第10章 直流无刷电机-4

1、控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机IntroductionBLDC motors are one of the motor types rapidly gaining popularity. BLDC motors are used in industries such as Automotive, Aerospace, Consumer, Medical, Industrial Automation Equipment and Instrumentation. As the name implies, BLDC

2、 motors do not use brushes for commutation; instead, they are electronically commutated. Brushless DC electric motor (BLDC motors) also known as electronically commutated motors are synchronous motors that are powered by a DC electric source via an inverter, which produces an AC electric signal to d

3、rive the motor (AC, alternating current, does控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机not imply a sinusoidal waveform but rather a bi-directional current with no restriction on waveform); additional sensors and electronics control the inverter output amplitude and waveform and frequ

4、ency (i.e. rotor speed). A Brushless DC motor consists of three parts, a motor, the rotor position sensors and electronic switching circuit. principle block diagram of a brushless DC motor is shown in fig.10-1.DC power supplySwitching circuitMotorPosition SensorOutputFig.10-1 principle block diagram

5、 of brushless DC motors控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机ScooterFigure 10-1 BLDC motors控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机BLDC motors hav

6、e many advantages over brushed DC motors and induction motors. A few of these are: Better speed versus torque characteristics High dynamic response High efficiency Long operating life Noiseless operation Higher speed ranges控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机In addition, the ra

7、tio of torque delivered to the size of the motor is higher, making it useful in applications where space and weight are critical factors. We will discuss in detail the construction, working principle, characteristics and typical applications of BLDC motors.控制电机控制电机 (Control Electrical Machine)第十章第十章

8、 无刷直流电动机无刷直流电动机10.2 FUNDAMENTAL CONSTRUCTION AND OPERATING PRINCIPLE BLDC motors are a type of synchronous motor. This means the magnetic field generated by the stator and the magnetic field generated by the rotor rotates at the same frequency. BLDC motors do not experience the “slip” that is normal

9、ly seen in induction motors. BLDC motors come in single-phase, 2-phase and 3-phase configurations. Corresponding to its type, the stator has the same number of windings. Out of these, 3-phase motors are the most popular and widely used.控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机10.2.1

10、 CONSTRUCTIONFigure 10-2 Construction控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机1) StatorThe stator of a BLDC motor consists of steel laminations with windings placed in the slots that are axially cut along the inner periphery. Traditionally, the stator resembles that of an induction

11、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 are placed in the slots and they are控制电机控制电机 (Cont

12、rol Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机Figure 10-3 Statorinterconnected to make a winding. Each of these windings are distributed over the stator periphery to form an even numbers of poles. Figure 10-3控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机控制电机控制电机 (Control Electrical Machine

13、)第十章第十章 无刷直流电动机无刷直流电动机The armature winding connections are shown in figure 10-4.(a)3-phase, star, 3-state; (b) 4-phase, star, 4-state(c) 3-phase, star, 6-state (d) 2-phase, orthogonal, 4-state控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机Figure10-4 Armature winding connection (e) 3-phase

14、, delta, 6-state; (f) 4-phase, closed, 4-state控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机2) RotorThe following figure10-6 shows cross sections of different arrangements of magnets in a rotor.Figure 10-6控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机控制电机控制电机 (Control Electri

15、cal Machine)第十章第十章 无刷直流电动机无刷直流电动机Unlike a brushed DC motor, the commutation 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

16、 following the energizing sequence. Rotor position is sensed using Hall effect sensors embedded into the stator. 3) Hall Sensors控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机Most BLDC motors have three Hall sensors embedded into the stator on the non-driving end of the motor. Whenever th

17、e 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.控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流

18、电动机无刷直流电动机CDROM Hall Sensor Positions控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机(4) Electro-magnetic position sensor控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机10.2.2 Theory of Operation1) The operation principle of 3-phase, star, 3-state system is explained with figure

19、8.Figure 10-8 Operation principle控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机 electrical angle 0 2/3 4/3 2conduction angles of state windingABCconducting transistorV1V2V3Table 10-1 Conduction sequence table of 3-phase, star, 3-state systemFigure 10-9 Phase voltages waveforms of BLDC控制电

20、机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机Fig.10-10 Torque waveform2) 3-phase, star, bridge connection控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机Fig.10-12 3-phase, star, bridge connectionV1 V6 (A+C-)V6V2 (B+C-)V2 V4 (B+A-)V4 V3 (C+A-)V3 V5 (C+B-)V5 V1(A+ B-)V1 V6 (A+C-)控制

21、电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机Table 10-2 Conduction sequence tableof 3-phase, star, 6-state systemElectrical angle 0 /3 2/3 4/3 5/3 2ConductionsequenceABCBCABV1Turn onV2Turn onV3Turn onV4Turn onV5Turn onTurn onV6Turn on控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流

22、电动机Figure10-13 Torque vector diagram30sin330cos2602sin260sinsin21mmTTTTT控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机3) 3-phase, closed, bridge connection.Figure10-14 3-phase, closed, bridge connection V1 V6 A+/(C-B-)V6V2 B-/(C+A+)V2 V4 C+ /( B-A-)V4 V3 A-/( B+C+)V3 V5 B+/ ( A-C-)V5 V1C

23、-/ ( A+B+)V1 V6 A+/(C-B-)控制电机控制电机 (Control Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机Table 10-3 Conduction sequence table of closed, star, 6-state systemElectrical angle 0 /3 2/3 4/3 5/3 2ConductionsequenceACBACBC BA BA CBCBAC AV1Turn onV2Turn onV3Turn onV4Turn onV5Turn onV6Turn onTurn on控制电机控制电机 (Con

24、trol Electrical Machine)第十章第十章 无刷直流电动机无刷直流电动机10.3 COMPARING BLDC MOTORS TO OTHER MOTOR TYPESCompared to brushed DC motors and induction motors, BLDC motors have many advantages and few disadvantages. Brushless motors require less maintenance, so they have a longer life compared with brushed DC motors. BLDC motors produce more output power pe