Capacitors Blog

Suntan Technology Company Limited
----All Kinds of Capacitors

A vacuum variable capacitor uses a high vacuum as the dielectric instead of air or other insulating material. This allows for a higher voltage rating and/or capacitance value using a smaller total volume. In addition to the higher voltage rating a vacuum dielectric greatly reduces the chance of arcing between the plates. There are several different designs in vacuum variables, the most common geometry of the capacitor plates is usually inter-meshed concentric cylinders. The meshed cylinders are contained within a glass or ceramic vacuum envelope, similar to an electron tube. A metal bellows is used to maintain a vacuum seal while allowing positional control for the moving parts of the capacitor.

Common Applications

Vacuum variable capacitors are commonly used in high voltage applications 5000 volts(5kV) and above. They are used in equipment such as high powered broadcast transmitters, Amateur radio RF Amplifiers and large Antenna tuners.

Other Variations

A fixed value vacuum capacitor. Other variations of vacuum capacitors include fixed value capacitors. Fixed value capacitors are designed very much like the variable versions with the exception of an adjustment mechanism.

Comparison

When compared to other variable capacitors vacuum variables tend to be more precise and more stable. This is due to the vacuum itself. Because of the sealed chamber the dielectric constant remains the same over a wider range of operating conditions. With air Variable capacitors the air moving around the plates may change the value slightly; often it’s not much but in some applications is enough to cause undesirable effects. Another common problem with air variables is dust and insects. Dust collected on the plates or a curious insect can raise havoc. A wandering spider is bound to make fireworks with the open frame design used on most air variable capacitors.

Vacuum variable capacitors are generally more expensive than Air Variable Capacitors this is primarily due to their design and the materials used. Although most use copper and glass some may use other materials such as ceramics and metals such as gold and silver. Vacuum variables also vary in adjustment mechanisms which range from course to fine.

Suntan is a Hong Kong based manufacturer of Ceramic Capacitors. Including High Voltage Ceramic Capacitors, Multilayer Ceramic Capacitors, Ceramic Disc Capacitor, Mini Type Ceramic Capacitors etc.

Suntan Technology Company Limited
----All Kinds of Capacitors

Suntan pictures of Capacitors. Notice that all these capacitors have two wires coming out of them, one attached to each plate.

Suntan is well established and specializes in service and quality with an extensive export and import network. We provide quick turn around for our customers all over the world. Almost 30 years experience with all types of passive components using good materials, state of the art equipment and technology and ongoing QC coupled with extensive R & D assure our customers of the best quality and on time delivery.

Suntan offer many kinds of capacitors. Don’t hesitate to send us inquire to sales@suntan.com.hk .We will show you good quality and best price.

Previous blog we have talk the simplest ceramic capacitor consists of a square or circular shaped ceramic with electrodes attached.

Manufacturing starts with finely powdered base ceramic material that are pressed into dies and fired at high temperatures. Individual capacitors may be cut from large sheets of ceramic material. The capacitor electrodes (i.e. the plates) are attached by screen printing a mixture of silver, finely powdered glass, and a binder on both sides of the disk, and firing the ceramic element again. This evaporates the binder, and the melted glass binds the silver to the ceramic surface. Next, hairpin wires are clipped onto the capacitor and it is dipped in solder. Once cooled the capacitor is dipped into paint, marked, and the lower ends of the hairpin cut off. Clearly the whole process lends itself to automation, and dipped ceramic capacitors are very inexpensive. Capacitor characteristics depend on the type of ceramic used.



Dipped ceramic capacitor construction. (a) Capacitor after electrode and hairpin attachment. (b) Capacitor after dipping and marking.

http://www.suntan.com.hk/Ceramic-Capacitors/

Suntan Technology Company Limited
----All Kinds of Capacitors

Dipped Ceramic Capacitors. The simplest ceramic capacitor consists of a square or circular shaped ceramic with electrodes attached (see figure). The capacitance is given by 

where A is the area of the two plates,  is the dielectric permittivity of vacuum, Kd is the dielectric's dielectric constant and d is the distance between the two plates.http://www.capacitors.hk/Ceramic-Capacitors/