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Zhujiang cable takes you to know the five major wire and cable testing projects in one article

wires and cables need to pass heavy tests before they are sent to the market for sale. These tests are the guarantee for our consumers to use products at ease. Therefore, a correct understanding of these tests is also more conducive to our consumers to identify products with better quality, Next, Zhujiang cable will introduce in detail the five inspection items that must be passed before leaving the factory. Take the selection of hard dashboard as an example. What tests must high-quality wires and cables undergo ~


the relevant national standards clearly stipulate that the DC resistance of cables must be based on the conductor resistance per kilometer, The measured DC resistance data of wires and cables must be converted into the DC resistance value per kilometer at a temperature of 20 ℃. After converting the measured DC resistance value into the DC resistance value under the condition of 20 ℃, if the value is less than the specified standard value, then the wire and cable sample is a qualified product, otherwise it is a unqualified product. At present, relevant domestic departments usually use bridge method and current method to measure the DC resistance of wires and cables. The measurement range of the bridge method is relatively narrow, which can be divided into single arm bridge method and double arm bridge method. When the resistance value of wires and cables is about 1 or more, the single arm bridge method is used; When the resistance value of wires and cables is less than 1, the double arm bridge method is used

current method is also called micro ohmmeter method. Its principle is to output different constant currents with constant current source according to the resistance value of wires and cables, and then accurately measure the voltage at both ends of the measured wires and cables. The measured data can be calculated according to Ohm's law to obtain the DC resistance of the measured wires and cables. The current method can output different currents, so its measurement range is relatively wide

II. Insulation resistance detection

the measured insulation resistance value of wires and cables must be converted into the insulation resistance value per kilometer. Unlike DC resistance, the insulation resistance value is inversely proportional to the length of wires and cables; There are four kinds of measuring voltages for insulation resistance detection of low-voltage wires and cables: 100V, 250V, 500V and 1000V, of which 100V and 500V detection voltages are widely used in quality inspection departments; The length of the measured wires and cables is not clearly specified, but for the convenience of measurement and calculation, 10m is generally taken for measurement. The charging time before measurement is generally 1 minute

the insulation resistance of wires and cables is generally measured by voltage and current method, also known as megger method. Some wires and cables have a metal protective sleeve, which has a certain shielding function. For this kind of wires and cables, the insulation resistance measurement mostly measures the insulation resistance between the conductor and the metal sleeve, shielding layer or armor layer; For wires and cables without metal sheath, when measuring the insulation resistance value, the measured wires and cables must be immersed in water first, and then the insulation resistance between the conductor and water shall be measured, and the tested samples must be matched with the water temperature during the detection

III. power frequency withstand voltage detection

AC voltage is generally used for power frequency withstand voltage detection. The national standard stipulates that the AC voltage used is an approximate sine wave with a frequency between 49hz and 61hz; For products with rated voltage of 450/750v of wires and cables, let the technicians lead us to have a detailed understanding!, 1500V high voltage is adopted when the insulation thickness is ≤ 0.6mm; When the insulation thickness is ≥ 0.6mm, use 2000V high voltage and pressurize for 5 minutes. If the tested wire and cable samples do not have breakdown or flashover, they are qualified products, otherwise they are unqualified. After testing, kyjv XLPE insulated cable of Zhujiang cable can withstand 3000V power frequency AC for 5 minutes without breakdown

IV. mechanical property test

mechanical property mainly refers to the tensile strength of wires and cables before and after aging. Relevant national standards stipulate that: use the forced ventilation aging box to prepare the aged wire and cable samples, and the sampling should be as close to the non aged part as possible during the test. The mechanical properties are generally measured directly by electronic tension measuring instruments. First, use the thickness gauge to accurately measure the width and thickness of the middle part of the measured wire and cable, then put the sample in the blast drying oven for artificial aging, and then use the electronic tensile machine to measure, record the elongation distance and the maximum tensile stress when the wire and cable are stretched and broken, and use the obtained data to calculate the tensile strength and elongation at break of the measured wire and cable before and after aging, It can be judged whether the product is qualified by comparing it with the product standard

v. other testing items and methods

in addition to the above main testing items, there are also insulation thickness testing, size and mark testing, sheath thickness testing and other items, which can generally be checked by some relatively simple measuring instruments or manual inspection. Insulation thickness refers to the thickness after removing all protective layers on the insulation layer. Advanced aluminum lithium alloy components with projectors and reading microscopes have accounted for 20% of the total aircraft materials; Boeing 787 and eh101 multi-purpose helicopters also adopt a large number of aluminum lithium alloy measurements. After taking the average value of the measured data and comparing it with the provisions of the product standard, the measured average value must be greater than the specified value to be a qualified product. The overall dimension can be measured by projector or wrapping tape. The ovality measurement method is to measure the outer diameter of any two points on the same cross section of the circular sheathed cable, take the difference, and then use the difference to specify that the ratio of the average outer diameter to the cable standard should not exceed 15%. The unqualified rate of the marks of wires and cables with elastic modulus in China is very high. The national standard stipulates that the marks of wires and cables must have continuity and abrasion resistance, and have high clarity. Among them, the abrasion resistance needs to be gently wiped back and forth with medical absorbent cotton dipped in alcohol for 10 times, and the clear printing is qualified

Zhujiang cable brand products pursue high quality and high quality. In order to ensure the quality of each wire and cable delivered to consumers, Zhujiang cable also introduces advanced testing equipment to protect the product quality, and strictly controls the quality system. Therefore, it has also passed the ISO9001:2008 international standard certification, which is the guarantee for consumers to buy at ease

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