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单端加热管

电流的巨细直接与功率有关,也与电压、相别、功率因数(又称力率)等有关。通常有公式可核算。因为工厂常用的都是380/220V三相四线体系,因而能够依据功率的巨细直接算出电流。 在380三相时(功率因数0.8左右),电动机每KW的电流约为2A。行将“KW数加一倍”(乘2)就是电流A。这电流也称电动机的额定电流。 (例1)5.5KW电动机按“电力加倍”算得电流为11A。 (例2)40KW水泵电动机按“电力另倍”算得电流为80A。 电热是指用电阻加热的电阻炉等。三相380V的电热设备,每KW的电流为1.5A。行将“Kw数加一半”(乘1.5)就是电流A。 (例3)3KW电加热器按“电热加半”算得电流为4.5A。 (例4)15KW电加热炉按“电热加半”算得The electric heater power calculation, calculation of a premise  general electric heater in the following three steps design 1 maintain medium temperature yesterday the actual needs of the maintenance temperature power 2 calculated from the initial temperature of the heating in a specified period of time to set the temperature to the required power of 3 according to the above two results context selection heater type and quantity. The maximum value of total power take the above two kinds of power and the 1.2 coefficient. Medium kg\/h 2 initial heating power KW=C2M3 △ T\/864+P formula  1 to maintain the temperature of the medium in the pump need  M3 per hour increased the required power KW = (C1M1 △ T △ T + C2M2) / 864\/P + P\/2 type of  C1C2 were containers and medium heat Kcal\/Kg ℃ exergy M1M2 respectively. Containers and medium quality Kg exergy △ T is the initial temperature of the heating container to the desired temperature time h exergy P final temperature of heat quantity Kw exergy two, electric heating performance curve is below some frequently used to calculate the electric heating of the performance curves for the temperature and the initial temperature of the difference ℃ exergy H. Three, the electric heater design example of calculation by a open container context size width 500mm context 1200mm context 600mm for high context container weight 150Kg. Built-in water deep container 500mm height are all around 50mm insulation materials for silicate yesterday. Water for 3 hours from 15 ℃ heated to 70 ℃ yesterday and then from the container extraction for 20kg\/h at 70 ℃ water deep and add the same weight of water. In order to meet the need of power much desired temperature. Technical data by 1, the proportion of water by the 1000kg\/m3 2, the specific heat of water by 1kcal\/kg at 3 ℃, steel heat  0.12kcal\/kg at 4 ℃, water at 70 ℃ surface loss of 4000W\/m2 5, the insulation layer exergy loss at 70 ℃ 32W\/m2 6, 0.6m2 7, the area of the container by the insulation layer of the area by 2.52m2 the initial heating power required by the water in the container heated  C1M1 △ T = 1 × 0.5 x 1.2 x 0.5 x 1000 exergy x (70  15) = 16500 kcal vessel’s heated  C2M2 △ T = 0.12 * 150 * (70  15) = 990 kcal average water surface heat loss by 0.6m2 * 4000W\/m2 * 3H * 1\/2 * 864\/1000 = 3110.4 kcal average insulation heat loss by 2.52m2 * 32W\/m2 * 3H * 1\/2 * 864\/1000 = 104.5 kcal (considering the rich content 20%) initial heating needs of energy required for the power of  heating needs  “16500 + 990 + 3110.4 + 104.5 x 1.2 = 70258.8 kcal\/kg ℃ when the work of the supplementary heat water  20kg\/H × (70 × 1kcal\/kg ℃ yesterday 15) = 1100kcal water surface heat loss  0.6m2 * 4000W\/m2 * 1H * 864\/1000 = 2073.6 kcal insulation heat loss  2.52m2 * 32W\/m2 * 1H * 864\/1000 = 69.67 kcal  considering rich volume 20% Power heating energy for  at 1100 + 2073.6 + 69.6 x 1.2 = 6486.54 kcal\/kg ℃ heating for power energy heater selection needs power  6486.54 / 864 / 1 = 7.5 kW initial heating than when working with at least 27.1kw. The heater power ultimately selected for 35kw电流为22.5A。这口诀应不专指电热,关于白治灯为主的照明也适用。尽管照明的灯泡是单相而不是三相,但对照明供电的三相四线仍属三相。只需三相大体平衡也可这样核算。此外,以KVA为单位的电器(如变压器或整流器)和以KVar为单位的移相电容器(进步功率因数用)也都适用。既是说,这后半句尽管说的是电热,但包含一切KVA.KVar为单位的用电设备,以及以KW为单位的电热和照明设备。 (例5)12Kw的三相(平衡时)照明干线按“电热加半”算得电流为18A。 (例6)30KVA的整流器按“电热加半”算得电流为45A(指380V三相沟通侧)。 (例7)100KVar的移相电容器(380v三相)按“电热加半”算得电流为150A。 (例8)在380/220V三相四线体系中,单相设备的两条线,一条接相线 而另一条接零线的(如照明设备)为单相220V用电设备。这种设备的功率因数大多为1,因而,口诀便直接阐明“单相(每)KW4.5A”。核算时,只需“将千瓦数乘4.5”就是电流A。 同上面相同,它适用于一切以KVA为单位的单相220V用电设备,以及以KW为单位的电热及照明设备,并且也适用于220V的直流。 (例9)1000W投光灯按“单相千瓦、4.5安”算得电流为4.5A。关于电压更低的单相,口诀中没有说到。能够取220V为规范,看电压下降多少,电流就反过来增大多少。比方36V电压,比220V为规范来说,它下降到1/6,电流就应增大到6倍,即每KW的电流为6×4.5=27A。比方36V、60W的行灯每只电流为0.06×27=1.6A,5只便共有8A。当前电气照明也广泛选用荧光灯、高压水银荧光灯、金属卤化物灯等,因为它们的功率因数很低(约为0.5),因而不能同口诀①、②中的白织灯照明相同处置。这时,可把KW换算成KVA后,再按本口诀核算。也能够直接记住:它们每1Kw在三相380V时为3A;在单相220V时为9A。因而例5若为荧光灯照明,电流将为36A;例10中若为高压水银荧光灯照明,电流将为9A。 (例10)在380/220三相四线体系中,单相设备的两条线都接到相线上的,习惯上称为单相380V用电设备(实践是接在两相上)。 这种设备当以KW为单位时,功率大多为1,口诀也直接阐明:“单相380,电流两A半”。它包含以KVA为单位的380V单相设备。核算时,只需“将千瓦或千伏安数乘2.5”就是电流A

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