Current Issue : July - September Volume : 2018 Issue Number : 3 Articles : 5 Articles
In this paper, an U-shape flux barrier rotor concept for a hybrid excited synchronous\nmachine with flux magnetic bridges fixed on the rotor is presented. Using 3D finite element\nanalysis, the influence of axial flux bridges on the field-weakening and -strengthening characteristics,\nelectromagnetic torque, no-load magnetic flux linkage, rotor iron losses and back electromotive force\nis shown. Three different rotor designs are analyzed. Furthermore, the field control characteristics\ndepending on additional DC control coil currents are shown....
In any drive system, there are always couplings between the motor and the load. Since the\nhardness of these couplings is finite, they have elastic properties, causing unwanted vibration and\nnegatively affecting system quality. When the couplings are springs with nonlinear characteristics,\ncontrol is particularly difficult because it is very difficult or impossible to define the parameters\nof the controlled object. To solve these difficulties, this article proposes an adaptive controller of\nthe major functions for controlling a drive system with nonlinear elastic couplings of unidentified\nparameters. For the proposed control system, we measure the response speed of the object, use a\nLuenberger observer to estimate the state variables of the system, and use an adaptive controller to\ncontrol the system. The experimental results demonstrate that the control object can be controlled\nwithout knowing the parameters: the control quality of the system is very good, close to that of a\nsystem with a hard coupling, there is no vibration or overshoot, and the transition time is small....
Small direct current (DC) motors are widely used due to their low cost and compact\nstructure. Small DC motors of various designs are available on the market in different sizes.\nThe smaller the motor, the more closely it may be used by individuals. Contrary to the size and\nsimplicity of these motors in terms of structural design, sources of motor noise and vibration can be\nquite diverse and complicated. In this study, the source of motor noise and vibration was visualized\nover a very wide range of frequencies. The particle velocity of the motor was reconstructed from\nnearfield sound pressure measurements of motor noise. In addition to noncontact measurements\nconducted on a motor running at constant speed, the particle velocity of a stationary motor due to the\nimpulse of an impact hammer was measured with an accelerometer. Furthermore, motor noise was\nmeasured under motor run-up conditions with different rotational speeds. As a result, by combination\nof these three methods, the sources of motor noise were accurately identified over a wide range\nof frequencies....
A DC cable short-circuit fault is the most severe fault type that occurs in DC distribution\nnetworks, having a negative impact on transmission equipment and the stability of system operation.\nWhen a short-circuit fault occurs in a DC distribution network based on a voltage source converter\n(VSC), an in-depth analysis and characterization of the fault is of great significance to establish relay\nprotection, devise fault current limiters and realize fault location. However, research on short-circuit\nfaults in VSC-based low-voltage DC (LVDC) systems, which are greatly different from high-voltage\nDC (HVDC) systems, is currently stagnant. The existing research in this area is not conclusive, with\nfurther study required to explain findings in HVDC systems that do not fit with simulated results or\nlack thorough theoretical analyses. In this paper, faults are divided into transient- and steady-state\nfaults, and detailed formulas are provided. A more thorough and practical theoretical analysis with\nfewer errors can be used to develop protection schemes and short-circuit fault locations based on\ntransient- and steady-state analytic formulas. Compared to the classical methods, the fault analyses\nin this paper provide more accurate computed results of fault current. Thus, the fault location method\ncan rapidly evaluate the distance between the fault and converter. The analyses of error increase and\nan improved handshaking method coordinating with the proposed location method are presented....
The need of a sustainable clean future has paved the way for environmental friendly\nelectric vehicle technology. In electric vehicles, overloading is limited by the maximum temperature\nrise in the electric motor. Although an improved cooling jacket design is of vital importance in\nlowering the maximum temperature of the motor, there has not been as much study in the thermal\nanalysis of motors compared to electromagnetic design studies. In this study, a three-dimensional\nsteady state numerical method is used to investigate the performance of a cooling jacket using water\nas the primary coolant of a three-phase induction motor with special emphasis on the maximum\ntemperature and the required pumping power. The effective thermal conductivity approach is\nemployed to model the stator winding, stator yoke, rotor winding and rotor yoke. Heat transfer by\ninduced air is treated as forced convection at the motor ends and effective conductivity is obtained\nfor air in the stator-rotor gap. Motor power losses, i.e., copper and iron losses, are treated as heat\ngeneration sources. The effect of bearings and end windings is not considered in the current model.\nPressure and temperature distributions under various coolant flow rates, number of flow passes and\ndifferent cooling jacket configurations are obtained. The study is successful in identifying the hot\nspots and understanding the critical parameters that affect the temperature profile. The cooling jacket\nconfiguration affects the region of maximum temperature inside the motor. Increasing the number of\nflow passes and coolant flow rate decreases maximum motor temperature but results in an increase\nin the pumping power. Of the cooling jacket configurations and operating conditions investigated,\na cooling jacket with six passes at a flow rate of 10 LPM with two-port configuration was found to be\noptimal for a 90-kW induction motor for safe operation at the maximum output....
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