The Testing of Sliding Electrical Contacts for Homopolar Generators

Due to the recent interest in homopolar generators as pulsed power supplies, the need has arisen for pulsed brush data on slip rings at high current levels and high surface velocities. Tests were conducted to examine the effect of varying the apparent area of contact on the coefficient of friction, voltage drop, and wear rate. Brush areas from 0.806-3.23 cm²were individually tested at current levels from 0.0-2800 A per brush. Experimental data are presented for a high copper grade of commerically available sintered copper graphite material. The data corroborate the "thermal mounding" phenomenon described by R. A. Marshall.