Outer Rotor Structure Research Articles

Performance Analysis of an Outer Rotor Variable Reluctance Resolver

Variable reluctance resolver (VR-Resolver) is a robust electromagnetic sensor that provides position information for closed-loop control systems of permanent magnet synchronous motors (PMSMs). For specific motion control applications, an outer rotor structure is presented for the VR-Resolver in this article with a nonoverlapping tooth-coil windings configuration to simplify the manufacturing process. The study on the structure of the proposed position sensor is carried out, followed by the description of the working principle. The presented outer rotor VR-Resolver is simulated and its performance is investigated in detail with the aid of transient finite-element analysis (TFEA). Sensitivity analysis is carried out on the rotor shape factors and slot opening, and the effect of manufacturing tolerances is investigated as well. Finally, the effectiveness of the optimal design is verified by 3-D TFEA.

A novel flywheel energy storage system: Based on the barrel type with dual hubs combined flywheel driven by switched flux permanent magnet motor

With the challenges of global carbon emissions and climate warming, energy recovery and reuse are becoming very important. Flywheel energy storage system (FESS), as a kind of energy storage systems (ESSs), can effectively convert electrical energy and mechanical energy to accomplish energy recovery and reuse. Additionally, the FESS has the characteristics of pollution-free, high energy, high efficiency, and durability. Thus, a novel FESS is proposed for the configuration, metal material and structure, and driving motor (M/G) to contribute to the development of FESS. First, the novel FESS is made of the metal materials rather than the carbon fiber, reducing manufacturing difficulty and cost. Second, the structure of dual hubs combined flywheel is designed to reduce the mass and obtain a larger moment of inertia, achieving higher energy storage. Third, a 12/10 switched flux permanent magnet motor (SFPM) with an outer rotor structure is designed to replace the conventional permanent magnet synchronous motor (PMSM) and is used as the M/G to achieve excellent operation performance. Finally, the barrel type of the configuration makes the novel FESS more compact and facilitates the realization of a vacuum chamber to remove the windage. Undoubtedly, the novel FESS is designed through the theoretical calculation of energy storage, structure strength and modal analysis, and M/G performance simulation. Accordingly, the novel FESS has a maximum speed of 13,500 rpm, storage energy of 20 kWh (discharge depth 99%), and the longest power consumption time of 2 h. Equally, a prototype is manufactured and tested. Consequently, the results testify the mechanical properties are excellent, the charging and discharging action is stable and rapid.

Design and analysis of a novel variable flux spoke-type motor for washing machines

This paper deals with the design and analysis of a novel variable flux spoke-type motor (VFSM) for washing machines by focally considering the performance at the laundry and spin-drying operating modes. The key design goal is to obtain the high efficiency for the two operating modes. At the laundry mode, the ferrite and AlNiCo magnets are utilized together as the excitations to obtain a high magnetic loading, thus to obtain high torque and efficiency. At the spin-drying mode, the AlNiCo magnets are demagnetized by a pulse negative d-axis current to reduce magnetic flux density, thus to obtain low iron loss and high efficiency. The outer rotor structure with the spoke-type magnet configuration is utilized to enhance the high output performances. The D2L method is utilized to design the key parameters of the VFSM. To demonstrate the superiority of the designed VFSM, the electromagnetic characteristics are predicted by the finite element method (FEM). As a result, the volume size of the proposed VFSM is decreased by 19.4%, and the efficiency at the low-speed laundry mode is increased by 25.4%, when compared to the referenced commercial washing machine motor.

Optimal rotor design of novel outer rotor reluctance synchronous machine

This paper presents the optimal design and performance analysis of a novel synchronous reluctance motor with outer rotor for determination of the effect of the rotor pole shape on the machine’s performances. The investigation has been made in order to find the possible ways to improve the power factor with refining the rotor geometry without using permanent magnets. Starting from the design of the machine with classical rotor pole that was implemented in FLUX 2D, a finite element analysis software coupled with an optimal design procedure implemented in MATLAB was performed. The purpose of this complex co-simulation was to obtain several outer rotor structures that increase the performances of the machine: saliency ratio, power factor and torque density. For the proposed structures, especially for the modular topology, the obtained results of saliency and power factor have never been presented in the past literature. Hence, this represents a useful starting point for the following analysis of outer rotor synchronous reluctance machines with improved power factor.

Optimal Design of Outer Rotor Interior Permanent Magnet Synchronous Machine With Hybrid Permanent Magnet

In this paper, an outer rotor interior permanent magnet synchronous machine (IPMSM) with hybrid permanent magnet (PM) material is proposed. The key is to adopt the outer rotor structure with two-layer crescent barriers and hybrid PM material to maximize the output torque and reduce the usage of high-cost rare-earth PM. The ferrite PMs are filled in the middle of the crescent barriers with thicker thickness, while the rare-earth PMs are filled into the bilateral of the crescent barriers with thinner thickness. To verify the effectiveness of the proposed rotor structure, optimizations are first carried out among the conventional rotor structures with single kind of PM material and the proposed rotor structure with hybrid PMs. Then, detailed comparisons have been investigated. Results indicate that the proposed machine has higher torque density than the machine with only ferrite PM and can reduce almost half the usage of rare-earth PM in comparison to the machine with only rare-earth PM. Moreover, the proposed rotor structure is further optimized considering productivity.

Radial-Flux Permanent-Magnet Limited-Angle Torque Motors

Slotless radial-flux permanent-magnet limited-angle torque motor with disturbed armature winding is analyzed in this paper. For the first time, the outer rotor structure is investigated for this type of the rotary actuator. The exact 2-D analytical modeling is applied to obtain the magnetic field parameters of the windings and excitation for both the outer rotor and the conventional inner rotor topologies. Also, the governing and geometrical equations are derived based on the analysis outcomes. Then, they are validated by applying the finite-elements tool. Both topologies are designed and compared with each other considering a variety of utilization parameters of these actuators. Avoiding saturation is considered as a designing criterion, which corresponds to the maximum torque production without distortion of linear characteristics in short-time operations. Experimental results show good accuracy of the theoretical design and numerical simulations. Comparison of the results shows significantly better performance of the new proposed actuator with the outer rotor structure against the conventional inner rotor type.

A New Hybrid-Structure Machine With Multimode Fault-Tolerant Operation for Mars Rover

This paper presents a new hybrid-structure machine, which possesses the distinct merit of multimode fault-tolerant operation for driving Mars Rover. Namely, the proposed machine is designed with three operation modes, including Mode I for the normal operation, Mode II for the remedial field-excited operation, and Mode III for the remedial rotor operation. To obtain these operation modes, the machine design adopts the outer rotor structure with a segmented-iron ring and a special teeth-split inner stator. In this way, the proposed machine is capable of providing the desired torque output at low speeds under the normal or fault situations. Both the machine design principle and the corresponding results are given to verify the validity of the idea. Furthermore, the different combinations of the torque outputs under different operation modes for four-wheel motors of Mars Rover are analyzed and discussed.

Design and validation of outer rotor magnetorheological brake with multiple poles

A magnetorheological brake with multiple poles and an outer rotor structure is introduced in this paper. It is designed to be used as a resistant source for bicycle training equipment. The outer rotor structures works as a roller against the bike rear wheel for indoor exercise. The key factors to affect the brake torque were found after an analysis of the magnetic circuit of the brake. Two structures with different pole numbers were simulated to find the optimal one which harmonises between the maximum output torque and the input power. Simulation results confirm the feasibility of the outer rotor magnetorheological brake concept. The optimal brake was later manufactured and experimented for validation. Its torque can be controlled precisely by an input current with a very fast response. The maximum brake torque is 5 Nm at a 0·9 A input current. Those phenomena are applicable for the bicycle training equipment. Moreover, the compact design of the brake shows advantages in weight and space reductions.

Structural Analysis and Validation of the Multi-pole Magnetorheological Brake for Motorcycles

Magnetorheological fluid (MR) has been developed and applied in various systems on vehicles such as suspension, engine mount and heavy-truck seat. However, due to its small maximum torque, conventional MR brake currently cannot be successfully applied on vehicles. In this paper, a multi-pole MR brake for motorcycle has been proposed. The targeted MR brake not only provides sufficient braking torque, but also maintains an acceptable size. With unique operation concept, two brake designs of the new MR brake, one has inner-rotor structure and another has outer-rotor structure, have been designed and analyzed for its application feasibility. For the ease of verification in braking performance, a comparison procedure was built in which braking torque is evaluated based on the torque-to-volume ratio. Magnetic simulation results show that the two designs can certainly reach the targeted torque while the one with outer-rotor structure has better compact design. This design proves its feasibility for using on motorcycle brake system.

A Study of Novel Hybrid Antilock Braking System Employing Magnetorheological Brake

A novel hybrid antilock braking system (ABS) with the combination of auxiliary brake and a multipole magnetorheological (MR) brake was proposed in this paper. The MR brake with innovative operation concept can replace existed hydraulic brake system or works as an auxiliary brake. Two simulation models of the MR brakes, inner rotor and outer rotor structures, have been built. The outer rotor design was chosen due to its better braking performance and suitable mechanism for using on motorcycle. After that, motorcycle simulation software was employed to validate the hybrid ABS system under appropriated working condition. Two controllers, the ordinary and self-organizing fuzzy logic controllers (FLC and SOFLC), were evaluated on ABS performance to pick the suitable one. Simulation results confirm the more adaptations to different road conditions of the SOFLC with 18% higher brake performance compared to ones of ordinary FLC. Brake performance can increase 12% more with the combination of SOFLC and road condition estimator (RCE). It is concluded that this hybrid ABS is feasible for actual application by effectively improving the brake performance for ensuring driving stability.

The Analysis of Magnetorheological Brake Structure with Multiple Poles

Magnetorheological (MR) brake is broadly applied in various fields. As the increase in demand of bicycle training equipment, this paper introduces a MR brake with multiple poles and outer rotor structure, which can be used as resistant source for bicycle-training equipment. With outer-rotor structure, the MR brake is suitable to use as a roller to fit the bike rear wheel on. The equipment is specifically designed for indoor exercise for users with their bikes. Magnetic circuit of the MR brake was built and analyzed. Key factors to affect brake torque were found. After that, two structures of the MR brake with different pole number were simulated to find the optimal one to harmonize between maximum output torque and input power. The simulation results confirm the feasibility of the designed MR brake. With compact design, its braking performance is enough to be use on bicycle-training equipment.

Integrated Generator for More Electric Engine: Design and Testing of a Scaled-Size Prototype

In this paper, the main design characteristics of a scaled-size prototype of an integrated generator for More Electric Engine application are presented. The reference electrical machine is a surface-mounted permanent-magnet machine directly integrated inside the aircraft main gas turbine engine. Therefore, as for the reference machine, the designed scaled-size prototype is characterized by an annulus-shape outer-rotor structure, and it is cooled by air flowing through the airgap. To satisfy the fault-tolerant requirements imposed by the aerospace application, the stator winding is constituted by multiphase single-layer nonoverlapping fractional-slot concentrated windings. In order to validate the designed machine, the experimental results of tests conducted on the prototype are reported. Among these ones, particular interest is focused on the cooling capabilities of the cooling air which flows through the machine airgap. Furthermore, based on the reduced-scale prototype experience, some considerations and the main design characteristics of the full-size machine design are reported too.

Design and Analysis a Small Permanent-Magnet Generator for Wind Power Applications

This paper aims to develop a small permanent magnet (PM) synchronous generator for direct-coupled, low-speed wind turbine applications. The generator, rated 3-phase 110 V and 1 kW is designed as an outer rotor structure. The design and optimization of the generator is done with the aid of the electromagnetic field analysis based on the finite element method.

Stator-Permanent-Magnet Reluctance Generator using Ferrite Magnet for Small-Scale Renewable Energy Generation

SummaryThis paper discusses a stator-permanent-magnet reluctance generator (PMRG) (Fig. 1). The PMRG has a doubly salient pole structure, and has permanent magnets embedded in the stator yoke. Concentrated windings are arranged individually around each stator pole. On the other hand, the rotor has neither permanent magnets nor windings. Therefore, the PMRG has a simple and robust structure, and permits a multipolar structure. It is expected that the PMRG is applied into a small-scale wind-turbine and hydroelectric power generation. However, two major technical problems still remain. One is the cost of rare-earth magnets, and the other is torque ripple due to the doubly salient pole structure. First, this paper presents a PMRG using ferrite magnets. The ferrite magnet has about three times lower residual magnetic flux density as compared to the rare-earth magnet, but has about 10 times lower cost. It is demonstrated that the proposed PMRG using ferrite magnets has almost the same output power as that using rare-earth magnets by employing an outer rotor structure (Fig. 4). In addition, its material cost is lower by about 45 %.Next, it is proposed a method for reducing torque ripple of the PMRG by stacking two rotors (Fig. 10). One rotor is shifted by 180° in electrical angle from the other rotor. In addition, the rotor pole-tips are cut off so that the torque waveform consists of only odd-harmonics. In such a structure, the torque ripple of the PMRG can be completely cancelled in theory.Finally, a trial two-stacked outer-rotor PMRG has been manufactured. The maximum output power is 777 W at 1000 rpm, and the efficiency at the point is 84.5 %. In addition, the efficiency at less than 1000 rpm is improved by over 10 % in comparison with the present PMRGs with rare-earth magnets (Fig. 19).

Design and finite-element analysis of an outer-rotor permanent-magnet generator for directly coupled wind turbines

This paper presents the design and finite-element analysis of a permanent-magnet generator using neodymium-iron-boron magnets for directly coupled wind turbines. For the sake of small size and light weight with extra low speed for direct coupling, the outer rotor structure is used. The simple magnetic equivalent circuit approach is used for initial design iteration, and the finite-element method is applied to analyze the detailed characteristics. Comprehensive experimental tests were conducted to verify the theoretical predictions. Agreement between the theoretical work and testing results was good.