A fluorescent light does not have the usual glowing filament of an incandescent bulb, but instead contains a mercury vapor that gives
off ultra violet light when ionized. The ultra violet makes particles that coat the
inside of the tube glow or fluoresce (see Question 236 for details).
Fluorescent starters are used in
of fluorescent lights. The starter is there to help the lamp light.
When voltage is applied to the fluorescent lamp:
- The starter (which is simply a timed switch)
allows current to flow through the filaments at the ends
of the tube.
- The current causes the starter's contacts to heat
up and open, thus interrupting the flow of current.
The tube lights.
- Since the lit fluorescent tube has a low resistance, the ballast now
serves as a current limiter.
When you turn on a fluorescent tube, the Starter is a closed switch. The filaments at the ends
of the tube are heated by electricity, and they create a
cloud of electrons inside the tube.
The fluorescent starter is a time delay switch which opens after a second or two. When it opens, the voltage across the tube allows a stream of electrons to flow across the tube and ionize the mercury vapor.
Without the starter, a steady stream of electrons is never created between the two filaments and the lamp flickers. Without the ballast, the arc is a short circuit between
the filaments, and this short circuit contains a lot of current. The current either vaporizes the filaments or causes the bulb to explode.
According to Sam's F-Lamp FAQ,
"The most common fluorescent starter is called a 'glow tube starter' (or just starter) and contains a small gas (neon, etc.) filled
tube and an optional radio frequency interference (RFI)
suppression capacitor in a cylindrical aluminum can with a 2 pin base. While all starters are
physically interchangeable, the wattage rating of the starter should be matched to the wattage rating of the fluorescent
tubes for reliable operation and long life.
"the glow tube incorporates a switch which is normally open. When power is applied a glow discharge takes place which
heats a bimetal contact. A second or so later, the contacts close and provide current to the fluorescent filaments. Since the
glow is extinguished, there is no longer any heating of the bimetal and the contacts open. The inductive kick generated at
the instant of opening triggers the main discharge in the fluorescent tube. If the contacts open at a bad time, there isn't enough inductive kick and the process repeats."
Some useful related links: