Lighting Ballasts

A lighting ballast starts a fluorescent or HID lamp by supplying a brief high-voltage pulse to strike the arc between the electrodes, then limits and stabilises the current so the lamp operates at its rated output without overheating or burning out. Without a ballast in the circuit, negative-resistance discharge lamps would draw an ever-rising current until failure.

RS Hong Kong supplies electronic and electromagnetic ballasts, covering fluorescent and HID options for lamps used in commercial, industrial, and infrastructure lighting across Hong Kong. The range includes stock from Osram, Philips Lighting, and our RS PRO in-house brand, so buyers can match specification, wattage, and lamp type from a single order.

Types of Lighting Ballasts

The most common types of ballasts are magnetic and electronic, and they come in several start technologies to suit different purposes.

Magnetic Ballasts

A magnetic ballast (also called an electromagnetic ballast or core-and-coil ballast) uses copper or aluminium coils wound on a steel core to limit lamp current through electromagnetic induction. In fluorescent circuits, it works alongside a glow-starter switch that preheats the electrode filaments before the arc strikes, and it typically operates the lamp at the mains frequency of 50 Hz.

Magnetic ballast units are still widely fitted to T8 ballast circuits in existing installations. Magnetic HID ballast versions add an ignitor to generate the high-voltage starting pulse for lamps such as metal halide, high-pressure sodium, and mercury vapour, and a capacitor to correct the power factor. Wattage matching between the ballast and the lamp is essential, since under- or over-driving shortens lamp life.

The construction is heavier and runs hotter than an electronic equivalent and produces the low-frequency hum long associated with older fluorescent luminaires, but low-loss electromagnetic units are robust and remain in service across many Hong Kong industrial and infrastructure sites where simplicity outweighs the higher energy usage.

Electronic Ballasts

An electronic ballast uses solid-state circuitry to convert the mains supply into a high-frequency waveform, typically in the 20 kHz to 60 kHz range, before delivering it to the lamp. Operating a fluorescent tube at high frequency raises luminous efficacy by roughly 10% at the same input power, removes visible flicker and stroboscopic effects, and eliminates the audible hum of 50 Hz magnetic units.

Electronic ballast units are the standard specification for T5 ballast circuits because the newer 16 mm T5 tubes are designed specifically to run on high-frequency control gear, and they are also used in many T8 retrofits where dimming, rapid start, or multi-lamp drive is required.

An electronic HID ballast can also drive metal halide and high-pressure sodium loads with tighter current regulation and lower total harmonic distortion than a magnetic equivalent, and typically runs cooler with lower circuit losses.

Applications of Lighting Ballasts

The ballast type and rating are matched to the lamp technology and the operating environment, from open-plan offices through to public street lighting.

Commercial & Office Lighting

In Hong Kong offices, T8 fluorescent tube lighting on ceiling grids remains a common installation, with high-frequency electronic ballasts specified for new-build and retrofit projects to improve luminous efficacy, eliminate flicker on workstation screens, and support dimming and daylight-response controls.

Industrial & Warehouse Lighting

Warehouse and factory high-bay fittings run metal-halide HID lamps to provide the required light output over production floors and racking. Matched HID ballast assemblies, with ignitors and power-factor correction capacitors, strike and stabilise the arc across long daily duty cycles.

Retail & Hospitality Lighting

Shopfronts, restaurant back-of-house, and hotel service areas continue to use fluorescent ballast assemblies with T5 and T8 tubes for general lighting, with electronic ballast versions favoured where audible noise from a magnetic unit would carry into customer-facing areas.

Outdoor & Street Lighting

Since the 1990s, Hong Kong's Highways Department has widely adopted high-pressure sodium (HPS) lamps for public road lighting, with efficacy ranging from about 90 lm/W for low-wattage lamps to 150 lm/W for high-wattage lamps. HID ballast units operate these lamps in applications including carriageway, high-mast, and footbridge lighting, as well as public transport interchanges, although many installations are now being progressively replaced with LED luminaires.

Buy Lighting Ballasts from RS Hong Kong

RS Hong Kong, a trusted supplier, offers lighting ballasts for commercial, industrial, and infrastructure projects from leading brands such as Osram, Philips Lighting, as well as the RS PRO in-house range.

Every product page displays the ballast price alongside key specifications, including wattage, lamp compatibility, dimming capability, and electrical ratings, helping procurement teams quickly and confidently identify the right ballast. Pair your lighting ballast with compatible Lamp Holders and Light Covers for a complete installation.

For Hong Kong stock, orders placed before noon on working days qualify for same-working-day delivery, while orders placed after noon are delivered on the next working day. Delivery is free for RS business account holders and free for other customers on eligible orders.

For more information on delivery times and charges, refer to our delivery information page.