What You Don't Know About Electronics Ballast

Electronics Ballasts

An electronic lamp ballast uses solid state electronic circuitry to provide the proper starting and operating electrical condition to power one or more fluorescent lamps and more recently HID lamps and help to increase the efficiency by reducing the power loss mostly through heat generated in the traditional coil in a magnetic ballast. Electronic ballasts convert the frequency of the power from the standard mains (e.g., 60 Hz in U.S.) frequency to 20,000 Hz or higher, substantially eliminating the stroboscopic effect of flicker (a product of the line frequency) associated with fluorescent lighting. In addition, because more gas remains ionized in the arc stream, the lamps actually operate at about 9% higher efficiency above approximately 10 kHz. Lamp efficiency increases sharply at about 10 kHz and continues to improve until approximately 20 kHz. Because of the higher efficiency of the ballast itself and the improvement of lamp efficiency by operating at a higher frequency electronic ballasts offer higher system efficiency. In addition, the higher operating frequency means that it is often practical to use a capacitor as the current-limiting reactance rather than the inductor required at line frequencies. Capacitors tend to be much lower in loss than inductors, allowing them to more closely approach an "ideal reactance".

There are various types of Electronics Ballast which will also affect the quality of lamp you will receive. A simple Electronics Ballast will only ensure the basic function of supplying the necessary electrical power to light up the fluorescent lamp and maintaining the light source without the consideration of other factors as in lifespan, efficiency and most importantly ; safety.

Instant start
An instant start ballast starts lamps without heating the cathodes at all by using a high voltage (around 600 V). It is the most energy efficient type, but gives the least number of starts from a lamp as emissive oxides are blasted from the cold cathode surfaces each time the lamp is started. However, this kind of ballast does not take into consideration the matching of the impedance of the fluorescent tube. It does not ensure the right power applied the filament inside the tube as not to over stress the filament. One common sign of this stress can be seen by a blank ring around both ends of the tube over time.




By overstressing the filament, it will sputter the tungsten-based filament with a black ring around both ends of the tube over time. Upon the tungsten been forced out of the filament, the lamp will not light up. This usually result a pre-matured End Of life in the lamp. Magnetic ballast are instant start and for this reason, the lifespan of the lamp is shorter than those used with Rapid or Programmed Start.

Rapid start
A rapid start ballast applies voltage and heats the cathodes simultaneously. Provides superior lamp life and more cycle life, but uses slightly more energy as the cathodes in each end of the lamp continue to consume heating power as the lamp operates. A dimming circuit can be used with a dimming ballast, which maintains the heating current while allowing lamp current to be controlled. With this method, the lamp will enjoy a longer lifespan as compared to Instant Start but with the heating element in the ballast, some power is used in the heating which mean that efficiency is lower due to losses.

Programmed-Start
A programmed-start ballast is a more advanced version of rapid start. This ballast applies power to the filaments first, then after a short delay to allow the cathodes to preheat, applies voltage to the lamps to strike an arc and after which, will cut off the preheat. This ballast gives the best life and most starts from lamps and will give a much longer lifespan over the other type of ballast. This kind of ballast requires much more understanding and circuitry design ; matching of the impedance of the filament and the ballast, the right preheat to apply and right voltage to strike the arc.


Safety Features Required in Electronics Ballast for End-Of-Life (EOL – IEC61347-2-3)

The fluorescent will experience the End-Of-Life when the emitter/filament becomes depleted during the lifetime of the lamp due to sputtering at ignition and gradual emitter loss during burning. A lamp reaches its end-of-life
when all the emitter is consumed. A symptom of emitter loss can be visual as it causes end-blackening by attaching itself to the phosphor in the electrode area. When all the emitter is gone, even the bare tungsten material starts to sputter off electrons, possibly causing
severe end-blackening and the failure of the electrode. The lamp has now reached the end of its lifetime and should be replaced as soon as possible.

A protection circuitry for the EOL will safely removes power from the lamp upon failure and helps to minimize maintenance concerns. Without effective protection or preventive circuitry, the ballast will continue to drive the lamp. The temperature in the region of the electrode increases rapidly and causes overheating easily reaching 800ºC for a very short time the wire can drop on the glass and even melt a hole in the tube. As soon as a leak occurs in the glass, the process of ignition will stop. Statistically, less than 1% of the lamps fail this way.

If the wire breaks but does not fall on the glass, however, a discharge can result between the wire of the electrode and the glass for a period of 60-180 seconds. The resulting temperature can be as high as 300ºC. Subsequently the glass can weaken and the ring of the electrode sags towards the glass. This could result in a discharge and create high temperatures at the lamp-ends. If the ring comes in contact with the broken wire of the electrode, the arc discharge created could be maintained for hours and even days with an ever increasing temperature rise. The process will stop eventually when a leak in the lamp has developed. Statistically, All fluorescent lamps can inherently have this problem. It is clear that in potentially explosive atmospheres, this phenomenon can have disastrous results that cannot be ignored.


In cases where a T5 Adaptor is used on a T8 fixture (the magnetic ballast is still in the T8 fixture), the T5 Adaptor is actually a electronics ballast by itself. Without the proper isolation of the circuitry to prevent the striking of the lamp, the adaptor or electronics ballast may attempt to re-strike the lamp at frequency of 4 times per second at a high voltage. This striking event will cause a high surge of voltage in the existing magnetic ballast in the fixture and prolonging this event will cause the breakdown in the insulation wire used in the coiling of the magnetic ballast. When this happens, it will result in a earth leakage by shorting the uninsulated wire to the casing of the ballast and apparently to earth. This will result in the Earth Leakage Circuit Breaker (ELCB) to trip and frequency tripping will cause heavy maintenance problems by having to troubleshoot the exact location of the cause and also eventually the failure of the ELCB.