Control of Electromechanical systems
Mohsen Dashtbani; Majid Hasanzadeh; Reza Roshanfekr
Abstract
The conventional direct torque control (DTC) method suffers a flux drop at low speeds, which is due to the long selection of zero (neutral) voltage vectors in these speed areas. Past studies with the continuous switch of direct and reverse active vectors to achieve proper flux adjustment, this procedure ...
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The conventional direct torque control (DTC) method suffers a flux drop at low speeds, which is due to the long selection of zero (neutral) voltage vectors in these speed areas. Past studies with the continuous switch of direct and reverse active vectors to achieve proper flux adjustment, this procedure causes high and consecutive overshoots in the hysteresis band that causes a sharp increase in the switching frequency and increase in the torque and current ripple, which means decrease in the drive efficiency. In this article, a modified method for setting the standard DTC current is introduced, which can be achieved by controlling only one band (low or high band) at low speeds. The introduced method by reducing the selection of zero voltage vectors and at the same time minimizing the number of reverse voltage vectors prevents the loss of flux in low speed areas. In addition, it is effective in reducing torque ripple and current in low speed mode and a significant reduction in switching frequency will also be achieved. The effectiveness of the proposed method in the simulation which is done in MATLAB software will be proved.
E. Dehjoo; R. Haghmaram; A. Mosallnejad
Abstract
In this paper, the problem of starting an induction motor is investigated and a solution is presented. The large current and considerable torque pulsation of the starting can damage the motor and other consumers connected to the feed line, and increasing the startup time will cause more heat and damage ...
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In this paper, the problem of starting an induction motor is investigated and a solution is presented. The large current and considerable torque pulsation of the starting can damage the motor and other consumers connected to the feed line, and increasing the startup time will cause more heat and damage to the winding insulators. Various methods exist for startup of the induction motor, including the stator voltage control via wye-delta circuit breaker, autotransformer, and new methods such as soft starter, as well as methods for controlling the rotor's resistance, and control of V/f. However, in this research, by connecting a torsion spring between the motor shaft and the load, a new method of startup has been proposed. Therefore, due to the delay in the rotation of the load during the absorption of energy in the torsion spring it is possible to rotate loads with a torque beyond the motor starting torque, and to reduce the motor startup time as much as 77%. These cases increase the lifetime of the motor, and reduce economic costs.
