- pressure sensitive resistance parameters and calculation Knowledge of electrical resistance

by:Thermistor-Mov     2020-06-22
Pressure sensitive resistance parameters and calculates the parameters of pressure sensitive is mainly introduced in this paper, in this paper, probably about 995 words, read the full article 10 minutes. Varistor generally used in parallel in the circuit, when the voltage at the ends of the resistance change and exceed the rating, resistance resistance decreases sharply, presents the short-circuit condition, the string in the circuit of current blown fuse, protection. Pressure sensitive resistance in the circuit, is often used to power over-voltage protection and voltage stability. Three parameters with pressure sensitive resistance tester, can detect pressure sensitive voltage, leakage current, linear coefficient. Under the condition of part-time jobs, when measuring, multimeter and 10 k file, pens and connected into the resistance on the multimeter should show the varistor marked on resistance, if deviate from this value is large, then varistor has been damaged. The parameters of the varistor pressure-sensitive voltage UN ( U1mA) Is: on the pressure sensitive resistance as well as by 1 ma when the direct current voltage to said it is a sign of conduction voltage, the voltage is called pressure-sensitive voltage UN. Pressure-sensitive voltage is also commonly used symbols U1mA said. Pressure-sensitive voltage error range is generally & plusmn; 10%. In test and actual use, usually the pressure-sensitive voltage from normal by 10% as the failure criterion of varistor. Maximum continuous working voltage UC: refers to the varistor can bear long-term maximum ac voltage ( RMS) Uac or maximum dc voltage Udc. General Uac≈ 0. 64 u1ma, Udc≈ 0. 83 u1ma maximum clamping voltage ( Limit voltage) VC: maximum clamping the varistor voltage value is refers to under regulation 8/20 of mu s shock current IX ( 一) The voltage on the varistor. Leakage current Il: to exert maximum dc voltage Udc varistor flow of electric current. When measuring the leakage current, usually adding Udc to varistor = 0. The voltage (83 u1ma Sometimes also with 0. 75U1mA) 。 General requirements Il&le static leakage current; 20μA( There is also a requirement & le; 10 mu A) 。 In practical use, the more care about is not the size of the static leakage current value itself, but its stability, namely after the impact test or the rate of change in high temperature conditions. Or after impact test at high temperature under the condition of its rate of no more than one times, that is the stable pressure sensitive voltage calculation: U1mA = KUac type: K related to power quality coefficient, generally take K = ( 2 ~ 3) Good city, the power supply quality is less desirable, poor quality of the rural power ( Especially the mountain) Desirable. Uac for ac power voltage RMS. For 220 v to 240 v ac power lightning protection device, should choose pressure-sensitive voltage of 470 v to 620 v varistor is more appropriate. Choose pressure-sensitive voltage higher pressure sensitive resistance, can reduce the failure rate, prolong service life, but the residual pressure is slightly increased. The calculation of nominal discharge current: varistor nominal discharge current should be more than requirement under the surge current or every year the wave surge current that may occur. Nominal discharge current should be pressure sensitive resistance surge in the number of life rating curve hit more than 10 times of numerical calculation, about 30% of the maximum impact on flow ( Is 0. 3IP) The left and right sides. Varistor parallel: when a varistor can't satisfy the request for the nominal discharge current, should be used in multiple pressure sensitive resistor in parallel. Sometimes in order to reduce the limit voltage, even if the nominal discharge current required also USES multiple pressure sensitive resistor in parallel. Pay special attention to the pressure sensitive resistance in parallel when using, must strictly selected parameters are consistent, For example: Δ U1mA & le; 3 v,Δα≤ 3) Match, for the evenness of current distribution. 文章/ ymdzdcsjjs。 HTML this paper label: an article on resistance pressure sensitive resistance: what are the next up: the parameters of the thermistor varistor selection and matters needing attention
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