Monday, February 11, 2008

Find Corona

If you suspect that corona is an issue in your system, here's one simple way to detect corona. The CoronaFinder, manufactured by Syntronics, is a real-time viewing system that looks for the ultraviolet glow of corona. If you look at their website at, you'll see a couple of dramatic photos. One shows wires using normal light, and the second shows the same view as seen through the CoronaFinder.

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Wednesday, February 6, 2008

Comparison: Ceramic and Film High Voltage Capacitors

Both ceramic and film capacitors are widely used in high voltage applications. Ceramic high voltage capacitors have the following advantages, as compared to film:
  • Lower equivalent series inductance (ESL) and equivalent series resistance (ESR)
  • Smaller size for the same value (capacitance & voltage)
  • Better temperature coefficient available, as well as a choice of temperature coefficient characteristics
Disadvantages of ceramic capacitors include:
  • Higher voltage coefficient, resulting in substantially lower capacitance as the applied voltage is increased. (This characteristic is often overlooked, and its effects are often more severe than you would think.)
  • Lower maximum available capacitance rating
  • Lower maximum available voltage rating
  • Susceptibility to piezoelectric effects
  • Typically smaller lead-to-lead distance