Temperature rise of solid junctions under pulse load

Junctions subjected to pulse currents have a temperature rise that depends on dimensions, materials, and cooling, as much as magnitude, duration, and form of the pulse. Short pulses heat only a part of the body containing the junction; longer pulses permit the heat to penetrate deeper. Short pulses of constant magnitude, or linearly increasing in time, or capacitor discharges, show only a small difference in temperature rise. Experiments conducted with capacitor discharges are easily interpreted for other pulse shapes. For larger pulses, successive approximations are useful: plane heat flow in the junction material, plane flow in the junction and in the main body, spherical diffusion in the body, and simultaneous heating of the body with external cooling. Each approximation has its range of validity, expressed as pulse durations. Approximations overlap between ranges and cover the full span from infinitely short pulses to continuous load. A complete example is discussed.