Oscillographing Commutation

To the designer of electric equipment, even these few curves indicate clearly the entire problem of commutation. The effect of variation in the adjustment of the commutating pole and of mutual inductance upon the rate of change of current is shown. The difficulty of getting the several coils in a slot to commutate equally is revealed. The need for brushes to absorb the residual voltages under the best of conditions is suggested. Commutation theory is proved to be correct, and a better understanding of commutation is promoted. Beyond this point, what use can be made of the oscillograph in extending the range of commutation? At this time we cannot answer this question. It is like asking whether the microscope is of any use as an instrument after having employed it on but one specimen. If we consider as specimens each type of armature coil, pitching, and arrangement, and if we consider the oscilloscope as a microscope for the examination of each, this device could be the tool to assist the designer to select the ones that are better and, what is more to tell why they are better. In this manner, it ultimately may point the way to extension of the commutation range of d-c apparatus.