Pressure sensitive resistance selection guide features - Knowledge of electrical resistance

by:Thermistor-Mov     2020-06-22
Pressure sensitive resistance selection guide features what is a varistor is mainly introduced in this paper, the main features, main parameters, the selection of guide, this article about 1030 words, read the full article 10 minutes. The so-called varistor ( English MOV) , it is a kind of nonlinear volt-ampere characteristic pressure limiting protection device. On market at present, the application in the low voltage electrical surge protection pressure sensitive resistance of zinc oxide as the main material, mixed with a variety of metal oxide, made of typical electronic ceramics, polycrystalline semiconductor ceramic circuit protection device. MOV has symmetrical volt-ampere characteristic curve, in practice, varistor generally parallel in the circuit, when the normal operation of the circuit, in the high impedance state, don't affect the work of circuit, when the abnormal voltage circuit and achieve MOV turn-on voltage, MOV quickly changed from state of high resistance to low resistance state, release the abnormal voltage caused by instantaneous over-current, at the same time the abnormal transient overvoltage rein in the range of a safe level, to protect against the destruction of the abnormal voltage level after circuit. Varistor main features 1, pressure sensitive resistance advantages of various surge absorbing ability: standard and high surge, surge, the physical size of the varistor determine its surge absorbing ability; Wide range of variable resistance voltage 18 v - 1800 v, its precision is usually around 10%, can meet the application requirements of low pressure to high pressure; Monomer through flow rate can be up to several hundred amperes to a few thousand amperes response speed ns level, slower than TVS diode, faster than the gas discharge tube; Size diversity, a variety of forms: lead straight, curved, and other special wire type. 2, pressure sensitive resistance faults parasitic capacitance is large, in the high frequency signal system will cause the high frequency signal transmission distortion; An aging model components in high-power power supply port protection, often with the gas discharge tube in series, slow down aging, prolong service life; The pros and cons of varistor itself characteristics, determines its application environment, general is mainly used in AC input terminal of lightning protection. Varistor varistor phyletic and various main parameters, type diversity, so, when faced with a wide variety of MOV, how should choose? Pressure sensitive resistance selection, circuit protection device has been one of the topics. Before the varistor type selection, main parameters is necessary to understand the MOV. Pressure-sensitive voltage V1ma: pressure sensitive resistance by 1 ma current, the voltage at the ends of the pressure sensitive resistance; Leakage current Ir: pressure sensitive resistance of leakage current is measured under 83% of pressure-sensitive voltage through the pressure sensitive resistance of current; Specified Vac: temperature is continuous sinusoidal ac RMS on opposite sides of the varistor. Vdc: under the specified temperature can impose continuously in dc voltage at the ends of the varistor. Ip: a shock waveform current peak; Vc: clamping voltage; Itm: applying pulse waveform of rating, single is a destructive test. Varistor selection guide 1, pressure-sensitive voltage selection, to consider the power supply voltage fluctuation, MOV voltage precision, MOV aging coefficient of factors such as; Should be less than 2, MOV clamping voltage level after protection circuit can afford the transient voltage security; 3, in the communication circuit or circuit, low power consumption should pay special attention to MOV junction capacitance and leakage current, can not affect normal operation; 4, MOV is aging model components in applications, consider using the environment, impact test standard and method, specific reference varistor derating curve; 5, packaging form, the size is proportional to the flux flow, large size, large flow, the greater the resistance to impact current, the protection of circuit more reliable; The vice. 文章/ ymdzxxzntx。 HTML this paper label: an article on resistance pressure sensitive resistance: varistor next application effect of main parameters: the main characteristics of thermistor definition
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