Brief introduction and principle of high pressure mercury lamp

High pressure mercury lamp is a high pressure mercury vapor discharge lamp with fluorescent powder coated on the inner surface of the glass shell It has soft white light and simple structure Low cost, low maintenance cost, can directly replace ordinary incandescent lamp, with the characteristics of long light efficiency, long life, energy saving economy, suitable for industrial lighting, warehouse lighting, street lighting, floodlighting safety lighting, etc The high-pressure mercury lamp does not contain red in the light, and the object under its irradiation is blue, so it is only suitable for square and street lighting In addition to the high-pressure mercury lamp for general lighting, there are also reflection type lamps (HR) with reflective film on the shell, copying lamps suitable for 300-500nm diazo sensitive paper, black light lamps for advertising and display, sun lamps with red spot effect for medical use, mercury lamps for photosynthetic chemistry of nylon raw materials, coatings, UV hardening of ink polymerization drying, etc High pressure mercury lamp is composed of quartz arc tube, outer bulb shell (usually coated with phosphor), metal bracket, resistor and lamp cap Arc tube is the core element, filled with mercury and inert gas When discharging, the internal mercury vapor pressure is 2-15 atmospheres, so it is called high pressure mercury lamp High pressure mercury lamp, the application of advanced lamp manufacturing technology, so that the high pressure mercury lamp light efficiency is higher, longer life White light, color temperature 4100k or so, and economic, is widely used in indoor and outdoor industrial lighting, road lighting field Self ballasting high pressure mercury lamp is very convenient to use because it does not need external ballast Its light efficiency is twice that of incandescent lamp, and its service life is 10 times that of incandescent lamp It is also economical and widely used in indoor and outdoor industrial lighting, courtyard lighting, street lighting and other fields High voltage mercury lamp usually adopts inductance ballast with parallel compensation capacitor Another kind of self ballasting high pressure mercury lamp is convenient to use because a tungsten wire is installed in the outer bubble shell as a ballast The high pressure mercury lamp with composition structure refers to the arc lamp with mercury vapor pressure of 51-507kpa, main emission wavelength of 365.0nm and equivalent energy of 327.3kj/mol High pressure mercury lamp is a standard UV curing lamp, which has high heat and needs to be cooled by air or water, but has high power It is suitable for the UV curing coating and ink coating line with fast curing rate High pressure mercury lamp is a kind of electric light source with high efficiency and long life It consists of two parts: the fluorescent bulb and the discharge tube The discharge tube is thin and short It is only the size of a person's finger It is filled with high-pressure mercury vapor There is a cotton spherical fluorescent bubble shell outside the discharge tube After being electrified, the discharge tube produces strong visible light and ultraviolet light, which radiates on the fluorescent bubble shell and emits a lot of visible light When the high-pressure mercury lamp works, the current passes through the high-pressure mercury vapor, which ionizes and excites it, forming the collision among the electrons, atoms and ions in the discharge tube, and then the lamp emits light During the discharge, the resonance line (external spectrum) with the wavelength of 253.7nm was absorbed, and the intensity of the visible line increased The main radiation was the visible lines of 404.7nm, 435.8nm, 546.1nm and 577.0-579.0nm In addition, the strong long wave ultraviolet of 365.0nm was also radiated When the lamp works, the mercury gas discharge lamp with the partial pressure of mercury vapor in its light-emitting tube above 105Pa The outer glass shell is transparent and coated with fluorescent powder The latter is called fluorescent high-pressure mercury lamp The ballast in the working circuit is replaced by the filament resistance, which is connected in series with the light-emitting tube and installed in the outer glass shell together This kind of mixed light lamp (mercury lamp mixed with incandescent lamp) is convenient and has good light color, but its light efficiency and service life are greatly reduced The color temperature of ordinary 400W fluorescent high pressure mercury lamp is about 5000K, the general color rendering index is about 40, the light efficiency is 60lm / W, and the service life is 6000 hours The mercury vapor leakage of mercury lamp and the broken glass chips after the lamp tube is used and discarded contain a certain amount of mercury, the latter is called "Mercury slag", which will pollute the soil and water body and harm the crops, fruits and vegetables or animals and human body if not properly treated When the high pressure mercury lamp is ignited, the vapor pressure of mercury is 2-5 atmospheres, and the inner tube is made of quartz glass The ultraviolet spectrum radiated by high pressure mercury lamp is widened and blue-green, which can be used for photochemical reaction, lithography, UV detection and fluorescence analysis High pressure mercury lamp is a standard UV curing lamp, which has high heat and needs to be cooled by air or water, but has high power It is suitable for the UV curing coating and ink coating line with fast curing rate Typical structure of high pressure mercury lamp typical structure of high pressure mercury lamp The central part of the lamp is a discharge tube made of quartz glass The tube is filled with a certain amount of mercury and argon Tungsten is used as the main electrode and filled with alkaline earth metal oxide The electrode and quartz glass are sealed by molybdenum foil Generally, the auxiliary electrode is used for start-up, which is connected with the non adjacent electrode through a resistance of 40-60 K Ω In addition to the protection function, the shell can also prevent the influence of the environment on the lamp The inner surface of the shell is coated with fluorescent powder to become a fluorescent high-pressure mercury lamp The function of fluorescent powder is to supplement the insufficient red spectral line in high pressure mercury lamp and improve the light efficiency of lamp Yttrium vanadate (Yvo □: EU) phosphor activated by europium has been used Photoelectric characteristics and basic parameters when the lamp is applied with the power supply voltage, a glow discharge is generated between the main electrode and the auxiliary electrode, which transiently transfers to the main electrode to form an arc discharge, and the mercury vapor reaches a stable state a few minutes later After the lamp goes out, it must be cooled naturally It can only be started after the vapor pressure drops to a certain value The time is about 5-10 minutes When the power supply voltage changes, the change of lamp parameters the change of power supply voltage and lamp characteristics of high-pressure mercury lamp (lighting with inductive ballast) The luminous efficiency of high pressure mercury lamp increases with the increase of power per unit arc length The general color rendering index (RA) is 40-45, and the spectral distribution of high pressure mercury lamp is 12000 hours The luminous flux of the improved 400W fluorescent lamp is 23500lm, the color temperature is 2350k, the general color rendering index is 53, and the service life is 20000 hours Ordinary high pressure mercury lamp has negative resistance characteristic, so it must be connected with corresponding ballast In order to overcome this disadvantage, the external ballast can be replaced by the filament installed in the shell of the high-pressure mercury lamp and connected in series with the discharge tube The corresponding light source is called the self ballasted high-pressure mercury lamp This lamp improves the color rendering of ordinary high-pressure mercury lamp by using mixed light, makes up for the shortage of red light of ordinary high-pressure mercury lamp, and reduces the start-up time of temperature rise However, when the start-up time and temperature rise time are shortened, the filament life is also shortened accordingly, so the life of self ballasting high-pressure mercury lamp mainly depends on the filament life; because the ratio of discharge power with high luminous efficiency to filament power with low luminous efficiency is unfavorable, the total luminous efficiency of self ballasting high-pressure mercury lamp decreases from 35-50lm / W of external ballasting to 18-25lm / W Self ballasting high pressure mercury lamp is easy to use In the 1980s, the output of self ballasted high-pressure mercury lamp in China accounted for about 50% of the total output of high-pressure mercury lamp The working principle of the lamp is a high-pressure mercury lamp with a glass shell, which is usually started with the help of an auxiliary electrode The auxiliary electrode is connected with a non adjacent electrode through a resistance R of 40-60 kohm When the lamp is connected to the power grid, an AC voltage of 220 V is applied between the auxiliary electrode and the adjacent main electrode The distance between the two electrodes is very close, usually only 2-3 mm, so there is a strong electric field between them Under the action of this strong electric field, the gas between the two electrodes is broken down and glow discharge occurs The discharge current is limited by the resistance R If R is too small, the electrode will burn out The glow discharge between the main electrode and the adjacent auxiliary electrode produces a large number of electrons and ions These charged particles diffuse to the two main electrodes, which causes the discharge between the main electrodes and quickly transits to the arc discharge between the two main electrodes In the initial stage of lamp ignition, the discharge of mercury vapor and hydrogen gas at low pressure, at this time, the pressure drop of the tube is very low, about 25 V; the discharge current is very large, about 5-6 a, which is called the starting current The heat released during the low-voltage discharge increases the temperature of the tube wall, the mercury vaporizes gradually, the mercury vapor pressure and the lamp voltage increase gradually, the arc begins to contract, and the discharge gradually transits to the high-pressure discharge When all the mercury evaporates, the tube pressure begins to stabilize and enters into a stable high-pressure mercury vapor discharge High pressure mercury lamp needs a period of time from start to normal operation, usually 4-10 minutes After the high pressure mercury lamp goes out, it cannot be started immediately Because after the lamp goes out, there is still a high mercury vapor pressure inside It can only be ignited again after the lamp tube is cooled and the mercury vapor condenses The cooling process takes 5 to 10 minutes At high mercury vapor pressure, the reason why the lamp can't be re ignited is that the free path of the electron is very short at this time At the original voltage, the electron can't accumulate enough energy to ionize the gas High pressure mercury lamp has a high luminous efficiency, which is above 35-65 current / watt Besides high luminous efficiency, high pressure mercury lamp can also emit strong ultraviolet rays Therefore, it can not only be used for lighting, but also for sunbathing, health care, chemical synthesis, aging test of plastics and rubber, fluorescence analysis, flaw detection, etc High pressure mercury lamp is suitable for outdoor lighting because of its high light efficiency, small illuminant and high brightness But its light color is blue and green, and it lacks red component, so the object can't show the original color completely If the vapor pressure of mercury in the high pressure mercury lamp is greater than 10 atmospheric pressure, it will become an ultra-high pressure mercury lamp, and its luminous efficiency will increase accordingly High pressure mercury lamp has high luminous efficiency, but its brightness is not high enough In many cases, such as in various optical instruments and projection systems, a high brightness light source of up to 10-10 Xi Ti (CD / cm) is needed, such as ultra-high pressure mercury lamp.