Ebrahim Amiri

On the role of magnetic shunts for increasing performance of transverse flux machines

This paper presents work completed in order to investigate the importance of magnetic shunts in transverse flux machines. Two types of transverse flux machines with different configurations were designed and tested in the laboratory. The first type of machine is a transverse flux generator with inner rotor. This machine was designed according to one of the patents. The second type of the machine is a transfer flux generator with double coil. Both types of the generators were designed in such a way so that it was possible to implement magnetic shunts inside the machines. Finite-element method analysis and experimental results showed that transverse flux machines without magnetic shunts had a number of disadvantages compared to those with magnetic shunts. These disadvantages are: higher flux leakage in the stator cores, partial cancelation of flux linkage in the coils, higher cogging torque, and increased torque ripple. This paper showed that magnetic shunts played a significant role in the performance of transverse flux machines. As study showed, magnetic shunts complicate a manufacturing process and increase the weight of the machine. However, power to weight ratio of the machines with magnetic shunts is higher than that of the machines without magnetic shunts.

Analysis of PM transverse-flux outer rotor machines with different configuration

This paper presents the electromagnetic analysis of two permanent magnet transverse-flux outer rotor machines with and without magnetic shunts. The research started with designing and analyzing a permanent magnet transverse-flux machine with an inner rotor, previously patented by J. Giearas in 2010. However, the results obtained from the prototype test differed significantly from the estimated results. Applying three-dimensional (3-D) finite element method (FEM), the main problem of the machine was detected. The problem was in high flux leakage that weakened magnetic flux density in the stator poles. Such observation led to designing two machines with outer rotor, with and without magnetic shunts. The role of the magnetic shunts is to minimize flux leakage in the stator in order to improve the performance of the machine. Electromechanical parameters of both outer rotor machines, with and without magnetic shunts, are compared in the paper. Three-D FEM results are supported by laboratory analysis of the machines’ prototypes. Experimental measurements proved that the machine with magnetic shunts demonstrated better performance as compared with the machine without magnetic shunts. Presence of the magnetic shunts in the machine resulted in reducing of flux leakage and cogging torque.

Optimal switching-flux motor design and its cogging effect reduction

This paper presents an optimal switching-flux motor design in terms of cheap cost, simple manufacturing process, and easy maintenance. The high cogging effect and its impact on the performance of the machine is studied by measuring the following electromechanical characteristics of the machine in both generating and motoring regimes: cogging torque, electromagnetic torque and induced voltage. The results showed that high cogging torque negatively affect the performance of the machine. The goal of the research was to reduce the cogging torque of the motor without changing the shapes of permanent magnets and magnetic poles, and to avoid any implementation of the magnetic shunts or magnetic bars into the machine. Parametric analysis of the outer rotor configuration with different air-gap diameters showed the optimal machine design which offered: five times lower cogging torque, 8 percent increase in electromagnetic torque, 24 percent decrease in volume, and 33 percent decrease in copper mass compared to initial design of the machine. Additional recommendations on the motor improvements based on Finite Element Analysis (FEA) are also provided.

Comparison analysis of AC PM transverse-flux machines of different designs in terms of power density and cost

This paper compares four different configurations of PM transverse-flux machines. The permanent magnet transverse flux machines with: internal rotor; outer rotor with magnetic shunts; double coil; and outer rotor without magnetic shunts with optimal average air-gap diameter — are designed, analyzed and tested in the laboratory. The study implies that each design has its own advantages and disadvantages in terms of power density, cogging torque, and cost. Special attention is given to the manufacturing process of the machines, materials, and components, which determine the total cost of the machine. Power densities, cogging torque, and cost of the machines are compared and discussed. Conclusions on practical use of the proposed configurations are provided in the paper.

Line start synchronous motor for multi-speed applications

This paper presents a design of Line Start Permanent Magnet (LSPM) synchronous motors capable of operating in two different synchronous speeds. The stator winding consists of two independent windings to switch the operating pole count for low and high speed applications. The rotor is especially designed to be capable of creating two different magnetic polarities (pole numbers) to match with the operating stator pole number. The proposed design combines Synchronous PM and synchronous reluctance motors and enables the motor to operate as a synchronous PM motor at high speed and synchronous reluctance motor at low speed. To verify the performance of the proposed design, the motor is analyzed in steady state and transient domain using 3-D finite element analysis (FEA).

Line start permanent magnet synchronous motor with dual magnetic polarity

This paper presents a design for Line Start Permanent Magnet (LSPM) motors capable of operating in two different synchronous speeds. The stator winding consists of two independent 4-pole and 8-pole windings to switch the operating pole count for low and high speed applications. The rotor is especially designed to create two different magnetic polarities to match with the operating stator pole number. This enables the motor to operate as a synchronous PM motor at two operating speeds. To verify the performance of the proposed design, the motor is analyzed in steady state and transient domain using 3-D finite element analysis (FEA).

Indirect speed estimation of high speed brushless DC motor drive using fuzzy logic current compensator

In this paper, a new indirect speed estimation of high speed brush-less DC motor drive using fuzzy logic current compensator is proposed. In this method, brush-less DC motor currents are first measured and by using a brush-less DC motor model, current errors of each phase are calculated. Current errors and their derivative are inputs of fuzzy logic current compensator. This compensator modifies the motor currents by generating a compensating signal. Compensated currents are applied to torque estimation of each phase and therefore, speed and rotor position can be easily obtained. In order to decrease the processing time, a speed proportional integral controller is utilized. Proposed high speed sensor-less scheme is simulated by MATLAB/SIMULINK software. Simulation results illustrate that the proposed sensor-less scheme can effectively estimate speed and rotor position with high resolution. Also, time response of the proposed algorithm shows that indirect speed estimation is useful for fast drive applications.

Switched Reluctance Motor Topologies: A Comprehensive Review

Switched reluctance motor (SRM) is gainingmuch interest in industrial applications such as wind energy systems and electric vehicles due to its simple and rugged construction, highspeed operation ability, insensitivity to high temperature, and its features of fault tolerance. With continued research, different topologies have emerged presenting less torque ripple, high efficiency, high power factor, and high power density. However, there has always been a trade-off between gaining some of the advantageous and losing some with each new technology. In this chapter, various SRM topologies, design, principle of operation, and respective phase switching schemes are extensively reviewed, and their advantages and drawbacks are discussed. On the other hand, some of SRM limitations (such as excitation penalty, control complexity, noise, and vibration) have prompted research into the incorporation of permanent magnets into the basic SRM structure, and therefore, the chapter also includes discussion on a new class of SRMwith permanent magnet assist (PM-assist) called doubly salient permanent magnet (DSPMM). The DSPM motor incorporates the merits of both the PM brushless motor and the SRM.

Surface-climbing Planar Induction Motor

This paper presents simplified design of a planar induction motor climbing an inclined steel plate. The motor set-up consists of two individually controlled linear motors firmly coupled via an aluminum frame with a drive system to provide 1-D translational and rotational motion. The motor set-up is also equipped with a position sensor to locate the mover in real time. To simplify the motor structure a strategy is deployed to have the steel plate functioning as a partial magnetic circuit of the motor set-up simultaneously providing thrust and attractive force between the motor and the inclined steel plane. The proposed model is analyzed using 3-D Ansoft, Finite Element Software Package.

Discharge characteristics of trapped charge in power lines with underground cable and overhead line segments

The use of underground cables as power lines, either alone or in combination with overhead lines, is steadily increasing. After a cable is isolated from the system, its trapped charge starts to slowly discharge. We may need to determine the discharge time for multiple reasons such as safety, and limitations on circuit breaker capabilities to withstand capacitive inrush currents. This paper will modify the existing method of discharge time calculation considering the fact that the ends of the cable remain connected to the switchgear bus after cable isolation. A procedure is also presented to calculate the discharge time for the combination (series connection) of underground cables and overhead lines. Sensitivity studies are performed to investigate the effects of different factors such as the type and conditions of the line insulator and design voltage level on the discharge characteristics. All the studies are conducted on a real transmission system. However, the procedure and findings are general and can be used in any application such as in a distribution system or any industrial power system.