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alculation method of carrying capacity of cable

Cable ampacity: refers to a cable line of current carrying capacity of the cable by the amount of current in the electric energy transmission, thermal conditions, when you reach the allowed continuous working temperature of cable conductor cable long-term allowable ampacity of current carrying capacity of the cable.

Estimating formula 2.5 times nine, walked to their reduction is a serial number on it. 35-by-3.5, both group five. Conditions have changed and discounted upgrade temperature 90 percent copper. Pipe number 234, 876 percent full flow. (1) the formulas for a variety of insulated wire (rubber and plastic coated wire) the ampacity (current) is not directly, but "cross multiply by multiples of certain" represented by mental arithmetic. Can be seen from table 5 3: multiple section increases. "2.5 multiplied by the JIU, minus one serial number to go on" said 2. 5mm' and the following section aluminum insulated wires, about section 9 times the number of times its carrying capacity. 2. 5mm' wire, ampacity is 2. 5X9=22. 5(A)。 Wire from 4mm' and above the carrying capacity and section several times along the line, line up, multiple successive reduction l, namely 4x8, 6x7, 10x6, and 16x5, and 25x4. "35-by-3.5, both groups minus point five", said 35mm "wire ampacity for section 3. 5 times, that is, 35x3. 5=122. 5(A)。 Wire from 50mm' and above, its carrying capacity and section number into multiples of relationships between two lines, as a group, multiple order minus 0. 5. 50, 70mm' section 3 times the number of times the carrying capacity of the wire for 95, 120mm "wire current carrying capacity is the number of area 2. 5 times, repeat. "The conditions change and conversion of high temperature of 90 percent copper upgrade." These mnemonics are aluminum insulated cable, laid in an ambient temperature of 25 ° c depending on the conditions of. If aluminum core insulation line Ming enough in environment temperature long-term above 25 ℃ of area, wire contains flow can by above formula calculation method is out, then again playing 90 percent can; Dang using of not aluminum line but copper core insulation line, it of contains flow to than with specifications aluminum line slightly big some, can by above formula method is out than aluminum line increased a line, of contains flow. 16mm' carrying capacity of copper wire, 25mm2 aluminium wire can be calculated. "Pipe number 234, 876 percent full flow. Means in pipe laying of two, three and four wire case, namely, electrical calculating carrying capacity of current carrying capacity (single installation), and 80%, and 60%. According to the current cable) related to the carrying capacity of the wire and wire cross section, and also wire materials, models, laying method and ambient temperature, and effects of many factors, calculation is more complicated. The carrying capacity of the wire can usually find from the manual. Formula coupled with some simple arithmetic, we can work out, don't look up table. 1. formula aluminum insulated wires carrying capacity and section five times under 10, second on the 100, 25, 35, four or three. 70, 95, twice and a half times. Pipe, temperature, BA, 90 percent. Bare wire and half. Copper upgrading work. Notes formulas on the carrying capacity of various sections of (an) is not directly, but by using the section must be expressed as a multiple of. The common conductor nominal section (mm) are as follows: 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185 ... ... First part of the formula (1) the formula in the first sentence that the aluminium core insulation line ampacity (Ann), which can be calculated by multiples of the section. Arab formula digital conductor cross section (mm), the Chinese said multiples. Section formulas and times line up is as follows: 1~10 16, 25, 35, 50, 70, 95 more than 120 〉〉〉〉〉 five times two times three times four times times times twice times times now and formula controls are more clear, pithy formulas "10 under five" refers to section 10 below carrying capacity is five times times the cross section values. "100 second" (read two hundred) refers to section carrying capacity of more than 100 of the section twice times the value. Sections 25 and 35 is the boundary four times and three times times. This is the mantra of "25, 35, and 43". Section 2.5 times times for 70, 95. Arranged as can be seen from the above: in addition to 10 following 100 and above, conductor cross section is in the middle of each multiples two specifications are the same. For example aluminum core insulation line, environment temperature for not is greater than 25 ℃ Shi of contains flow of calculation: Dang section for 6 square mm Shi, calculated contains flow for 30 Ann; Dang section for 150 square mm Shi, calculated contains flow for 300 Ann; Dang section for 70 square mm Shi, calculated contains flow for 175 Ann; from above of arranged also can see: multiples with section of increases and reduced, in multiples change of junction, errors slightly big some. Sections 25 and 35 are the boundary four times and three times, four times times the range of the genus 25, which according to the formula for 100, but according to the manual for 97; 35, on the contrary, according to the formula for 105, but look up table for 117. However, this has little impact on the use of. Of course, if the "xiongzhongyoushu" in choosing wire cross section, and does not let it be full of 25 to 100 a, 35 is slightly more than 105 will be more accurate. Likewise, the 2.5 mm square wire location in five times at the beginning, actually more than five times (maximum up to 20 above), but in order to reduce energy loss in the wire, usually not so much current, generally only in the Manual: 12. Second part of the formula (2) behind the three formulas is to handle his condition changes. "Wear tube, and temperature, eight or nine folding" is refers to: If wear tube laying (including slot Board, laying, and that wire added has protection sets layer, unknown dew of), calculation Hou, again playing 80 percent; if environment temperature over 25 ℃, calculation Hou again playing 90 percent, if both wear tube laying, temperature and over 25 ℃, is playing 80 percent Hou again playing 90 percent, or simple by once playing 70 percent calculation. On the ambient temperature, in accordance with the regulations refer to summer is the hottest month with an average maximum temperature of. In fact, changes in temperature are, under normal circumstances, it does not affect current is large. Therefore, only some warm room or hot areas when there are more than 25 ℃, considered compromised. Insulated wire under different conditions such as aluminum heart download flow calculations: when 10 mm square section tube, and the carrying capacity is 10x5x0.8 ═ 40 if high temperatures, the carrying capacity is 10x5x0.9 ═ 45; if a pipe and heat 10x5x0.7 ═ 35 ampere of current carrying capacity. Third part of the formula (3) for bare aluminum wire, ampacity, formula States that "bare and half" calculation, and then add in half. This refers to the same section of bare aluminum wire and aluminum insulated wires, carrying capacity can be increased by half. For example the calculation of carrying capacity of bare aluminum wire: when 16 mm square section, and the carrying capacity is 16x4x1.5 ═ 96 a, at higher temperatures, the carrying capacity is 16x4x1.5x0.9=86.4. Part four of the formula (4) copper conductor ampacity, formula States that "copper wiring upgrades," and is about to order copper wire cross section level, then press the appropriate wire condition. For example section of 35 mm square bare copper wire is 25 ℃ ambient temperature, load flow calculation for: upgrade to a 50 mm square bare aluminum wire 50x3x1.5=225. For cable, pithy formula did not introduce. Direct buried HV cables, generally can be directly applied to the formula in the first sentence of the relevant compensation. 35 mm square high pressure aluminum armored cable buried current carrying capacity for 35x3=105. Approximately 95x2.5 ≈ 95 mm square: 238. Zero line in three-phase four-wire cross section, usually selected for the phase wire cross section of 1/2. Of course shall be not less than the minimum allowed by the mechanical strength requirements section. In single phase circuits, because the zero line and the line through the same load current, so the zero line cross sections should be identical to the phase wire cross section.

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