Abstract
Recently, in ordor that rotational speed of DC machines may become faster, conditions on commutation are strict more than ever. In these cases, it is important to evaluate the performance of carbon brush materials accurately.
This paper describes the new method evaluating brush materials and experimental results based on the new proposed method.
Performance of brush materials has been evaluated by the tests obtaining characteristics of sliding contact and of commutation. However, a tendency of results obtained by these tests has not agreed with that of experimental results by using DC machines.
In this paper, the authors propose a new method to evaluate characteristics of commutation and sliding contact. The features of a proposed method are as follows:
(1) ‘Degree of contact disturbance’ is used as a way of estimations for sliding contact characteristics. The degree is time-dependent fluctuation of sliding contact voltage.
(2) Performance of commutation is reviewed by using a new expression of the spark region.
In order to realize these evaluation, testing machine for observation of flash was produced. The tendencies between obtained characteristics by produced testing machine and experimental results tested by DC machine, show good agreement. The validity of these evaluating method is confirmed.
