International Journal of Advance Engineering and Research Development

Transcription

1 Scientific Journal of Impact Factor (SJIF): 4.14 International Journal of Advance Engineering and Research Development Volume 3, Issue 3, March DESIGN OF AXIAL FLUX HUB MOTOR Mrs. N. M. Rao 1,Anurag Patil 2, Shunham Panghate 3, Saranniyaa B Electrical Engineering, AISSMS s IOIT e-issn (O): p-issn (P): Abstract This paper presents the design of an inside-out axial-flux permanent magnet brushless dc motor. The prototype motor is a double-sided axial-flux permanent-magnet motor with non-slotted stator. The design was simulated via Finite Element Method Magnetics (FEMM) Software, for obtainment of design parameters. Keywords- axial flux permanent magnet inside-out motor, optimal design,electric vehicle wheel INTRODUCTION Now a days world is plagued with global issues like fuel shortage, global warming. No doubt Electric Vehicles are the solution for fighting against these issues. As normal vehicles has fuel as energy source and engine as prime mover, Electric vehicles uses battery as energy source and electric motor as the prime mover to drive. The various options available for driving electric vehicle are DC motor, induction motor, and Brushless DC motors. And out of these BLDC is highly efficient and reliable. Medical Applications :-Sensor less brushless-dc-drives have evolved to a point where they have wide appeal within the medical-design community. One reason: A life expectancy of 10,000 hr compared to a brushed motor life of 2,000 to 5,000 hr. Brushless DC motors are typically characterized as having a trapezoidal back electromotive force (EMF) and are typically driven by rectangular pulse currents.this mimics the operation of brushed DC motors. From this perspective,the name brushless DC fits even though it is an AC synchronous motor. Brushed DC motor has some disadvantages such as :-sparking due to the use of commutator and brushes[electromechanical switches],requires high maintenace The BLDC motor is electrically commutated by power switches instead of brushes. Compared with a brushed DC motor or an induction motor, the BLDC motor has many advantages: Higher efficiency and reliability Lower acoustic noise Smaller and lighter Greater dynamic response Better speed versus torque characteristics Higher speed range Longer life The BLDC motor is widely used in applications including appliances, automotive, aerospace, consumer, medical, automated industrial equipment and instrumentation. CONSTRUCTUION A brushless DC motor consists of two primary parts:- 1. Stationary/non-moving part stator 2..Rotating part rotor There are three classifications of brushless DC motors:-single phase,two phase,three phase There are two types of construction on the basis of the direction of flux flow- 1. Radial flux BLDC motor 2. Axial flux BLDC motor In case of a permanent magnet brushless DC motor the stator is made up of an electromagnet and the rotor is made up of permanent magnet. For a three phase brushless DC motor the stator construction is similar to that of an three phase induction All rights Reserved 662

2 Fig1:- Single stator and three phase stator construction Fig2:-Different types of permanent magnet rotor WORKING OF THREE PHASE BLDC MOTOR The operation of a BLDC is based on the simple force interaction between the permanent magnet and the electromagnet. Motor operation is based on the attraction or repulsion between magnetic poles. The process starts when current flows through two of the three stator windings and generates a magnetic pole that attracts and repels the closest permanent magnet of the opposite pole and like pole respectively. The rotor will move if the current shifts to an adjacent winding. Sequentially charging each winding will cause the rotor to follow in a rotating field. The torque in this example depends on the current amplitude and the number of turns on the stator windings, the strength and the size of the permanent magnets, the air gap between the rotor and the windings, and the length of the rotating arm. Fig3:-Switch configuration COMMUTATION The primary difference between brushed-dc and BLDC motors is the method in which each type is commutated. Commutation is the act of reversing the polarity of the phase currents in the motor windings at the appropriate time All rights Reserved 663

3 produce continuous rotational torque. Without commutation the magnetic fields of the windings and permanent magnets would align and lock the rotating shaft in place. The polarity of the windings must reverse at the right time to change from magnetic attraction to magnetic repulsion and back again to keep the motor shaft spinning. Brushed-dc motors use brushes and a commutator that acts as an electromechanical switch to connect the windings in the proper polarity. The mechanical switch is replaced with electronic switches in BLDC motors with the polarity-reversal timing controlled by an electronic circuit. Each commutation sequence has one of the windings energized to positive power (current enters into the winding), the second winding is negative (current exits the winding) and the third is in a non-energized condition. In order to keep the motor running, the magnetic field produced by the windings should shift position, as the rotor moves to catch up with the stator field. What is known as Six-Step Commutation defines the sequence of energizing the windings. Ordinarily, BLDC motors use Hall-effect devices (HFD) to sense rotor position and control the electronic drive of the motor. However, by monitoring motor back- EMF, its possible to eliminate the HFD and create a sensorless BLDCmotor drive. The fact that motors without HFDs can be less expensive is one of the driving forces spurring the adoption of BLDC motors within the medical- design community. Fig4:- Drive system to the rotor Most BLDC motors have three Hall sensors embedded into the stator. Each is mounted 120-degrees or 60- degrees apart on the back of the motor. Whenever the rotor magnetic poles pass near the Hall sensors, they give a high or low signal, indicating the N or S pole is passing near the sensors. Based on the combination of these three Hall sensor signals, the exact sequence of commutation can be determined. Fig5:- Hall All rights Reserved 664

4 Fig6:-three phase bldc motor sensor versus driver timing Fig7:- 2-D schematic of axial All rights Reserved 665

5 FORMULAE E= n Ns A B Ω Bg E-back electromotive forece(e.m.f) n-module number Ns-number of slots per phase De-external diameter of axial flux motor Di-internal diameter of axial flux motor Ω motor angular speed Bg-flux density in the air gap Electromagnetic torque(tm) developed by motor is expressed as:- Tm=2x(ExI)/ Ω I-maximum value of motor phase current Tm= 2x nx Nsx A xbx Bg xi I=Tm/(2xnxNsxAxBx Bg The motor weight is expressed as following:- WM =Wsy + Wt +Wc +Wry + Wm WM-motor weight Wsy-weight of stator yoke Wt-weight of All rights Reserved 666

6 Wc-copper weight Wry-weight of rotor yoke Wm-weight of magnets International Journal of Advance Engineering and Research Development (IJAERD) Where d is the density of the metal sheet, dc is the density of copper, dm is the magnet density, Aa is the magnet angular width, Ad is the angular width of principal teeth and Ae is the slot angular width. length Le of machine is given by: Lr is axial length of rotor, and g is air-gap length. Axial length of stator Ls can be written as: Axial length of stator core Lcs can be written as: where Bcs is flux density in stator core, and p is ratio of average air-gap flux density to peak air-gap flux density. Axial length of rotor Lr becomes: Lpm is permanent-magnet length; axial length of rotor core Lcr is: where Bcr is flux density in rotor disc core, and Bu is attainable flux density on permanent-magnet surface. Permanent-magnet length Lpm can be calculated as: where μr is magnet s recoil relative pe Br ispermanent-magnet material residual-flux density, Kd isleakage flux factor, Kc is Carter factor, Kf =Bgpk/Bg ispeak value corrected factor of air-gap flux density inradial direction of AFPM All rights Reserved 667

7 The assumptions were: a) Three-phase motor. b) All slots lled; the number of slots is thus a multiple of the number of phases (i.e., Ns = k Nph); for three-phase motors, the number of slots is thus always a multiple of three. c) Two coil-sides in each slot, the winding can be classi ed as double-layer winding. d) Balanced-windings only, i.e., only pole and slot-count combina-tions that result in back EMF of phases B and C being 120±Eo set from back EMF of phase A. e) Coils have equal number of turns, all spanning equal number of slots, implying same-sized coils and therefore same resistance and same inductance. The assumptions routinely lead to motors capable of high performance, and to motors that are readily wound. TABLE1:-Winding configuration CONCLUSION An analytical model dimensioning the whole motor converter is developed together with a validation and complementarity study by finite element method. This model is coupled to an optimization program in order to find the design and control parameters of the whole motor-converter minimizing the power train energy losses and the electric vehicle cost. This study aims to encourage the manufacture procedure of electric vehicles in big series REFERENCES [1] N. A. Rahim, W. P. Hew, A. Mahmoudi International Review of Electrical Engineering (I.R.E.E.), Vol. 6, N. 2 March-April 2011 Manuscript received and revised March 2011, accepted April 2011 Copyright 2011 Praise Worthy Prize S.r.l. - All rights reserved 760Axial-Flux Permanent-Magnet Brushless DC Traction Motor for Direct Drive of Electric Vehicle [2] Progress In Electromagnetics Research, Vol. 122, 467{496, 2012AXIAL-FLUX PERMANENT-MAGNET MOTOR DESIGN FOR ELECTRIC VEHICLE DIRECT DRIVE USING SIZING EQUATION AND All rights Reserved 668

8 ELEMENT ANALYSISA. Mahmoudi*, N. A. Rahim, and H. W. PingUMPEDAC, Engineering Tower, University of Malaya, Kuala Lumpur,Malaysia [3] DESIGN OF AN AXIAL FLUX BRUSHLESS DC MOTOR WITH CONCENTRATED WINDING FOR ELECTRICS VEHICLES [4] S. TOUNSI and R. NEJIEcole Nationale d Ingénieurs de Sfax (ENIS)Laboratoire d Electronique et des Technologies de l InformationBP Sfax TUNISIEsouhir.tounsi@isecs.rnu.tn ; rafik.neji@enis.rnu.tnbrushless DC Motor Fundamentals Application Note Prepared by Jian Zhao/Yangwei Yu July 2011 All rights Reserved 669