A Brief Analysis of the Efficiency and Heat Dissipation Issues of Professional Stage Lighting Dimming Systems

Light is the life of television art. The safety and reliability of the dimming system is a strong guarantee for using light to shape the objective world. Any professional dimming system has a very high power. A single bulb is 5kW or even 10kW, and a performance can use thousands of bulbs. It can be seen that the total power consumption of a dimming system is amazing. Therefore, the efficiency and heat dissipation of the dimming system are very important, which is the key to the dimming system to operate for a long time and maintain its reliability.

Dimming devices have gone through four generations: the first generation is the resistor type dimmer. The second generation is the transformer type dimmer. The third generation is the electromagnetic amplifier type dimmer. The fourth generation is the thyristor dimmer. The first generation has the lowest efficiency, and the fourth generation has the highest efficiency.

If the efficiency of the dimming system is not high, the power it consumes is considerable. Assuming its efficiency is 96% (which seems to be a very good number), when it is driving a 6kW load, its power consumption is already: 6×(100%-96%)=0.24kW. Assume that a dimming cabinet has 60 6kW loads. In this case, its total power consumption is as high as: 0.24×60=14.4kW. Therefore, it is very important to improve the efficiency of the dimming system. It not only reduces the temperature rise of the dimming cabinet (because the temperature rise is proportional to the power consumption), but also reduces the power consumption, thereby reducing the operating cost. At present, the most advanced dimming system adopts the latest solid-state switch and high efficiency.

The efficiency of the choke is as high as 98%, which reduces the great interference caused by the sharp rise of current due to non-100% dimming. (The thyristor adjusts the voltage by changing the conduction angle. Its conduction time is only about 1μs. This current waveform is actually a pulse with a very steep leading edge.)

However, even for a very efficient dimming system, the performance and design of the heat dissipation system are still very important. Even if the efficiency is 98%, taking the above example, its own power consumption is still as high as 7.2kW. In order to effectively discharge such a large power consumption outside the system and keep the internal components of the system working in a reasonable temperature environment, the reasonable design of the heat dissipation system cannot be ignored.

At present, there are three popular cabinet cooling systems in the world: forced air supply, forced exhaust and intelligent exhaust.

(1) Forced air supply

This cooling system installs the fan at the bottom of the cabinet, so that fresh air enters from the bottom of the cabinet and blows upward at an accelerated speed, thereby taking away the heat generated by the thyristor. The advantage of this method is that it is highly efficient, and a large amount of heat can be removed with a small fan. Its disadvantage is that the cold air drawn in from below is constantly heated by the power consumption of the thyristors on the way up, so the temperature of the thyristors at the top is much higher than that at the bottom, which reduces the reliability and life of the thyristors at the top.

(2) Forced ventilation

The design of this system is to install the exhaust fan on the top of the cabinet. Through appropriate process design, fresh air enters from the front of each thyristor, and then exhausts the hot air out of the cabinet through exhaust. This method, through precise design (fluid dynamics) and rigorous process control, can ensure that the air intake of each thyristor from top to bottom is roughly the same, so that each thyristor can operate within an acceptable temperature range, ensuring the reliability of each thyristor. However, this design also has disadvantages, that is, the wind resistance is large, the power of the exhaust fan needs to be increased, and the noise is also large.

(3) Intelligent ventilation

Under normal operating conditions, the dimming system is rarely fully loaded, so the required exhaust volume can be relatively reduced. Intelligent ventilation is based on this theory. It detects the temperature rise in the cabinet and then determines the ventilation volume. Under normal operating conditions, the fan only needs to run at a low speed, and the noise is relatively reduced. However, when the load increases, the fan will speed up accordingly. In this way, the advantages of forced ventilation are retained, and the disadvantages of high noise are solved at the same time.

Finally, it is worth mentioning that although it has high dimming efficiency and a good heat dissipation system, the dimming system is still an extremely powerful electrical system. It is impossible to completely avoid high temperature and arc sparking. Only on the basis of high efficiency and good heat dissipation, supplemented by necessary high temperature and fire prevention measures (such as the use of high temperature flame retardant wire), can the safe use of the entire dimming system be guaranteed.

I hope this article can give you a better understanding of the efficiency and heat dissipation issues of professional stage lighting dimming systems.