Lighting Control Gear

The Ballast Explained

Ballasts function to start and control the electricity flow through a lamp. So, there is sufficient electrical current and light is emitted without destroying the bulb. In other words, ballasts regulate the electric current flowing through HID lamps so that they work properly.

Different Types of Ballasts

There are several different kinds of ballasts, but the 3 basic types are electronic ballasts, magnetic ballasts and digital.

Electronic and High Frequency Electronic Ballasts

Electronic ballasts regulate the electric flow inside the bulb through electronic circuitry. Sometimes referred to as control gear, the electronic ballast limits the current which flows in an electric circuit. This type of ballast is employed to balance the negative resistance to power supplies with positive resistance. As a result, the current is kept at a level that prevents the bulb from burning out. Electronic ballasts may operate in parallel or in a series mode. The series mode is preferred because the failure of a single lamp does not disrupt the working of all other lamps. The high frequency electronic ballast is another type that makes use of electric circuitry. It uses frequencies that are above 20,000Hz.

The Simplest Type: Magnetic Ballasts

Magnetic ballasts employ core and coil transformers to operate lamps. They are intended to control the electric current and the flow at an appropriate level for the bulbs. Some magnetic ballasts employ an igniter which comes together with metal halide or sodium lamps. Although this type is the simplest, it is characterized by higher robustness. The magnetic ballast is capable of withstanding exposure to fluctuations and transients within an electric system, along with temperature extremes. Typically, the magnetic type of ballasts is used with fluorescent and neon lamps. The low frequency electronic ballast is a variation of the magnetic one, incorporating some electronic components.

Types of Ballasts

Optimum Results with Digital Ballasts

Digital ballasts operate at higher frequencies and produce larger amount of light while using less energy. The digital component regulates temperature levels so that the bulb lasts longer. With digital ballasts, the flow is low at the initial point and increases when temperature goes up inside the bulb. Research has demonstrated that low pressure sodium lamps, used together with digital ballast, lost between 20 and 25 percent luminescence in 1 year. In comparison, lamps used with other types of ballasts lost more than twice this amount during the same period. It is important to note that the reliability of digital ballasts may vary depending on the manufacturer. Effective digital ballasts shut down automatically if a damaged or defective bulb is detected or in case of a short circuit. In this manner, safety hazards are avoided.

Digital Ballast

Philips BSN/BMH Ballast range

SON, Ceramic Metal Halide and CDOTT lamp

50w - 400w available


Improved thermal features – much cooler ballast
All ballasts are equipped with ThermoSwitch for protection against
end-of-lamp-life phenomena
Ballast can also be used in combination with series (superimposed)
Equipped with screw terminal blocks as standard; insert contacts
available upon request
Ballasts for alternative mains voltages/frequencies available upon

Philips BSN/BMH Ballast


Outdoor lighting


Electromagnetic system requires ballast, ignitor and capacitor Semi-parallel circuit: if ballasts with “L” in their description (e.g. BSN 100 L307…) are used, SN(D)… ignitors are required; if ballasts with “K” in their description (e.g. BSN 100 K307…) are used, SK(D)… ignitors are required. Capacitor value to match system power can be found on lamp/ballast combination sheet. Series circuit: all ballasts are designed to work with series ignitors No ignitor needed for SON-I lamps

Philips BSN/BMH Ballast Drawing

Philips BSN/BMH Ballast Information

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