Digital simulation of nonlinear electromagnetic circuits

Magnetic devices are well known for their inherent ruggedness, economy, and reliability. However, design of nonlinear electromagnetic circuits is difficult and, if done improperly, prevents the realization of the full benefits of magnetic devices. This paper describes a digital simulation technique which enables accurate performance prediction of circuits containing saturable magnetic devices and nonlinear electronic devices such as diodes, transistors, 4-layer diodes, silicon-controlled rectifiers, field-effect transistors, tunnel diodes, etc. More specifically, a computer program is described which was developed for a large scientific digital computer such as the IBM 7094 or equivalent. This computer program is user oriented ; it only requires topological input data describing the interconnections of the various circuit elements; and, in turn, produces graphical output plots similar to visual representations obtained in a laboratory from an oscilloscope. The heart of the computer program is the built-in transient solution procedure. From the input data describing the circuit topology the computer program writes its own internal equations, solves for steady-state initial conditions using an iterative Newton-Raphson technique and solves for the transient or time-history response using a combination time step integration and Newton-Raphson technique. The paper describes the digital simulation technique in further detail. It presents some of the mathematical models stored in the program, and illustrates the use of the technique by means of a practical circuit problem, namely the magnetic pulse-width modulator.