Light is the life of TV art. The safety and reliability of the dimming system is a powerful guarantee for using light to shape the objective world. The power of any professional dimming system is very large, a single light bulb is 5kW or even 10kW, and a performance can use thousands of light bulbs. From this, it can be seen that the total power consumption of a dimming system is staggering. Therefore, the efficiency and heat dissipation of the dimming system are very important, and it is the key to maintain the reliability of the dimming system for a long time.
The dimming equipment has gone through four generations: the first generation is a resistive dimmer. The second generation is a transformer-type dimming equipment. The third generation is an electromagnetic amplifier type dimming equipment. The fourth generation is a thyristor dimming device. 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 consumed by itself is considerable. Assuming it has an efficiency of 96% (which already seems like a pretty good number), when it wants to push a 6kW load, its own power consumption is already as follows:
6×（100%－96%）=0.24kW
Suppose a dimming cabinet has 60 loads of 6kW, then its total power consumption is as high as:
0.24×60＝14.4kW
Therefore, it is 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, thus reducing the operating costs. At present, the more advanced dimming system uses the latest solid-state switch and high efficiency.
Chokes, with an efficiency of more than 98%, reduce the great interference caused by a sharp rise in current due to non-100% dimming. (The SCR adjusts the voltage by changing the on-angle, and its on-time is only about 1μs, and this current waveform is actually a pulse with a steep front edge.) ）
However, even for a highly efficient dimming system, the performance and design of the cooling system are still important. Even with an efficiency of 98%, the above example still consumes up to 7.2kW of power consumption. In order to effectively discharge such a large power consumption out of 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 3 types of vertical cabinet cooling systems that are popular in the world: forced air supply, forced exhaust and intelligent exhaust.
(1) Forced air supply
This heat dissipation system is to install the blower at the bottom of the cabinet, so that fresh air enters from the bottom of the cabinet and then accelerates to blow upward, so as to take away the heat generated by the thyristor.
The advantage of this approach is that it is highly efficient, and a large number of tropics can be carried away with a small fan. Its disadvantage is that the cold air extracted from below is constantly heated by the power consumption of the thyristor on the way up, so the temperature of the thyristor at the top is much higher than that at the bottom, resulting in the reliability and life of the thyristor at the top.
(2) Forced convulsions
The system is designed to mount the exhaust fan on top of the cabinet. Fresh air enters from the front of each SCR through proper process design, and then the hot air is exhausted outside the cabinet by exhausting air.
Through precision design (fluid dynamics) and rigorous process control, this approach ensures that each thyristor has approximately the same air intake from top to bottom, so that each thyristor operates within an acceptable temperature range and ensures the reliability of each thyristor. However, this design also has the disadvantage, that is, the wind resistance is larger, and the power of the exhaust fan needs to be increased, so the noise is also larger.
(3) Intelligent ventilation
Since the dimming system is rarely fully loaded under normal operating conditions, the required exhaust air volume can be reduced comparatively. Intelligent exhaust is based on this theory, by detecting the temperature rise in the cabinet, and then determining the amount of exhaust air, in the general operating environment, the fan only needs to run at low speed, the noise is relatively reduced, but when the load increases, the fan will accelerate accordingly. In this way, the advantages of forced exhaust are retained, and the disadvantages of high noise are solved at the same time.
Finally, it is worth mentioning that although there is a high dimming efficiency and a good heat dissipation system, the dimming system is always a very powerful electrical system. It is impossible to completely avoid high temperatures and the occurrence of electric arc ignition. Only on the basis of high efficiency and good heat dissipation, supplemented by necessary anti-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.
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