Dc-excited Flux-switching Machine Research Articles

Sensorless Control System for a Single-Phase DC-Excited Flux-Switching Machine With Self-Starting Capability

Single-phase dc-excited flux-switching machine (DCFSM) exhibits low manufacturing cost and rugged structure. This type of machine has better efficiency and torque density than single-phase induction machine and universal machine. In addition, single-phase DCFSM can generate lower torque ripple than other types of single-phase machines, e.g. switch reluctance machine and brushless DC machine. These advantages make it suitable for low-cost variable speed applications. However, single-phase DCFSMs requires accurate position feedback from a position sensor to generate smooth torque. The position sensor such as an encoder is not permitted in the low-cost applications due to its high cost. To eliminate the position sensor, this paper presents a novel sensorless control scheme for single-phase DCFSMs. Rotor position is estimated with the position-dependent armature current ripple induced by injecting high-frequency square-wave voltage to the field winding at standstill and low speeds. At medium and high speeds, armature mutual flux linkage is calculated and used to estimate the rotor position. A seamless transition between these two methods is achieve by mixing the calculated position error signals as the input for a single position estimator. The experimental results show that with the proposed scheme, the single-phase DCFSM can accelerate from standstill to the rated speed with 50% load, and to the maximum speed with 25% load, respectively.

A Novel Analysis on a New DC-Excited Flux-Switching Machine Using Modified MEC Method for Ground Power Unit Application

This article presents a novel analysis on a new DC-Excited Flux-Switching Machine (DC-FSM) for Ground Power Unit (GPU) application. The performance of machine under different structures can be studied by a flexible Magnetic Equivalent Circuit (MEC), where the core non-linearity can be fixed on the material B-H curve. The model accuracy can also be adjusted arbitrary by determining the number of proposed MEC elements (flux tubes) for a given structure. The performance analysis of two sample DC-FSMs as two high-frequency 120 V generators is performed by the proposed MEC and validated by 2D and 3D FEM based simulations. The obtained results show a very good improvement in processing time with valuable accuracy. In general, introducing a new DC-FSM for the GPU application and analyzing its performance by proposing a modified MEC approach are the paper novelties which are studied in this work. Since the suggested MEC is more flexible than FEM, it is recommended for designing, modeling, and optimization purposes.

Control System for a Single-Phase DC-Excited Flux-Switching Machine With a Torque Ripple Reduction Scheme

Single-phase dc-excited flux-switching machines (DCFSMs) are suitable for operations in harsh environments and cost-sensitive applications due to their rugged structure. However, the practical application of DCFSMs is limited because significant torque ripple is generated in them as the armature current commutates. However, with a marginal modification to the rotor structure, the single-phase DCFSM exhibits a unique property that its reluctance torque is complementary to its electromagnetic torque. A significant reluctance torque can be generated by the field current near the commutation positions. To explore the characteristics of the complementary torque, this paper presents a speed control system with a torque ripple reduction scheme for single-phase DCFSMs. In this scheme, the armature and field currents are controlled with precalculated profiles such that the reluctance torque compensates for the loss of the electromagnetic torque near the commutation positions. The experimental results indicated that with the proposed control scheme, the maximum torque ripple reduced to 56% near the commutation positions when the machine provided the rated torque. Moreover, because the studied DCFSM generated highly linear torque, satisfactory speed control performance was achieved.

Design of a High Starting Torque Single-Phase DC-Excited Flux Switching Machine

Because single-phase dc-excited flux switching machines (DCFSMs) consist of only copper windings and iron cores, they have great potential in low-cost and high-speed applications, such as home appliances. However, similar to other types of single-phase ac machines, single-phase DCFSMs have insufficient initial torque at some rotor positions. A novel single-phase, eight-slot, four-pole DCFSM design is presented in this paper. The key feature of this design is the enhancement of reluctance torque at positions where the machine cannot deliver sufficient initial torque output. This is accomplished by modifying the outline of a section of the rotor. Consequently, the machine has a two-layer rotor structure along the axial direction. The proposed design is validated experimentally using a prototype. The results show that the machine can start from any rotor positions with initial torque higher than 50% of the rated output torque.

Modeling Torque Characteristics and Maximum Torque Control of a Three-Phase, DC-Excited Flux-Switching Machine

Three-phase, dc-excited flux-switching machines have been widely researched in recent years. They use dc field windings to produce a field that interacts with the flux produced by the armature windings to generate torque. Numerous studies have discussed designing this type of machine; however, only a few studies have investigated controlling their maximum torque. This paper examines the torque characteristics of a three-phase, 24-slot, 14-pole, outer rotor, dc-excited flux-switching machine, and presents a control strategy for achieving maximum torque output. This machine is designed for traction applications. The mathematical model was derived from the finite-element analysis results. In addition to the theoretical analysis, the proposed control strategy was also verified experimentally.

Energy Conversion in DC Excited Flux-Switching Machines

This paper initiates a study on energy conversion in dc excited flux-switching machines (DCEFSMs) to reveal the torque production mechanism of this type of machines. The flux linkage components and self- and mutual inductances of a single-phase two-rotor-tooth DCEFSM are investigated. Based on the understanding of the relation between these variables and the rotor position, two different switching strategies are implemented to the armature current of this machine. Current-flux linkage loops are sketched for each switching strategy, resulting in different torque expressions. These torque expressions, validated using finite element analysis, show that the DCEFSM is a reluctance machine in which torque is generated due to variation of self- and mutual inductances. In addition, the torque component related to the mutual inductance can be dominant with certain current commutation in the armature winding.

Flux-Switching Machine With DC Excitation

This paper proposes a topology of flux-switching machine with dc excitation to improve the field-weakening capability of flux-switching machines. This dc-excited flux-switching machine preserves the structure of typical flux-switching permanent-magnet machines while replacing the permanent magnets with dc field windings. The combined advantages of this type of machine in torque production and field weakening are exhibited and validated by finite element analysis.