Basic Introduction:
High voltage ceramic capacitors, commonly used in power systems, are typically used in products such as measurement, energy storage, and voltage division in power systems. High voltage ceramic capacitors have found wide applications and a significant position in the LED lighting industry as well. They are made by extruding capacitive ceramics with a high dielectric constant (barium titanate or titanium dioxide) into cylindrical tubes, discs, or discs as dielectric materials. Silver is then deposited on the ceramics as electrodes using a sintering process.
Units and Symbols:
The basic unit of capacitance is the Farad (F). Additionally, microfarads (μF), picofarads (pF), and nanofarads (nF) are also commonly used units. Due to the large capacity of the Farad, you typically encounter units like μF, nF, and pF rather than F. The conversions between these units are as follows:
1 F = 1,000,000 μF
1 μF = 1,000 nF = 1,000,000 pF
Function:
High voltage ceramic capacitors are known for their ability to withstand high DC voltages and are suitable for use in high-voltage bypass and coupling circuits. The low-loss, high-voltage circular discs have low dielectric losses and are especially suitable for use in circuits like TV receivers and scanners to eliminate high-frequency interference.
In high-power, high-voltage applications, high-voltage ceramic capacitors are required to be compact, high-voltage resistant, and have good frequency characteristics. In recent years, with advancements in materials, electrodes, and manufacturing technology, high-voltage ceramic capacitors have made significant progress and are widely used. They have become an essential component in high-power, high-voltage electronic products.
The main applications of high-voltage ceramic capacitors are in power transmission, distribution systems, and equipment for handling pulse energy. These capacitors are subjected to challenging conditions in power systems, such as high AC voltages, high frequencies, outdoor environments (-40°C to +60°C), high lightning voltages/currents, etc. These factors make the development and production of high-voltage ceramic capacitors challenging, requiring them to have exceptional stability, low variation rates, and minimal partial discharge in harsh environments.
Self-Recovery Period:
High-temperature sintering is one of the most crucial processes in the manufacturing of high voltage ceramic capacitors. After undergoing processes like stamping and casting under high pressure and sintering at temperatures above a thousand degrees Celsius, the internal structure of the ceramic chip in high voltage ceramic capacitors forms a crystalline structure. Subsequent high-temperature baking and insulation for six hours disrupt the internal crystal structure.
To restore the chip's structure and stabilize its characteristics, high voltage ceramic capacitors require a recovery period. Natural recovery (storage at room temperature) for at least 60 days is ideal. Moreover, products stored for one year or two years perform better over time. Longer recovery periods significantly improve the performance of capacitors, and capacitors without recovery periods exhibit poorer voltage resistance and current tolerance. It has been observed that high-voltage ceramic capacitors with longer storage times have smaller loss angle values and better high-frequency characteristics.
Features:
High-voltage generators require many high-voltage ceramic capacitors and large-capacity high-voltage capacitors. Traditionally, customers often use high-voltage thin-film capacitors, but as the advantages of ceramic capacitors become increasingly apparent, thin-film capacitors will become less common in high-voltage generators.
The advantages and disadvantages of high-voltage ceramic capacitors compared to high-voltage thin-film capacitors mainly include:
Longer lifespan for high-voltage ceramic capacitors. The lifespan of thin-film capacitors is typically three to five years, even for well-made products, while high-voltage ceramic capacitors are different. For example, Deki capacitors publicly promise a minimum of 10 years of use based on a 20-year design.
Lower internal resistance for high-voltage ceramic capacitors, due to their structural characteristics. High-voltage ceramic capacitors have very low internal resistance, while thin-film capacitors, due to their winding method, tend to have higher internal resistance. This increased internal resistance can lead to further degradation of thin-film capacitors during repeated charging and discharging in a circuit.
Relatively higher working voltage for high-voltage ceramic capacitors. The working voltage of thin-film capacitors is generally lower compared to ceramic capacitors.
However, ceramic capacitors tend to have smaller capacitance compared to thin-film capacitors.
Testing Methods:
Reliability testing of high-voltage ceramic capacitors, also known as aging testing or life testing, includes various test parameters such as:
Series resistance testing and insulation resistance testing.
Tensile strength testing, ensuring the firmness of lead wires to the chip.
Positive and negative temperature coefficient testing, evaluating the change in capacitance under temperature fluctuations ranging from -40°C to +60°C.
Aging testing, where high-voltage ceramic capacitors operate for 30 to 60 days under simulated working conditions to measure changes in various parameters.
Voltage withstand tests, including 24-hour testing at rated working voltage and breakdown voltage testing, determining the breakdown voltage just before failure.
Partial discharge testing:
Life testing, which involves subjecting capacitors to rapid charge and discharge cycles under high-frequency conditions after extended aging. The number of charge and discharge cycles determines the life expectancy. It's important to note that this life expectancy is determined after prolonged aging.
Usage Precautions:
Operating Voltage: When using capacitors with rated DC voltage in AC circuits or ripple current circuits, ensure that the applied voltage (Vp-p value or Vo-p value including DC bias voltage) remains within the rated voltage range. Sudden voltage changes during circuit startup or shutdown may lead to resonance or switching, causing temporary abnormal voltage. Capacitors should cover these abnormal voltages within their rated voltage range.
Operating Temperature and Self-Heating (Applicable to B/E/F characteristics): Maintain the surface temperature of the capacitors below the upper limit of their rated operating temperature range. Consider the self-heating of capacitors, which can occur due to dielectric losses when used with high-frequency or impulse currents. The additional voltage should keep the self-heating load within a 20°C range at 25°C. Use a 0.1mm low-capacity (K) thermocouple for measurements, and ensure that the capacitors are not affected by heat dissipation from other components or fluctuations in ambient temperature. Overheating can lead to decreased capacitor characteristics and reliability (avoid measurements when cooling fans are running to ensure measurement accuracy).
Voltage Withstand Test Conditions:
(1) Test Equipment: AC voltage withstand test equipment should be capable of generating a sinusoidal wave similar to 50/60Hz.
Overloaded voltage or distorted sinusoidal waves may cause faults.
(2) Voltage Application Method: When applying voltage withstand tests, ensure that the capacitor's leads or terminals are securely connected to the output terminal of the voltage withstand test equipment. Then, gradually increase the voltage from nearly zero to the test voltage. Avoid directly applying the test voltage to the capacitor without gradual increase, as it may result in surge voltages leading to failure. The term "crossing zero" refers to the point where the sinusoidal voltage crosses through
UF capacitors produces high voltage disc ceramic capacitors to replace parts from 1st tier brands like VIshay, TDK/Epcos, Murata and Kemet. Here below our cross reference for your easy review. We are committed to cost down with reliable quality.
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Photo |
Descriptiom |
Vishay |
TDK/Epcos |
Murata |
Kemet |
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High Voltage Disc Ceramic Capacitors 500V~6KV |
S Series 561R Series 562R Series 564R Series 565R Series |
CK45 Series CC45 Series |
DEB DHR Series DEH DEA Series DEB DEC Series HBU HBZ Series HBE HBX Series |
KHB Series KHC Series |
