power switch. The three-phase fully-controlled controllable rectifier and inverter operate independently on their respective control boards, while the IGBT drive is outfitted with an imported thick-film drive circuit. Additionally, an input grid filter, a smoothing reactor and a capacitor make up the filter circuit. The power conversion system of the power supply is remarkably advanced, contributing to optimal power conversion.
The high-voltage section of the device boasts cutting-edge features. It incorporates state-of-the-art amorphous materials for the magnetic core of the high-voltage transformer. Moreover, the high-frequency high-voltage winding process is employed, along with the stacking of double high-voltage transformers. To maintain stability and reliability, advanced rectification techniques, a well-designed voltage multiplier circuit, and high-voltage equalization technology are implemented. Accurate and reliable high-voltage regulation is achieved through a precise voltage divider that samples the feedback and high-voltage indication signals directly from the high-voltage output terminal. This also ensures precise voltage measurement accuracy. Additionally, optimal high-voltage filtering techniques are applied to eliminate ripple. The high-voltage section is securely housed within a tank for enhanced safety.
