Measuring the dynamic forces to identify the friction of a graphite–copper contact for variable temperature and current

In this paper we present experimental and analytical techniques for identifying the coefficient of friction (COF) of a graphite electric brush sliding against a commutator for different contact temperatures and electric current densities. A direct measurement of the instantaneous dynamic forces is used to identify the coefficient of friction. The experimental example shows that the presented procedures can be used to determine the optimum operating ranges for the temperature and the electric current density.