High-altitude brush problem

THE rapid development of military aircraft during the past three years has been accompanied by an equally vigorous development and use of electric motors and generators necessary for their operation and control. This dynamoelectric equipment covers not only the d-c and a-c applications but also a wide range of power output, voltage, current, and speed. Some of the d-c machines are compensated fully for best commutation, while others are partially compensated, and still others are without compensation and depend on the brush shift and brush grade for satisfactory operation.