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through replacement of voltage sources by short circuits and of current sources by open circuits.
Keep in mind that superposition is based on linearity. For this reason, it is not applicable to the effect on power due to each source, because the power absorbed by a resistor depends on the square of the voltage or current. If the power value is needed, the current through (or voltage across) the element must be calculated first using superposition.
Thevenin’s Theorem. It often occurs in practice that a particular element in a circuit is variable (usually called the load) while other elements are fixed. As a typical example, a household outlet terminal may be connected to different
appliances constituting a variable load. Each time the variable element is changed, the entire circuit has to be analyzed all over again. To avoid this problem, Thevenin’s theorem provides a technique by which the fixed part of the circuit is replaced by an equivalent circuit.
According to Thevenin’s theorem, the linear circuit in Fig.(a) can be replaced by that in Fig. (b). (The load in Fig. may be a single resistor or another circuit.) The circuit to the left of the terminals in Fig. 4.23(b) is known as the Thevenin equivalent circuit; it was developed in 1883 by M. Leon Thevenin (1857–1926), a French telegraph engineer.
Thevenin’s theorem states that a linear two-terminal circuit can be replaced by an
equivalent circuit consisting of a voltage source V Th in series with a resistor R Th, where V Th is the open-circuit voltage at the terminals and R Th is the input or equivalent resistance at the terminals when the independent sources are turned off.
In 1926, about 43 years after Thevenin published his theorem, E. L. Norton, an American engineer at Bell Telephone Laboratories, proposed a similar theorem. Norton’s theorem states that a linear two-terminal circuit can be replaced by an equivalent circuit consisting of a current source I N in parallel with a resistor R N, where I N is the short-circuit current through the terminals and RN is the input or equivalent resistance at the terminals when the independent sources are turned off.
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Thus, the circuit in Fig. (a) can be replaced by the one in Fig. (b).
Задание на СРСП: решение задач по вариантам: нахождение параметров разветвленной цепи методами эквивалентных преобразований.
Основная литература:
1. Алехин В.А. Электротехника. Мультимедийный курс лекций с использованием компьютерного моделирования. Москва, МИРЭА, 2016. - с. 41-62.
Дополнительная литература:
2. Носов Г.В. и др. Теоретические основы электротехники. Установившийся режим: учебное пособие. − Томск: Изд-во ТПУ, 2011. – с. 41-50.
3. Ray Powell. Introduction in Electrical Circuits. Arnold, London. 2005. –p.45-61.
