Device for the control and measurement of brush forces to an accuracy of a few grams-force while monitoring brush resistance and brush wear at currents up to 500 A or more

A brush holder is described which permits the electrical performance of a brush to be tested under currents of up to at least 500 A and speeds of up to at least 70 m s^?1 and under brush forces that can be applied and maintained within close limits. Simultaneously, the brush wear can be monitored continuously.