Over the past few years, fluorescent lamps have become the lighting of choice for contractors looking to save on both energy and maintenance costs. Although fluorescent lighting may cost a bit more upfront when it comes to initial installation, it makes up for it in the amount of energy saved when compared to traditional incandescent lighting. All fluorescent lamps need fluorescent ballasts in order to operate, but how do they work?
A fluorescent lamp generates light through the use of two elements -- electricity and mercury vapor. A current of electricity – also known as the arc – passes through the vapor, resulting in an ultraviolet light. That light then bounces off a phosphor layer on the inside of the lamp, which makes the bulb light up. The fluorescent ballasts regulate the process.
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What are Fluorescent Ballasts?
Quite simply, the ballast keeps the fluorescent lamp from burning out. Without a ballast, the fluorescent lamp would keep increasing the electric current flowing through it until it self-destructed. The job of the ballast is to control the amount of current running through the lamp so that does not happen.
Another job of the ballast is to provide the energy -- or voltage -- the lamp needs to get going. The ballast gives the lamp the amount of voltage it needs to create the current – or arc – between its electrodes, and then automatically lowers and monitors the voltage to make sure there is the perfect amount to keep the light going.
Fluorescent ballasts come in a variety of types to meet the needs of different light fixtures. For instance, ballasts will specify how many fluorescent lamps they can regulate at one time (such as one or four). They also say what types of lamps they work with (such as T5, T8, T10 or T12). Additionally, the fluorescent ballast will also state the amount of voltage it can accommodate (such as 120 or 277 volts).
How Fluorescent Ballasts Work
When a fluorescent lamp is turned on, the lamp's electrodes heat up and release electrons. These mix with the mercury gas and other gases that are in the lamp. When this happens, the electrons bump into atoms that are in the gas, releasing wavelengths of ultraviolet light that are consumed by the fluorescent coating on the inside of the lamp. This then ultimately produces the light we can see.
The job of the fluorescent ballast is to manage this entire process by giving the lamp the voltage it needs to get the process done. It also makes sure the lamp doesn't take in so much voltage that it burns out. That is because a fluorescent lamp inherently has a negative resistance, meaning it will continue taking in voltage until its power supply can't take anymore. To combat this, the fluorescent ballast supplies the opposite resistance -- positive -- to restrict the current.
In its simplest form, a ballast uses magnetic energy that erupts into the lamp when it is turned on, stimulating the electrodes to make a current and the lamp glows. Today's fluorescent ballasts are mainly electronic, and they have a number of positive attributes including energy efficiency, reduced flicker of light, and even dimming capabilities.
Types of Fluorescent Ballasts
There are a few different types of fluorescent ballasts to know about.
One of the more popular types of ballasts is the instant-start ballast. Rather than warming up the lamp's electrodes gradually, the ballast gives a rather large initial voltage to get it going. Although this helps save energy since there's less energy used when compared to other ballast types, the lamp degrades quicker. We recommend this for light fixtures that will not turn off and on regularly.
A rapid start ballast works differently from an instant start as it does allow the lamp time to preheat by initially using a low voltage. When the lamp's cathodes are nice and warm, the voltage increases to light the lamp. One advantage of rapid start ballasts is that they work in a parallel lamp service. That means if you have four lamps running on the one ballast and two go out, the other two will continue working.
The programmed start ballast operates much like the rapid start. It gradually heats up the lamp's cathodes before initializing the ignition of the lamp. The ballast is able to warm the cathodes at an even higher temperature, allowing less burn out. You can also use these with lighting fixtures that will turn on and off frequently.