Voltage modulation on aircraft electric power systems as a function of the flexibility of the alternator drive shaft

A mathematical analysis is presented here which shows how the action of a flexible alternator shaft is significant in the production of voltage modulation (VM) in aircraft power systems. The analysis discloses a phenomenon in which VM and frequency modulation (FM) are sustained in an electric power system even though no external disturbances exist, and the respective basic closed-loop control is stable. The modulation is the result of the interaction of electrical load, flexible shaft, and the basic voltage-regulating system. In addition, the implication of the flexible shaft is shown in an analysis of forced VM due to various torque-type disturbances.