【導(dǎo)讀】設(shè)計的主要目標(biāo)是綜合傳動機構(gòu)的各項指標(biāo)，即降低重量、減小體積與。誤差、降低成本。深入研究中的一項是初級和中級的飛行驅(qū)動表面。盡管EMAs具有自動的泄漏解決。方案,但EHAs通常寧愿在EMAs安全關(guān)鍵時使用可能性問題EMAs機械堵塞。這項工作將著眼于駕駛滾筒螺絲直接連接。到電機的協(xié)調(diào)問題，而不是通過齒輪箱驅(qū)動。機轉(zhuǎn)矩，從而成為較重的，更大的執(zhí)行機構(gòu)。桿設(shè)計，在改善執(zhí)行機構(gòu)的可靠性的同時并使齒輪系統(tǒng)達(dá)到同一功率密度。的極數(shù)上升，從而機器的中心會留有一中空的空間。使用多相電機確保相繞組與電場。使用多相電機的主要缺點是電動力和電控的。擾流層對飛行有雙重影響。空比變化在飛行期間，著陸階段具有較高的關(guān)稅和較低的期間郵輪之一。是在機艙減壓的情況下緊急下降。這最后一種情況對擾流器要求最大，因為它需。這項工作的兩個考慮機器是20和22桿機，雙方有一個24槽定子。率，低幅度齒槽轉(zhuǎn)矩。對這些類型的繞組的主要缺點是高的定子磁勢諧波含量。

　　

【正文】 dl) as detailed in Table. 1. However, as loading goes up, this advantage is lost as it saturates earlier due to the higher parasitic fluxes and the different machine magic loading as shown in Fig. 7. . NoLoad Back EMF for 22 pole motor rms phase current . Torque constant for the three machines rms phase current . Iron loss variation with load at rated speed Figure 6 shows the iron loss variation with phase current for the three machines at rated speed. These losses are estimated based on the magic flux density distribution and the loss data for the magic steel used. VI. FAULT TOLERANCE The degree of fault tolerance the electrical machine is required to achieve depends on the actuator system configuration and on the number of redundant backups. In order to have a modular system, each phase has to be supplied from an independent converter thus having electrically isolated phases. The foreseeable machine related fault scenarios can either winding open circuit faults, in the winding itself or in the converter. The other type of fault which is more difficult to control and manage is a winding short circuit fault, either at the machine terminals or an interturn fault shorting part of the winding. The short circuit current and the braking torque in case of a terminal short circuit fault can be limited by having a high enough phase inductance. In case of an inerturn fault the short circuit current is likely to reach high values as it is merely limited by the resistance of the shorted turns especially with a few turns being shorted. This current can be limited to rated value by shorting the phase terminals as explained in [4]. Inter turn shorts can be detected by the controller as demonstrated in [5]. A) Magic Decoupled Windings In order to have a controllable machine after a shortcircuit fault it is essential to be able to limit the short circuit current to an acceptable level and ensure that it does not magically couple the other phases so as to allow full control of the remaining phase currents. Fig. 7. shows the magic flux distribution for the three machines when only one phase is excited. One can note that there is minimal flux linking the other nonexcited phases. One can however spot the differences in the magic flux path for the three machines. The flux distribution in the alternate teeth wound motor is seen to have a return path through the backiron section extending a whole quarter of the stator back iron. Although the magic coupling, considering linear iron is minimal, one can expect a reasonable cross coupling in a non linear machine. Fig. 8 shows the backemf across the three phases when only phase c excited. The magic decoupling is evident. a) 24 slot 20 pole alternate teeth wound b) 24 slot 20 pole all teeth wound c) 24 slot 22 pole – all teeth wound Fig. 7. Resulting flux distribution due to one phase excitation . Back Emf with one phase excitation B) Open Circuit Faults A machine can operate with an open circuit fault as long as a positive sequence stator field synchronous with the air gap flux is maintained. This can be achieved with at least two separately controlled phase windings, even if not spatially symmetrically distributed. In a three phase machine with a faulted phase this can be achieved by controlling the remaining healthy phase currents to shift by π /6 away from the faulted phase as illustrated in Fig. 9. Fig. 10. and Fig. 11. show the torque produced before and after an open circuit fault occurs with the a 20 pole single and alternate teeth wound motor respectively. If the machines are to be designed to carry on operating with the faulted phase they have to be rated accordingly. In such a case a higher phase number than three is likely to be more advantageous. In the system considered here the machine has only to operate in fault tolerant mode for the time to get a back up system into operation. In order to achieve the same torque after a phase open circuit, the phase currents have to increase by with the stator copper loss doubling in value as shown in . Although the fundamental torque is maintained after an open circuit phase fault, a torque ripple ponent at twice the fundamental excitation frequency is present. This is due to the interaction between the fundamental current and the third harmonic air gap flux density due to iron saturation. It can be noted that the torque ripple for the alternate teeth wound motor is larger due to higher saturation. . Phase currents before and after a phase open circuit fault Fig. 10. Torque produced by the 20 pole machine with all teeth wound before and after one phase is open circuited. Fig. 11. Torque produced by the 20 pole machine with alternate teeth wound before and after one phase is open circuited. C) Terminal Short Circuit Faults Short circuit faults are limited by having a high phase inductance. In the case of a surface mount machine, this is mainly slot leakage inductance. Having deep slots with a large bridge depth enables us to reach the required inductance value. Fig 12. and 13. show the braking torque and short circuit current after a symmetric phase short circuit with the machine running at rated speed. All the three machines respond similarly to a short circuit fault as their phase impedance is nearly identical. Fig. 12. Braking Torque with a terminal short circuit fault at rated speed for the 22 pole motor Fig. 13. Short circuit currents with a balanced three phase terminal short circuit for the 22 pole motor. VII. CONCLUSIONS The design challenges for having an EMA directly driven by an electrical machine without an intermediate gearbox were highlighted. A mid spoiler actuator using a directly driven EMA is currently being developed. It is shown that a directly driven EMA improves reliability, r