畢業論文設計無刷直流電動機控制系統設計-資料下載頁

　　

【正文】 參考文獻1 :科學出版社，20052 李鐘明,:國防工業出版社，19993 ，19964 陳清泉，:清華大學出版社，廣州:暨南大學出版社，20005 ，2004 6 :江蘇科學技術出版社，20017 ，19968 韋敏，20049 盧靜，陳非凡，200210 梁正峰，200411 陳鋼，12 ，200013 謝運祥,. 機械工業出版社，200714 ，200715 許大中,，200216 王成元,夏加寬,楊俊友,，200617 姚國強,錢銳,. 辭學出版社，200618 . 機械工業出版社，200419 [日]，200620 黃俊,. 機械工業出版社，200421 余永權,汪明慧, ，200322 ，199623 ，199724 張立,．北京機械工業出版社，199525 余永權,李小青,. 北京航空航天大學出版社,199126 李志民,199527 ．北京機械工業出版社,2004附錄1Brushless DC (BLDC) Motor FundamentalsBrushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are used in industries such as Appliances, Automotive,Aerospace, Consumer, Medical, Industrial Automation quipment and the name implies, BLDC motors do not use brushesfor mutation。 instead, they are electronically mutated. BLDC motors have many advantages over brushed DC motors and induction motors. A few ofthese are:(1) Better speed versus torque characteristics(2) High dynamic response(3 High efficiency(4) Long operating life(5) Noiseless operation(6) Higher speed rangesIn addition, the ratio of torque delivered to the size of the motor is higher, making it useful in applications where space and weight are critical factors.In this application note, we will discuss in detail the construction, working principle, characteristics and typicalapplications of BLDC motors. Refer to Appendix B: “Glossary” for a glossary of terms monly used when describing BLDC motors.CONSTRUCTION AND OPERATING PRINCIPLEBLDC motors are a type of synchronous motor. This means the magnetic field generated by the stator and the magnetic field generated by the rotor rotate at the same frequency. BLDC motors do not experience the “slip” that is normally seen in induction motorsBLDC motors e in singlephase, 2phase and 3phase configurations. Corresponding to its type, the stator has the same number of windings. Out of these,3phase motors are the most popular and widely application note focuses on 3phase motors.StatorThe stator of a BLDC motor consists of stacked steel laminations with windings placed in the slots that are axially cut along the inner periphery (as shown inFigure3). Traditionally, the stator resembles that of an induction motor。 however, the windings are distributed in a different manner. Most BLDC motors have three stator windings connected in star fashion. Each of these windings are constructed with numerous coils interconnected to form a winding. One or more coils areplaced in the slots and they are interconnected to make a winding. Each of these windings are distributed over the stator periphery to form an even numbers of poles. There are two types of stator windings variants: trapezoidal and sinusoidal motors. This differentiation is made on the basis of the interconnection of coils in the stator windings to give the different types of back Electromotive Force (EMF). Refer to the “What Is Back EMF” section for more information.As their names indicate, the trapezoidal motor gives a back EMF in trapezoidal fashion and the sinusoidal motor!ˉs back EMF is sinusoidal, as shown in Figure and Figure2. In addition to the back EMF, the phase current also has trapezoidal and sinusoidal variations in the respective types of motor. This makes the torque output by a sinusoidal motor smoother than that of a trapezoidal motor. However, this es with an extra cost, as the sinusoidal motors take extra winding interconnections because of the coils distribution on the stator periphery, thereby increasing the copper intake by the stator windings.Depending upon the control power supply capability, the motor with the correct voltage rating of the stator can be chosen. Fortyeight volts, or less voltage rated motors are used in automotive, robotics, small arm movements and so on. Motors with 100 volts, or higher ratings, are used in appliances, automation and in industrial applications.RotorThe rotor is made of permanent magnet and can vary from two to eight pole pairs with alternate North (N) and South (S) poles.Based on the required magnetic field density in the rotor, the proper magnetic material is chosen to make the rotor. Ferrite magnets are traditionally used to make permanent magnets. As the technology advances, rare earth alloy magnets are gaining popularity. The ferrite magnets are less expensive but they have the disad vantage of low flux density for a given volume. In contrast, the alloy material has high magnetic density per volume and enables the rotor to press further for the same torque. Also, these alloy magnets improve the sizetoweight ratio and give higher torque for the same size motor using ferrite magnets.Neodymium (Nd), Samarium Cobalt (SmCo) and the alloy of Neodymium, Ferrite and Boron (NdFeB) are some examples of rare earth alloy magnets. Continuous research is going on to improve the flux density to press the rotor further.Figure4 shows cross sections of different arrangements of magnets in a rotor.Hall SensorsUnlike a brushed DC motor, the mutation of a BLDC motor is controlled electronically. To rotate the BLDC motor, the stator windings should be energized in a sequence. It is important to know the rotor position in order to understand which winding will be energized following the energizing sequence. Rotor position is sensed using Hall effect sensors embedded into thestator.Note: Hall Effect Theory: If an electric current carrying conductor is kept in a magnetic field, the magnetic field exerts a transverse force on the moving charge carriers which tends to push them to one side of the conductor. This is most evident in a thin flat conductor. A buildup of charge at the sides of the conductors will balance this magnetic influence, producing a measurable voltage between the two sides of the conductor. The presence of this measurable transverse voltage is called the Hall effect after E. H. Hall who discovered it in 1879.