Auxiliary equipments are of two types, Ballasts and Transformers. Both consume a little amount of power, adding to the total wattage of the Light Source.
Transformers are used in low-voltage light sources. These low-voltage lamps work on current between 6 to 24 V (12V being the most common). However a building generally receives anything from 120 to 125 V. Transformers convert the high voltage to low voltage before directing the current to the light source/lamp.
Transformers can be installed within a lighting system or it can be external. With smaller transformers available today, it is possible to embed them into small and compact lighting fixtures. Transformers in Recessed luminaries are hidden out of view above the ceiling. For surface luminaries and pendants the transformer is generally hidden within the lighting system. Where ceiling conditions (i.e. low ceilings) allow pendants too can have their transformers hidden above the ceiling.
Track mounted lighting systems can either have their transformer hidden along the track or at an external place like above the ceiling. If external transformer is used, it is necessary to connect it with the lamps with thick wires, to prevent voltage drop.
High amperage level (high strength of electric current) of low-voltage lamps, limit the number of track lights per transformer. This can be calculated via the formula: Watts divided by Voltage equals amperes (W/V=A). Thus a 50 wattage, 12 volts lamp (60/12 = 4.16amps) draws the same amperage as a 500 watts 120 V lamp (600/120 =4.16 amps).
Two types of transformers are used for low-voltage lamps: Magnetic (core-and-coil) and electronic (solid-state). In Magnetic Transformers copper wire is wound around a steel core. Magnetic transformers are large and heavy, but have a long life span. They also emit noises at times.
Torodial transformers are a type of doughnut-shaped Magnetic transformers, which are relatively quieter than normal magnetic transformer. But they also emit sounds when the dimmer option in lamp is used or when they are used on too many lamps simultaneously. The sound becomes louder if there is a fault in the design of the lamp, as the lamp too tends to resonate with the transformer’s sound.
Electric Transformers are based on electric circuits. They are quieter, light-weight and more compact. But their life spans are shorter than magnetic transformers and are more likely to fail. They are also incompatible with certain kind of dimmers. However due to their compact size they are used more often than magnetic transformers.
All discharge lamps require Ballasts (incandescent lamps being the only exception). If the electric arc is allowed to form without a regulated supply from the Ballasts, it will draw a large amount of current and thereby burnout in no time. The Ballast regulates the amount of light received by discharge lamps and also the amount of light required for the lamp to start.
Traditionally different types of Ballasts were created for different types of lamps. Where Ballast manufactured for a certain lamp didn’t work with other types of lamps. Newer Ballasts allow various lamps to work with the same Ballast, and are also capable of operating 2 to 3 discharge lamps at the same time.
In discharge lamps, electricity wattage is dependent on the Ballast. If a 50 wattage lamp is given 500 watts by the Ballast, the lamp will work at 500 watts, but will burnout or experience ballast failure. Lamp wattage for discharge lamps thus represents the wattage at which it is designed to operate and not the wattage it can operate on. Simply changing the bulb wattage of a discharge lamp to higher or lower watts is of no use, as the Ballast also needs to be changed accordingly.
Two-Lamp Ballasts are used to reduce ballast cost and installation cost. These are available in two forms: Two-Lamp Series design and Two-Lamp Parallel design. Two-Lamp Series are used more often as they are more cost effective. In such lamps a single Ballast provides current to two lamps. When one lamp goes off, the other one stops working too.
Two-Lamp Parallel design lamps feature two ballasts providing current to the two different lamps. These are more expensive, but when one lamp goes off the other keeps working, in this kind of set-up.
Till 1980’s all lamps featured Electromagnetic Ballasts. These Ballasts convert electric current to the necessary amperes to start the lamp and thereafter to regulate it. The parts of the Ballasts can be divided into three parts: Transformer, Inductance coil and a capacitor.
The transformer converts the voltage received from the electric source to a voltage that is suitable to start the lamp. The inductance coils limits the amount of voltage that can be used by the lamp. Whenever current is changed in a Ballast (inductor) it gives rises to an opposing electromotive force. The capacitor is built to counter this force and bring about the original balance.
Electromagnetic Ballasts equipped with Capacitors are called High Power-Factor Ballasts.
Power Factor calculates how efficiently a Ballasts converts electricity received by it, to electric current required by the lamp. The Perfect relationship is 100%. The formula used for calculating Power Factor is: Power Factor = Input Watts (w)/ Line Volts (V) x Line Amperes (A).
The Power Factor of Inductive Ballasts lags behind; while Power Factor of Capacitive Ballasts is much better. Magnetic Transformers are Inductive, while Electronic Transformers are Capacitive by nature. Adding a capacitor to Inductive systems can convert them into capacitive systems.
On the basis of Power Factor, Ballasts can be divided into three groups: High Power Factor – Ballasts that have a Power Factor of 90% and above; Power Factor Corrected Ballasts, with 80 to 89% Power Factor; and Low (normal) Power Factor Ballasts, for Ballasts with Power Factor below 79%.
High Power Factor Ballasts use the minimum amount of current needed and can be used to power a number of lamps. Low Power Factor use much more power (twice the level) limiting the number of lamps that it can operate.
Power Factor doesn’t determine the amount of light emitted by the luminarie but the amount of current that can be regulated by the Ballast. As such it is not a determining factor when calculating light output/intensity.
Lamp Ballasts System Efficacy
The Initial-Lumen and Mean-Lumen ratings that you see displayed on lamp boxes are based on lamp operations by a Reference Ballast. Reference Ballast is an instrument used to measure lumen output under laboratory conditions; this measurement forms the Baseline, which helps us to compare various lamps in the market against it. Some commercially manufactured Ballasts operate more efficiently than the Reference Ballasts and a few with lower efficiency.
In practice lamp efficiency of market Ballasts is always lower than that of Reference Ballasts. This is due to electrical resistance, which happens when electric current passes through the core-and-coil. As the core-and –coil transforms a little amount of power into heat energy, while converting electricity into light. This loss in power is called Ballast Loss.
The difference between light provided by Reference Ballast and light provided by market Ballast is called Ballast Factor. Some Ballast have more than one Ballast factor, this occurs when the Ballast can be used for different types of lamps say a standard lamps and an energy-saving lamp.
Ballast Efficacy Factor is the ratio between the Ballast Factor and the power input (watts) of the Ballast.
Electromagnetic Ballasts produce a low level noise called the Hum. The degree of the sound level/hum varies from Ballast to Ballast. For easy identification and selection of Ballasts, manufactures rate Ballasts by their sound level from A to F; where Hum A is the quietest with 20 decibels sound and F the loudest with 49 decibels.
Electronic Ballasts are more efficient, lighter and more compact than Electromagnetic Ballasts. Made of electronic components they convert power to light more efficiently than the traditional core-and-coil set-up. It is to be noted that they are not used to produce more light but instead use less power for the same amount of light, thereby reducing energy costs. Since they consume less power they tend to produce less heat.
HID Electronic Ballasts also regulate and help maintain a good level of colour rendering –CCT and CRI. They provide better voltage regulation to lamps, even when operating with low power input; and also ensure more efficient starts.
The humming sound associated with Electronic Ballasts is 75% lower than Electromagnetic Ballasts. They also operate Fluorescent lamps at a higher frequency thereby increasing efficiency and eliminating flicker.
Electronic Fluorescent Dimming Ballasts can dim T5 (including T5 high output lamps), T8 and T12 lamps to 1% of measured light (which equals 10% of perceived light). T4 triple and quad lamps, and Twin T5 lamps can be dimmed up to 5% of measured light (or 22% of perceived light) using Electronic Dimming Ballasts.
Fluorescent Heater-Cutout Ballasts
Heater Cut-out electromagnetic Ballasts in Rapid Start Lamps feature an electric circuit which cuts out the electricity supply to the electrode heaters (present in the cathodes) once the lamp switches on. This enables a lamp to consume less power (20%) and save energy.
There are various kinds of energy saving Ballasts in additions to the ones discussed. These Other Ballasts fall into two categories: 1. Ballasts that save energy by reducing power (wattage) consumed and reducing light output and 2. Ballasts that save energy by reducing power (wattage) loss in its operation. The latter is achieved through more efficient design.
Class P Ballasts come with automatic thermal protectors, which turn off power if the heat level increases beyond a certain point to avoid overheating. The limit of desired voltage is set by UL (Underwriters Laboratories).
The UL symbol on lamps indicates that Underwriters Laboratories has tested the sample unit of the concerned lamp and that it complies with the standard safety standards. The UL symbol can also appear on Ballasts and Transformers where it indicates that the product measures up to the set safety standards. When applied to a luminarie the UL symbol indicates that the lamp as a whole including its various parts (Ballasts etc) meet the required safety standards.