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In recent years, researchers have proposed transformerless solutions for connecting renewable-energy power plants to the grid. Apart from lack of efficiency and increased cost and weight of the transformer, one of the reasons is the dc input current that causes transformer saturation. The purpose of this paper is the development of a finite-element computational tool that is going to aid transformer manufacturers in designing distribution transformers specifically for the renewable-energy market. It is based on a generalized macroscopic representation of electrical steels used in the transformer manufacturing industry that enables the accurate evaluation of electromagnetic field distribution of transformer cores under heavily saturated conditions. Its advantages over conventional formulations include numerical stability, numerical accuracy, and reduction of iterations of the Newton–Raphson method. An experimental verification of the proposed method is carried out. [ABSTRACT FROM PUBLISHER]

This paper presents the measured experimental results from a four-pole toroidally wound induction machine, where the stator is constructed as a prewound foldable strip. It shows that if the machine is axially restricted in length, the toroidally wound induction machine can have substantially shorter stator end windings than conventionally wound induction machines, and hence, it shows that a toroidally wound induction machine can have lower losses and a higher efficiency. This paper also presents the employed construction method, which emphasizes manufacturability, and highlights the advantages and disadvantages of this method. [ABSTRACT FROM PUBLISHER]

This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator. The standard dq model of the machine is connected to a resistive load. A switching function is defined in order to fulfill control objectives, and the ideal sliding dynamics is proved to be stable. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes. [ABSTRACT FROM AUTHOR]

This paper introduces an alternative implementation of the traditional LC filter, called hybrid LC filter (HLCF). The construction described in this paper contains two foil windings that integrate inductance and capacitance into one unit. The main aspects of the HLCF design are considered. The experimental data show that the device proposed here can be used, instead of traditional LC filters, as an alternative solution for the mitigation of the adverse effects of the pulse-width modulation (PWM). [ABSTRACT FROM AUTHOR]

The objectives of this paper arise through the investigation of a motor with a high starting torque, although with limited intensities, weak intensity variations depending on the load, controlled losses in no-load tests, and an acceptable performance in steady state, and with a good response in transient periods. All these requirements would have to be obtained without the help of power electronics; in this way, the motor would be more robust, longer lasting, and without the need for auxiliary equipment. In this paper, the operation principle, the characteristic parameters, and the obtained results for the spiral sheet motor are analyzed for three speed regimes, namely, 1000, 1500, and 3000 r/min. In addition, the spiral sheet motor is compared with the squirrel cage rotor, the solid rotor with rings, the wound rotor with additional resistances in the rotor circuit, and the hollow diamagnetic rotor. [ABSTRACT FROM AUTHOR]