An Analysis of D-C Machine Commutation

When a d-c machine commutates, abrupt pulsations of bar-to-bar voltage occur under the brushes. This paper presents an analytical method of determining bar-to-bar voltage as a function of time during commutation. The results of the method are applied to several large d-c machines and compared with oscillograph data. With the advent of highspeed digital computers, the method is readily adaptable to design use, and provides the designer with a new tool for predicting commutation performance.