A vacuum capacitor is a capacitor that utilizes a vacuum as its dielectric medium. It consists of concentric cylindrical copper electrodes hermetically sealed within a vacuum enclosure, with the electrodes formed through a die-drawing process using high-conductivity oxygen-free copper strip. Based on the material of the insulating envelope, these capacitors are classified into two categories: glass-envelope types (including series CKB and CKBB) and ceramic-envelope types (including series CKT, CKTB, and CKTBS). They are characterized by high voltage withstand capabilities (reaching hundreds of thousands of volts), compact size, low dielectric loss, high rated current (with RF currents reaching the kiloampere range), and a wide capacitance adjustment range (up to 150:1).
The electrode structure of this capacitor is designed to prevent arcing and corona discharge, making it suitable for operation in high-altitude environments. Its primary applications include tuning and coupling circuits in broadcasting and communication equipment, semiconductor manufacturing systems, high-frequency industrial heating apparatus, medical analysis and therapeutic instruments, and high-energy particle accelerators. Potential failure modes include vacuum leakage, cracks in the ceramic insulator, and electrode deformation; contributing factors typically involve mechanical stress, insufficient cooling, environmental humidity, and corrosion caused by harmful gases. During transport, appropriate shock-proofing measures must be implemented; during maintenance, the integrity of the envelope seal and the presence of corrosion on metal components should be carefully inspected.