Electromagnetic or conventional ballast
An electromagnetic ballast (also known as magnetic ballast) is comprised of a ballast (coil), a capacitor (in order to limit the current) and an igniter (starter).
A ballast (VSA) is used to limit the electrical current through a fluorescent tube or other gas discharge lamp. A conventional ballast uses a coil and magnetism. An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil, spiral or helix. Either an electric current is passed through the wire of the coil to generate a magnetic field, or conversely an external time-varying magnetic field through the interior of the coil generates an EMF (voltage) in the conductor. This voltage source is meant for the lamp. It is possible to generate different voltages depending on the amount of windings on the coil. The disadvantage of this type of gear is that a high heat development is effected. For that reason, some conventional ballasts have a built-in thermal protection, which ensures that if the ballast is too hot it will automatically (temporarily or permanently) be disabled.