Fixed Vacuum Capacitor

Product overview

 

A fixed vacuum capacitor uses high vacuum as its dielectric and provides one preset capacitance. It has no shaft or other tuning mechanism. Typical applications include medium-wave, short-wave and ultra-short-wave transmitters, high-frequency induction heating equipment, high-voltage test systems, particle accelerators and dielectric-loss measuring equipment. In these systems, it is used for filtering, coupling, neutralization and DC blocking where the circuit needs a defined capacitance at high frequency and high voltage.

RF current ratings up to 400 A at 13.56 MHz

The listed models cover 100 to 400 A of maximum RF current at 13.56 MHz. In transmitter output stages and induction-heating resonant circuits, this allows the selected model to be matched directly to the high-frequency current carried by the circuit.

Working voltage up to 30 kV

The shown fixed models provide 21 to 30 kV high-frequency peak working voltage and 30 to 42 kV peak test voltage. This suits coupling, filtering and neutralization positions where one preset capacitance must remain in a high-voltage RF circuit.

Fixed capacitance values with ±5% tolerance

The listed 250, 500 and 2000 pF models each use a ±5% capacitance tolerance. In preset resonant and DC-blocking positions, the circuit can use a defined value without adding a shaft, bellows or other tuning assembly.

A high-strength ceramic body and metal end fittings enclose the vacuum cavity. First-grade oxygen-free copper is formed into concentric cylindrical electrodes inside the body. Their spacing and overlap are set during assembly to produce the specified capacitance.

Ceramic-to-metal joints seal the vacuum cavity and connect the internal electrode system to the external terminals and mounting parts. Once the unit has been furnace sealed, the internal assembly cannot be corrected. Electrode alignment, terminal position and the fit of the ceramic and metal parts are therefore established beforehand.

Electrical rating selection

Custom selection covers capacitance, rated voltage, peak voltage and RF current capacity. Operating frequency, duty cycle and cooling conditions are reviewed with these values, since nominal capacitance alone is not enough to define the correct model.

Dimensions and connection interface

Housing length, outside diameter, terminal layout and mounting interface can be matched to the space available in the equipment. For replacement work, an existing drawing or physical sample can be used to retain the original installation boundary and connection points.

Electrode assembly before sealing

Before vacuum processing, the ceramic body, copper electrode parts and metal fittings are checked for dimensions, surface condition and assembly fit. The electrode position and ceramic-to-metal sealing surfaces are also confirmed at this stage because they cannot be adjusted after the enclosure is sealed.

Electrical checks by model

Finished capacitors are tested against the confirmed model for capacitance, insulation and voltage withstand. Before packing, staff compare the model, terminal position, mounting interface and key electrical results with the order information and batch record.

Electro-vacuum production since 1966

Wanping has produced electro-vacuum components since 1966. Its manufacturing work includes vacuum processing, ceramic-to-metal sealing and electrode-system production for capacitors, relays and other enclosed high-voltage devices.

Production controlled by the complete model

The factory has 12 vacuum furnaces and eight post-assembly processing systems. Production is scheduled by the complete capacitor model, including electrode structure, ceramic dimensions, terminals and mounting interface. Units that look alike on the outside are kept separate when these details differ.

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