First, the electronic ballast fluorescent lamp electronic ballast was introduced in the early 1980s, first developed by the Dutch company Philips. Because it is more unique in electrical performance than traditional inductive ballasts. Therefore, electronic ballasts have a strong vitality. Inductive ballast electronic ballast low power factor (generally about 0.5) high (up to 0.7 or more, with correction circuit can reach 0.9 or more), large power loss (generally about 20% loss power) is small ( Power saving 15 - 20% or so) low voltage start performance is poor (less than 180v start difficulty) very good (150v can still start normally) stroboscopic effect 50Hz strobe can not be overcome, the line of sight is unfavorable because the working frequency is above 20KHz, Therefore, there is no flickering feeling. The audio noise has 50Hz hum, no volume, small weight, light weight (only inductive 2/10 weight), high frequency radiation, large price, cheaper, more expensive, more expensive manufacturing process. Fluorescent electronic ballasts have a variety of circuit designs. Today, with the rapid advancement of science, the design of fluorescent electronic ballasts is becoming integrated or modular, with the aim of simplifying the circuit structure. Electrical performance is more reliable, stable and safe. The following is a circuit diagram of an electronic ballast using a module and a small number of electronic components. The HD9712 module is mainly composed of rectification, current tracking and grading filtering. The power factor, the lamp current crest factor and the current harmonic content in the fluorescent electronic ballast are collectively referred to as three technical indicators. In the general fluorescent electronic ballast, it is difficult to achieve the three indicators while meeting the ministerial standards.
The electronic ballast of the HD9712 module can achieve these three indicators and meet the requirements of the H-level specified in the standard. When the power is turned on, the current is input to pins 1 and 2 of the HD9712 circuit via F1 and C1. After the HD9712 circuit rectification, current tracking and step-by-step filtering, the DC voltage of about 300V is output from the 3 pin as the working power of the ballast; the voltage is applied to the C3 and D2 sawtooth generators after being stepped down by R2. A sawtooth pulse is generated through C3 and D2 to trigger the oscillator circuit to start the oscillator. After the high-frequency voltage of the operating frequency of 25 30 KHz is sent to L4 and C4 for boosting, the gas in the fluorescent tube is ionized, and the lamp is lit. At the same time, a small amount of current through the C4 constitutes a loop to assist the heating of the filament to maintain stable illumination. R5 is used to soften the glow and extend the life of the lamp. R1 is an overvoltage protection resistor.
Figure 1 Electronic ballast type fluorescent lamp schematic
Second, the tungsten halogen lamp tungsten halogen lamp is a new type of light source successfully developed in the late 1980s. It has the characteristics of high luminous efficiency, small volume, light weight and long life. In order to make this new light source with small volume and high luminous efficiency effectively promoted and applied, the researchers put a small tungsten halogen bubble into a cold light cup made of quartz glass. Its shape is shown in Figure 2. This kind of light source combined with quartz glass cold cup and tungsten halogen bubble is called quartz cold light (commonly known as cold light source, or cold light). It has a luminescent light. The light is bundled, and the angle of the cold cup can be selected as needed, and has a range function. Ordinary incandescent lamps are incomparable. Therefore, such light spotlights are widely used in counters of store malls. The effect is illuminated and illuminated in the window. In recent years, due to the improvement of people's living standards, living conditions have continued to improve. Cold spotlights are also becoming more popular in the home. In order to make people live and work in peace and contentment, cold spotlights are also widely used in security products. Since the working voltage of the cold spotlight is ultra-low voltage, 6V, 12V, power 20W, 50W, it must be used after the transformer is stepped down in actual use. Generally, the 50W, 12V inductive transformer has a large volume and weight. Too heavy, not suitable for use in shopping malls. To this end, the scientific and technological personnel have successively introduced an electronic transformer, which features: small size, light weight, low cost and convenient use. Disadvantages are: electromagnetic interference (can increase the absorption loop to absorb its interference). The circuit diagram of the electronic transformer: (12*8cm) works in the same way as the electronic ballast, that is, the output voltage is isolated by the ferrite transformer and then dropped to 12V to the point of the cold light.
Figure 2 Electronic transformer electrical schematic
Third, high-pressure gas discharge lamp description: The content of this section does not belong to the scope of electronic energy-saving lamps. However, the high-pressure gas discharge lamp is a new type of electric light source, which is widely used. As a new scientific knowledge, this section gives a brief introduction for teachers' reference. High-pressure sodium lamps, metal halide lamps, xenon lamps, xenon lamps, etc. are all high-pressure gas discharge lamps. The high-pressure gas discharge lamp bulb draws two electrode rods and is filled with chemical elements of various components. After being energized and working normally, different colors of light are emitted. The working circuit is shown in Figure 3. Working principle: At the moment of turning on the power, the power supply voltage is applied to the trigger and the bulb through the ballast. When the bulb is not lit, the resistance is very large and it is open. The trigger starts working immediately under the power supply voltage (220V or 380V), and generates a pulse high voltage of 3KV or more, which is applied to both ends of the bulb L to activate the normal temperature element in the bulb L into a gas and penetrate, and L is in a low resistance and large current state. Therefore, the voltage across the bulb L drops, about 30 to 50V, and the trigger stops working because the voltage is too low. The entire process of starting the glow is about 0.8 seconds. As the temperature of the gas in the bulb L rises, the gas pressure can reach several atmospheres, the working current gradually drops to the normal working current range, and the lamp voltage gradually rises to the normal working voltage. Since the bulb L and the ballast are connected in series, the ballast limits the increase of the lamp current, the lamp voltage is always lower than the supply voltage, and is always lower than the turn-on voltage of the trigger to ensure that the bulb operates stably for a long time. From Qihui to fully enter the normal state of illumination, about 30 minutes.
Figure 3 Electrical schematic diagram of high pressure gas discharge lamp
Uses: High-pressure sodium has the highest light efficiency, economical and practical, the color of the light is sodium yellow, and the ability to wear fog is extremely strong, which is widely used in the lighting of road squares. Lamp power ranges from 55 to 400 watts. Color metal halide lamps have been developed, which are available in various colors such as red, green, blue and purple, and have been widely used for reflective lighting of buildings. The trigger voltage and power of the metal halide lamp are higher than that of the sodium lamp. Lamp power ranges from 100 to 1000 watts. Xenon lamp power is generally between 300 and 3500 watts, and the light color is white light. It is generally used for large-area lighting such as construction sites. The power supply voltage is 220V or 380V.
〠teaching objectives】
First, know the names and main uses of several common high-pressure gas discharge lamps;
Second, know the names and uses of two types of civil electronic energy-saving lamps;
Third, initially learned to assemble an electronic energy-saving lamp.
[teaching priorities and difficulties]
Key points: 1. The significance of using a new electric light source; 2. Learn how to use assembly drawings.
Difficulties: 1. The working principle of the new electric light source; 2. Read the assembly drawing.
[Teaching equipment] 1. 55-125W high-pressure sodium lamp teaching board; 2. Electronic energy-saving lamp assembly, one for each of the two finished lamps; 3. A set of electronic energy-saving lamp assemblies for the installation of slides.
〠Teaching Process Structure 】
First, the introduction of new lessons (Part 1) (1) Teachers can use self-made video, slides or display pictures to introduce the names and use values ​​of 3 to 4 new electric light sources to arouse students' enthusiasm for learning. (2) Demonstrate the triggering process of the high pressure sodium lamp. (3) Display two electronic energy-saving lamps. Note: (1) It is recommended to use a sodium bulb of about 100W. The demonstration time should not exceed 1 minute, otherwise the light will gradually become brighter and affect the students' vision. (2) It is also possible to directly replace the sodium lamp with a green metal halide lamp of the same power for demonstration. The same light bulb is triggered again after the bulb has cooled down. (3) The triggering process (working principle) of the high-pressure gas discharge lamp is not the key content of this chapter, but it is similar to the circuit and working principle of the ballast-type fluorescent lamp.
Second, a brief description of the energy-saving principle of energy-saving lamps: (1) Generally, while displaying two kinds of electronic energy-saving lamps, the incandescent lamps are illuminated by a comparative method, which merely illustrates one aspect of luminous efficiency. Because junior high school students have limited knowledge, don't spend a lot of time on power factor issues. (2) The working modes and energy-saving principles of the above three energy-saving lamps are different. They should not be confused or elaborated. For example, the electronic ballast type fluorescent lamp (fluorescent lamp) principle introduction: 220V mains is rectified into 300V DC, and then the switch circuit oscillates and boosts, converts into high frequency pulse voltage, can directly illuminate the fluorescent lamp tube. The advantages of electronic energy-saving lamps (also known as electronic fluorescent lamps) are quick start and no flicker. The switching circuit itself has low energy consumption, large output power, and high power factor. If equipped with high-efficiency lamps, the energy saving effect is better. The electronic energy-saving lamps have higher requirements on the devices, and the cost is (temporarily) higher. The power factor of most low-cost finished products is only 0.55, which needs to be further improved.
Third, the installation steps of electronic energy-saving lamps (Part 2)
1. According to the drawing, first connect the low-voltage end or the wire of one end of the lamp;
2. Connect the high voltage end or the power supply line end wire;
3. Strengthen the insulation of the power supply and lead the power cord.
4. Secure the plate and plastic case with self-tapping screws
5. Installation of lamps or bulbs (except cold light) Description: (1) When assembling students to assemble electronic ballast type fluorescent lamps (electronic fluorescent lamps) or electronic transformer halogen lamps (cold lights), according to the existing conditions Choose one of the sources of supply. (2) In order to facilitate student internship, the printed circuit board should be looser, the parts should be more thick, and the input and output ends of the printed circuit board should be clearly marked. (3) During assembly and commissioning, students must not directly touch 220 volts. Suppliers are required to provide high-frequency transformers (cold lights) with an insulation of 3000 volts or more and a withstand voltage of 3000 volts or more.
A. Operating process requirements:
(1) Select two different color wires as input lines and output lines to show the difference;
(2) Welding with a 20W internal heating soldering iron, the welding time per solder joint does not exceed 3 seconds;
(3) The solder joint is bright and has no solder joints and no burrs;
(4) Use a soft sheathed wire to make a 220 volt power cord;
(5) Phase line break switch.
B. Technical key:
(1) Suppliers must provide quality, problem-free, initially commissioned assemblies and ensure absolute interchangeability.
(2) Try to avoid or reduce the welding work. Students with a certain foundation are allowed to do a little welding work, but it is not suitable for large-scale promotion.
C. Typical errors and prevention methods:
(1) The wire selection power cable can be selected as a power cable with a double-core soft sheath wire. It is absolutely not possible to replace the lamp wire. The wiring of the cold light lamp holder should be made of high temperature wire and high temperature casing. In addition to the power supply lead, other wires may be hardwired BV 1×1/0.5 or cord RV 1×16/0.15.
(2) The use of welding flux is too much, or the soldering iron is burned for a long time, and the soldering iron will be burned to death. This is a common mistake made by beginners, which is the main cause of false welding. To avoid the occurrence of false welding, please refer to the description of the relevant contents of "Labor Technology and Electronic Technology".
(3) The connection between the wire and the wire is too short, which makes the assembly difficult; the incoming and outgoing lines are reversed. If the correction is not found in time, the consequences are serious after the power is turned on; the bare part of the wire is not wrapped with insulating tape, resulting in a short circuit accident. . Please refer to the first section of this chapter for related content.
(4) The fixed self-tapping screws are not tightened and the number is not in place.
[Learning Evaluation] 1. After the student's work is completed, according to the relevant content of the test manual P.11, self-evaluation and student mutual evaluation will be carried out, and the form will be filled out. 2. Any item that needs to be evaluated in the test manual will be recorded in the manual after the evaluation is given by the Greek teacher. 3. For the merits and demerits of the entire work, I hope that the teacher will also give a final assessment.
Figure 4 Electronic fluorescent lamp
Figure 5 Electronic energy-saving lamp appearance
Figure 6 Internal structure of the electronic energy-saving lamp
Figure 7 Cold light cup
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