Theoretical Calculation of the Transient Temperature Rise and the Welding Limit Current of Point Contact Due to Momentary Current Flow

Calculations of the transient temperature rise of point contacts with large contact areas were carried out using a hemisphere contact model. The results obtained are as follows. 1) The temperature thetam at the contact surface is not a function of I/a (I is the current, a the real contact radius) as in the stationary contact theories, but is a function of a, I, and /´s frequency. 2) A relation between thetam and contact voltage U shows hysterisis characteristics. 3) Transient calculation gives a higher welding limit current than the stationary theories, particularly for large real contact areas. 4) When taking into consideration the change of real contact area during current flow, the particular contact voltage wave forms and the relation between U and the contact resistance Rc, which have been observed experimentally, can be explained by the calculation.