三相磁通切换型双凸极永磁电机的电感特性分析

Abstract
This paper investigates the inductance characteristics of a novel 3-phase (12-stator-tooth/10-rotor-pole) fluxswitching permanent magnet (FSPM) machine with doubly-salient structure based on finite element analysis (FEA). Firstly, the topology and operation principle of the FSPM machine are introduced. Secondly, the apparent and incremental inductances are defined. Then, the conventional calculation method of transforming the inductance in stator frame into rotor frame is performed. To overcome the shortcoming of the conventional method, e.g. time-consuming, a new simplified and fast method is proposed to obtain the d-axis and q-axis inductances directly and accurately at two special rotor positions. The proposed method is validated by the comparison of the predicted results by two ways. Key words: Flux-switching, doubly-salient, permanent magnet machine, inductance, finite element analysis
ψ pm
0
θ
e
0
ψ
Incremental Apparent inductance inductance
θ
i
i
0
θ
Figure 2 Operation principle of FSPM machine
Figure 3 ψ-i curve
The operation principle of FSPM machine can be described in Fig. 2. It can be seen that both the value and polarity of the PM flux-linkage per phase vary with the rotor position [7]. Due to the waveforms of flux-linkage and thus the back-emf are essentially sinusoidal [6][7], it makes the FSPM machine an excellent candidate for brushless AC drive operation. The detailed analysis of the structure of the FSPM machine is presented in [7].
A2 Stator B2 C1 PM
C2
B1
A1
A1
S C2 N N B2 S S A2 N
N C1
S
S B1
N
N A1
S
B1
C2
Winding C1 A2 B2
Rotor
(b) Configuration of PMs and windings
(a) 3-phase FSPM machine
Figure 1 Topologies of FSPM machine
Projects supported by National Natural Science Foundation of China (50377004), Specialized Research Fund for the Doctoral Program of Higher Education (20050286020) and the Foundation for Excellent Doctoral Dissertation of Southeast University
2 Topologyg. 1 shows the cross-sections of a 3-phase, 12/10-pole FSPM machine. It can be noted that the rotor of the machine is similar to that of a switched reluctance (SR) machine. In addition, the concentrated windings, similar to those in a SR machine, are employed, which leads to low copper consumption and low copper loss due to short end-windings. Besides, in FSPM machine a concentrated coil is wound around the two adjacent teeth with a piece of PM in the middle. Compared to a SR machine, the main difference lies in the configuration of PMs in the stator, which contains 12 segments of “U”-shape magnetic cores, between which 12 pieces of magnets are inset pre-magnetized circumferentially in alternative opposite directions. Compared to the conventional PM machines having magnets in the rotor, the placement of both PMs and
1 Introduction
Conventional permanent magnet (PM) brushless machines usually have magnets on the rotor. However, brushless machines having magnets on the stator [1], namely doubly-salient permanent magnet (DSPM) machines [2]-[4], flux-reversal permanent magnet (FRPM) machines [5], and flux-switching permanent magnet (FSPM) machines [6][7], have recently been the subject of considerable research. Since inductances are essential parameters for the dynamic performance predictions of PM brushless machines, which significantly affect the output torque/power and the field-weakening capability. Besides, the inductances gradually reduce with an increase in current due to magnetic saturation. Hence, it is necessary to calculate the inductance accurately for the control of the machine taking the saturation-effect into account. For those novel machines, both the self-inductance and mutual-inductance are mostly calculated by the conventional method step by step for each phase based on finite element analysis [3][5][6], which consumes much time and a large quantity of data need to be dealt. In this paper, in addition to the conventional way of transforming the inductance in stator frame into rotor frame, a new simplified and fast method is proposed which can directly calculate d-axis and q-axis inductances at two special rotor positions avoiding the transforming procedure, significantly saving time and workload. The proposed method is validated by the comparison of the predicted results from two methods.