Advancements in capacitor design and manufacturing have greatly increased the energy densities of metallized film capacitors over the past decade. Among the factors contributing to this phenomenon are: • Improved dielectric breakdown strength • Self-healing electrode properties • Enhanced impregnation processes • Higher purity materials
Polypropylene dielectric film capacitors of varying types are used in large power systems due to their low heat dissipation and inherent reliability. This paper examines the construction of these capacitors for power applications and compares their heat rise performance with respect to electrodes, terminals, form factors, and packaging. Thermal behavior is measured for the internal construction of the capacitors and packaging with respect to various external cooling methods including convection, conduction and liquid cooling. In addition, heat induced from eddy currents from electromagnetic interference in relation to the position of the capacitors will also be considered.
High crystalline segmented metallized polypropylene capacitors are the component of choice for many more DC Filter, energy storage and similar applications for the 21st century. With the introduction of higher crystalline and higher temperature dielectric, the size of segmented metallized polypropylene capacitors were reduced at least 33 percent while increasing the life expectancy and reducing the costs over previous designs. Higher temperature operation of at least 110ºC is also accomplished with this material type. Capacitors are now manufactured using the combined segmented and high crystalline metallized polypropylene technology that allow denser power system packaging and lower manufacturing costs than other capacitor choices.
Renewable energy (wind and solar) has finally begun to fulfill its promise as a legitimate mainstream power generation alternative to fossil fuel sources. There has been tremendous growth in the number of suppliers for both home-based and larger commercial units. In order for these systems to succeed, the power conversion assemblies must provide a combination of high efficiency, high reliability, and competitive cost.
IGBT modules now achieve blocking voltages of 6kV or higher, so dc capacitors of 1mF to 100 mF at 3.3kV are used for the associated dc bus. Different capacitor technologies have been used for these applications, including aluminum electrolytic, oil or gas-impregnated metallized film, or metallized paper. Ideally, a single capacitor should be able to operate continuously with an extended life of over 100,000 hours at these dc bus voltages.
High-power resonant capacitors are designed to handle large voltages and currents in small compact package sizes. As a result of their small size, these capacitors need to be cooled. Failure to cool the capacitors properly will result in the capacitors failing prematurely. Proper cooling of high-power resonant capacitors is to be done by the use of water-cooled heatsinks or bus bars.
Conduction cooled capacitors are designed for use in high-power resonant (tank) circuits. Typically, these circuits consist of a capacitor and an inductor connected either in series or parallel.