Academic literature on the topic 'Axial Flux Brushless Dc Motor'

A high efficiency axial-flux brushless DC motor assisted by self axial magnetic bearing and used in flywheel energy storage system is proposed in this paper. In this design, the rotor with composite rim acts as the flywheel of the system and is sandwiched between two disk type stators which are made of amorphous metal to reduce iron losses. The dual-stator machine combines the functions of axial flux brushless DC motor and axial magnetic bearing to rotate the flywheel-rotor and levitate it in vertical orientation. The other four degrees of freedom in radial directions are constrained by ceramic ball bearings for simple operation, high efficiency and long life span. Optimized design approaches are employed to achieve low losses, and high power density. Three-dimensional FEM analyses are implemented, and the analysis results support the feasibility of the proposed motor.

Technology that is growing rapidly and innovations that have sprung up in the electrical field today are driving the use of electricity as a source of energy to do work. Electric motor is one component that is very popular in the industrial world and households that are useful to human life. In addition to DC motors and induction motors, there are also 3 phase brushless direct current (BLDC) motors which are a type of synchronous motor where magnetic fields are produced by rotor and stator at the same frequency. The rotor is a moving part of the brushless direct current motor which is a place of permanent magnet called a pole. This paper discusses the performance of brushless direct current 3 phase axial flux motors with different diameters of neodymium type permanent magnets. Tests carried out using neodymium permanent magnets with diameters of 15mm x 2mm and 20mm x 2mm were tested without using a load and using load. The parameters used in testing motor performance include speed, torque, and motor power with a source voltage of 12V, 16V, 20V, and 24V. The test results shows that the speed value of a BLDC motor using permanent magnets with a size of 20mm x 2mm is greater than that of permanent magnets of 15mm x 2mm. The same thing applies to the value of the power produced while, for the value of torque when the motor uses a permanent magnet of 15mm x 2mm will be greater than that of a motor using a permanent magnet of 20mm x 2mm.

This paper presents the Finite Element Analysis (FEA) based design, optimization and development of an axial flux permanent magnet brushless DC motor for Left Ventricular Assist Device (LVAD). With the design objective of improving the existing motor's efficiency , different topologies of AFPM machine has been examined. Selection of optimal magnet frac-tion, Halbach arrangement of rotor magnets and the use of Soft Magnetic Composite (SMC) material for the stator core results in a novel motor with improved efficiency and torque profile. The results of the 3D Finite element analysis for the novel motor have been shown.Thermal analysis for the existing motor has also been done and the FEA results are compared with the analytical and experimental results.Finally the test results for the novel motor and the general conclusions are also discussed.

This paper presents a technique for attenuating the external disturbances acting on the rotor of a prototype flywheel energy storage device. The approach uses a three-phase axial flux brushless dc motor to simultaneously produce a torque and a radial force. This is accomplished by using two phases of the motor for torque generation, and one phase to produce the radial force. The paper develops a set of equations that can be used to predict the forces generated by the motor coils. These equations are used to implement a feedback control system to suppress the effects of external excitations. The nonlinear controller requires the velocity measurements and the angular displacement of the flywheel. The controller essentially adds damping to the system, and the constant feedback gains solve an optimization problem that involves a H∞ bound on the disturbance attenuation. The experimental results clearly demonstrate that the dc motor can be used to suppress unwanted radial vibrations due to external disturbances.

In this thesis axial flux and radial flux brushless dc motors will be studied as a drive motor for the control of moment gyroscope wheel. Design equations for axial flux and radial flux brushless dc motor topologies will be reviewed. Based on these equations radial and axial flux motors with different number of poles will be designed that meet control moment gyroscope wheel application requirements. The results will be evaluated in terms of efficiency, torque/mass and torque/volume, and suitability for the control moment gyroscope application.

碩士
逢甲大學
電機工程所
95
The purpose of this thesis is to design a high performance axial-flux permanent magnet brushless machine (AFPM). First, an equivalent magnetic circuit model of the motor is derived by using the magnetic circuit theory and the parameters of the motor are calculated. Then, the performance of the AFPM is obtained. The finite element analysis software, Flux 3D is employed to obtain the performance of the machine. Finally, the Taguchi method is used to make robust design of AFPM and improve the performance. The optimized results provide higher electromagnetic torque and minimize the torque ripple. It is shown that the Taguchi method is a very efficient and effective approach in robust design a high performance AFPM.

碩士
國立交通大學
工學院精密與自動化工程學程
100
The characteristics of brushless direct current (BLDC) motors include high speed, high torque, high power density, rapidly transient response, and ease of control. With many advantages, BLDC motors have become more and more popular in our life and are applied to a wide variety of applications like DVD player, hard disk, i-Robot, electrical vehicles, compressor, etc. Conventional BLDC motors use internal magnetic sensors, e.g. Hall effect sensors to feedback signals and obtain rotor position. However, due to cost and size subject to mechanical or environment constraints, and reliability of thermal effect that may cause commutation error. Sensorless control methods without Hall-effect sensors have been widely used in recent years. According to stator winding patterns, BLDC can be radial or axial windings. Axial-flux BLDC motors outperform radial field in aspects of torque, power, efficiency, and compact geometry shape [Krishnan and Beutler, 1985]. Hence this thesis focuses on analyzes and then realizes a sensorless drive for the axial-flux BLDC motor with a position estimation method to control the motor from standstill state to desired speed based on back-EMFs zero-crossing of floating phase; i.e. not excited phase of BLDC motor estimated method and arrange in pairs with open-loop start-up algorithm to implement velocity control of BLDC motors. Finally, simulation and experimental results will demonstrate effectiveness of the proposed sensorless control method. Keywords: Axial-Flux, Sensorless, BLDC, Velocity control

碩士
國立臺灣大學
機械工程學研究所
90
This thesis is proposed to discuss the optimal driving phase current waveform for an axial-flux brushless DC wheel motor. By the way of mathematical proving, numerical analysis, and experimentation, the optimal driving phase current waveform for brushless DC motor is its phase back EMF waveform was proved in this thesis. The relationship about alignment torque, phase current, and back EMF of DC brushless motor is derived by the motor torque equation. And then, expanding phase current and phase back EMF function proves that the motor has the maximum output torque when the phase current and the back EMF waveform are proportional. This is confirmed by the magnetic circuit analysis and the finite element analysis, and the phase back EMF waveform is considered in motor design process so as to obtain the maximum efficiency and the minimum torque ripple. Finally, three different phase current waveforms, the phase back EMF waveform extracted from experiments, the optimal driving current waveform designed by the 2D magnetic circuit model, and the traditional square waveform, were used with the same root mean square value in experiments to verify the conclusion in this thesis.

碩士
國立雲林科技大學
機械工程系碩士班
99
Integrated design of an axial flux brushless motor with a magnetic coupling is a new design concept. Traditionally, axial flux brushless motor and magnetic coupling are independently designed and manufactured. Then, they are combined appropriately to meet needed drive requirements. This kind of design strategy, however, suffers from inherent disadvantages on more complex power transmission link, transmission components easier to wear and tear, and incompact work space arrangements. This study is to Combined into one integrated device-based mechanical and electrical by integrated design of an axial flux brushless motor with a magnetic coupling, First, introduction axial flux brushless motor with axial magnetic coupling characteristics of the structure and driving principle, and propose two new design concept of integration, The first program is permanent magnet of the motor rotor and permanent magnet of the magnetic coupling design for shared components, the second program is permanent magnet of the motor rotor and permanent magnets of the magnetic coupling attached to the magnetic yoke. Next, the equivalent magnetic circuit method is presented to determine the main dimensions of the axial flux brushless motor and magnetic coupling, while the validity is verified by the finite element analysis (FEA). Finally, the detail design of the proposed integrated device is presented. Based on the results of FEA, the integrated design case one have lower electromagnetic torque, but the torque ripple is reduced form 45.21% to 44.93%, and the integrated design case two although the torque ripple is too high, but its output torque is only slightly decreased 14.50 %.

碩士
國立臺灣大學
機械工程學研究所
91
This thesis proposes a design of digital circuit of the current-mode pulse-width modulation controller of a brushless DC axial-flux wheel motor for electric vehicles. In addition, the field weakening control method is also studied for its possible implementation to increase the maximum speed of the wheel motor. The relationship between the alignment torque and phase current of the brushless DC motor is established from the torque equation which is derived by the energy method. In the light of two-axis theorem, the voltages, currents, flux linkages, and inductances of the motor are expressed in terms of the d-q coordinates, and the corresponding torque and voltage equations are derived. The physical meanings of constant torque and field weakening controls are then discussed. To implement the control structure discussed above, the digital chip named “field programming gate array” is adopted, and the hardware description language is used to describe the behavior of digital circuits of the controller. This controller produces four-phase PWM signals to the motor drive switched by power MOSFETs. Finally, the characteristics of the speed, torque and efficiency of the wheel motor are tested by an eddy-current dynamometer. The experimental results show that the wheel motor performs well and stable with the dedicated digital controller.

In the past two decades the core aircraft technology is going through a drastic change. The traditional technologies that is almost half a century old, is going through a complete revamp. In the new “More Electric Aircraft” technology many mechanical, pneumatic and hydraulic systems are being replaced by electrical and power electronic systems. Airbus-A380, Boeing B-787 are the pioneers in the family of these new breed of aircrafts. As the aircraft technology is moving towards “More Electric”, more and more electric motors and motor controllers are being used in new aircrafts. Number of electric motor drive systems has increased by about ten times in more electric aircrafts compared to traditional aircrafts. Weight of any electric component that goes into aircraft needs to be low to reduce the overall weight of aircraft so as to improve the fuel efficiency of the aircraft. Hence there is an increased need to reduce weight of motors and motor controllers in commercial aircraft. High speed ironless axial flux permanent magnet brushless dc motors are becoming popular in the new more-electric aircrafts because of their ability to meet the demand of light weight, high power density, high efficiency and high reliability. However, these motors come with very low inductance, which poses a big challenge to the motor controllers in controlling the ripple current in motor windings. Multilevel inverters can solve this problem. Three-level inverters are proposed in this thesis for driving axial flux BLDC motors in aircraft. Majority of the motors in new more electric aircrafts are in the power range of 2kW to 20kW, while a few motor applications being in the range of 100kW to 150kW. Motor controllers in these applications run from 270Vdc or 540Vdc bus which is the standard in new more electric aircraft architecture. Multilevel Inverter is popular in the industry for high power and high voltage applications, where high-voltage power switching devices like IGBT, GTO are popularly used. However multilevel inverters have not been tried in the low power range which is appropriate for aircraft applications. A detail analysis of practical feasibility of constructing three-level inverter in lower power and voltage level is presented in this thesis. Analysis is presented that verify the advantages of driving low voltage and low power (300Vdc to 600Vdc and less than 100kW) motors with multilevel inverters. Practical considerations for design of MOSFET based three-level inverter are investigated and topological modifications are suggested. The effect of clamping diodes in the diode clamped multilevel inverters play an important role in determining its efficiency. SiC diodes are proposed to be used as clamping diodes. Further, it is realised that power loss introduced by reverse recovery of MOSFET body diode prohibits use of MOSFET in hard switched inverter legs. Hence, a technique of avoiding the reverse recovery losses of MOSFET body diode in three-level NPC inverter is conceived. The use of proposed multilevel inverter topology enables operation at high switching frequency without sacrificing efficiency. High switching frequency of operation reduces the output filter requirement, which in turn helps reducing size of the inverter. In this research work elaborate trade-off analysis is done to quantify the suitability of multilevel inverters in the low power applications. For successful operation of three-level NPC inverter in aircraft electrical system, it is important for the DC bus structure in aircraft electric primary distribution system to be compatible to drive NPC inverters. Hence a detail study of AC to DC power conversion system as applied to commercial aircraft electrical system is done. Multi-pulse rectifiers using autotransformers are used in aircrafts. Investigation is done to improve these rectifiers for future aircrafts, such that they can support new technologies of future generation motor controllers. A new 24-pulse isolated transformer rectifier topology is proposed. From two 15º displaced 6-phase systems feeding two 12-pulse rectifiers that are series connected, a 24-pulse rectifier topology is obtained. Though, windings of each 12-pulse rectifiers are isolated from primary, the 6-phase generation is done without any isolation of the transformer windings. The new 24-pulse transformer topology has lower VA rating compared to standard 12-pulse rectifiers. Though the new 24-pulse transformer-rectifier solution is robust and simple, it adds to the weight of the overall system, as compared to the present architecture as the proposed topology uses isolated transformer. Non-isolated autotransformer cannot provide split voltage at the dc-link that creates a stable mid-point voltage as required by the three-level NPC inverter. Hence, a new front-end AC-DC power conversion system with switched capacitor is conceived that can support motor controllers driven by three-level inverters. Laboratory experimental results are presented to validate the new proposed topology. In this proposed topology, the inverter dc-link voltage is double the input dc-link voltage. An intense research work is performed to understand the operation of Trapezoidal Back EMF BLDC motor driven by three-Level NPC inverter. Operation of BLDC motor from three-Level inverter is primarily advantageous for low inductance motors, like ironless axial flux motors. For low inductance BLDC motor, very high switching frequency is required to limit the magnitude of ripple current in motor winding. Three-level inverters help limiting the magnitude of motor ripple current without increasing the switching frequency to very high value. Further, it is analysed that dc link mid-point current in three-level NPC inverter for driving trapezoidal BLDC motor has a zero average current with fundamental frequency same as switching frequency. Because of this, trapezoidal BLDC motors can easily be operated from three-level NPC inverter without any special attention given to mid-point voltage unbalance. One non-ideal condition arrives in practical implementation of the inverter that leads to non-zero average mid point current. Unequal gate drive dead time delays from one leg to other leg of inverter introduce dc-link mid-point voltage unbalance. For the motoring mode operation of trapezoidal BLDC motor drive, simple gate drive logic is researched that eliminates need of the gate drive dead-time, and hence solves the mid-point voltage unbalance issue. Simple closed loop control scheme for mid-point voltage balancing also is also proposed. This control scheme may be used in applications where very precise control of speed and torque ripple is warranted. All the investigations reported in this thesis are simulated extensively on MATHCAD and MATLAB platform using SIMULINK toolbox. A laboratory experimental set-up of three-Level inverter driving axial flux BLDC motor is built. The three-level inverter, operating from 300Vdc bus is built using 500V MOSFETs and 600V SiC diodes. All the control schemes are implemented digitally on digital signal processor TMS320F2812 DSP platform and GAL22V10B platforms. Experimental results are collected to validate the theoretical propositions made in the present research work. At the end, in chapter 5, some future works are proposed. A new external voltage balance circuit is proposed where the inverter dc-link voltage is same as the input dc-link voltage. This topology is based on the resonant converter principle and uses a lighter resonant inductor than prior arts available in literature. Detail simulation and experimentation of this topology may be carried out to validate the industrial benefits of this circuit. It is also thought that current source inverters may work as an alternative to voltage source inverters for driving BLDC motors. Current source inverters eliminate use of bulky DC-link capacitors. Long term reliability of current source inverters is higher than voltage source inverters due to the absence of possibility of shoot-through. Further, in voltage source inverters, the voltage at the motor terminal is limited by the source voltage (dc-link voltage). This issue is eliminated in current source inverters. An interface circuit is conceived to reduce the size of dc-link inductors in current source inverters, pending detail analysis and experimental verification. The interface circuit bases its fundamentals on the principles of operation of multilevel inverters for BLDC motors that is presented in this thesis.

碩士
國立成功大學
工程科學系碩博士班
97
Electrical machines have already become the major source of motive power in the present age. The brushless dc motors possess some advantages such as higher power density, higher efficiency, and simpler controllability. Hence synchronous ac motors become rather popular for many applications, such as compressors, automotive, and household products etc. For the speed drive of a BLDC motor, information on rotor position is indispensable. However, mounting a position sensor on the rotor causes several drawbacks from the viewpoints of reliability, cost, size, and cable wiring. In order to cope with these drawbacks, a number of sensorless control methods have been proposed so far. In the last two decades, several approaches on sensorless control for BLDC motor have been proposed and developed. This thesis proposes a sensorless control method using a rotor flux state observer to estimate rotor position and speed estimator. In the proposed rotor flux state observer, the flux due to rotor magnet is chosen as the state variable, and the rotor position and speed could be estimated. The Lyapunov stability theorem is used to prove the rotor flux state observer system is stable. Finally, simulated and experimental results are presented and verify the proposed sensorless method is feasible.

碩士
國立臺灣大學
機械工程學研究所
88
Direct-driven wheel motor is one of the solutions to increase the efficiency of electric vehicles, especially, at low speed with required large torque. This paper aims to the design of the optimal current waveform for an axial-flux brushless permanent magnet motor, so that its output torque is maximized under prescribed constraints. First, the torque equation is derived by he energy method and modified according to the characteristics of the wheel motor. Second, the parameters that describe the relationship between torque and input current are introduced in the magnetic circuit model. Three different sets of constraints are then prescribed for various driving and winding structures. Finally, the optimal current waveform for independent winding with constrained copper loss is proved to be best in terms of maximum efficiency and output torque.

This paper presents a technique for vibration suppression in a rotordynamic system. The approach implemented involves using a DC motor for simultaneous torque and radial force actuation. Here, the rotor is supported via passive permanent magnetic bearings. The permanent magnets are arranged so that, for small motions, the rotor can be treated as a spinning top that is supported radially by linear springs. The device includes an axial flux, three phase, brushless DC motor that is used to produce a torque. The same motor is also used to develop radial forces to control the vibration of the rotor. This is accomplished by using two phases of the motor for torque generation, and one phase to produce radial forces. The paper develops a set of equations that can be used to predict the radial force generated by the motor coils. These equations are used to implement a feedback control system to regulate the radial position of the rotor. Experiments are conducted to verify the coil force equations and demonstrate the effectiveness of the feedback control scheme.