Not all lights are created equal. In fact, some require additional equipment to operate. Ballasts, or ‘control gear’, are devices that ensure the correct amount of current is flowing to a fluorescent light bulb.
How ballasts work
Ballasts regulate the amount of power flowing through a load and stabilise it to prevent power fluctuations. They work in a number of ways, varying in complexity from something as simple as a resistor, to complex computerised systems. When the gases in fluorescent bulbs heat up, their electrical resistance goes down, causing them to draw more power. If left to continue heating, fluorescent bulbs will inevitably destroy themselves with constantly increasing heat. Ballasts work to limit and stabilise the current flow to the light, preventing this continuous heating. They also help in some cases with starting the light, and to control or prevent flickering.
Self-ballasted and external ballasts
Most ballasts, particularly in smaller globes such as compact fluorescents, are built in to the base of the bulb itself, which saves you from having to worry about a separate piece of electrical equipment. These globes are referred to as ‘self-ballasted’. That being said though, the type of ballast that is included in your bulb can dramatically alter the way in which is operates.
Types of ballast
At a very basic level, there are three types of ballast. The fundamental differences between the three types of ballast are the way in which the light is activated, and the impact that has on the bulb’s longevity.
‘Instant start’ ballasts could be described as a ‘cold start’. While other ballasts first warm the the end of the fluorescent globe from which the electricity flows (the ‘cathode’), instant start ballasts work by applying a large voltage across the globe (far greater than the normal operating voltage), which causes the light to turn on instantly. Because they don’t preheat the cathode, they are the most efficient type of ballast. Instant start ballasts tend not to last as long as the alternatives though, so they’re better for applications where the lighting isn’t switched on and off regularly.
‘Rapid start’ ballasts warm up the cathode at the same that they apply voltage. This means your lamp will last longer, but will consume more energy.
‘Programmed-start’ ballasts offer more of a structured approach to activating a lamp. They go through a complex series of actions, including heating and regulating voltage, to ensure the light source is protected, and as such they offer the best lifespan.