Abstract
The acceleration time of induction machines (IMs) is essential for proper protection-relay settings of the machine to prevent voltage sags in local power areas. In this paper, mathematical modeling of IMs’ speed-time characteristics during no-load direct startup has been presented. Unlike the approaches presented in the literature, the proposed approach includes the bearing losses, in which two expressions of the speed-time characteristics of IMs during no-load direct startup are derived. The first expression was derived based on the Kloss equation used for representing the torque, and the second expression was derived based on the torque expression determined from the Thevenin equivalent circuit of the machine. The derived expressions’ accuracy was validated using laboratory measurement and computer simulation approaches. The results obtained show a good agreement between the measured and simulated speed-time characteristics of two IMs. Finally, the proposed formulations can provide a simple analytical base to enable accurate IM modeling.
Highlights
Induction machine (IMs) are the oldest electrical machines, but they are widely used in industrial and domestic operations
To demonstrate the accuracy of the proposed expression for speed-time characteristics determination of an induction machines (IMs) during a direct startup, we studied an IM whose parameters are given in Table A2 in the Appendix B
The proposed expression for the speed-time curve during no-load direct startup based on the Thevenin theorem is very close to the results obtained by the Simulink model
Summary
Induction machine (IMs) are the oldest electrical machines, but they are widely used in industrial and domestic operations. This machine’s fundamental problem is its starting period, as starting this type represents a set of processes that occur during acceleration of the machine from zero speed to a specific speed (rated speed, no-load speed, or others) [1]. Many IMs’ starting methods can be found They can be classified into two broad categories—conventional motor starters and modern power electronicbased devices to start the machine. The second category involves methods that rely on power electronics devices or soft starters [2]. The DOL method is much more beneficial in parameters estimation of IMs [10,11,12]
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