Most high-voltage ceramic capacitors have a disc-shaped appearance, primarily in blue color, although some manufacturers use yellow ceramic discs. In contrast, cylindrical high-voltage ceramic capacitors, with their bolt terminals at the center of the housing, have epoxy sealing layers that vary in color among different manufacturers, such as blue, black, white, brown, or red. The main differences between the two types are as follows:
1）In terms of production capacity in the market, ceramic disc-type high-voltage ceramic capacitors have relatively higher production capacity. They are used in various applications, such as electrostatic devices, negative ions, high-voltage power supplies, voltage doubling circuits, CT/X-ray machines, and other situations that require high-voltage components. Cylindrical high-voltage ceramic capacitors have lower production capacity and are mainly used in equipment with high power, high current, emphasis on pulse impact, discharge, etc. For example, they are used in smart grid equipment like high-voltage measurement boxes and switches, high-voltage pulse power supplies, high-power CT and MRI equipment, and various civil and medical lasers as charging and discharging elements.
2）Although cylindrical bolt terminal high-voltage ceramic capacitors can theoretically use various ceramic materials such as Y5T, Y5U, Y5P, the main material used is N4700. Customers choose bolt terminals because they prioritize the higher voltage ratings of this type of capacitor. For example, the maximum voltage of lead-type capacitors is around 60-70 kV, while the maximum voltage of cylindrical bolt terminal capacitors can exceed 120 kV. However, only N4700 material can provide the highest withstand voltage level within the same unit area. Other ceramic types, even if they can barely produce capacitors, have much shorter average service life and capacitor lifespan than N4700, which can easily lead to hidden risks. (Note: The lifespan of N4700 bolt capacitors is 20 years, with a warranty period of 10 years.)
N4700 material also has advantages such as small temperature coefficient, low resistance, good high-frequency characteristics, low loss, and low internal impedance. Some blue high-voltage ceramic chip capacitors also use N4700 material and are commonly used in low-power and low-current devices, such as Philips/Siemens X-ray machines and CT scanners. Similarly, their service life can reach 10 to 20 years.
3） The high-frequency characteristics and high current capacity of cylindrical high-voltage ceramic capacitors are superior to those of disc-type ceramic capacitors. The frequency range for cylindrical capacitors is typically between 30 kHz and 150 kHz, and some models can withstand instantaneous currents of up to 1000 A and continuous working currents of several tens of Amperes or more. Ceramic disc capacitors, such as those using N4700 material, are often used in the high-frequency range of 30 kHz to 100 kHz, with current ratings typically ranging from tens to hundreds of milliamperes.
4） When selecting suitable high-voltage capacitors, engineers at the factory should consider not only the price but also the following details:
HVC sales personnel typically inquire about the customer's equipment, operating frequency, ambient temperature, enclosure environment, pulse voltage, overcurrent, and whether there are requirements for partial discharge values. Some customers also require low resistance, small size, or other specifications. Only by understanding these specific details can HVC sales personnel quickly recommend and provide suitable high-voltage capacitor products.