外文翻译---永磁牵引电机的崛起

1、.大连交通大学2013届本科生毕业设计（论文）外文翻译外文原文The Rise Of The Permanent-magnet TractioMotorTechnology offering benefits in terms of mass, size and energy consumption, the permanent-magnet synchronous machine is increasingly being adopted for traction drives, despite the need for complex control systems and potenti

2、al failure modes.In the past couple of years, many of the bids for new rolling stock placed with major international suppliers have proposed the use of permanent-magnet synchronous traction motors, which are smaller and lighter than the three-phase induction motors that have dominated the market in

3、recent times.Permanent-magnet motors first came to prominence with the use of two powered bogies from Alstom's AGV in the V150 trainset which broke the world speed record on April 3 2007, but they have subsequently been used in a variety of applications, ranging from the Citadis-Dualis tram-trai

4、n to SBB's Twindexx double-deck inter-city trainsets (Table I).Although railway operators are often viewed as conservative in the adoption of new technologies, the designers and manufacturers of rail traction systems tend to capitalise on the latest drive technologies, which are rapidly deployed

5、 in service if they promise significant performance improvements. This was the case for the early choppers supplying series-connected DC traction motors, separately-excited DC motors, synchronous AC motors and drives (as used on the first generations of TGVs) and for the various generations of async

6、hronous (squirrel-cage) three-phase drives. As technology moved forward, traction drives became more efficient and more controllable, allowing better use of available adhesion while reducing energy consumption.The permanent-magnet synchronous machine, with its associated control electronics, represe

7、nts the latest such advance in traction technology. Millions of small PMSMs are already being used in the transmissions of hybrid cars, thanks to their low mass and good controllability. Larger machines offer a similar potential to enhance the overall performance of the railway traction package. The

8、 technology is now beginning to be introduced into a variety of new rolling stock, but the integration of PMSMs into traction packages presents some significant technical challenges which must be overcome.Fundamental requirements Petrol and diesel engines for automotive applications generally requir

9、e complex gearboxes to allow the prime mover to operate in the optimum speed band. By contrast, electric motors for rail traction are expected to operate effectively and efficiently over the entire speed range, allowing a permanent coupling to the axles and wheels, either directly or via a single ra

10、tio gearbox. This mechanically elegant solution results in highly reliable drives which need relatively little maintenance.Thus the first requirement placed on the design of traction motors is the ability to provide torque or tractive effort over a wide speed range, such as from 0 to 320 km/h.Whilst

11、 it is essential for the traction motor to operate reliably, it is equally important from the driver's and railway operator's perspective that modern traction systems control the torque accurately and smoothly throughout the speed range. Excellent torque control results in optimum use of ava

12、ilable adhesion between wheel and rail, along with smooth acceleration and the ability to cruise at a constant speed and to brake the train electrically (dynamic braking).Tractive effort, power and speed The torque produced in a traction motor is translated into a linear force at the wheel-rail inte

13、rface. This force, which causes the train to accelerate or brake dynamically, is normally referred to as the tractive effort. Fig 1 shows the TE curve of a typical drive system, together with the associated train or vehicle resistance curve. The TE curve intersects the resistance curve at the so-cal

14、led balancing speed, that is, the theoretical maximum speed. Close to this speed, there is only a very small amount of tractive effort available to accelerate the train, as indicated by the red arrow in Fig 1. Fig 2 shows the power produced by the drive and the propulsion power required, which is th

15、e product of speed and tractive effort.Traction motors are generally designed to match a particular duty. The motor must produce the required full torque at zero speed and sustain this torque up to the so-called base speed, throughout region 1 of the TE curve. Above this speed, the machine operates

16、at its maximum power output, and in region 2 the tractive effort is therefore inversely proportional to the speed v. In the third region, tractive effort has to reduce in inverse proportion to v² because of machine limitations.Torque control At low speeds, the motor can in theory provide a torq

17、ue that is greater than that which can be transmitted by means of the adhesion available at the wheel-rail interface. However, this would overload the motor beyond the normally accepted level and must therefore be avoided either by driver action or an electronic control system.Early DC traction driv

18、es were controlled by adjusting the supply voltage using series resistances and by changing the motor group configuration. Today, both DC commutator motors and classic synchronous and asynchronous AC motors are controlled electronically, by varying either the voltage or the voltage and frequency. Mo

19、dern power drives with relatively simple algorithms achieve very good control of tractive effort throughout the speed range.Power control of permanent-magnet synchronous machines can easily deliver good performance in the constant-torque region, but this needs complex algorithms to control the machi

20、ne in the constant power region.AC and DC motors, as well as PMSMs, fundamentally rely on the same physics to generate accelerating and braking torques. Hence the control strategies are similar to some extent. In all types of machines, the torque is created through the interaction between two magnet

21、ic fields. To generate a torque, there must be an appropriate electrical angle (ideally 90°) between the two magnetic fields. These fields can be generated by currents flowing through windings or by permanent magnets.Although today's traction applications mostly use three-phase induction mo

22、tors, it is important to understand the nature and behaviour of the magnetic fields in the stator and rotor of the different types of machine.In a conventional DC traction motor, the north and south poles of the stator field are always oriented in the same direction while the rotor field is maintain

23、ed at a 90° (electrical) angle by the action of the commutator. In a series-connected machine, the same current flows through the stator and rotor windings (Fig 3), while a separately-excited machine allows the armature and stator fields to be controlled independently (Fig 4).In a classic synch

24、ronous three phase machine, the rotor field is produced by a current supplied via slip rings, and the orientation of the field is determined by the physical position of the rotor winding (Fig 5). The stator field is created by currents flowing in the stator windings and rotates at the speed determin

25、ed by the inverter frequency. The angle between stator and rotor fields increases as more torque is produced, but the rotor speed is the same as that of the stator field. A braking action develops if the angle becomes negative.In an asynchronous three-phase machine, the magnetic field rotating in th

26、e stator induces currents in the rotor cage (Fig 6) that, in turn, generate a magnetic field which interacts with the stator field to produce either motoring or braking torque. In motoring, the rotor speed is lower than the rotating stator field speed set by the inverter, and in braking it is faster

27、. No torque is produced if the two speeds are the same. This difference can be expressed as slip frequency or percentage slip.In a PMSM, the rotor field is created by magnets that are either distributed on the surface of the rotor or buried in openings in the rotor laminations (Fig 7). The latter ar

28、rangement offers greater mechanical strength and much lower eddy-current losses in the rotor. The material with the strongest magnetic properties is Neodymium Iron Boron (Nd2Fe14B). The stator field is generated by means of a relatively standard three-phase multipole winding on a laminated core.In a

29、ll electric machines, the rotating magnetic field leads to the generation of voltages that oppose the supply voltage(s), the so-called back EMF. At zero speed this is zero, but it grows linearly with speed. Thus the supply voltage must be increased to maintain a constant torque in region 1.The torqu

30、e supplied or absorbed by an electric machine is given by the product of the magnetic flux and current. It is the role of the electronic power converter to condition the DC or single-phase AC supply voltage such that a suitable current or currents flow in the motor. Many different types of converter

31、s are available, but most modern traction systems use insulated gate bipolar transistors (IGBTs) and some form of pulse-width modulation.In the region of constant tractive effort, the voltage (and frequency in the case of induction machines) applied to the terminals needs to increase linearly with m

32、otor speed so as to maintain the product of flux and current, that is the torque, at a constant level. Beyond the base speed, the applied voltage cannot be increased further due to the limitations of the power electronics and the insulation capability of the machine. However, mechanically, the machi

33、ne can go faster.So region 2 is entered by field weakening, thereby reducing the level of back EMF or, in the case of a PMSM, counteracting its influence. In DC machines this is achieved by reducing the current flowing through the field windings (see the resistance RFW in Fig 3) and in a conventiona

34、l synchronous machine it is achieved by reducing the current supplied to the rotor. In an induction machine, field weakening happens automatically as the supply frequency is increased while the supply voltage is kept constant. In a PMSM, field weakening is more difficult to implement because the rot

35、or field is created by permanent magnets.In region 3, the flux and current are reduced at a greater rate than in the constant power region to avoid exceeding the machine's electrical or mechanical limits. In the separately-excited DC motor, for example, the armature current is also reduced as a

36、function of speed.Advantages and drawbacks The main reason why permanent-magnet machines are being more and more widely adopted for railway traction drives is that they offer very significant advantages compared with equivalent three-phase induction motors. The level of efficiency is 1% to 2% higher

37、 across 80% of the operating range. The specific power is 30% to 35% greater, resulting in a machine that is about 25% smaller and lighter for the same power rating.Whereas in an asynchronous motor heating of the rotor is caused by the inherent slip power, this is virtually eliminated with a PM driv

38、e, avoiding the need for rotor cooling. Normally, PM machine stators are completely sealed and cooled by means of a heat transfer fluid, thus leading to potentially more reliable drives. PMSMs also allow dynamic braking down to very low speeds and, in theory, it should be possible to produce a self-

39、controlled retarder by electro-mechanically short-circuiting the stator windings.Of course, these benefits are not available without compromise. There are seven main drawbacks to the use of permanent-magnet traction motors, although appropriate mitigation measures have been developed.Limitations on

40、the size and cost of the four-quadrant converter and machine do not allow operation across the whole speed range by the simple expedient of supplying the machine with a voltage that is sufficiently higher than the back EMF to permit the flow of current required to achieve the desired torque. This co

41、nstraint is solved by means of field weakening, creating the constant torque and constant power regions. Since the field generated by the permanent magnets cannot be adjusted, field weakening is achieved by injecting currents into the stator windings which set up fields to oppose those of the rotati

42、ng permanent magnets.These extra currents cause copper losses in the stator windings that negate, to some extent, the efficiency gains that are achieved by the use of the low-loss permanent-magnet rotor.In order to be able to control the currents that create the field weakening effect, it is necessa

43、ry for the electronics to know the position of the rotor, to an accuracy of between 1° and 2° (the field angle). For a four-pole machine this requires a mechanical resolution of better than 1.5°. If a sensor is used, its integrity and reliability must be extremely high to ensure adequ

44、ate performance. Sensorless approaches can be used, such as that developed by Schrödl1, but these can lead to a reduction in the accuracy of control.The magnetic flux is temperature-dependent in that the field strength reduces by about 1% per 10K increase in rotor temperature. With PMSMs operat

45、ing over a temperature range of 200K (-40°C to a maximum permissible 160°C), this can have a significant impact. Hence it is necessary for the electronics to monitor the operating temperature and to take this into account when controlling the electrical supply to the machine.Each PMSM requ

46、ires its own individual highly-dependable electronic power controller to ensure that currents are injected at the right moment. However, modern traction systems increasingly use individual controls for each motor to optimise performance, so this is less of a consideration.Irreversible demagnetisatio

47、n occurs if very high currents flow in the machine at high temperatures, even if the rotor does not reach the Curie temperature of between 310°C and 370°C. Potentially more critical, though, a short-circuit in the stator windings can lead to the destruction of the machine, because the movi

48、ng permanent magnet field will continue to induce high currents in the stator. However, demagnetisation helps to mitigate this problem.Similarly, in no-load operation, when the train is coasting, the permanent-magnet rotor continues to induce currents in the stator core. These eddy currents, togethe

49、r with hysteresis effects, result in iron losses, which reduce the overall efficiency of the machine.The rare-earth magnets used in PMSMs are magnetically strong but relatively delicate, both mechanically and thermally. The rotor construction is thus more complex than in the case of rotors for induc

50、tion motors, and the design processes must be adapted accordingly. The control of the supply to the stator windings is also more complex since multiple feedback loops and signal transformations are required (Fig 8).Although this list of potential drawbacks may seem extensive, there are many applicat

51、ions where the benefits of PMSMs greatly outweigh the disadvantages, which makes these machines highly attractive to traction designers. The smaller dimensions and lighter weight are beneficial where space in bogies is limited, such as where it is desired to integrate the drive in a stub-axle withou

52、t a gearbox. The significantly better efficiency and much lower rotor losses offer significant benefits in terms of performance and reduced energy consumption. A good example is the use of PMSMs on the V150 trainset mentioned at the beginning of this article. The asynchronous motors in the power car

53、s had to be suspended from the body (RG 5.07 p71) while the PMSMs could be mounted in the articulation bogies between pairs of intermediate cars, reducing the complexity and mass of the transmission system.Hence we can expect to see a much wider adoption of permanent-magnet traction motors in the co

54、ming years, in the same way that three-phase induction motors were taken up with increasing popularity from the mid-1980s onwards.The authors would like to thank Dr Harald Neudorfer and Markus Neubauer of Traktions-systeme Austria, and Dr Colin Goodman of BCRRE for their assistance in the preparatio

55、n of this article.中文翻译永磁牵引电机的崛起永磁同步电机，即使需要复杂的控制系统和潜在的失效模式，但鉴于其提了质量、尺寸和能耗方面的益处，越来越多地应用于牵引传动装置。在过去的几年中，许多大型国际供应商竞相投标那些使用永磁同步牵引电机的机车车辆，这种电机相比近期已经占据市场的三相异步电动机体积更小，重量更轻。 由于应用了Alstom公司AGV的V150小火车的两个强有力装置。永磁同步牵引电机名声大噪，而这个小火车曾在2007年4月3日打破了世界速度纪录，但它们随后被使用在各种各样的装置上，从Citadis车到SBB的Twindexx双层城际列车。在采用新技术方面，铁路运营商往

56、往被视为是保守的，但铁路牵引系统的设计者和制造商倾向于利用最新的驱动技术，如果这些技术有望带来显著的性能改进，就会很快地被应用。正如早期的斩波器提供情况串联的直流牵引电机，分别激式直流电动机，交流同步电动机和驱动器（使用第一代的TGVs）和各代的鼠笼式异步（）三相驱动器。随着技术的不断发展，牵引驱动器变得更高效，更可控，从而能更好地利用现有的附着力，同时降低能源消耗。永久磁铁同步机及相关的控制电子装置，代表了最新的牵引技术。由于质量轻及良好的可控性，数以百万计的小型永磁同步电机被应用在混合动力汽车的变速器上。较大的机器使得提高铁路牵引包整体性能成为了可能。这项技术现在开始被引入各种新的机车车辆

57、，但集成的永磁同步电机牵引包所带来的一些重大技术挑战必须克服。 用于汽车应用的汽油和柴油发动机通常需要复杂的齿轮箱，以允许原动机操作的最佳速度频带。相比之下，用于轨道牵引的电动马达被期望在整个速度范围内能够有效和高效地运作，使一个永久耦合的车轴和车轮，直接地或通过一个单一的比变速箱。这种机械优雅的解决方案能带来高度可靠的驱动器，而这种驱动器需要相对较少的维护。因此，牵引电机设计的第一个要求是在很宽的速度范围内，如从0到320公里每小时能够提供转矩或牵引力。 现代牵引系统对牵引电动机稳定地运作是必不可少的。同样重要的是，从驾驶者的和铁路运营商的角度，现代牵引系统又能在宽泛的速度范围内准确而又平稳

58、地控制转矩。良好的转矩控制可导致车轮和钢轨之间有效附着力的最佳利用，平稳的加速度及以恒度巡航和电力刹车的能力的获得（动态制动）。牵引力，动力和速度 牵引电动机产生的转矩在轮轨接口处被转换成一个线性力。这个力通常被称为作为牵引力，它会导致列车的加速或动态制动。图1示一个典型的驱动系统的TE曲线，以及与之相关联的铁路列车或车辆的阻力曲线。TE曲线与阻力曲线相交于所谓的均衡速度，即理论上的最大速度。如图1中的红色箭头所示：越接近这个速度，使火车加速可利用的牵引力越小。图2所示：驱动器产生的功率和所需的推进功率即是速度和牵引力的乘积（相互作用的结果）。 牵引电机要遵循特定的要求去设计。在整个区域1的T

59、E曲线上，电机必须在零速度产生所需的全转矩，并持续这一转矩至所谓的基本速度。超过这个速度，机器在其最大输出功率上工作，因此在区域2可见牵引力和速度。在区域3上，由于机器的限制性，使牵引力减少，与v²成反比。 转矩控制 电机在低速条件下，可以提供的理论转矩是大于那些利用轮轨界面上有效粘附的可传送装置。然而，这将使电机超载，并超出通常可以接受的水平，因此，必须避免由驾驶员或电子控制系统操作。 早期直流牵引驱动器是通过使用串联电阻调节电源电压，并通过改变电机的组配置来控制的。如今，无论是直流换向器电动机，还是经典的同步、异步交流电机都是通过改变电压或电压和频率电子控制的。现代电力驱动器有相对简单的算法，可以在宽泛的速度范围内实现对牵引力很好的控制。 永磁同步电机的功率控制可以很容易地在恒转矩区提供良好的性能，但其需要用复杂的算法在恒功率区内控制机器。AC和DC电机，与永磁同步电机一样，本质上都依赖于相同的物理加速和制动力矩。因此，控制策略在一定程度上相似。在所有类型的机器中，转矩都是通过两个磁场之间的相互作用产生的。要产生扭矩，两个磁场之间必须有一个