light is the life of television art. the safety and reliability of the dimming system is a powerful guarantee for using the light to shape the objective world. for any professional dimming system, its power is very large. a single bulb is 5kw or even 10kw, and a show can use thousands of bulbs. this shows that the total power consumption of a dimming system is staggering. therefore, the efficiency and heat dissipation of the dimming system are very important. it is the key to the long-term operation of the dimming system to maintain its reliability.
the dimming device has gone through four generations: the first generation is a resistance dimmer. the second generation is a transformer-type dimming device. the third generation is an electromagnetic amplifier type dimming device. 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 its efficiency is 96% (it looks like already a pretty good number), when it wants to push a 6kw load, its power consumption is already:
assume also that a dimming cabinet has 60 6kw loads, and its total power consumption is as high as:
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 and power consumption are proportional), but also reduces the power consumption, thereby reducing operating costs. at present, the more advanced dimming systems use the latest solid-state switches and high efficiency.
the choke coil has an efficiency of more than 98%, which reduces the great interference caused by the non-100% dimming which causes the current to rise sharply. (the scr regulates the voltage by changing the conduction angle. its on-time is only about 1μs. this current waveform is actually a very steep pulse.)
however, even a very efficient dimming system, the performance and design of the cooling system is still very important. even with 98% efficiency, taking the above as an example, its own power consumption is still as high as 7.2kw. to effectively dispose such large power consumption outside the system and keep the internal components of the system working under a reasonable temperature environment, the rational design of the heat dissipation system cannot be ignored.
at present, there are three types of cabinet cooling systems that are popular in the world: forced air supply, forced air extraction, and smart air exhaust.
(1) forced air supply
the cooling system is to install the blower at the bottom of the cabinet, so that fresh air enters the bottom of the cabinet and then blows up to accelerate, so as to take away the heat generated by the scr.
the benefits of this approach are high efficiency, and a small wind turbine can take a lot of tropical walks. its disadvantage is that the cold air drawn from below is continuously heated by the power consumption of the thyristor during the upward flow, so the thyristor temperature at the top is much higher than that at the bottom, resulting in a scr at the top. the reliability and life expectancy have declined.
(2) forced ventilation
the design of this system is to install the exhaust fan on the top of the cabinet. with proper process design, fresh air enters from the front of each thyristor, and then the hot air is discharged through the exhaust air outside the cabinet.
this method, through precise design (hydrodynamics) and rigorous process control, allows each thyristor's air intake from the top to the bottom to be approximately the same, so that each thyristor is acceptable operating within the temperature range ensures the reliability of each thyristor. however, this design also has the disadvantage that the wind resistance is large and the power of the exhaust fan needs to be increased, so that the noise is also large.
(3) smart ventilation
due to the general operating conditions, the dimming system is rarely fully loaded, so that the required amount of ventilation can be relatively reduced. smart exhaust is based on this theory, by detecting the temperature rise in the cabinet, and then determine the amount of ventilation, in the general operating environment, the fan needs to run at low speed, the noise is relatively reduced, but when the load increases, the fan will accelerate accordingly. in this way, it not only retains the advantages of forced ventilation but also solves the disadvantage of high noise.
finally, it is worth mentioning that although there is a high dimming efficiency and a good cooling system, the dimming system is always a very powerful electrical system. it is impossible to completely avoid phenomena such as high temperatures and arc flashes. only on the basis of high efficiency and good heat dissipation, and then supplemented with necessary anti-high temperature and fire prevention measures (such as the use of high-temperature flame-retardant cable) can ensure the safe use of the entire dimming system.