Damping and synchronizing torque of the double-fed asynchronous machine

I. Introduction THE double-fed asynchronous machine has become important in recent times as fan drive with wide speed range. The system consists of five main machines and the fan (see figure 1). It has many springs, masses, and dampings and therefore many natural frequencies. In order to determine these frequencies, i.e. the dynamic stability of the system, the damping and synchronizing torques of all parts of the system have to be known. Some papers have been published concerning the torques of the synchronous machine. It is easy to determine torques for the D.C. machines of the system. The object of this paper is to derive formulas for the damping and synchronizing torque of the double-fed asynchronous machine. As in the case of the synchronous machine, a complicated derivation and complicated results cannot be avoided.