Capacitors

With Magnetic HID ballasts (i.e. Metal Halide Ballast Kits), (175 Watt and Up) capacitors are required to improve the power factor. This allows the number of light bulbs that can be operated on a circuit nearly doubles (more fixtures can be put on one line). In large projects, power factor correction (HPF) is also required to avoid power quality issues and the utility companies can penalties you. Capacitors are integral components of CWA and they will not operate at all without capacitors. Both oil-filled (wet) and dry-film capacitor are most commonly used with ballasts.

Oil-filled capacitors
Oil-filled capacitors have metal cases and have dielectric fluid in them. Oil-filled capacitors are rated up to 100°C, although 90°C is the most common rating used today. They typically have two 1/4″ spade terminal connections that are located on the top of the capacitor for connection with the HID ballast. Most HID ballasts come with the matching terminals that is attached to the appropriate terminals. Oil-filled capacitors are extremely reliable and have ratings up to 525 Volts. In many higher (1000W +) wattage HID ballasts, they are the only choice.

Dry-Film capacitors
Dry-Film capacitors do not contain dielectric fluid. Most of these capacitors are rated up to 400 Volts. Many are available in ratings of 100°C or more. Dry-Film capacitors have become increasingly attractive alternative to oil-filled capacitors. Dry-Film capacitors are packaged in thermal-plastic housings and do not need to be grounded. A lot of manufactures are doing away with Oil-filled capacitors due to expense and environmentally sound practices.