CPPM混合励磁同步电动机的基本原理与特性

CPPM 混合励磁同步电动机的基本原理与特性TAKAYUKI MIZUNO, KAZUTOSHI NAGAYAMA,TADASHI ASHIKAGA and TADAO KOBAYASHI日本明电舍公司(MEIDENSHA CORP.)摘 要 永磁同步电动机在工业上得到了广泛应用。众所周知，由于不需要励磁输入，电机 运行效率高。然而，由永磁材料特性决定的磁通大致保持恒定，导致永磁电机的气隙磁场 难以调节。另一方面，电励磁同步电动机的气隙磁场容易调节，但在额定负载时励磁铜耗 较大。为使磁通易于控制并改善传统同步电机的性能，作者提出了一种带永磁体和励磁绕 组的混合励磁同步电动机(HSY), HSY的主要优点有：无刷(免维护)，所需的励 磁容量很小(高效率)， 容易实现较强的磁场控制等。正因如此，混合励磁同步电动机 在不同领域都有良好的应用前景。本文主要讨论和分析混合励磁同步电动机的基本原理与 特性。SUMMARY Permanent magnet type synchronous machines have been widely used for industrial applications. It is commonly known that they are operated at high efficiency since no excitation input is required. However, it is difficult to control the air-gap magnetic flux, because the magnetic flux is determined by the property of the permanent magnet and approximately kept constant. On the other hand, synchronous machines with the field winding make it easy to control the air-gap magnetic flux. But the copper loss of the field winding becomes large at the rated load.In order to realize the magnetic flux control easily and improve the performance of the conventional synchronous machine, we propose a hybrid excitation type synchronous machine (HSY) with the permanent magnets and the field winding. Advantages of HSY are (1) it has no brushes (maintenance free), (2) required excitation input is small (high efficiency), (3) it is easy to get a sufficient magnetic flux control, and others. Therefore, HSY has a great possibility of use for various applications.In this paper, basic principles and characteristics of HSY are mainly discussed and made clear.关键词 同步电机，永磁，励磁绕组，混合励磁，磁场控制，有限元方法Keywords: Synchronous machine; permanent magnet; field winding; hybrid excitation; field control; finite element method.1. 引言与其它旋转电机相比，永磁同步电动机(PMSY)的特点是无刷设计，并且不需要电励 磁，可以实现高效率。正因如此，随着稀土永磁材料的出现，永磁同步电动机在工业领域得 到了广泛应用，而且容易制造出数十千瓦的PMSY。然而，PMSY也有明显的缺点。如前述， 由于永磁体特性所决定的电机气隙磁场几乎不变，绕组感应电压随转速变化，这妨碍了作为 电动机使用时的恒输出运行，或作为发电机使用时的恒压运行。对于电动机，可采用具有弱 磁控制的嵌入式永磁(flush-magnet)电机实现宽范围的恒输出运行。然而，若采用高性能 的稀土永磁，即使在空载情况下，也需要很大的电枢电流来实现弱磁控制，这意味着电机轻 载时的性能会变坏。此外，由直流电供电的PMSY需要按其额定容量选择晶闸管和逆变器, 从而加大了体积。Permanent magnet synchronous machines (PMSY) feature brushless design, and need no excitation which provides higher efficiency compared to other types of rotating machines. Because of this, PMSY have found a wide industrial application in a variety of fields, and with the advent of rare-earth magnets, PMSY of several tensof kilowatts are easily manufacturable. However, PMSY suffer from a considerable drawback. Since magnetic flux is dictated by the characteristics of the permanent magnet being nearly constant, voltage induced in windings varies with the number of revolutions, which hinders constant-output operation when used as a motor or constant-voltage operation when used as a generator. In case of motors, constant-output operation in a wide range is achieved by using flush-magnet motors with field-weakening control l,2. However, when employing high-performance magnets such as rare-earth magnets, large armature current is required for this field-weakening control, even with no load, which means deterioration in performance at light-load operation 3. Besides, PMSY-based dc power plants 4 require choppers and converters, according to the rated capacity, with a consequent large size.另一方面，通过通入励磁绕组的直流励磁电流，电励磁同步电动机(FWSY)可以容易 地控制气隙磁通，于是能解决前述 PMSY 与磁场相关的控制问题，特别是对于基于电力供 电的FWSY，采用小体积、低容量的励磁电源，可以方便地实现电压控制。然而，对于FWSY， 需要额外增加如励磁绕组、电刷和光滑环，这将导致设计上的复杂、励磁损耗带来的效率恶 化以及需要维护。尽管与PMSY不同，然而FWSY也有本身的问题。On the other hand, field-winding synchronous machines (FWSY) allow for easy control of magnetic flux by means of dc field current flowing through field winding, thus alleviating the aforementioned problems of PMSY related to the field control. Particularly, it is common knowledge that with FWSY-based power plants. Voltage control can easily be performed by a small-size low-capacity exciter. In case of FWSY , however, additional parts are required such as field windings, brushes and slip rings. This results in complicated design, deterioration of efficiency due to magnetic loss, and the need for maintenance. Thus, FWSY have their own problems, even though different from those of PMSY.于是可以说，同步电动机可能的应用范围主要取决于其励磁方案。也就是说，如果在拟 开发的同步电机中结合PMSY和FWSY的优点，同步电动机的应用范围将被极大拓宽。本 文中，我们提出一种带有永磁励磁和直流励磁绕组励磁的混合励磁同步电动机(以下简称为 HSY)，并从理论和试验两方面讨论它的运行原理、基本特性以及应用。Therefore, we can say that the possible range of application of synchronous machines depends heavily on excitation schemes, and that use of synchronous machines could be widened significantly if a synchronous machine was developed that combines advantages of permanent magnets and field windings. In this context, we have proposed a hybrid excitation synchronous machine featuring both permanent magnets and dc field windings 5, 6 (below referred to as HSY), and discussed its operating principle and basic characteristics in theoretical and experimental terms, as well as possible applications.首先，本文介绍了带有永磁极和励磁绕组HSY的基本结构、采用直流励磁电流对气隙 磁通有效控