b&r electrical components, German b&r models, b&r pricing

b&r electrical components are commonly used low-current master control devices. They utilize the collision of moving parts of production machinery to actuate their contacts, thereby connecting or disconnecting control circuits to achieve specific control objectives. Typically, such switches are used to limit the position or travel of mechanical motion, enabling moving machinery to automatically stop, reverse, change speed, or perform automatic reciprocating motion according to a specified position or travel. In electrical control systems, the role of position switches is to implement sequence control, positioning control, and detection of position status. They are used to control the travel of mechanical equipment and provide limit protection. Construction: Composed of an operating head, contact system, and housing. In actual production, limit switches are installed at predetermined positions. When a module mounted on the moving part of the production machinery strikes the limit switch, the contacts of the limit switch actuate, achieving circuit switching. Therefore, a limit switch is an electrical device that switches circuits based on the travel position of moving parts; its operating principle is similar to that of a pushbutton. Limit switches are widely used in various machine tools and lifting machinery to control their travel and provide terminal limit protection. In elevator control circuits, limit switches are also used to control the speed of opening and closing car doors, provide automatic door opening/closing limit protection, and provide upper and lower limit protection for the car.

b&r electrical component principles

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 differ, with one junction at temperature T (called the working end or hot end) and the other at temperature T0 (called the free end or cold end), an electromotive force (EMF) is 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 components: the contact EMF between the two conductors and the temperature-difference EMF within a single conductor. 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 materials of the two thermocouple electrodes are fixed, the thermoelectric EMF is a function of the difference between the temperatures t and t0 at the two junctions. This relationship is widely applied in practical temperature measurement. Since the cold end t0 is kept constant, the thermoelectric EMF generated by the thermocouple changes only with the temperature of the hot end (measurement end); that is, a specific thermoelectric EMF corresponds to a specific temperature. Thus, temperature measurement can be achieved by measuring the thermoelectric EMF. The basic principle of thermocouple temperature measurement is that a closed loop formed by two conductors of different compositions generates a current when a temperature gradient exists between the two ends, resulting in an EMF—thermoelectric EMF—between the ends, known as the Seebeck effect. The two homogeneous conductors of different compositions serve as thermoelectrodes; the end with the higher temperature is the working end, and the end with the lower temperature is the free end, which is usually maintained at a constant temperature. Based on the functional relationship between thermoelectric EMF and temperature, thermocouple calibration tables are created; these tables are derived under the condition that the free end temperature is 5℃, 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 identical, the thermoelectric potential generated by the thermocouple remains unchanged, meaning it is unaffected by the introduction of the third metal into the loop. Therefore, during thermocouple temperature measurement, a measuring instrument can be connected; after measuring the thermoelectric EMF, the temperature of the measured medium can be determined. Thermocouple temperature measurement requires that the temperature of the cold end (the measurement end is the hot end; the end connected to the measurement circuit via lead wires is called the cold end) remains constant, so that the thermoelectric potential maintains a proportional relationship with the measured temperature. If the (ambient) temperature of the cold end 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 cables 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 the sum to temperature; (2) From temperature to millivolts: Measure the actual temperature and the cold end temperature, convert them separately to millivolt values, subtract one from the other to obtain the millivolt value, and thus determine the temperature.

b&r electrical component characteristics

Operating characteristics: The main characteristics characterizing the performance of a synchronous generator are the no-load characteristic and the load operating characteristic. These characteristics are important bases for users when selecting a generator. No-load characteristic: When the generator is not connected to a load, the armature current is zero, which is referred to as 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 rotational speed is exactly equal to the rotor speed, and both rotate synchronously. The armature reaction magnetic field of a synchronous generator and the rotor excitation magnetic field can both be approximated as distributed according to a sinusoidal law. The spatial phase difference between them depends on the time phase difference between the no-load EMF E6 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, causing the generator voltage to decrease; when the load is capacitive, the armature reaction magnetic field has a magnetizing effect, causing the generator output voltage to increase. Load operating characteristics: These mainly refer to the external characteristic and the regulation characteristic. 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 constant. The regulation 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.

b&r electrical component principles

A resistor consists of three parts: the resistive element, the backbone, and the lead terminals (in solid-core resistors, the resistive element and backbone are combined into one), but only the resistive element determines the resistance value. The volt-ampere characteristic is represented by a graphical curve showing the relationship between voltage and current at the resistor terminals. When voltage and current are proportional (the characteristic is a straight line), it is called a linear resistor; otherwise, it is called a non-linear resistor. The maximum power dissipation allowed for continuous operation of a resistor at the rated temperature (maximum ambient temperature) tR. For each type of resistor, a maximum operating voltage is also specified; that is, even if the rated power is not reached, the maximum operating voltage must not be exceeded when the resistance value is high. The rated power of a resistor refers to the maximum power it is allowed to consume during long-term continuous operation in DC or AC circuits. Load characteristics: When the ambient operating temperature is below tR, the resistor must not exceed its rated power; when the temperature exceeds tR, the load power must be reduced. Each type of resistor has specified load characteristics. Additionally, the allowable load may be correspondingly reduced under low atmospheric pressure. Under pulse load conditions, the average pulse power is far lower than the rated power, and separate specifications generally apply.

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