卤钨灯（halogen lamp）详解

卤钨灯产生的背景
普通白炽灯灯丝上的钨原子蒸发出去后，沉积在玻璃泡壳上，时间一长，灯丝越来越细，泡壳越变越黑。1959年时，发明了碘钨灯，利用卤钨灯循环的原理消除了这一发黑的现象。

工作原理
卤钨灯是利用卤钨再生循环原理工作的。在一定的温度范围内，从灯丝上蒸发出的钨在灯壳内壁附近与卤素反应生成气态的卤化钨，再通过对流和扩散到达灯丝的 高温区，分解成钨和卤素，钨沉积在灯丝表面，而卤素则被扩散到温度较低的灯壳内壁附近再继续与蒸发的钨化合。这一过程称为卤钨再生循环。卤素与钨反应的基 本形式为：

式中W为钨原子，X2为卤素分子。钨和各种卤素充分生成无色气态的卤化钨的温度范围是不同的。碘钨 灯要求的灯壳温度为250～600℃；溴钨灯为200～1100℃;氯、氟钨灯灯壳温度范围更宽。但是，氯、氟会对灯内低温部分的灯丝、支架以及石英玻壳 产生较强的腐蚀，缩短灯泡寿命，故目前的卤钨灯多数是充填溴的化合物。　　
由于卤钨循环减少了钨的蒸发量，卤钨灯灯丝工作温度可达3000℃以上，发光效率根据用途可达17～33lm/W，光衰可低于5％。
卤钨灯与普通白炽灯相比，发光效率可提高到30%左右，高质量的卤钨灯寿命可以提高到普通白炽灯寿命的3倍左右。

结构 　
卤钨灯的主要部件是玻壳、灯丝和充填卤化物。根据卤钨循环原理，卤钨灯灯壳的温度在200～800℃时才能形成充分的卤钨再生循环。为此，玻壳须选用耐 高温的石英玻璃、高硅氧玻璃或低碱硬质玻璃，石英玻壳表面负载取20～40(W/cm2);灯的体积须缩小到同功率白炽灯的0.5～3％。也有几种规格的 卤钨灯使用硬质玻璃代替石英玻璃，其色温比石英玻璃的低100K。
　　卤钨灯的结构有双端管形、单端圆柱形和反射形3种形式（见图）。

双端管形卤钨灯的灯丝发光体呈线状。
单端圆柱形卤钨灯的灯丝发光体呈面光源或点光源。
反射形卤钨灯 带有金属或玻璃介质膜反光镜。介质膜反光镜是一种利用光学折射原理镀制成的多层宽带反射膜，能反射95％以上的可见光，透射80％的红外线和紫外线，相应 的反射形卤钨灯又可分为光束温度较低的聚光型和红外、紫外有害辐射少的定向照明型。

卤钨灯的光谱图

注：此图片不清晰，请点击图片放大浏览

类型 　

卤钨灯按用途可分为如下6类。

　　照明卤钨灯 有高压双端灯、低压单端灯和多平面冷反射低压定向照明灯3种。高压双端灯色温2900～3100K、发光效率17～22lm/W、工作电压 100～240V、功率300～2000W、寿命1500～2000h，水平燃点，广泛用于大面积泛光照明。低压单端灯电压6～110V、功率 5～300W、寿命1000～3500h、体积小、发光体小，配上相应的反光镜时光利用率高，是一种节能型室内照明光源。多平面冷反射低压定向照明灯的节 能效果和照明效果更为显著。主要有12V20W、12V50W、12V75W3种功率，相当于50～200W的普通PAR型灯(射灯)的照明效果，色温 3050K，寿命2000～3500h。低压定向照明灯又分为宽角泛光照明灯（照射角30°～40°）、窄角泛光照明灯(照射角15°～25°)和窄点照 明灯(照射角6°～14°)3种照射角的灯泡，均采用多平面介质膜反光镜，约80％的红外线透过反光镜而不被投射到被照物上，故光束温度低，被照面照度均 匀，定向性好，有利于商品保鲜、显色逼真和突出效果。改变介质膜反射光的带宽和波长，可以镀出红、黄、绿、蓝等彩色的定向照明灯。与低压定向照明灯配套发 展起来的一种小而轻的电子变压器，采用开关电路、高频工作(20～400kHz)原理，用高频磁芯代替笨重的铁芯。它可以单独配装在射灯灯具外，也可以与 卤钨灯制成采用普通E27螺口灯头的一体化定向照明灯，还可与普通PAR型灯互换，使用更加方便。多平面冷反射定向照明灯因节能效果显著，发展非常迅速， 已广泛用于商店、橱窗、展览厅、家庭室内等场所照明。
　　汽车卤钨灯 　汽车上已使用12～24V、8～60W单端卤钨灯，色温为3000～3100K，寿命200h。其中前灯采用H4型12V60W/55W的双灯丝灯泡， 近光灯丝精确装配在灯内的防眩钼制反光罩内，射程远、防眩效果好、定向性好；转弯灯、刹车灯等采用12V、8～25W的灯泡。
　　红外、紫外辐照 卤钨灯 色温2500K以下的卤钨灯有丰富的红外辐射，热效率高、体积小，广泛用于加热照干燥设备和复印机上。这类灯多数是双端管形。复印机灯泡的灯丝分段绕制， 保证热辐射均匀。色温高于3000K的卤钨灯有一定量的长波紫外辐射(约占总辐射量的 0.1％)，已开始用于牙科固化粉的固化工艺上。　
　　摄 影卤钨灯 　功率200～20000W、色温3200±50K、发光效率27～36lm/W、寿命15～300h，电压分为12～36V、110V和220V 3种。12～36V的摄影卤钨灯为低压单端圆柱形，功率200～400W；110V和220V的为双端管形，功率500～2000W，更大功率的，灯丝由 几段单螺旋丝排成均匀的发光面。摄影卤钨灯色温稳定、光衰小，已在舞台影视和新闻摄影照明中取代了普通钨丝白炽灯。
　　仪器卤钨灯 　功率2～400W、色温3000～3200K、电压3～36V、寿命50～200h。广泛用于现代显微镜、投影仪、幻灯以及医疗仪器等光学仪器上。
　 　冷反射仪器卤钨灯 　它是与椭球面介质膜反光镜经预聚焦组合成一体化的灯泡。功率50～250W、色温3200～3600K，光束温度低、光利用率高，反光镜最大直径 50cm，电压 8～110V。广泛用于轻便型电影机、幻灯机、医用和工业用内窥镜、牙科手术着色固化、彩色照片扩印仪等光学仪器上。

发展趋 势 　
卤钨灯是处于发展中的新一代白炽灯。其发展趋势：①继续发展节能型小功率产品，代替白炽灯全面进入室内照明。②研究氟、氯化合物充填剂以及防腐工艺，提 高发光效率和寿命，使氯、氟钨灯得以实用。③研究反射红外线透射可见光涂层的节能型卤钨灯。④逐步采用硬质玻璃灯壳。

附Wikipedia 的解释。

Halogen lamp

From Wikipedia, the free encyclopedia

A halogen lamp is an incandescent lamp where a tungsten filament is sealed into a compact transparent envelope filled with an inert gas, plus a small amount of halogen such as iodine or bromine. The halogen cycle prevents darkening of the bulb. The halogen lamp can operate its filament at a higher temperature than in a standard gas filled lamp of similar wattage without loss of operating life. This gives it a higher efficacy (10-30%). It also gives light of a higher color temperature compared to a non-halogen incandescent lamp. Alternatively, it may be designed to have perhaps twice the life with the same or slightly higher efficacy. Because of their smaller size, halogen lamps can advantageously be used with optical systems that are more efficient.

Principle of operation

---

The function of the halogen is to set up a reversible chemical reaction with the tungsten evaporating from the filament. In ordinary incandescent lamps, this tungsten is mostly deposited on the bulb. The halogen cycle keeps the bulb clean and the light output remains almost constant throughout life. At moderate temperatures the halogen reacts with the evaporating tungsten, the halide formed being moved around in the inert gas filling. At some time it will reach higher temperature regions, where it dissociates, releasing tungsten and freeing the halogen to repeat the process. In order for the reaction to operate, the overall bulb temperature must be higher than in conventional incandescent lamps. The bulb must be made of fused silica (quartz) or a high melting point glass (such as aluminosilicate). Quartz being very strong, the gas pressure can be higher, which reduces the rate of evaporation of the filament, permitting it to run a higher temperature (and so efficacy) for the same average life. The tungsten released in hotter regions does not generally redeposit where it came from, so the hotter parts of the filament eventually thin out and fail.

Regeneration of the filament is also possible with fluorine, but its chemical activity is so great that other parts of the lamp are attacked. .[1]^{[1] [2]}

The first commercial lamps used elemental iodine, were called Quartz Iodine Lamps,and were launched by GE in 1959. ^{[3] [4]} Quite soon bromine was found to have advantages, but was not used in elemental form. Certain hydrocarbon bromine compounds gave good results. ^{[5] [6]}. The first lamps used only tungsten for filament supports, but in some designs it has been possible to use molybdenum - an example being the molybdenum shield in the H4 twin filament headlight for the European Asymmetric Passing Beam.

High temperature filaments emit some energy in the UV region. Small amounts of other elements can be mixed into the quartz, so that the doped quartz (or selective optical coating) blocks harmful UV radiation. Hard glass blocks UV and has been used extensively for the bulbs of car headlights. ^[7] Alternatively, the halogen lamp can be mounted inside an outer bulb, similar to an ordinary incandescent lamp, which also reduces the risks from the high bulb temperature. Undoped quartz halogen lamps are used in some scientific, medical and dental instruments as a UV-B source.

For a fixed wattage and life, the efficacy of all incandescent lamps is greatest at a particular design voltage. Halogen lamps made for 12 to 24 Volt operation have good light outputs, and the very compact filaments are particularly beneficial for optical control (see picture). The range of MR16 (50 mm diameter) reflector lamps of 20W to 50W were originally conceived for the projection of 8 mm film, but are now widely used for display lighting and in the home. More recently, wider beam versions are available designed for direct use on supply voltages of 120 or 230V.

Effect of Voltage on Performance

---

Tungsten halogen lamps behave in a similar manner to other incandescent lamps when run on a different voltage. However the light output is reported as proportional to voltage to the power 3, and the efficacy proportional to the power 1.3 ^[8] The normal relationship regarding life is that it is proportional to voltage to the -14. For example, a bulb operated at 5% higher than its design voltage would produce about 15% more light, and the efficacy would be about 6.5% higher, but would be expected to have only half the rated life.

Halogen lamps are manufactured with enough halogen to match the rate of tungsten evaporation at their design voltage. Increasing the applied voltage increases the rate of evaporation, so at some point there may be insufficient halogen and the lamp goes black. Over-voltage operation is not generally recommended. With a reduced voltage the evaporation is lower and there may be too much halogen, which can lead to abnormal failure. At much lower voltages, the bulb temperature may be too low to support the halogen cycle, but by this time the evaporation rate is too low for the bulb to blacken significantly. There are many situations where halogen lamps are dimmed successfully. However, lamp life may not be extended as much as predicted. The life span on dimming depends on lamp construction, the halogen additive used and whether dimming is normally expected for this type.

Halogen Lamp Spectra

---

Safety

---

Halogen lamps get hotter than regular incandescent lamps because the heat is concentrated on a smaller envelope surface, and because the surface is closer to the filament. This high temperature is essential to their operation. Because the halogen lamp operates at very high temperatures, it can pose fire and burn hazards. Some safety codes now require halogen bulbs to be protected by a grid or grille, or by the glass and metal housing of the fixture to prevent ignition of draperies or flammable objects in contact with the lamp. Similarly, in some areas halogen bulbs over a certain power are banned from residential use.

Additionally, it is possible to get a sunburn from excess exposure to the UV emitted by an undoped quartz halogen lamp. To reduce unintentional UV exposure, and to contain hot bulb fragments in the event of explosive bulb failure, general-purpose lamps usually have a UV-absorbing glass filter over or around the bulb. Alternatively, lamp bulbs may be doped or coated to filter out the UV radiation. When this is done correctly, a halogen lamp with UV inhibitors will produce less UV than its standard incandescent counterpart.

Handling precautions

---

Any surface contamination, notably fingerprints, can damage the quartz envelope when it is heated. Contaminants will create a hot spot on the bulb surface when the bulb is turned on. This extreme, localized heat causes the quartz to change from its vitreous form. into a weaker, crystalline form. which leaks gas. This weakening may also cause the bulb to rapidly form. a bubble, thereby weakening the bulb and leading to its failure or explosion, and creating a serious safety hazard. Consequently, manufacturers recommend that quartz lamps should be handled without touching the clear quartz, either by using a clean paper towel or carefully holding the porcelain base. If the quartz is contaminated in any way, it must be thoroughly cleaned with rubbing alcohol and dried before use.

References

标签： 卤钨灯 halogen lamp