In lighting, a ballast is used with certain types of lamps or bulbs to ensure that they don't burn out or explode. While ballasts are not needed for incandescent (including halogen) or LED bulbs, ballasts are required with any kind of gas discharge bulb including fluorescent, metal halide, and high pressure sodium bulbs.
This is because these lamps cannot regulate the flow of electricity through them, and this flow quickly gets out of hand and destroys the bulb if not regulated. So the ballast is used to generate the necessary voltage for starting the lamp from the main voltage line and then it regulates the ongoing flow or current of electricity through the bulb.
A lighting ballast is not a one-size-fits-all kind of tool. It needs to fit the electrical requirements of the lamp that it will run. Ballasts and lamps are often tied together by a code so, when purchasing a ballast, you'll need to read the type of lamps it's designed for, how many lamps it operates, and the voltage the lamps will run on. Choosing the right ballast for a lamp will optimize the light output and life of the bulb.
(If you're confused about this during a purchase from Lighting Supply, simply call our friendly experts at 877-231-2852 for help with your order. They can help you to choose the correct ballast. The easiest approach to replacing a ballast is to order by the part number on the ballast, but our team can also provide you with compatible ballast options from other brands when needed.)
There are two main types of ballast technology: electromagnetic (commonly just called “magnetic”) and electronic. Magnetic ballasts are an older technology, and they modulate current at a lower cycle rate. This leads to an audible hum and the flickering noticed in older fluorescent lighting systems. Newer electronic ballasts largely eliminate both problems, though there are some lighting instances where magnetic ballasts are still required. There is also a hybrid style ballast with all the components of a magnetic ballast but also with some electronics to help the ballast run more efficiently.
Within these technologies are a few different types of starting methods for ballasts, and we'll mention the three primary methods here:
Instant Start Ballasts
These are the most energy efficient ballasts but, because of the way they start the lamps, the lamps will burn out more quickly due to the “Instant on” feature. Lamps that start with ballasts have an “emitter” on the electrode and, when this runs out, the lamps will no longer start. The Instant Start method reduces the emitter the most quickly of these three starting methods. So these ballasts are best used in cases where the bulbs will be left on for long periods of time -- for instance on a factory floor where lights are turned on just once in the morning and then shut off at night.
Rapid Start Ballasts
These aren't as efficient as instant start ballasts, but they're gentler on bulbs when they are turned on, allowing the bulbs to last longer. These can also be found as dimming ballasts in case bulbs will need to be dimmed.
Programmed Start Ballasts
These are a kind of rapid start ballast, but they are more advanced. They give the best possible life to bulbs, especially those that are frequently turned on and off, which makes them an excellent ballast choice for locations like bathrooms.
We hope this is a useful introduction to lighting ballasts for you and that it helps you in choosing the right ballasts for your lighting needs. To learn more, you can visit our Complete Introduction to Lighting Ballasts, which includes written DIY instructions for How to Replace a Fluorescent Ballast.