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发表于 2012-11-16 17:22:16
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不同的机器:尼古拉·特斯拉的感应电动机
ONCE again, worrywarts in Washington are wringing their hands over possible shortages of so-called “critical materials” for America’s high-tech industries. In particular, the Department of Energy frets about certain metals used in manufacturing wind turbines, electric vehicles, solar cells and energy-efficient lighting. The substances in question include a bunch of rare-earth metals plus a handful of other elements which—used a pinch here, a pinch there—enhance the way many industrial materials perform.
在华盛顿,一些自寻烦恼的人们又一次对高科技产业所谓的“重要物资短缺”的可能性感到焦虑不安。这种焦虑在美国能源部尤其严重,能源部对用于生产风力发电机涡轮、电动汽车、太阳能电池和节能灯的特殊材料的缺少感到特别揪心。这些特殊材料包括一些稀土及其他元素,这些特殊材料只要添加一点点到工业材料里,工业材料的性能就能大幅度提高。
Tesla's invention is, in essence, a rotating transformer. Its primary windings reside in a stationary steel casing (the stator) and and secondary conductors are attached to an inner shaft (the rotor). The stator surrounds—but does not touch—the rotor, which is free to rotate about its axis. An alternating current applied to the stator’s windings creates a rotating magnetic field, while simultaneously inducing a current in the separate conductors attached to the rotor. With an alternating current now circulating within it, the rotor creates a rotating magnetic field of its own, which then proceeds to chase the stator’s rotating field—causing the rotor to spin in the process and thereby generate torque.
尼古拉·特斯拉发明的感应电动机本质上就是一台旋转变压器——首先在电动机的固定钢制外壳(定子)上安装上绕组,然后将导体安装入内轴(转子)。定子将转子包裹起来,但定子与转子并不接触,这使得转子能以自己的轴心线为中心进行选择。当给定子的线圈通以交流电,线圈能够产生一个旋转磁场,同时由于受到旋转磁场的感应,转子内被绝缘体隔离的导体也将产生交流电流,随着转子内部交流电流的产生,转子也相应地产生出旋转磁场,并与定子的旋转磁场相吸引,在定子旋转磁场的带动下,转子开始旋转来产生扭矩。
Modern induction motors usually have three (or more) sets of stator windings, each using a different phase of the alternating current being applied. Having three “waves” of magnetism induced in the rotor with every revolution, instead of just one, smooths out the induction process and allows more torque to be generated.
现代的感应电动机一般是定三个(或更多)定子线圈,每个定子线圈单独通以交流电流。在异步电动机工作时,三个定子线圈都被通以交流电流,这样转子每转一圈就不是感应到一个旋转磁场,而是感应到三个旋转磁场,这使得转子的电磁效果更好,并且能让转子产生出更多的扭矩。
Such machines are known as asynchronous motors, because the rotor’s magnetic field never catches up with the stator’s field. That distinguishes them from synchronous motors that use a permanent magnet in their rotors instead of a set of aluminium or copper conductors. In a synchronous motor, the stator’s rotating magnetic field imposes an electromagnetic torque directly on the fixed magnetic field generated by the rotor's permanent magnet, causing the rotor-magnet assembly to spin on its axis in sync with the stator field. Hence the name.
这种感应电动机就是众所周知的异步电动机,之所以有这样的名称,是因为转子的磁场没法与定子的磁场同步,这也正是异步电动机与同步电动机的区别所在。同步电动机在其转子内使用永磁体而不是一套铝质或铜质的导体,如果要让同步电动机的转子旋转,定子产生电磁转矩来推动转子的永磁体的磁场旋转围绕转子的轴心线进行旋转,并且同步电动机的定子和转子的磁场是同步的,这就是同步电动机名称的来源。
In the past, the main disadvantage of asynchronous induction motors was the difficulty of varying their speed. That is no longer an issue, thanks to modern semiconductor controls. Meanwhile, the induction motor’s big advantage—apart from its simplicity and ruggedness—has always been its ability to tolerate a wide range of temperatures. Providing adequate cooling for the Toyota Prius’s permanent-magnet motor adds significantly to the vehicle’s weight. An induction motor, by contrast, can be cooled passively—and thereby dispense with the hefty radiator, cooling fan, water pump and associated plumbing.
在过去,异步电动机的最大的缺陷就是很难改变转子的旋转速度,但随着现代半导体控制技术的发展,这一问题已经被解决。同时,异步电动机的优点除了结构简单且强度好外,异步电动机还能在温度大幅度变化的环境下正常工作。丰田普锐斯电动车采用的永磁电动机是该电动车重量不小的一个部件,如果使用感应电动机来替代普锐斯电动车上的永磁电动机,那么为永磁电动机配备的臃肿散热器,冷却风扇、水泵及相关的管路都可以省去了。
Better still, by being able to tolerate temperatures that cause permanent magnets to break down, an induction motor can be pushed (albeit briefly) to far higher levels of performance—for, say, accelerating hard while overtaking, or when climbing a steep hill. Hybrid vehicles like the Toyota Prius or the Chevrolet Volt have to use their petrol engines to get extra zip. Pure electric vehicles such as the Nissan Leaf depend on gearboxes to generate the extra torque for arduous tasks. By contrast, the Tesla Roadster uses just one gear—such is the flexibility of its three-phase induction motor.
感应电动机能耐受温度的变化更是他的一大优点,要知道,温度大幅度变化会导致永磁电动机损坏;此外,感应电动机能在超车加速或爬陡坡时被强制提高输出扭矩(虽然时间很短)。像丰田普锐斯电动车或雪佛兰Volt这样的混合动力汽车在提速是需要使用发电机来提高速度,而日产聆风这样的纯电动汽车只能依靠齿轮箱来输出更多的扭矩来实现提速的目的,特斯拉跑车则只使用一个三相感应电动机来作为动力机构。
So far, Toyota has remained mum about its neodymium-free electric motor-generator. The design used in the current version of the Toyota Prius (the car actually has two such units, one for propulsion and regenerative braking, and the other to run all the on-board accessories) combines both conductors and a permanent magnet in its rotor core. On light loads, the unit works more like a permanent-magnet motor. On heavier loads, the induction features predominate.
迄今为止,只有丰田没有对外透露一点其研发无钕电动/发电机的进展情况,无钕电动/发电机在其转子上结合了永磁体和导体感应磁体技术。丰田普锐斯电动车就是运用了无钕电动/发电机技术(普锐斯电动车装配有两套无钕电动/发电机,一套用于推进和反馈制动,另一套用于为车载配件供电。)普锐斯电动车在载荷不高时,无钕电动/发电机以永磁电动机方式工作,在载荷较重时,无钕电动/发电机会转换到感应电动机方式工作。
In moving to a pure induction design, Toyota could do worse than take a page out of the Tesla car company's manual. Weighing in at 52kg (115lb), the Tesla Roadster’s tiny three-phase induction motor is no bigger than a watermelon. Yet it packs a hefty 288 horsepower punch. More impressively, the motor’s 400 Newton-metres (295 lb-ft) of torque is available from rest to nearly 6,000 revolutions per minute. Having access to such a wide torque band eliminates the need for a second or third gear in the transmission. The result is a power unit that is light, compact and remarkably efficient.
如果谈到单纯感应电动机设计,丰田公司要落后于特斯拉公司。特斯拉公司时间的微型三相感应电动机的重量不过52公斤(115磅),比一个西瓜大不了多少,但却能输出288马力的动力;更令人印象深刻的是,特斯拉公司设计的这个感应电动机转速能达到每分钟6000转并且能产生最高为400牛顿米的扭矩,由于该感应电动机的输出的扭矩可以在大范围内调整,因此无需安装第二套乃至第三套传动机构。因此,特斯拉跑车的动力系统具有重量轻、效率高及结构紧凑的优点。
Overall, the Tesla Roadster is said to achieve a battery-to-wheels efficiency of 88%—three times better than a conventional car. With Nikola Tesla's robust and reliable induction motor making such a successful comeback, it is puzzling to see why anyone should worry about potential shortages of neodymium and other rare-earths for alternative power and transport.
总的说来,特斯拉跑车据称电池电力转为轮胎扭矩的比率为百分之八十八,高于传统汽车转换比率三倍。尼古拉·特斯拉发明的感应电动机如此的强悍且可靠,人们又重新将其成功运用到新领域,我们没有必要担心钕及其他稀土材料可能的缺乏对研发替代动力及运输方式产生的干扰。
[ 本贴由 号号 于 12-11-16 17:42 最后编辑 ] |
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