网格分析

Mesh analysis is a method that uses mesh currents as circuit variables to reduce the number of simultaneous equations needed for circuit analysis. Unlike nodal analysis, which determines unknown voltages, mesh analysis applies Kirchhoff's voltage law to find unknown currents. This approach is particularly convenient for planar circuits, making complex circuit problems more manageable.

Mesh analysis requires the circuit to be planar, meaning it can be drawn on a flat surface without branches crossing one another. The circuit must have identifiable independent meshes, where each mesh is a closed loop containing no other loops within it. These conditions ensure that mesh currents can be properly assigned and analyzed using Kirchhoff's voltage law.

Each independent mesh in the circuit is assigned a mesh current, typically assumed to flow in a clockwise direction within its respective loop. For a circuit with multiple independent meshes, each mesh receives its own current variable. These mesh currents are then used to express element voltages and apply Kirchhoff's voltage law to generate the necessary equations.

First, assign mesh currents to each independent mesh in the circuit. Second, apply Kirchhoff's voltage law to each mesh, expressing element voltages in terms of mesh currents using Ohm's law. Third, solve the resulting simultaneous equations to obtain the mesh current values, which can then determine various branch currents within the circuit.

When a circuit contains current sources, mesh analysis can be extended using specialized techniques. The mesh analysis with current sources method modifies the standard approach to accommodate known current values at specific locations. This allows engineers to analyze more complex circuits while maintaining the efficiency of the mesh analysis framework.

Mesh currents are the variables assigned to each independent mesh in the circuit, while branch currents are the actual currents flowing through individual circuit elements. Mesh currents and branch currents are distinct unless a mesh is isolated. Branch currents can be calculated from mesh currents by analyzing how mesh currents combine at circuit nodes.

Mesh analysis applies only to planar circuits because the method relies on identifying independent meshes and applying Kirchhoff's voltage law to each one. In non-planar circuits with crossing branches, mesh definition becomes ambiguous and the systematic approach breaks down. Planar circuits ensure clear mesh identification and reliable equation formulation for solving circuit problems.