Estimating busbar temperatures

A tutorial on calculating the temperature of naturally and liquid-cooled DC buses is presented. Estimation of time constants allows calculations of time-varying bus temperatures, while the determination of span constants is helpful in calculating heating gradients along busbars. Sample calculations are included. The methods shown allow the estimation of the steady-state temperature within about 5°C of busbars carrying DC. Should the bus consist of several bars in parallel, these equations should still hold by taking the convective area as the sum of the individual bars and the radiating area as the envelope around the bar cluster. Hewlett Packard 41CX calculator programs which produce the steady-state temperatures of a naturally cooled DC bus, and the bus´s time and span constants, are given. An analysis of a water-cooled bus system is also presented