wera werk electrical components Germany wera werk models wera werk prices

wera werk electrical components utilize the good conductivity and fluidity of mercury to control the opening and closing of electrical circuits. They consist of a glass tube, mercury, fixed electrodes, lead wires, etc. After evacuating the air from the tube, it is filled with various gases and sealed. They are suitable for environments with dust, oil, water vapor, and corrosive gases, and can also be used as explosion-proof switches in locations with explosive gases. Due to the high surface tension and specific gravity of the mercury inside the tube, along with its fluidity, the position of the mercury changes immediately upon slight tilting of the glass tube, making contact with the electrodes via surface contact, thus enabling the switching of high AC and DC currents. Additionally, these switches feature a lifespan of up to several million cycles at rated current, compact size, high sensitivity, no mechanical noise, and low cost, making them widely used as automatic control switches.

wera werk electrical component parameters

1. Voltage temperature coefficient: Refers to the rate of change of the nominal voltage of a varistor within a specified temperature range, i.e., the relative change in voltage across the varistor when the temperature changes while the current through the varistor remains constant. 2. Current temperature coefficient: Refers to the relative change in current flowing through the varistor when the temperature changes while the voltage across the varistor remains constant. 3. Nominal voltage: Refers to the voltage value across the varistor when DC current flows through it. 4. Voltage ratio: Refers to the ratio of the voltage generated by the current in the varistor to the voltage generated by the current in the varistor. 5. Maximum clamping voltage: Refers to the highest voltage value that the varistor can withstand across its terminals. 6. Leakage current: Also known as standby current, it refers to the current flowing through the varistor under specified temperature and maximum DC voltage conditions. 7. Residual voltage ratio: When the current through the varistor is at a certain value, the voltage generated across its terminals is called the residual voltage for that current value. The residual voltage ratio is the ratio of the residual voltage to the nominal voltage. 8. Surge current capacity: Also known as surge current, it refers to the maximum pulse (peak) current value allowed to pass through the varistor under specified conditions (specified time intervals and number of times, applying standard impulse current). 9. Static capacitance: Refers to the inherent capacitance of the varistor itself. 10. Insulation resistance: Refers to the resistance value between the lead wires (pins) of the varistor and the insulated surface of the resistive body. 17. Voltage nonlinearity coefficient: Refers to the ratio of the static resistance value to the dynamic resistance value of the varistor under a given applied voltage.

wera werk electrical component structure

Solid-state relays consist of three parts: input circuit, isolation, and output circuit. Depending on the input voltage category, input circuits can be divided into DC input circuits, AC input circuits, and AC/DC input circuits. Some input control circuits also feature compatibility with TTL/CMOS, positive/negative logic control, and inversion functions, allowing convenient connection to TTL and MOS logic circuits. For control signals with fixed control voltage, resistive input circuits are used. The isolation and coupling methods between the input and output circuits of solid-state relays include optocoupling and transformer coupling: Optocoupling typically uses photodiode-phototransistor, photodiode-triac optocoupler, or photovoltaic cells to achieve isolation control between the control side and the load side; High-frequency transformer coupling utilizes the self-excited high-frequency signal generated by the input control signal, which is coupled to the secondary side, demodulated, rectified, and processed by logic circuits to form a drive signal. The power switch of the solid-state relay is directly connected to the power supply and load terminals to realize the switching of the load power. Mainly used components include high-power transistors, SCRs, triacs, power MOSFETs, and IGBTs. The output circuit of solid-state relays can also be divided into DC output circuits, AC output circuits, and AC/DC output circuits. Based on load type, they can be classified into DC solid-state relays and AC solid-state relays. Bipolar devices or power MOSFETs can be used for DC output, while two SCRs or one triac are typically used for AC output. AC solid-state relays can be further divided into single-phase AC solid-state relays and three-phase AC solid-state relays. AC solid-state relays can be classified into random-turn-on AC solid-state relays and zero-crossing AC solid-state relays based on the timing of turn-on and turn-off.

wera werk electrical component principle

When two different conductors or semiconductors A and B form a loop with their ends connected, as long as the temperatures at the two junctions are different, with one end at temperature T (called the working end or hot end) and the other end at temperature T0 (called the free end or cold end), an electromotive force (EMF) will be generated in the loop. The direction and magnitude of this EMF depend on the materials of the conductors and the temperatures of the two junctions. This phenomenon is called the "thermoelectric effect," the loop formed by the two conductors is called a "thermocouple," the two conductors are called "thermoelectrodes," and the generated EMF is called "thermoelectric EMF." Thermoelectric EMF consists of two parts: the contact EMF between the two conductors and the thermal EMF of a single conductor due to temperature difference. The magnitude of the thermoelectric EMF in a thermocouple loop depends only on the conductor materials forming the thermocouple and the temperatures of the two junctions, and is independent of the shape and dimensions of the thermocouple. Once the electrode materials of the thermocouple are fixed, the thermoelectric EMF is a function of the difference between the junction temperatures t and t0. This relationship is widely used in practical temperature measurement. Since the cold end t0 is constant, the thermoelectric EMF generated by the thermocouple changes only with the temperature of the hot end (measurement end), meaning a specific thermoelectric EMF corresponds to a specific temperature. We can achieve temperature measurement by measuring the thermoelectric EMF. The basic principle of thermocouple temperature measurement is that two dissimilar homogeneous conductors form a closed loop; when there is a temperature gradient between the two ends, current flows through the loop, creating an EMF—thermoelectric EMF—between the ends, known as the Seebeck effect. The two dissimilar homogeneous conductors are thermoelectrodes, the higher temperature end is the working end, and the lower temperature end is the free end, which is usually kept at a constant temperature. Thermocouple calibration tables are created based on the functional relationship between thermoelectric EMF and temperature; these tables are obtained under the condition that the free end temperature is 3°C, and different thermocouples have different calibration tables. When a third metal material is introduced into the thermocouple loop, as long as the temperatures at the two junctions of this material are the same, the thermoelectric EMF generated by the thermocouple remains unchanged, i.e., it is not affected by the introduction of the third metal. Therefore, during thermocouple temperature measurement, measuring instruments can be connected; after measuring the thermoelectric EMF, the temperature of the measured medium can be determined. Thermocouple temperature measurement requires the cold end temperature (the end connected to the measurement circuit via lead wires, while the measurement end is the hot end) to remain constant so that the thermoelectric EMF is proportional to the measured temperature. If the cold end (ambient) temperature changes during measurement, it will seriously affect measurement accuracy. Taking measures at the cold end to compensate for the effects of cold end temperature changes is called thermocouple cold junction compensation. Special compensation wires are used to connect to the measuring instrument. Thermocouple cold junction compensation calculation methods: (1) From millivolts to temperature: Measure the cold end temperature, convert it to the corresponding millivolt value, add it to the thermocouple's millivolt value, and convert to temperature; (2) From temperature to millivolts: Measure the actual temperature and cold end temperature, convert them separately to millivolt values, subtract to obtain the millivolt value, and thus determine the temperature.

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