Toroidal Winding Research Articles

A Dual-Rotor Axial-Flux PM Motor With Equidirectional Toroidal Winding and 3-Slot/4-Pole Unit Block for Torque Density Improvement

A Dual-Rotor Axial-Flux PM Motor With Equidirectional Toroidal Winding and 3-Slot/4-Pole Unit Block for Torque Density Improvement

Unified Analytical Modeling of Armature Magnetic Field of Slotless PM Motor With Equidirectional Toroidal Winding

Unified Analytical Modeling of Armature Magnetic Field of Slotless PM Motor With Equidirectional Toroidal Winding

Inductance Calculation and Analysis of Axial-Flux Slotless Surface-Mounted Permanent Magnet Machine With Equidirectional Toroidal Winding

Inductance Calculation and Analysis of Axial-Flux Slotless Surface-Mounted Permanent Magnet Machine With Equidirectional Toroidal Winding

A 10 µH Inductance Standard in PCB Technology with Enhanced Protection against Magnetic Fields

Low-frequency working standards of inductance are generally uniformly wound toroids on a ceramic core. Planar inductors made using printed circuit board (PCB) technology are simple and cheap to manufacture in comparison to inductors wound on toroid cores, but they are significantly prone to the influence of external magnetic fields. In this paper, we propose the design of a PCB inductance working standard of 10 μH, consisting of a duplex system of planar PCB coils, electrostatic shielding, and an enclosure. Alongside an electromagnetic analysis and design procedure, the measurements on the manufactured prototype included the generated magnetic field, the thermal time constant of the enclosure, temperature coefficients, and its error analysis. The measurements show negligible generated magnetic fields (<1.68 nT at 7 cm, 49 mA, 10 kHz). The minimum thermal time constant of the enclosure is 1270 s and the temperature coefficient of resistance is 0.00384 1/℃. The presented method of temperature coefficient measurement using a climate chamber allows for measurements in the temperature range of 10 °C to 40 °C. In this temperature range, the results show an inductance variation of 0.05 µH at 50 kHz, while the uncertainty of inductance measurement at this frequency was 0.03 µH (k = 2).

Comparative Study of High-speed Permanent Magnet Synchronous Motors with In-line Slot Conductors and Equidirectional Toroidal Windings

The high-speed permanent magnet synchronous motor (HSPMSM) plays an important role in a wide range of engineering fields due to its high power density, high efficiency, and light weight. In this paper, a HSPMSM equipped with in-line slot conductors(I-LSC) is proposed and compared with one equipped with equidirectional toroidal winding (ETW). Firstly, the differences between them are revealed, including topology, back-electromotive force (EMF), slot fill factor, copper loss, and torque. Secondly, two-dimensional finite element method (2D-FEM) tools are used to obtain more precise performance such as air-gap field, back-EMF, torque characteristics, efficiency maps, and the unbalanced magnetic force (UMF). Considering the end-windings of copper loss of ETW and the end ring copper loss of I-LSC, the losses and efficiency of two motors are simulated by three-dimensional finite element method (3D-FEM). Finally, the simulation results validate the feasibility of the newly proposed winding and indicate that in-line slot conductors have superiority in power density due to the high slot fill factor.

Electro-thermal co-design of a variable pole toroidal induction motor

The United States Department of Energy targets an 88 % reduction in motor and power electronics volume by the year 2025 while minimizing or eliminating magnet usage. Induction machines are a magnet-free alternative with advantages such as low cost, high reliability, and capability of withstanding high short-term overload. To meet these societal goals, we develop an induction machine that uses an electro-thermal co-designed converter-integrated thermal management approach. The machine utilizes toroidal windings in the stator, and an 18-phase power converter to achieve 40 kW/L power density. An optimized jacket design was developed to enable the effective thermal management of the stator and integrated power electronics. The toroidal winding configuration provides advantages for thermal performance over conventional distributed windings due to an increased winding copper surface area without reducing slot-fill factor, thereby allowing for a higher stator density. The improved thermal performance of the toroidal winding design was verified using three-dimensional conjugate computational fluid dynamic simulations. A reduced-order transient model was then developed to generate torque-speed-temperature plots at various load conditions. The transient thermal analysis was extended to verify safe operation of the motor during a typical drive cycle for the desired application. The thermal design models developed in this work are robust and scalable to other motor sizes providing a framework for co-designing and developing thermal management systems for electric motors.

Analytical model for magnetic field distribution and electromagnetic characteristics analysis of permanent magnet synchronous motor with toroidal winding stator and sinusoidal Halbach array rotor

Analytical model for magnetic field distribution and electromagnetic characteristics analysis of permanent magnet synchronous motor with toroidal winding stator and sinusoidal Halbach array rotor

Comparison of Toroidal and Tooth-Coil Winding 2-Pole Slotted High-Speed Permanent Magnet Motors

Comparison of Toroidal and Tooth-Coil Winding 2-Pole Slotted High-Speed Permanent Magnet Motors

AC-Winding-Resistance Calculation of Toroidal Inductors with Solid-Round-Wire and Litz-Wire Winding Based on Complex Permeability Modeling

This paper has investigated a method for calculating the frequency-dependent winding resistance of toroidal inductor windings with Litz-wire as well as solid-round wire. The modified Dowell’s model is employed to address the effectiveness for inductor windings with the low and high filling factors. To overcome the limitation of this model, especially for a winding densely wound around the core, an alternative approach based on the complex permeability and iterative calculations is proposed. For the calculated AC-resistance factor of five inductors with different numbers of turns, layers with the same wire diameters are compared with that of FEA, and the three air-core toroidal windings are manufactured and tested within the frequency where the self-resonance can be neglected. The proposed model demonstrates the versality of the AC-resistance calculation of both solid- and Litz-wire windings within an error of 15% across a wide range of frequencies up to 1 MHz, compared with FEA.

A Novel Robust Double-Side Linear Resolver Proposal With Toroidal Windings

A Novel Robust Double-Side Linear Resolver Proposal With Toroidal Windings

Core Loss Analysis of Flux Switching PM Machines with Toroidal Winding and Concentrated Winding by Field Modulation Theory

Core Loss Analysis of Flux Switching PM Machines with Toroidal Winding and Concentrated Winding by Field Modulation Theory

High-Frequency Motor Impedance Analysis and CM Current Estimation of Electric Motors with Concentrated and Toroidal Windings

High-Frequency Motor Impedance Analysis and CM Current Estimation of Electric Motors with Concentrated and Toroidal Windings

General Analytical Modeling for Armature Magnetic Field of Equidirectional Toroidal Winding Motor Based on CDMPF Method

General Analytical Modeling for Armature Magnetic Field of Equidirectional Toroidal Winding Motor Based on CDMPF Method

Winding Layout Considerations for Variable-Pole Induction Motors in Electric Vehicles

Winding layout plays a crucial role in enabling variable-pole operation in an induction machine (IM). Several winding design alternatives, which consist of toroidal and distributed single- and double-layer windings, have been shown to increase speed range and improve partial load efficiency in traction applications. These windings have different pole-changing capability, end-winding length, leakage, harmonic content, and inverter requirements. This paper compares these winding alternatives with a generalized variable-pole machine design framework that captures the impact of winding selection on key performance metrics such as losses, volume and torque-speed envelop. This framework shows that the core aspect ratio, defined as ratio of stack length to rotor diameter, selected to minimize losses depends on whether a distributed or toroidal winding is used. When a toroidally-wound IM is designed with a low aspect ratio, it can provide the largest torque-speed envelop with highest efficiency over a wide speed range. An experimental toroidally-wound IM driven by an 18-leg converter is used to validate the design framework. The experimental setup is configured externally to emulate a single-layer winding and to show benefits gained from the extra pole-changing flexibility of a toroidal winding.

Analysis of Stator-Slot and Rotor-Pole Combinations of Axial Modular-Flux Reversal Permanent Magnet Machine

This paper investigates the influence of stator-slot and rotor-pole combinations on torque performances in axial modular-flux reversal permanent magnet (AM-FRPM) machines. Based on the slot-conductor back-EMF star vector theory, the winding factors of all stator-slot and rotor-pole combinations are improved by adopting toroidal windings. In addition, based on a magnetomotive-force and permeance model, the candidates of stator-slot and rotor-pole combinations with higher torque capacity can be determined by analyzing the harmonic combinations between the PM and armature reaction field. Besides, the cogging torque is suppressed by selecting the corresponding angle between rotor modules for different stator- slot and rotor-pole combinations. Finally, an electromagnetic performance comparison between a conventional FRPM machine and three AM-FRPM machines candidates with attractive torque performances is conducted, and the experiments are constructed to verify the theoretical analysis.

Research and Analysis of Toroidal and Conventional Windings in Permanent Magnet Synchronous Machine

Reasonable design of winding can improve the performance of the machine without increasing the weight and cost. The toroidal (TO) and tooth-coil (TC) windings have different spatial positions in the electromagnetic field and generate vertical magnetic field. If the characteristics of winding factor and the unified analysis method of the both can be researched, the windings with better performance can be obtained. Based on this, the winding characteristics considering harmonics and the design methods of single winding and combination of windings are analyzed. The "Halbach Winding" with the same effect as Halbach PM are designed and researched based on the study of TO, TC windings and their combination. According to the characteristics of the magnetic field mentioned above, the improved method of the machine using only winding to generate the traveling wave of Halbach magnetic field is proposed and analyzed. By improving the Halbach winding, it is possible to achieve a magnetic field that enhances one side and weakens the other side while reducing the minimum repetitive unit. And the feasibility of the above methods is verified by finite element analysis (FEA).

Electromagnetic Characteristics Analysis of a Novel Differential Dual‐Rotor Contra‐Rotating Axial‐Flux PM Motor with Equidirectional Toroidal Winding

In this paper, a novel differential dual‐rotor contra‐rotating axial‐flux PM (DDC‐AFPM) motor with equidirectional toroidal winding (EDTW) applied to electric propulsion of ships is proposed. Different from the conventional AFPM motor with contra‐rotating rotors (CR), the rotors of the proposed motor on both sides of the stator rotate oppositely at different speeds. The structure of the proposed motor is introduced and the operation principle is clarified. Initial parameters of the proposed motor are given, and the correctness of the simulation results is indirectly verified through the prototype of the AFPM motor with dual‐rotor and EDTW. In order to further improve the electromagnetic performance of the proposed motor, parameters of the motor are preliminarily improved. Finally, the electromagnetic characteristics including armature field, no‐load and on‐load characteristics of the proposed motor are analyzed based on three‐dimensional finite element method (3D‐FEM). The simulation results show that the proposed motor has good electromagnetic characteristics and is suitable for ship propulsion. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Analytical Modeling of Slotless Axial Flux Permanent Magnet Motor With Equidirectional Toroidal Winding

This study proposes a two-dimensional (2D) analytical model (AM) of slotless axial flux permanent magnet (AFPM) motor, which includes two submodels of armature winding (AW) and permanent magnet (PM) magnetic fields. It can reveal the operating mechanism of equidirectional toroidal winding (ETW) armature magnetic field in the theory and quantitatively analyze its AW and PM magnetic fields. The proposed AM is characterized in that AW magnetic field submodel is established only based on the current density distribution of the effective conductors on one side of a single toroidal coil considering its width and thickness. First, based on the proposed equivalence principle, the analytical submodels of AW and PM magnetic fields of AFPM motor with ETW are established separately, and the formulas of back EMF and torque of the motor are derived. Second, the electromagnetic performance of a slotless AFPM motor with ETW is studied by the proposed 2D AM, including the waveforms of AW and PM magnetic fields, phase back EMF and torque, which are verified by the finite element model. Finally, a prototype of AFPM motor with ETW is manufactured and tested in open-circuit and on-load conditions, which verifies the accuracy of the proposed AM.

Novel High-Order-Harmonic Toroidal Winding Design Approach for Double-Sided Vernier Reluctance Linear Machine

Double-sided DC-Vernier reluctance linear machine (DS-DC-VRLM) is very suitable for long stroke industrial processing applications, taking advantages of magnet-free design, eliminated magnetic pull and high dynamic response. However, its low trust force density due to poor excitation ability of DC windings, has been a long-existing bottleneck. Aiming to boost the output thrust force of the DS-DC-VRLM, a novel high-order harmonic non-overlapped toroidal winding design is proposed. The key is that the proposed armature winding makes full use of working harmonics modulated from both fundamental order and third-order harmonics generated by DC excitations, contributing to enhanced winding factor. Based on the finite element analysis (FEA), with the proposed winding design approach, DS-DC-VRLM could achieve 2.26 times higher thrust force than those with conventional concentrated winding under the same copper loss. In this paper, new winding arrangement of DS-DC-VRLM and its operation principle are introduced, along with some design considerations of it, such as slot/pole combinations, DC/AC current distributions and extra end teeth dimensions are discussed for performance improvement. Finally, the performances of this proposed machine are evaluated by prototype experiments to verify the correctness of FEA simulation results.

Design and Analysis of Axial-Modular Flux-Switching Permanent Magnet Machine

This paper proposes a novel axial-modular-flux switching permanent magnet (AM-FSPM) machine, which contains two modular parts and integrated toroidal windings. After investigating the operation principle of the AM-FSPM machine, the modular PM field complementarity and integrated armature reaction field complementarity principles of two axial modular parts are revealed based on the field modulation theory. Then, a comprehensive comparison of the modulation principle between the AM-FSPM and conventional FSPM machines is conducted from perspectives of PM field, armature reaction field, cogging torque and electromagnetic torque production mechanism. It can be found that the modulation principle reveals the difference between the operation principles of two flux switching machines. In addition, the cogging torque reduction capability of AM-FSPM machine is investigated, which provides guidance on stator-slot and rotor-pole combinations in the design stage of industrial applications. Moreover, compared with conventional FSPM machines, the AM-FSPM machine exhibits high torque capability and flux weakening capability, meanwhile maintains high efficiency at high speed. Further, its characteristics are verified by the experiments.