Alija Cosic

Induction machine at unity power factor with rotating power electronic converter

A new configuration for the self-excitation of the induction machine invented by Magnus Lindmark is presented. The power electronic converter using solid state switches is connected to the rotor while the stator is directly connected to the grid. Using appropriate control, the reactive power consumed by the motor can be generated in the rotor resulting in unity power factor operation. The rotor connected power electronic converter is also used for constant speed operation of the induction machine at variable torque.

Design and Manufacturing of a Linear Transverse Flux Permanent Magnet Machines

In general transverse flux machines (TFM) are considered to be complex and difficult to manufacture. However, there are some exceptions. In the linear TFM the flux plane is the same as for the conventional rotating electrical machine. Therefore, iron laminations from conventional rotating machines can be used to manufacture the stator. The manufacturing process of the stator becomes then more simple compared to the manufacturing process of the conventional linear machine. This paper deals with a novel design of a linear TFM machine for the free piston energy converter application. It describes earlier designed and manufactured prototypes and a new manufacturing approach in order to avoid the loss in flux and thereby also loss in the force production.

Transverse Flux Machines for Sustainable Development - Road Transportation and Power Generation

The higher specific torque and power density of a transverse flux machine (TFM) in comparison to a conventional machine makes it a promising energy converter in various applications. In this paper, a free piston energy converter and a direct-driven wind turbine are considered. The analytical investigation of the novel TFM topology applied in these two cases is presented. The cogging torque is evaluated by use of a three-dimensional finite element method. The results of simulating generators rated in the range of 3-12 MW are discussed. Manufacturing of a linear prototype is presented.

Power Factor Improvement and Dynamic Performance of an Induction Machine With a Novel Concept of a Converter-Fed Rotor

This paper investigates an induction machine with a novel concept of the rotor fed by a converter. The stator is Y-connected and directly connected to the grid, while the rotor windings are open-ended and fed by a back-to-back converter with a floating capacitor. Power factor and efficiency improvements of the induction motor are studied with different settings of phase-shift angle between the two converters. Moreover, the dynamic performance of the induction machine is explored in MATLAB/Simulink and verified experimentally on a 1.8-kW induction machine in the laboratory. The result shows good agreement between simulation and experiment. At a constant speed, variable load operation of the induction machine is obtained by setting the frequency of the rotor voltage.

Design and optimization procedure of a single-sided linear induction motor applied to an Articulated funiculator

The paper describes the design of a single-sided linear induction motor (SLIM) intended for an Articulated Funiculator (AF). A procedure is proposed where first an analytical design is carried out to obtain a preliminary geometry. The analytical design is based on approximate equivalent circuits under constrained conditions. In the second step a two-dimensional finite element method (2D-FEM) analysis is performed to validate the accuracy of the analytical models. The modification and optimization are conducted to acquire the best design.

Analysis of an induction machine using a rotor integrated converter with a floating capacitor

A novel topology of induction machine with a rotor integrated converter with a floating capacitor is investigated in this paper. The stator windings of the induction machine are directly connected to the grid. While the rotor windings are connected to a converter with a floating capacitor. The steady state mathematical model is presented and used to predict the operating range of the induction machine. The result shows that the induction machine can operate in a wide torque and speed range instead of working on the original torque-speed curve. In addition, the relationship between capacitance and capacitor voltage is studied for the constant speed and variable load operation. It is shown that it is possible to choose a low volume and high capacitance capacitor since the average DC-link voltage is quite low.

Construction of a rotating power electronic converter for induction machine operation

This paper describes the construction of the rotating power electronic converter. By mounting the power electronics on the rotor of an induction machine, the rotor winding can be made easily accessible without the use of slip-rings and brushes. This offers certain advantages regarding motor control. However, it is evident that the rotating mass, communication with the converter and maintaining the mechanical stability and reliability of the system are huge challenges that must be overcome. This paper describes some solution that are partly investigated and some solutions that still needs to be investigated in more detail.

Synchronous operation of a rotating power electronic brushless doubly-fed generator

This paper presents the synchronous operation of a novel generator termed as the rotating power electronic brushless doubly-fed induction generator (RPE-BDFIG). It is shown that the generator operates well at the synchronous speed of the main machine, delivering the desired power to the grid. Furthermore, it is illustrated that the RPE-BDFIG behaves similar to a synchronous generator in the synchronous mode. The closed-loop control of the generator is implemented in real-time, and the current and voltage waveforms of the stator and rotor of the RPE-BDFIG are experimentally analyzed. The paper highlights the stable operation and full control of the generator during synchronous mode.

Investigation on the dynamic performance of an induction machine using a novel concept of a rotating converter with a floating capacitor

This paper explores a topology of induction machine drive with a novel concept of a wound rotor fed by a converter with a floating DC-link capacitor. The Y-connected stator windings are connected to the grid, while Y-connected rotor windings are connected to a three phase converter with a floating DC-link capacitor. By integrating the converter into the wound rotor, the slip-rings and the brushes becomes unneeded. Constant speed operation can be achieved at various loads by controlling the fundamental frequency of the converter. The stator power factor can be effectively improved over a wide range of load at constant speed. Particularly, unity power factor can be obtained within ±25% of the rated load. Moreover, harmonic spectra of the stator and rotor currents are presented.

3D analyses of a novel Transverse Flux machine for a free piston energy converter

The electrical machine is one of the key parts in the free piston energy converter (FPEC), and as such the electrical machine faces very tough requirements such as low weight of the translator and high power density. During the design process great emphasis has been put not only on the machine performance but also on the manufacturing process. This paper investigates a novel Transverse Flux Linear machine for the FPEC application. At first, the analytical calculations are performed based on some estimation of the leakage flux in the machine. However, during the FEM analysis and measurements it was obvious that a more detailed analysis was required in order to achieve a better agreement in results. A more detailed reluctance network is developed and used for the analysis. The results are compared with both FEM simulations and the measurements.