A brief history of electric light

Lighting was historically one of the first uses of electricity. The mains voltages 110 and 220 Volts and the standardized mains frequencies 50 or 60 Hertz originate in

Bulb

The first light bulb was an incandescent lamp (Thomas Edison, 1879) that is still very recognizable more than 130 years later. Inside the glass bulb is a thin wire that conducts the current. That glows and begins to emit light. To prevent oxidation of the filament, the glass bulb is filled with an inert (chemically inactive) gas. In addition to light, the incandescent bulb produces a lot of heat (typically 95 percent); it is a highly valued but not an efficient light source.

• A light bulb is a pure Ohmic resistor. This means that the current through the lamp is in phase with the voltage across the lamp. Power (40, 60, 75 watts) is used as a prefix to differentiate between the lamps offered.
• The brightness of a lamp can be adjusted with a dimmer that controls the amplitude of the supply voltage. Adjustable transformers or resistors can be used for this purpose, but they are large, expensive and inefficient. Modern dimmers work electronically: they chop up the supply voltage, changing the shape of the voltage, and thus the power flowing through the lamp and also the amount of light.
• A side effect of dimmers is mains voltage distortion. This is because dimmers send non-sinusoidal currents through the power grid. Those interfering currents cause a voltage drop across each impedance connected in series with it, which leads to distortions of the mains voltage. Higher-order harmonics in particular can lead to a significant voltage drop because the inductive impedance increases with frequency, and thus so does the voltage drop across the impedance. The result of the distortions is that the mains voltage at the customer’s connection point no longer has the ideal sine wave form.

Halogen lamp

The halogen bulb is an improved version of the incandescent bulb. In an ordinary light bulb, the filament slowly evaporates and the metal vapor precipitates on the inner wall of the glass bulb. Eventually, the filament burns out and the bulb must be replaced.

In a halogen lamp, the glass envelope is filled with a halogen gas that binds to the metal vapor and deposits the metal particles back onto the filament. This self-repairing mechanism allows the temperature of filament to become higher than in an ordinary incandescent lamp. Because of this, a halogen lamp has a greater light output.

Fluorescent bar

Today, the fluorescent lamp is the most common light source. Within these, electrical discharges take place, releasing ultraviolet radiation due to the collisions of electrons with mercury ions. Fluorescent powder on the inside of the lamp converts ultraviolet radiation into visible light. Fluorescent bulbs give off less heat (than incandescent bulbs for the same amount of light) and they also last longer.

However, unlike an incandescent bulb, they cannot be connected to the mains voltage without fail. A ballast is needed (implemented as a coil in series with the lamp) to limit the flow of gas discharge through the lamp. In addition, a starter is required to create the gas discharge. Usually ballast and starter are installed in the luminaire of the lamp. Nowadays there is also the electronic ballast that both limits the current and generates a starting voltage. Fluorescent lamps have an inductive nature due to the ballast and the current is almost 90 degrees behind the supply voltage. In large office buildings, this results in a large reactive current (a current that is _+/- 90 degrees out of phase with the voltage) and significant “reactive” power. This is electrical power that due to the phase difference between current and voltage is not registered by the consumption meter. Therefore, in offices, fluorescent tubes are often compensated with capacitors, so that the capacitors provide the reactive power, not the electric utility.

Economy Lamp

Compact fluorescent or energy-saving lamps have a ballast integrated into the housing. Energy-saving bulbs today are designed to take up no more space than an incandescent bulb. As a result, they can easily be used in place of incandescent bulbs. One drawback then is that they cannot be dimmed.

LED

It is anticipated that eventually all lighting will be replaced with Led lighting. The main advantage of a light emitting diode (LED) is its low energy consumption, coupled with a long lifespan. Those properties contribute to the fact that LEDs, mostly in (colored) clusters, are increasingly preferred to incandescent and energy-saving light bulbs.