ABSTRACT
When investigating transient and high-frequency steady-state phenomena, all the conductors such as a transmission line, a machine winding, and a measuring wire show a distributed-parameter nature. Well-known lumpedparameter circuits are an approximation of a distributed-parameter circuit to discuss a low-frequency steady-state phenomenon of the conductor. That is, a current in a conductor, even with very short length, needs a time to travel from its sending end to the remote end because of a finite propagation velocity of the current (300 m/μs in a free space). From this fact, it should be clear that a differential equation expressing the behavior of a current and a voltage along the conductor involves variables of distance x and time t or frequency f. Thus, it becomes a partial differential equation. On the contrary, a lumped-parameter circuit is expressed by an ordinary differential equation since there exists no concept of the length or the traveling time. The aforementioned is the most significant differences between the distributedparameter circuit and the lumped-parameter circuit.
