Computer analysis of multi-port operation using analogue variables

The full capabilities of electrical circuit analysis programs can be utilized in evaluating the performance of multi-port systems by defining analogous conjugate port variables. These variables represent intensive (across) and extensive (through) variables such that their product represents a universal system quantity such as energy or power. A three-port electro-mechanical-thermal system is used as an example. This system consists of a full-wave rectifier circuit driving a permanent-magnet DC motor. Mechanically, the motor is represented by inertia, friction, stiction (breakaway friction), step-up speed gear and a nonlinear fan load. The thermal equivalent circuit tracks the thermal behavior in time and includes thermal resistance, thermal capacitance and thermal power sources.