Name: thevenin circuit equivalents
Uploaded: 2024-04-11T12:48:31.000Z
Duration: 1 min 15 s
Channel: JoVE

Thevenin의 정리에 따르면 모든 선형 2단자 회로는 저항과 직렬로 연결된 단일 전압 소스가 있는 등가 회로로 대체될 수 있습니다.
부하가 없을 때 열린 단자의 전압은 Thévenin 전압이 됩니다.
Thévenin 저항성을 찾기 위해 모든 독립적 인 소스가 꺼져 있습니다. 그런 다음 단자를 가로 질러 보이는 저항은 Thévenin 저항입니다.
회로에 종속 소스가 포함된 경우 독립 소스는 여전히 꺼져 있지만 알려진 테스트 소스가 터미널에 적용됩니다.
결과 단자 전압 또는 전류에서 Thévenin 저항을 결정할 수 있습니다.
마지막으로 부하는 등가 회로에 연결됩니다. 부하를 통과하는 전류는 전류 분배기 공식을 사용하여 계산됩니다. 옴의 법칙을 사용하여 부하 양단의 Thévenin 전압이 결정됩니다.
배터리는 Thévenin 등가 회로로 나타낼 수 있습니다. Thévenin 전압은 배터리의 개방 회로 전압이고 저항은 내부 저항입니다.
Thévenin 매개변수를 알면 전체 회로를 다시 검사하지 않고도 다양한 부하에 대한 전류를 쉽게 계산할 수 있습니다.

테브낭의 정리

테브낭의 정리는 전기 회로 분석에서 중추적인 역할을 하며 회로 내의 가변 부하로 인해 발생하는 문제에 대한 솔루션을 제공합니다. 실제 응용 분야에서는 특정 요소는 고정된 상태로 유지되고 다른 요소는 변동하는 회로(종종 "부하"라고 함)를 접하는 것이 일반적입니다. 일반적인 가정용 전기 콘센트는 고유한 전기적 특성을 지닌 다양한 가전제품에 연결될 수 있으므로 가변 부하의 대표적인 예입니다. 새 기기를 연결하거나 제거할 때마다 전체 회로에 대한 새로운 분석이 필요합니다. 테브낭의 정리는 회로의 고정 부분을 등가 회로로 대체하는 기술을 제공하여 분석 및 설계를 단순화합니다.

테브낭의 정리에 따르면 선형 2단자 회로는 저항과 직렬로 연결된 전압원으로 구성된 등가 회로로 표현될 수 있습니다. 이 등가 회로는 외부 관점에서 원래 회로의 동작을 효과적으로 캡슐화합니다. 두 가지 중요한 매개변수가 이 테브낭 등가 회로를 정의합니다. 즉, 단자의 개방 회로 전압에 해당하는 테브낭 등가 전압(VTh)과 단자의 입력 또는 등가 저항을 나타내는 테브낭 등가 저항(RTh)입니다. 독립 소스는 비활성화됩니다.

개념을 더 자세히 설명하기 위해 Figure 1과 Figure 2에 표시된 두 회로를 생각해 보세요. 이러한 회로는 터미널에서 동일한 전압-전류 관계를 공유할 때 동등한 것으로 간주됩니다. 단자를 개방 회로로 놔두어 전류가 흐르지 않으면 개방 단자 양단의 전압은 테브낭 전압이 됩니다. 모든 독립 소스가 꺼진 경우. 그러면 단자 전체에 나타나는 저항이 테브낭 저항입니다.

<img alt="Figure1" src="/files/ftp_upload/15053/15053_PT_Figure_1.svg" style="text-align: center; height: 128px;">
Figure 1
<img alt="Equation1" src="/files/ftp_upload/15053/15053_PT_Equation_1.svg" style="text-align: center; height: 14px;">

<img alt="Figure2" src="/files/ftp_upload/15053/15053_PT_Figure_2.svg" style="text-align: center; height: 128px;">
Figure 2
<img alt="Equation2" src="/files/ftp_upload/15053/15053_PT_Equation_2.svg" style="text-align: center; height: 14px;">

이 아이디어를 실제로 적용하고 테브낭 저항을 결정하려면 두 가지 시나리오를 고려해야 합니다.

사례 1: 네트워크에 종속 소스가 없는 상황에서는 모든 독립 소스가 비활성화되고 입력 저항(단자 a와 b 사이에 나타나는 저항)이 확인됩니다.

사례 2: 네트워크에 종속 소스가 통합되면 모든 독립 소스를 계속 비활성화합니다. 그러나 종속 소스는 회로 변수에 의해 제어되므로 비활성화하지 않아야 합니다.

테브낭 저항(RTh)의 값이 때때로 음수일 수 있다는 점은 주목할 가치가 있습니다. 이는 회로가 전력을 소비하는 것이 아니라 공급하고 있음을 의미합니다. 이 시나리오는 종속 소스가 있는 회로에서 가능합니다.

Thevenin의 정리에 따르면 모든 선형 2 단자 회로는 단일 전압 소스가 직렬로 연결된 등가 회로로 대체 될 수 있습니다.

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

DC Circuit Analysis

DC 회로 분석

KEY TERMS AND CONCEPTS

주요 용어 및 개념

Thevinin's Theorem

thevenin circuit equivalents

Thevenin circuit equivalents simplify linear two-terminal circuits by replacing the fixed part of a network with one equivalent source and one resistor. This method is useful when a circuit has a fixed section and a load that can change. A household electrical outlet is a familiar example, because different appliances can be plugged in or removed. Each change in load can require a new circuit analysis, so an equivalent circuit makes the work easier.

Thevenin's theorem states that a linear two-terminal circuit can be represented by a voltage source in series with a resistor. From the outside, this equivalent circuit has the same behavior as the original network. Two circuits are considered equivalent when they have the same voltage-current relationship at their terminals. The Thevenin equivalent voltage, VTh, is the open-circuit voltage at the terminals, and the Thevenin equivalent resistance, RTh, is the input resistance seen at the terminals when the independent sources are turned off.

To find the Thevenin resistance, the method depends on the kind of sources in the network. If the circuit has no dependent sources, all independent sources are deactivated and the resistance between terminals a and b is found. If the network includes dependent sources, the independent sources are still turned off, but the dependent sources stay active because they are controlled by circuit variables. In some cases, RTh can be negative. That means the circuit is supplying power instead of consuming it, which can happen in circuits with dependent sources.

Thevenin Circuit Equivalents

nodal analysis

Using Node Voltages in Circuit Analysis

Nodal analysis uses node voltages to simplify circuit analysis. In this method, the voltage at each node becomes the main variable. Once those voltages are known, they can be used to find other values, such as the current through specific circuit parts. The process begins by choosing a reference node, also called a datum node. This node is selected for convenience and assigned a voltage of zero. The other nodes, called non-reference nodes, are then measured relative to that point. In the...

nodal analysis with voltage sources

Supernode Equations in Nodal Analysis

Nodal analysis uses node voltages and Kirchhoff’s laws to solve circuits with voltage sources. It is a systematic method for breaking a complex circuit into smaller parts that are easier to analyze. In this example, the circuit includes four resistors and two voltage sources. One voltage source is connected between a non-reference node and the reference node. In that case, the non-reference node voltage can be written directly as the source voltage. This removes one unknown and makes the...

mesh analysis

Mesh Currents for Circuit Analysis

Mesh currents give students a simpler way to analyze planar circuits. In mesh analysis, the unknowns are currents, not voltages. The method uses Kirchhoff's voltage law, or KVL, to build the equations needed to solve the circuit. A mesh is a closed loop in a circuit that does not contain any smaller loops inside it. Each independent mesh is assigned a mesh current, and this current is usually drawn in the clockwise direction. These mesh currents are used as the main circuit variables during...

mesh analysis with current sources

Current Sources in Mesh Circuit Analysis

Current sources make mesh circuit analysis easier because they can reduce the number of equations needed. This applies to both independent and dependent current sources. The method depends on where the current source is placed in the circuit. When a current source appears in only one mesh, the setup is simple. Assign mesh currents as usual, but leave out the mesh that contains the current source from the equation process. Then apply Kirchhoff's voltage law, or KVL, to the remaining mesh to get...

source transformation

Circuit Source Equivalents

Circuit source equivalents make it easier to simplify electrical circuits in circuit analysis. A source transformation replaces a voltage source in series with a resistor by a current source in parallel with a resistor, or it replaces a current source in parallel with a resistor by a voltage source in series with a resistor. The key idea is that the equivalent resistance at the circuit terminals stays the same when the original sources are turned off. When making the change, the current source...

linear circuits

Circuit Linearity and Resistor Behavior

Circuit linearity describes how a circuit responds when its input changes. A linear circuit has an output that is directly proportional to its input. This behavior follows two rules: homogeneity and additivity. Homogeneity means that if the input, or excitation, is multiplied by a constant factor, the response is multiplied by the same factor. For example, if the current is increased by a constant k, the voltage also increases by k times. Additivity means that the response to a sum of inputs...

superposition theorem

Analyzing Circuits with Superposition

Superposition is a circuit analysis method for linear circuits with more than one independent source. It lets you find the voltage across or current through an element by adding the separate effects of each source acting alone. To use superposition, keep one independent source active and turn off the others. A voltage source is replaced by a short circuit, and a current source is replaced by an open circuit. Then calculate the output from the single active source. Repeat the process for each...

thevinin's theorem

Thevenin circuit equivalents simplify linear two-terminal circuits by replacing the fixed part of a network with one equivalent source and one resistor. This method is useful when a circuit has a fixed section and a load that can change. A household electrical outlet is a familiar example, because different appliances can be plugged in or removed. Each change in load can require a new circuit analysis, so an equivalent circuit makes the work easier. Thevenin's theorem states that a linear...

norton's theorem

Norton Equivalent Circuit in DC Analysis

Norton equivalent circuit in DC analysis shows how a linear two-terminal circuit can be replaced by a simpler network. The replacement uses a current source, called I_N, in parallel with a resistor, called R_N. I_N is the short-circuit current through the terminals, and R_N is the input or equivalent resistance seen at the terminals when the independent sources are turned off. To find Norton's resistance, all independent sources in the circuit are set to zero. The resistance measured at the...

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Load Matching in Thevenin Circuits

Load matching in Thevenin circuits helps a source deliver the most power to a connected load. This matters in engineering fields such as telecommunications, where power delivery must be optimized. Even then, internal losses can be significant and may equal or exceed the power sent to the load. The Thevenin equivalent circuit is a useful way to study this situation. It replaces the full linear circuit with a simpler source and resistance while keeping the load in place. In this setup, the load...

design example: strain gauge bridge or wheatstone bridge

design-example-strain-gauge-bridge-or-wheatstone-bridge

Wheatstone Bridge Output for Strain Gauge Design

A strain gauge and Wheatstone bridge work together to turn mechanical strain into an electrical signal. In engineering, this setup is often used to measure force or pressure. Each part of the bridge has a resistance that changes slightly when strain is applied. The main goal is to turn a very small voltage output into a larger, easier-to-read signal. A voltmeter can then measure that output more clearly. To do this, an engineer designs the strain gauge circuit and figures out how much...

key terms and concepts

Learn how Thevenin’s theorem replaces a linear two-terminal circuit with a voltage source and resistor, and how to find VTh and RTh in circuit analysis.

Thevenin Circuit Equivalents | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Thevenin Circuit Equivalents

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