How Does Current Establish in Transient Electromagnetic Field

Eddy current fields are usually used to describe the electromagnetic phenomena in fast-response devices, but this numerical simplification has errors in explaining the current establishment mechanism of conductors. This paper uses the full-wave Maxwell equations and takes an axisymmetric power source-coaxial line-axisymmetric load loop as a typical example to clarify the current establishment mechanism in the conductor under sudden voltage excitation. The field in the air is not established instantaneously, but is sent from the power source to the load in the form of electromagnetic waves along the waveguide. If the characteristic impedance of the waveguide does not match the load resistance, the wave will refract and reflect repeatedly, progressively delivering energy into the load. And the load voltage and current rise in steps, and the rise time is related to the matching degree of the waveguide and the load. Then the solution of the full-wave equation is compared with transmission line theory. The transmission line theory is a circuit simplification from the full-wave equations, but cannot take into account the dynamic circuit parameters of the waveguide and load, which can cause distortion of the solution.