Abstract
The electromechanical systems under analysis include electric drives, working machines that perform specific tasks in the technological process, and working mechanisms that transmit mechanical power between the electric drive and the working machine. The vast majority of electric motors included in drive systems require rotational speed control. This task is most often performed with the use of closed-loop control structures based on speed controllers. A step or overly rapid change in the speed reference causes a temporary lock of the speed controller due to the applied limitations at its output. Particularly, unfavorable effects of such a lock can be observed in drive systems in which there is a long elastic coupling (transmission shaft) between the electric motor and the working machine. As a consequence, shaft torsion and accompanying twisting moments of considerable amplitudes appear. This article proposes an uncomplicated active torque limiter structure, which enables the uninterrupted operation of the speed controller thanks to the automatic adaptation of the rate of the speed reference change to any moment of inertia of the rotor and attached rotating masses. The results of the investigations confirm the effectiveness of the proposed structure.
Highlights
The aim of the research presented in this article is to analyze the behavior of an electromechanical system containing (a) a drive system consisting of an induction motor, a motor power supply system, and a vector control system, (b) a transmission shaft, and (c) a working machine, the role of which in the system under consideration is played by a DC brake generator
The tested drive system consists of an induction motor with a power of 4 kW coupled with a DC brake generator via a steel drive shaft 0.66 m long and 8 mm in diameter
The moment of inertia of the total mass containing the rotor of the DC generator and the disc installed at the end of the shaft is 0.17 kg·m2, while the moment of inertia of the total mass containing the rotor of the induction motor and the clutch is 0.042 kg·m2
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In order to analyze the operating states of electrical and electromechanical systems, there is a need to conduct complex tests that are long and expensive The solution to this problem is an analysis of the tested system presented in the form of a mathematical model. The unfavorable effects of such a lock can be observed in drive systems where there is a long elastic coupling (transmission shaft) between the electric motor and the working machine [5,6,13,17]. The aim of the research presented in this article is to analyze the behavior of an electromechanical system containing (a) a drive system consisting of an induction motor, a motor power supply system, and a vector control system, (b) a transmission shaft, and (c) a working machine, the role of which in the system under consideration is played by a DC brake generator. The authors’ own contribution is to identify the cause of the occurrence of weakly damped oscillations in the electromechanical system and to develop the structure of the module, which, when attached to a standard electric motor control structure, enables the uninterrupted operation of the speed controller and, the effective damping of oscillations in the mechanical system
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