PR Electronics electrical components German PR Electronics models PR Electronics prices

PR Electronics electrical components are instruments used to transform voltage. However, the purpose of a transformer in transforming voltage is to facilitate the transmission of electrical energy, so its capacity is large, generally calculated in kilovolt-amperes or megavolt-amperes; whereas the purpose of a voltage transformer in transforming voltage is mainly to supply power to measuring instruments and relay protection devices, to measure the voltage, power, and electrical energy of the line, or to protect valuable equipment, motors, and transformers in the line when a fault occurs. Therefore, the capacity of a voltage transformer is very small, generally only a few volt-amperes or tens of volt-amperes, with a maximum not exceeding one thousand volt-amperes.

PR Electronics electrical component characteristics

Operating characteristics: The main characteristics characterizing the performance of a synchronous generator are the no-load characteristics and the load operating characteristics. These characteristics are an important basis for users to select generators. No-load characteristics: When the generator is not connected to a load, the armature current is zero, which is called no-load operation. Armature reaction: When the generator is connected to a symmetrical load, the three-phase current in the armature winding produces another rotating magnetic field, called the armature reaction magnetic field. Its speed is exactly equal to the rotor speed, and the two rotate synchronously. The armature reaction magnetic field of a synchronous generator and the rotor excitation magnetic field can both be approximately considered to be distributed according to a sinusoidal law. The spatial phase difference between them depends on the time phase difference between the no-load electromotive force E9 and the armature current I. The armature reaction magnetic field is also related to the load condition. When the generator load is inductive, the armature reaction magnetic field has a demagnetizing effect, which will cause the generator voltage to decrease; when the load is capacitive, the armature reaction magnetic field has a magnetizing effect, which will cause the generator output voltage to increase. Load operating characteristics: Mainly refer to external characteristics and adjustment characteristics. The external characteristic is the relationship between the generator terminal voltage U and the load current I when the speed is at the rated value, and the excitation current and load power factor are constants. The adjustment characteristic is the relationship between the excitation current If and the load current I when the speed and terminal voltage are at rated values, and the load power factor is constant.

PR Electronics electrical component classification

Classification by application: toggle switches, band switches, record/playback switches, power switches, preselection switches, limit switches, control switches, changeover switches, isolating switches, travel switches, wall switches, intelligent fire protection switches, etc. Classification by structure: micro switches, rocker switches, toggle switches, slide switches, push-button switches, key switches, as well as fashionable membrane switches and point switches. Classification by contact type: Switches can be divided into a type contacts, b type contacts, and c type contacts based on contact type. Contact type refers to the relationship between the operating status (pressing the switch) and the contact state, where "contacts close after operating (pressing) the switch". It is necessary to select switches with suitable contact types according to the application. Classification by number of switches: single-control switches, dual-control switches, multi-control switches, dimmer switches, speed control switches, splash-proof boxes, doorbell switches, sensor switches, touch switches, remote control switches, smart switches, card-insertion power switches, dedicated switches for bathroom heaters.

PR Electronics electrical component characteristics

(1) Volt-ampere characteristics: When a forward voltage is applied to a diode, the current is extremely small when the voltage value is low; when the voltage exceeds a certain value, the current begins to increase exponentially, which is usually called the turn-on voltage of the diode. The diode is in a fully conductive state, and this voltage is usually called the conduction voltage of the diode. For germanium diodes, when a reverse voltage is applied to the diode, the current is extremely small when the voltage value is low, and its current value is the reverse saturation current. When the reverse voltage exceeds a certain value, the current begins to increase sharply, which is called reverse breakdown, and this voltage is called the reverse breakdown voltage of the diode. The breakdown voltage values of different diode models vary greatly, from tens of volts to thousands of volts. (2) Forward characteristics: When a forward voltage is applied, in the initial part of the forward characteristics, the forward voltage is very small and insufficient to overcome the blocking effect of the electric field within the PN junction, so the forward current is almost zero. This section is called the dead zone. The forward voltage that cannot make the diode conduct is called the dead zone voltage. When the forward voltage is greater than the dead zone voltage, the electric field within the PN junction is overcome, the diode conducts in the forward direction, and the current rises rapidly with increasing voltage. Within the normal operating current range, the terminal voltage of the diode during conduction remains almost constant, and this voltage is called the forward voltage of the diode. When the forward voltage across the diode exceeds a certain value, the internal electric field is quickly weakened, the characteristic current grows rapidly, and the diode conducts in the forward direction, which is called the threshold voltage or knee voltage. (3) Reverse characteristics: When the applied reverse voltage does not exceed a certain range, the current flowing through the diode is a reverse current formed by the drift motion of minority carriers. Since the reverse current is very small, the diode is in the cutoff state. This reverse current is also called reverse saturation current or leakage current, and the reverse saturation current of the diode is greatly affected by temperature. Generally, the reverse current of silicon tubes is much smaller than that of germanium tubes. The reverse saturation current of low-power silicon tubes is in the order of nA, and that of low-power germanium tubes is in the order of μA. When the temperature rises, the semiconductor is heated and excited, the number of minority carriers increases, and the reverse saturation current also increases. (4) Breakdown characteristics: When the applied reverse voltage exceeds a certain value, the reverse current will suddenly increase. This phenomenon is called electrical breakdown. The critical voltage causing electrical breakdown is called the diode reverse breakdown voltage. During electrical breakdown, the diode loses its unidirectional conductivity. If the diode does not overheat due to electrical breakdown, the unidirectional conductivity is not necessarily permanently destroyed, and its performance can still recover after the applied voltage is removed; otherwise, the diode will be damaged. Therefore, excessive reverse voltage applied to the diode should be avoided during use. Reverse breakdown is divided into Zener breakdown and avalanche breakdown based on the mechanism. In the case of high doping concentration, because the width of the barrier region is very small, a large reverse voltage destroys the covalent bond structure within the barrier region, causing valence electrons to break free from covalent bonds and generate electron-hole pairs, resulting in a sharp increase in current. This breakdown is called Zener breakdown. If the doping concentration is lower, the barrier region is wider, and Zener breakdown is not easy to occur. Another type of breakdown is avalanche breakdown. When the reverse voltage increases to a large value, the external electric field accelerates the electron drift speed, causing collisions with valence electrons in covalent bonds, knocking valence electrons out of covalent bonds and generating new electron-hole pairs. The newly generated electron-hole pairs are accelerated by the electric field and knock out other valence electrons, causing an avalanche-like increase in carriers and a sharp increase in current. This breakdown is called avalanche breakdown. Regardless of the type of breakdown, if the current is not limited, it may cause permanent damage to the PN junction. (5) Reverse current: Reverse current refers to the current flowing through the diode when it is subjected to ambient temperature and the maximum reverse voltage. The smaller the reverse current, the better the unidirectional conductivity of the tube. It is worth noting that reverse current is closely related to temperature; the reverse current doubles. Therefore, silicon diodes have better stability at high temperatures than germanium diodes. (6) Dynamic resistance: The ratio of the change in voltage to the corresponding change in current near the static operating point of the diode characteristic curve. (7) Voltage temperature coefficient: The voltage temperature coefficient refers to the relative change in stable voltage for every one degree Celsius increase in temperature. (8) Maximum operating frequency: The maximum operating frequency is the upper frequency limit for diode operation. Since the diode, like the PN junction, has a junction capacitance composed of barrier capacitance, the value of the maximum operating frequency mainly depends on the size of the PN junction capacitance. If this value is exceeded, the unidirectional conductivity will be affected. (9) Maximum rectified current: The maximum rectified current refers to the maximum allowable average forward current value when the diode operates continuously for a long period. Its value is related to the PN junction area and external heat dissipation conditions. Because current passing through the tube causes the core to heat up and the temperature to rise, if the temperature exceeds the allowable limit, the core will overheat and be damaged. Therefore, under specified heat dissipation conditions, the diode should not exceed its maximum rectified current value during use.(10) Maximum reverse working voltage: When the reverse voltage applied across the diode reaches a certain high value, the tube will break down and lose its unidirectional conductivity. To ensure safe use, the maximum reverse working voltage value is specified.

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