They are the most common type of ballast nowdays. The simplest ballast technically consists principally of a wire-wound choke, together with a starter switch. Once the discharge is established, the starter switch plays no further part in the operation of the lamp; the current through the lamp is limited by the reactive choke. Other types of electromagnetic lamp/ballast systems do not require the use of a starter. These can be Rapid Start systems (with ballast energise the lamp cathodes prior to exciting the lamp and also during operation) or Instant Start systems (requiring high voltages to start the lamp).
The energy losses in a wire-wound ballast are determined by the materials from which the ballast is made and its shape:
The low-loss ballasts
(sometimes called hybrid ballasts) use copper windings on high quality
steel laminated cores. They are contained in two classes B1 and B2 in the
manufacturers' classification. They are wire-wound chokes specifically
designed to be more energy efficient. The energy losses are lower than
in conventional ballasts, but the ballasts may be more bulky. These low-loss
ballasts are also relatively expensive compared to the other types of magnetic
ballasts. These low-loss ballasts may be satisfactorily incorporated into
new installations. However, their large size can make them difficult to
fit into existing luminaires; in addition, thermal problems may be encountered
and manufacturers should be consulted before such action is attempted.
Conventional ballasts, also called “class C ballast” in the manufacturers' classification may be made with slightly higher quality materials (e.g. copper) than “high-loss” ballasts (see below). As a result, the energy losses in the ballasts are decreased, but the cost is higher.
High-loss ballasts, also called “class D ballast” in the manufacturers' classification are generally made from poor quality materials. These ballasts are generally quite cheap but offer the worst performance. These ballasts will soon be phased out by the upcoming directive on Energy Efficiency Requirements for Ballasts for Fluorescent Lighting.
