Current-limiting thermistors for high-power applications

Applications of positive-temperature-coefficient polymer thermistors as current-limiting elements in high-power systems are complicated by the nonlinear scaling of device parameters. The spatial and temporal evolution of the internal quantities temperature and electric field, and the temporal evolution of the external device property resistance, are described here as calculated according to a one-dimensional electrothermal model. Under a steeply ramping current excitation, a longitudinal heating instability compresses the electric field into the center of the material, thereby inducing dielectric failure. Insight into the design of a useful device is provided by results of calculations under three different conditions.