WEIDMUELLER electrical components Germany WEIDMUELLER model WEIDMUELLER price

WEIDMUELLER electrical component is a resistive device with nonlinear voltage-current characteristics, mainly used for voltage clamping when the circuit is subjected to overvoltage, absorbing excess current to protect sensitive devices. The resistor body material of the varistor is semiconductor, so it is a type of semiconductor resistor. The currently widely used "zinc oxide" varistor has a main body composed of divalent element zinc and hexavalent element oxygen. Therefore, from a material perspective, the zinc oxide varistor is a "II-VI group oxide semiconductor". In Taiwan, China, varistors are called "surge absorbers", sometimes also referred to as "electric shock (surge) suppressors (absorbers)". A varistor is a voltage-limiting protection device. Utilizing the nonlinear characteristics of the varistor, when overvoltage appears between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, thereby achieving protection for the downstream circuit. The main parameters of a varistor include: varistor voltage, current handling capacity, junction capacitance, response time, etc. The response time of a varistor is in the ns range, faster than gas discharge tubes, but slightly slower than TVS tubes. Generally, its response speed can meet the requirements for overvoltage protection in electronic circuits. The junction capacitance of a varistor is generally in the order of hundreds to thousands of Pf, making it unsuitable for direct application in the protection of high-frequency signal lines in many cases. When applied in AC circuit protection, its larger junction capacitance will increase leakage current, which needs to be fully considered in the design of protection circuits. The current handling capacity of a varistor is relatively large, but smaller than that of gas discharge tubes. Varistors are abbreviated as VDR, which are voltage-sensitive nonlinear overvoltage protection semiconductor components.

WEIDMUELLER electrical component classification

Thyristors have various classification methods: (1) Classification by turn-off, conduction, and control methods: Thyristors can be divided into conventional thyristors, bidirectional thyristors, reverse-conducting thyristors, gate turn-off thyristors, BTG thyristors, temperature-controlled thyristors, and light-controlled thyristors, among others, based on their turn-off, conduction, and control methods. (2) Classification by pins and polarity: Thyristors can be divided into two-pin thyristors, three-pin thyristors, and four-pin thyristors based on their pins and polarity. (3) Classification by package type: Thyristors can be divided into three types based on their package type: metal-packaged thyristors, plastic-packaged thyristors, and ceramic-packaged thyristors. Among them, metal-packaged thyristors are further divided into bolt-type, flat-type, round-case type, etc.; plastic-packaged thyristors are divided into two types: with heat sink and without heat sink. (4) Classification by current capacity: Thyristors can be divided into three types based on current capacity: high-power thyristors, medium-power thyristors, and low-power thyristors. Usually, high-power thyristors mostly adopt metal case packaging, while medium and low-power thyristors mostly adopt plastic or ceramic packaging. (5) Classification by turn-off speed: Thyristors can be divided into conventional thyristors and high-frequency (fast) thyristors based on their turn-off speed. (6) Zero-crossing triggering - generally for power regulation, i.e., triggering occurs when the phase of the sinusoidal AC voltage crosses zero; triggering must occur at the zero-crossing point to conduct the thyristor. (7) Non-zero-crossing triggering - the thyristor can be triggered to conduct regardless of the phase of the AC voltage; common method is phase-shift triggering, i.e., changing the output percentage by altering the conduction angle (phase angle) of the sinusoidal AC voltage.

WEIDMUELLER electrical component composition

Transformer components include the core assembly (core, windings, insulation, leads), transformer oil, oil tank and cooling device, voltage regulation device, protection devices (moisture absorber, safety airway, gas relay, oil conservator and temperature measuring device, etc.), and outlet bushings. Specific composition and functions: (1) The core is the main magnetic circuit part of the transformer. It is usually made by stacking hot-rolled or cold-rolled silicon steel sheets with high silicon content and coated with insulating paint on the surface. The core is divided into two parts: the core column and the yoke; the core column is fitted with windings; the yoke is used to close the magnetic circuit. (2) The winding is the circuit part of the transformer, wound with double-insulated flat wire or enamel-coated round wire. The basic principle of a transformer is electromagnetic induction. Taking a single-phase two-winding transformer as an example to explain its basic working principle: when voltage is applied to the primary winding, current flows, generating alternating magnetic flux in the core. This flux is called the main flux, under its action, electromotive force is induced in the windings on both sides, finally driving the transformer control device.

WEIDMUELLER electrical component principle

NPN type bipolar transistor can be viewed as two diodes connected together with a common anode. In the normal operating state of a bipolar transistor, the base-emitter junction is forward-biased, while the base-collector junction is reverse-biased. Without external voltage, the electron concentration in the N region of the emitter junction is greater than that in the P region, and some electrons will diffuse into the P region. Similarly, some holes in the P region will also diffuse into the N region. Thus, a space charge region forms on the emitter junction, generating an internal electric field directed from the N region to the P region. This electric field hinders the further occurrence of the aforementioned diffusion process, thereby achieving dynamic balance. At this point, if a forward voltage is applied to the emitter junction, the dynamic balance between the aforementioned carrier diffusion movement and the internal electric field in the depletion layer will be broken, causing thermally excited electrons to inject into the base region. In NPN type transistors, the base region is P type doped, where holes are the majority dopant, so electrons in this region are called "minority carriers". Electrons injected from the emitter into the base region partly recombine with the majority carrier holes here; on the other hand, due to the low doping level and thin physical dimensions of the base region, and because the collector junction is reverse-biased, most electrons will reach the collector region through drift motion, forming the collector current. To mitigate electron recombination before reaching the collector junction as much as possible, the base region of the transistor must be made sufficiently thin so that the time required for carrier diffusion is shorter than the lifetime of semiconductor minority carriers, and the base thickness must be much smaller than the electron diffusion length. In modern bipolar transistors, the typical value of the base region thickness is a few tenths of a micron. It should be noted that although both the collector and emitter are N type doped, their doping levels and physical properties are not identical, so a bipolar transistor must be distinguished from two diodes connected in series in opposite directions.

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