Low Speed High Torque Research Articles

Research on Thermal Calculation and End Winding Heat Conduction Optimization of Low Speed High Torque Permanent Magnet Synchronous Motor

Research on Thermal Calculation and End Winding Heat Conduction Optimization of Low Speed High Torque Permanent Magnet Synchronous Motor

Control Method of Redundant Winding BLDC for Deep Lunar Soil Drilling

The deep lunar soil loading process is complicated and volatile; it is difficult to achieve stable and reliable drilling sampling. In order to realize the rotary drive control of low-speed high torque start-up and high-speed cutting dumping of the spiral drilling tool, the redundant double backup winding BLDC motor is used as the driving source of the spiral drilling tool, the mathematical model of torque and speed of the double winding BLDC motor is established, and a dual winding BLDC motor is designed. The drive circuit topology scheme of synchronous operation of winding is simulated and analyzed, and the control performance experiment is carried out combined with the prototype. The test results show that the topological structure of the driving circuit can meet the driving control requirements of lunar soil and lunar rock drilling sampling process, and improve the safety and reliability of the drilling sampling process.

Influence of Pole and Slot Combination on Torque Characteristics and Radial Force of Fractional Slot Permanent Magnet Machines

The fractional slot concentrated winding structure effectively solves the difficulty of low‐speed and high‐torque permanent magnet (PM) machines with a large number of poles and slots, but it also brings a wealth of magnetomotive force (MMF) harmonic. The winding function method is used to compare and analyze the stator MMF distribution and harmonic content of the fractional slot PM machines with different pole and slot combinations, and the cogging torque waveform and torque ripple are calculated by the finite element method. The influence of pole and slot combination on radial force and vibration modes of fractional slot PM machines is studied. The main vibration mode can be determined from the lowest order of radial force harmonics. The results show that in a fractional slot PM motor, the radial force is the main cause of noise and vibration, rather than the cogging torque and torque ripple. The dominant radial force is mainly produced by the interaction of rotor field harmonics and armature reaction field harmonics, and the vibration and noise will significantly increase with the decrease of the dominant vibration mode order, which largely depends on the pole and slot combination. This paper provides a certain reference for the selection of pole and slot combination in the electromagnetic design process of low speed high torque fractional slot PM motors. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Loss Study of Dual Stator Low Speed High Torque Synchronous Motor with Hybrid Rotor

Low speed and high torque machines are widely used in industrial production, oilfield mining, wind power generation, etc. Low speed high torque motors have large internal space, in order to make full use of internal space this paper proposes a dual stator low speed high torque synchronous motor. The rotor adopts a surface-mounted permanent magnet rotor structure on one side, and a spliced reluctance rotor structure on the other side. A magnetic ring is added in the middle to make permanent magnet and magnetic resistance independent of each other. The motor has a special structure, and the loss distribution is different from that of a normal motor. The loss will affect the performance of the motor. This paper establishes the iron loss model considering the effects of alternating magnetic field, rotating magnetic field, and harmonics. Considering the influence of temperature on copper loss. Then establish a mathematical model of core loss and copper loss. Then studying the motor iron loss and copper loss distribution characteristics. Finally, the results are compared with the finite element method (FEM) to verify the effectiveness of the loss calculation in the paper.

A review: high power density motors for electric vehicles

The review of High Power Density Motor (HPDM) is presented, the high power density refers to ratio of output power to volume of the motor. As a result even a small envelope motor can have high power output. HPDM are also known as low speed high torque motors. The HPDM are compact, lightweight, has high torque and less cogging torque, finding application in automotive field, especially in electric and hybrid electric vehicles. This paper analyses the design, performance and efficiency of various HPDM. Comparative analysis of thirteen different HPDM are reviewed and tabulated for power density, speed, weight, rating and its applications.

Electromagnetic and Structural Design of a Novel Low-Speed High-Torque Motor With Dual-Stator and PM-Reluctance Rotor

The low-speed high torque motor has attracted more and more attention in many fields. The objective of this paper is to investigate the electromagnetic design principle, mechanical structure and cooling system of a novel dual-stator low-speed high-torque motor (DS-LSHTM) with permanent magnet-reluctance hybrid rotor. The proposed motor has the advantages both of the permanent magnet (PM) motor and reluctance synchronous motor. In addition, the greatest feature of this proposed motor is to explicitly separate magnet torque and reluctance torque components so that the two stators can be designed individually with more flexibility. Design principles including electromagnetic characteristics, sizing equation and structure configuration are elaborated. The electromagnetic performance, mechanical properties and temperature rise characteristics of the proposed motor are simulated and analyzed by the finite element analysis (FEA) method. The simulation results show that the rationality of the design and the feasibility of the motor.

Distribution Performance Analysis and Experimental Research on the Port Plate Pairs of Low Speed High Torque Seawater Hydraulic Motor

The current research of seawater hydraulic motor mainly focused on piston motor and vane motor, but seldom regarded low speed high torque seawater hydraulic motor. Low speed high torque seawater hydraulic motor as a kind of energy conversion device and actuator plays an important role in seawater hydraulic transmission system. However, the physical and chemical properties of seawater, such as low viscosity, high causticity and poor lubrication, result in numerous problems. In this paper, the flow distribution characteristics of port plate pairs for the seawater hydraulic motor are investigated, and the leakage flow and power loss models of port plate pairs are established. Numerical simulations are carried out to examine the effects of water film, inlet pressure and rotating speed on the pressure distribution and leakage flow. And the friction and wear tests of port plate pairs are also carried out. Moreover, the test system of the seawater hydraulic motor is constructed and the performance of prototype with no-load or loading is conducted. The results indicate that the clearance of port plate pairs and inlet pressure have a significant effect on distribution characteristics, but the effect of rotating speed is not very obvious. The experimental results show that the minimum error rate can be maintained within 0.3% by the proposed flow model and the counter materials of 316L against carbon-fiber-reinforced polyetheretherketone (CFRPEEK) are suitable for the port plate pairs of seawater hydraulic motor. Finally, based on the seawater hydraulic experiment platform, the volumetric efficiency of no-load and loading are obtained that the maximum can achieve 94.71% and 90.14%, respectively. This research work may improve the flow distribution performance, lubrication and the friction and wear properties, enhance energy converting efficiency of port plate pair and provide theoretical and technical support for the design of high-performance water hydraulic components.

A Novel Fault Tolerant Machine With Integral Slot Non-Overlapping Concentrated Winding

A novel fault tolerant machine with integral slot non-overlapping concentrated winding (ISNCW) is proposed in this paper. With the distribution of phase windings in axial, the proposed machine realized excellent isolation capability between different phases. The performance comparisons between the proposed machine and the traditional integer slot overlapping winding (ISOW) machine are made by the analytical method and finite element analysis (FEA). Compared to the ISOW machine, the proposed machine has better performance in low speed high torque applications, and much better fault tolerant capability and flux weakening capability. Especially, the proposed machine appears excellent performance in limiting the short circuit current and preventing the irreversible demagnetization of permanent magnet under short-circuit fault. The phase independent structure makes the maintenance and replacement of the fault module convenient and saves the maintenance cost further.

Dynamic structural design of offshore direct-drive wind turbine electrical generators

Direct-drive permanent magnet generators for multi-MW wind turbines are low speed high torque electrical machines requiring large, heavy and robust structures to maintain the airgap clearance open and stable. The structural mass of radial-flux generators can be estimated at an early phase of the design process. Using distinct approaches, the integrity of a 3 MW electrical machine structure has been addressed from a dynamic perspective by carrying out modal analyses with a view to minimize its mass. A versatile tool has also been developed to help the engineers with the dynamic design of generator disc structures. Conical structures have been analysed and compared with the baseline disc model obtaining very promising results. Potential improvements have been proposed for more ambitious structural designs.

Grey Wolf based control for speed ripple reduction at low speed operation of PMSM drives

Speed ripple at low speed-high torque operation of Permanent Magnet Synchronous Machine (PMSM) drives is considered as one of the major issues to be treated. The presented work proposes an efficient PMSM speed controller based on Grey Wolf (GW) algorithm to ensure a high-performance control for speed ripple reduction at low speed operation. The main idea of the proposed control algorithm is to propose a specific objective function in order to incorporate the advantage of fast optimization process of the GW optimizer. The role of GW optimizer is to find the optimal input controls that satisfy the speed tracking requirements. The synthesis methodology of the proposed control algorithm is detailed and the feasibility and performances of the proposed speed controller is confirmed by simulation and experimental results. The GW algorithm is a model-free controller and the parameters of its objective function are easy to be tuned. The GW controller is compared to PI one on real test bench. Then, the superiority of the first algorithm is highlighted.

Optimal Pole Number and Winding Designs for Low Speed–High Torque Synchronous Reluctance Machines

This paper studies the feasibility of using synchronous reluctance machines (SynRM) for low speed–high torque applications. The challenge lies in obtaining low torque ripple values, high power factor, and, especially, high torque density values, comparable to those of permanent magnet synchronous machines (PMSMs), but without resorting to use permanent magnets. A design and calculation procedure based on multistatic finite element analysis is developed and experimentally validated via a 200 Nm, 160 rpm prototype SynRM. After that, machine designs with different rotor pole and stator slot number combinations are studied, together with different winding types: integral-slot distributed-windings (ISDW), fractional-slot distributed-windings (FSDW) and fractional-slot concentrated-windings (FSCW). Some design criteria for low-speed SynRM are drawn from the results of the study. Finally, a performance comparison between a PMSM and a SynRM is performed for the same application and the conclusions of the study are summarized.

Power-on shifting in dual input clutchless power-shifting transmission for electric vehicles

The purpose of this paper is to study the practical application of a two motor electric vehicle powertrain utilizing a combination of fixed and multiple speed gear ratios. To realize power-on shifting without torque hole and maximize overall efficiency, a high-speed motor is adopted as the primary motor connecting to the multiple speed clutchless automated manual transmission and a low-speed high torque electric motor is employed as the assisting motor connected to the final shaft with fixed gear ratio. Motor torque and speed are controlled using improved model predictive flux control method in conjunction with synchronizer mechanism actuation to best fill the torque hole to improve both drivability and driving comfort. To evaluate the proposed system, a complete mathematical model is built and compared with a conventional single motor transmission system. The detailed transient dynamic results in terms of final shaft torque, acceleration and vehicle jerk demonstrate the effectiveness of the proposed powertrain.

Comparison of the steady-state performance of hydrostatic drives used in the rotary head of the drill machine

This article presents a comparative analysis of steady-state behavior of hydrostatic drives of a drill machine used in mining application. Usually, a closed-circuit hydrostatic drive rotates the cutter head (drill bit) of a drill machine through its rotary head. In this respect, performance investigation of two such alternative drives is carried out through modeling, simulation and experimentation. One of the drives comprises a variable displacement pump and two high speed low torque (HSLT) bent axis motors with a gear reducer, whereas another one consists of an identical pump and a low speed high torque (LSHT) radial piston motor. To simulate the hydrostatic drives, the bondgraph models are made, where various losses are considered as resistive elements. Considering the characteristics of the losses obtained experimentally, the predicted performances of the systems obtained through simulation are validated with the test data. The dependencies of the losses on the pump displacement and the load torque on the drives are also analyzed. The characteristics of the drives with respect to the operating speed range of the drill machine used in mining operation are studied at different torque levels. On the basis of the results obtained, suitability of the hydrostatic drives for the rotary head of the drill machine is also discussed for different rock characteristics.

Numerical Investigation on Mini Internal Gear Forging Process

Gear transmission system is closely related to the consumer electronics products, factory automation industry, science and technology toys, medical equipment, electric hand tools, home appliances and the low-speed high torque applications of automotive industry. In the past, the almost manufacturers produced the metal gear of transmission system mostly by machining method. The gear machining tools of relative processing are mired in difficulties when the gear was miniaturized. In terms of the way of micro forging to produce the gear transmission components, not only a high accuracy and production rate being much times of gear machining, which achieves a significant competitive advantage. This study aims to conduct a research for a mini internal gear forging formability. For this purpose, the finite element method was used to analyze the mini internal gear forging process based on a die set of involute gear profile model. From the simulation results, the characteristic of flowing field of material filled into the gear mold and the induced strain and stress distribution were observed. All findings can be significantly provided to develop the manufacturing process of mini gear forging.

Power Smoothening of Grid Connected Direct- Driven Permanent Magnet Synchronous Generator (PMSG) Wind Turbines

Objectives: The main objective of this paper is smoothening of the power fluctuation of a variable speed PMSG wind generator with the help of Energy Capacitor System (ECS). ECS consists of a voltage source inverter, dc-dc converter and an ultra-capacitor bank including their control strategies. Methods/Analysis: In this paper two back-to-back voltage source Insulated Gate Biopolar Transistor (IGBT) converters controlled through highly efficient variable frequency drive control method is considered. By using this method, efficiency of wind farm can be improved and voltage regulation for interconnecting the wind farm with grid can be achieved. Findings: Recent application of power electronic devices and scaling up of MegaWatt (MW) wind turbines, Low-speed high torque Permanent Magnet Synchronous Generator (PMSG) has become the ultimate choice for wind power extraction. At present, a commercial PMSG based wind generator primarily makes use of a rectifier followed by an IGBT converter. Novelty /Improvement: The real power reference for ECS is generated accurately. Simulation is carried out through MATLAB/SIMULINK.

Dynamic analysis and estimator design of a hydraulic drive system

This paper deals with the dynamic analysis and state of the art estimator design through system inversion of a pedagogical hydraulic system, comprising variable displacement axial piston pump, high speed low torque hydraulic motor, proportional direction control valve, loading pump (bent axis) and a pressure relief valve at loading circuit. The hydraulic system has been modeled for simulation study and both the transient and the steady state responses have been validated experimentally. The necessary and sufficient conditions for the system to be observable have been obtained with respect to the minimum number of sensors placement. Thereafter, an estimator adaptive to varying load condition has been designed to have a good estimate of all the states using minimum sensors. All the estimated states have been compared with the responses from the test bed.

Comparison of the efficiency of the high speed low torque hydrostatic drives using bent axis motor: An experimental study

This article is aimed at analysing the steady-state performance of four hydrostatic drives and compares their overall efficiency. The speed of the hydrostatic drives is controlled by speed controlled vane pump, variable displacement flow compensated pump, variable displacement pressure compensated pump and proportional direction controlled valve. Bondgraph simulation technique is used to model the hydrostatic drive. The relationships of the loss coefficients with the state variables obtained from the model are identified through experimental investigation. Using them, at different torque levels, the performances of the hydrostatic drives are studied on their slips, torque losses and the overall efficiencies and they are validated experimentally. It is found that hydrostatic drive using speed controlled vane pump exhibits the maximum efficiency, whereas the poorest efficiency is shown by the valve controlled system out of the four drives considered in the analysis.

Guest Editorial Optimal Design of Electric Machines

The papers in this special section cover the advances in multi-objective design and optimization based on genetic algorithms, surrogate, polynomial regression, and particle swarm optimization techniques. Design of novel trans-rotary magnetic gear, hybrid machines for dc generation, and two degrees of freedom split-stator induction machines highlight new magnetic configurations and their performance evaluations. Multiphysics analysis of magnetothermal and magnetostructural behavior of Switched Reluctance Machine (SRM) and brushless doubly fed machines shed light on analytical and practical aspects of design in electromechanical converters. Finally, control of torque undulation, loss minimization, low speed high torque operation, and advanced digital control of adjustable speed motor drives conclude this unique collection of papers.

고속·저토크용 표면부착형 영구자석 동기 전동기의 운전 안정성 확보를 위한 손실 및 열전달 특성 분석

It is essential to predict the coil temperature under over load and over speed conditions for reliability in high speed low torque surface mounted PM synchronous motors(SPM). In the present study, the losses and coil temperature are measured under rated condition and calculated under over speed and over load conditions in the three different motors with 35PN440, 25PN250 and 15HTH1000. The heat transfer modeling has been performed based on acquired losses and temperature. The difference of coil temperature between heat transfer modeling and experiment is less than 6.4% under no load, over speed and over load conditions. Subsequently, the coil temperature of the motor with 15HTH1000 is 84.4% of the coil temperature of the motor with 35PN440 when speed is 0.9 and load is 3.0. The output of motor with 15HTH1000 is 85.2% greater than the output of the motor with 35PN440 when the dimensionless coil temperature is 1.0.

Steady State Performance Analysis of Hydrostatic Transmission System using Two Motor Summation Drive

Hydrostatic transmission (HST) system used in heavy earth moving machineries (HEMMs) has high power density, wide range of speed control and good overall efficiency. Hydrostatically coupled two motor summation drive is an alternative power transmission system, compared to existing closed-loop HST system with low speed high torque motor, used in HEMM. Such drive arrangement has made the possibility to design the transmission system, used in heavy vehicles, in an efficient way to cover wide range of torque-speed demand. This article studies the concept of two motor summation drive and its steady state performance. Experiments have been carried out to analyze the performance of such system. The characteristics of single and two motor drive systems are compared at different load-torque and speed levels. It is concluded that two motor hydrostatic drive systems is more effective at high load-torque and low speed compared to single motor drive system.