PRA HT

This natural mineral insulator has outstanding dielectric properties that are ideal for long-life high-stability capacitors with low loss at all frequencies, and high dielectric strength. This type of capacitor is used particularly for high frequency and delay line applications, oscillating circuits, emission devices and calibrators.

Mica dielectric capacitor technology allows for several custom design applications including: 

• High voltage capacitors (up to 50 kV)
• High temperature capacitors (up to 250°C)
• Precision capacitors (up to ± 0.1%)
• High stability capacitors (– 20 + 30 ppm/°C)
• High frequency capacitors ( up to several GHz). 

The majority of these capacitors are manufactured to comply to specifications NF-C-83120;MIL-C-5 and MIL-PRF-39001 standards.

Mica capacitors are noted for the following characteristics:

• Temperature performance
• Low loss at all frequencies
• High dielectric strength
• Stability over time

Silver mica capacitors provide superior stability and low loss when used in RF power circuits that require low pico farad (pF) and nano farad (nF) ranges. Older silver mica capacitors were manufactured in layers of mica and silver, but the layering allowed room for air gaps that reduced the stability and could also create stress fractures in the assembly.

Modern manufacturing uses silver plated to mica layers, eliminating the gaps. When the desired number of layers is obtained, the assembly is coated in an epoxy or ceramic resin. The coating reduces fracturing of the layers and seals the assembly from moisture and particles that could interfere with the capacitance value.

Mica capacitors are useful in circuits for ripple filtering and are often found in time constant, coupling or resonance circuits. In addition to radio circuits, they are used in TV transmitters and Cable TV amplification circuits. Mica is also a superior choice in high-voltage inversion and power conversion for energy absorbing snubber applications with capacitances of up to 10 nF.

Standard silver mica capacitors are normally designed to handle voltages from 100 to 1000 volts. High-voltage RF transmitter applications can call for higher tolerances. Mica capacitors are available for voltages up to 20kV.

Our expert engineering team can create the mica capacitor with the characteristics you require. Send us your drawing or file and we will work with you to manufacture the correct size, lead style and capacitance you desire.

Our high voltage capacitors are specifically designed to be able to withstand a larger amount of electrical charge than other types of capacitors can offer. They use two main mechanisms to store the energy that is being transmitted, which is contrary to the conventional dielectric method that is used with other types of capacitors. The first main method used to store electricity is called double layer capacitance, while the second is called pseudo capacitance. These methods are electrostatic and electrochemical in origin, respectively, which allows high voltage capacitors to combine the energy storing methods of normal capacitors with the methods used during the operation of a normal battery.

High voltage capacitors can be made from a few different types of material. High voltage ceramics capacitors and metalized polyester film capacitors are just two of the main types. They are notable for a few different characteristics:

Charge time – Even though different types of technology are at work with regards to the way high voltage types of capacitors operate, they still have both discharge and charge times that are very comparable to those of regular capacitors. These charge times are possible due to the low internal resistance in the materials at play.

Specific power – Another main characteristic that sets these types of capacitors apart is specific power, which means that they have a specific power of up to ten times larger than regular batteries.

Cycle life and safety – High voltage capacitors are much safer than traditional capacitors and batteries, even when they’re being mistreated. A traditional battery, for example, has been known to fully explode if it is short circuited, experiences excessive heat or is involved in other types of situations.

Unlimited charging – High voltage capacitors can also be charged and discharged a virtually unlimited number of times. Traditional capacitors and batteries can only be charged around 500 times before they start to lose some of their original power.

Because of these reasons, high voltage capacitors made from all types of materials are very useful during situations where energy needs to be stored and released on a frequent basis.