Electric devices of Power supply and Lighting Control
By Michael Lvov

Pressing the button of the lightning switch we rarely think about how effectively is the luminarier used. That is not surprising, as requirements to the domestic lightning are relatively low. However twinkling of the luminescent lamp and buzzing of the electromagnetic starting regulator, in other words throttle, usually start to annoy. And the increase in tiredness also reminds about itself. But this is the beginning. The decrease in vision can become the result of the poor lightning. But if in life you can put up with the disadvantages in lightning somehow, then in TV production they are absolutely impossible. Besides when conducting television shooting usually appears the problem of controlling the luminariers, mainly remote from the lighter (hanging under the ceiling of the studio, set on the shooting area, etc. That is why for the improvement of the quality parameters of the luminariers and for their control different electric facilities were developed, that remove mentioned and many other disadvantages.

In general these electric facilities can be divided in the following:

• ballasts are the systems assigned for the power supply of different types of the lamps, main fluorescent lighting;
• dimmers are the devices that by the changing of voltage provided in the lamp power the;
• controllers and remote-control stations are the devices of hand or automatical control of the complex that consists of the luminariers, dimmers, etc.

Ballasts

Lighting device with adjustable ballast

The electronic ballast is device that provides the effective starting of the lamp and guarantees the stability of its operation. When using traditional electromagnetic starting regulators, first of all, instability of the network voltage influences the lamp operation. The voltage fluctuation provokes the changes of the light flow created by the lamp and the network frequency of 50 Hz is caused by the twinkling. Besides, electromagnetic starting regulators are not capable of providing fast starting of the lamp and are also characterized by high noise while operation. The low frequency noise (frequency of 50 Hz) is provoked by the mechanic fluctuations of the plates from which the magnetic starting system consists of. It is doubtful that we should mention that noise is accompanied with power losses what decreases the output of the whole system. One more advantage of ballasts is the wide range of input voltage. Usually the bottom line of the working capacity of these facilities is 90 V and upper is 240 V. Electromagnetic facilities usually stop operating when the power voltage falls lower than 190 V. One of the most important parameters that defines not only the light flow but also the service life of the lamp is its current. The electric ballasts provide the stability of the current strength of lamp's power supply. That is especially critical at its starting moment as the currents on the starting conditions are much higher than the nominal value and that can lead to the falling out of the lamp (damage of electrodes, and sometimes of quartz envelope). The frequency of voltage provided on the lamp is also very important. Usually it is about 40...50 kHz what allows excluding the twinkling effect when the fluorescence of the luminescent lamp. As the electromagnetic element (throttle) is excluded from the scheme of the electric ballast that allows to get rid from the noise and to increase the output as the losses on the vortical current and warming of display had disappeared. It is also important that with the help of the ballast turning on the lamp passes almost instantly and without the usual twinkling.

Waveforms of balast consumption voltage and current (red - voltage, blue - current)

Later due to the scheme of the automatical current stabilization the equal fluorescence without stroboscopic effects and independent from the fluctuation of the network voltage is provided. The power coefficient of ballasts also approaches one, what can be explained by the consumption of the harmonic current with zero phase shift. As statistics show the general decline of the luminariers power consumption when using the electron ballast can achieve 20%, service life of the source of light (lamps) increases for almost 50%. This economy absolutely recovers the relatively high cost of the ballasts. Except for the high quality figures electric ballasts significantly increase the level of security of luminariers using as it provides the protection from the short circuit and overheating, suppression of the radio-frequency interference, shutting down of the broken light sources, fluent automatic reset of the lamp. One more important advantage of ballasts is that they not only allow reaching the stability of the lightning parameters, but also provide an opportunity of luminariers control.

Ballast with discreet adjustable power

To finish with the ballasts it is necessary to mention that these facilities are very popular and are produced by such well known companies Osram, Philips, General Electric, etc. During the last years the Russian producers also start to master in the production of electron starting regulators.

Dimmers

Dimmers are the devices of lighting control. With their help the change of light flow created by a lamp of any kind is done.

The rheostat and autotransformer can be called the simplest dimmers.

The rheostat allows fluently changing the voltage of the lamp power, however its main disadvantage is high level of losses on the heating as when turning on in series with the lamp the same current passes through the rheostat as through the lamp. That leads to the high losses accompanied with allocation of big amount of heat. The bigger the power of the load connected to the rheostat is the higher the losses on the rheostat are.

Autotransformer is different by the much bigger output however it has its own disadvantages. First of all it is its unhanding and big weight. The bigger the power of the load is the more massive the magnetic system of the transformer should be. And in case of using the autotransformer there is a big part of losses on the vortical currents, dispersion, and heat. Also the low frequency noise while operating with the autotransformer is not an exception.

Multichannel dimmer

The electronic lighting controllers, in other words dimmers are free from all these disadvantages. Usually they are the thyristor devices with different types of control over the key elements. It is not a secret that the value of acting voltage on the outlet of the device with thyristor regulation can be changed by the delay of the thyristor opening moment (square that is limited by the voltage curve is its acting value). So by changing the time delay of signal provision on the controlling thyristor electrode provide regulations of power given to load and so of the light flow.

Dimmers differ in the channel quantity (this number can be more than 100 for big stage light systems), power (current) of each channel, control type (hand, analogous, digital) and also by other less important parameters.

Dimmers with hand control are equipped with the usual slide faders by moving of which operator can control the time of opening of dimmer's control element by changing the power given to load. During the analogous control on the entry of each of the channels the controlling continuos voltage is given, and by varying it the changes of the parameters of luminarier can be reached. Usually the control voltage can vary in the range of 0...10 V what allows regulating the output voltage of dimmer channels from zero to the maximum bearable. So the light current of the connected luminarier also changes from zero to maximum. When the digital control the dimmer is equipped with the port by which the control digital signal passes provoking the voltage changes on the output.

The most often facilities with the DMX512 (modified RS-434) port, which is on of the most spread control standard in that field.

It is obvious that almost all of the models of contemporary dimmers have the protection against overloading and short circuit. Some of them have some service functions, for example, memory, opportunity of programming, etc.

Controllers and control panels

Controllers and control panels of luminariers are functionally analogous to the control facilities of any other systems. They generate the signal, which is then given on the control facility, for example, to the dimmer. Depending on the type of dimmer (analogous or digital) the corresponding control panels and controllers are used.

Equipson Scan812 console

Lately more and more often the PC with corresponding software connected to the control systems by the defined interface are used as the controllers. Besides there are some contemporary control panels of light that include all functions: can have up to 250 dimmer channels, big amount of control channels of other luminariers (scrollers, scanners, etc.), provide the big amount of memory cells to operator, have few build-in ports of different assignment, different entries/outlets, etc.

The choice of this or that electron equipment for the power and control of luminariers depends on the assortment of the latter as well from the concrete tasks.

next >>