جستجوی مقالات مرتبط با کلیدواژه "موتور القایی" در نشریات گروه "مکانیک"

It is very important to improve the parameters of the electric motor in order to improve its performance. One of the ways to improve the performance of electric motors is to use permanent magnets in the structure of induction motors. These types of motors are known as line start motors. The use of permanent magnets eliminates ohmic losses and increases efficiency. Due to the fact that permanent magnetism plays the most important role in these motors, the smallest change in the magnetic properties of the used magnet will cause malfunction of the machine. One of the important phenomena that changes the properties of the core magnet is the phenomenon of demagnetization. Although this phenomenon has very destructive effects on engine performance, the design of electric motors is still done without considering this issue. In this article, a line start motor is designed. The numerical simulation results show that the performance and efficiency of the motor in the demagnetization mode are significantly reduced. Also, the increased current in demagnetized motors causes a further decrease in the magnet's magnetic properties. This effect is progressively repeated many times until the property of the applied permanent magnet is lost. Finally, an analytical model was presented for examining and designing electric motors, considering the effects of demagnetization. The results showed that the use of the analytical model of motor design considering the effects of demagnetization can be a suitable alternative to the use of conventional methods in the design of electric motors.

This paper investigates the sophisticated analysis of a novel switching strategy for a matrix converter (MC) based direct torque control (DTC) of an induction motor (IM) drive. The proposed switching paradigm utilizes twelve 30° sectors for both flux and voltage vectors. Analytical expression of change rates of torque and flux for IM as a function of MC’s voltage vectors are derived. The influence of MC’s voltage vectors on the stator flux and electromagnetic torque variation is scrutinized and  an advanced switching scheme independent of any load and speed variation is developed. To decrease the switching losses of MC, the optimum switching state is selected by means of discretization and averaging on the flux variations. The performance of the proposed switching strategy is corroborated under rated conditions, and is also compared to the conventional hexagonal boundary switching scheme. The proposed method is characterized by low torque ripples, no need for rotational coordinate transformation and minimized switching frequency. The results verify that the degree of freedom to select proper voltage increases, and the torque ripple is hence significantly reduced up to 40%.

Fault propagation analysis is a method based on graph theory used to study the propagation of the effects of faults and disturbances in the system parts. The inclusion of fault propagation and interference of fault and disturbance effects in the design of fault detection algorithms increases reliability and reduces false alarms in critical equipment. In this paper the failure mode and effects analysis (FMEA) method was used to prepare a list of the possible faults and disturbances of each part of a system including of an induction motor and a centrifugal pump. Then a logical model is obtained through the fault propagation analysis to explain the connection between different parts of this system and the propagation of the electrical, vibrational and process effects. This model can be used to consider the propagation of the effects of faults and disturbances in system parts, and the interference of these effects and to select the appropriate effects or sensor configurations required for robust fault detection. The concept of this method is illustrated in this paper by applying this technique to an experimental system.