Part two: Linear superposition speeds thermal modeling

The application of superposition, in a thermally linear system, can predict the transient response of the system to step changes in input power. The thermal transient response can be determined by turning each matrix element into its corresponding time-varying counterpart. The advantage of linear thermal networks is that there is generally a mathematically equivalent Foster solution for every node in the system. It is necessary to square up the time-varying power input to apply time domain superposition for analyzing a time-varying heat source. The resolution of the squaring basically depends on how accurate it is needed to be at critical points. Each step-change of power turns into its own power-scaled version of the transient-response curve for the heat source, it starts when the change is applied and ends when the simulation ends. Linear superposition permits to characterize the system just once, and then do all the simulations with Excel in seconds instead of hours.