Some Applications of Controlled Electrical Drives
The preceding chapters were dealing mainly with the different types of electrical drives and their control; applications were only mentioned as they affected the operation of the machines and the associated equipment. Also, the driving specifications of a mechanical load are normally not met by just one type of electrical drive and the variety of applications can be bewildering; in this chapter some problems associated with controlled electrical drives will be explained in more detail. For this we begin with a 4-quadrant drive, be it DC or AC, the basic structure of which is contained within the dashed lines in Fig. 15.1. The moving masses are at first assumed to be rigidly coupled, forming a lumped inertia. The inner loop which comprises the power converter and part of the electrical machine assures fast torque control; with an integrating controller it exhibits unity gain and serves for linearisation. Once the torque loop with the equivalent lag Te is closed, there is little difference between a DC and an AC drive.
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