To overcome the disadvantage that the detent force of the permanent magnet linear synchronous motor (PMLSM) with short primary is large, a scheme of the modular PMLSM with flux barriers is proposed in this paper. First, the detent force model is established and verified. The phase-angle characteristics of the harmonics in the detent force waveforms are analyzed. Then, the design principles of the scheme with different sectional combinations are analyzed, and two series of the combinations are demonstrated. The detent force and thrust characteristics of these combinations are subsequently compared. In addition, to improve the thrust density, the auxiliary teeth set at the ends of the sectional primary cores are proposed. Finally, the corresponding conclusions obtained by comparing the modular motors with the traditional motor are presented.

Modularization design has been widely used to reduce the detent force of permanent magnet linear synchronous motor (PMLSM). For modular PMLSM, ideally, unit motors are independent of each other and the detent force of the whole motor is the sum of that of unit motors, thus the whole motor detent force can be suppressed by adjusting the phase difference among the unit motor detent forces. But in fact, there is coupling effect between adjacent unit motors, which has adverse effect on the detent force suppression. The influence of the coupling effect is often neglected in current research. Hence, this paper carries out the research on the coupling effect for modular PMLSM: the influence of the coupling effect on the air magnetic field is clarified through magnetic field calculation; the coupling force is isolated by finite element analysis (FEA), and then the effects of key parameters are discussed; the detent force model considering the coupling effect is established, and an optimal design method adjusting the flux barrier length is presented to suppress the detent force.

A novel flux switching permanent magnet linear motor (FSPMLM), which has the advantages of high thrust density (the ratio of average thrust to permanent magnet volume) and low cost for long-stroke application, is proposed and investigated in this paper. The topology of the novel FSPMLM with 12 slots is introduced and the basic operating principle is analyzed firstly. The optimalgeometric parameters are selected by using the layered orthogonal optimization method. Then the electromagnetic performance of the motor is investigated by the analytical method based on the equivalent magnetic network model (MNM). Finally, a scheme of setting auxiliary teeth in the primary component is adopt to suppress the unbalance of the three phase flux linkages.

Conventionally, for a tubular permanent magnet synchronous linear motor (TPMSLM), adopting a modular structure can effectively reduce the detent force; however, the thrust density is sacrificed via the large proportion of the flux barrier to the total primary component volume. To overcome this disadvantage, this paper proposes a novel modular TPMSLM, in which the unit primary component adopts the large slot structure containing several coils. Focusing on this motor, research on the flux linkage characteristic is performed to obtain the design principle, and then the detent force is analyzed and suppressed by reasonable design of end teeth. First, the flux linkage characteristics of the unit motor and the whole motor are investigated. Variation rule of the coil flux linkage affected by the end tooth is discussed, and the principle of realizing three-phase balance for the whole motor flux linkage is elaborated. Moreover, the principle of the detent force suppression is verified and the detent force is further suppressed through the end tooth design. Finally, a prototype is developed. The back electromotive force (EMF) and the detent force were tested, which verified the effectiveness of the novel modular TPMSLM proposed.

A segmental permanent magnet linear synchronous motor (S-PMLSM) with non-integer pole number, which has low detent force and high thrust, is presented in this paper. For the S-PMLSM, the non-integer pole structure makes up for the defect that the conventional integer pole structure cannot suppress the third and its times harmonics in the detent force, thereby can further reduces the thrust ripple rate of the motor. Special winding arrangement is adopted for non-integer pole structure, of which the winding factor is relatively high. Another advantage of the non-integer pole structure is the decoupling between the detent force and the cogging force. When designing cogging parameters and structures, it is not limited by the requirement of the detent force, which enlarges the range of cogging parameters and finally helps to improve the motor thrust. In this paper, 18-slot 24-pole and 18-slot 19.2-pole S-PMLSMs, representing integer and non-integer pole structures, respectively, are selected as samples for comparative analysis. The results show that the later removes almost all detent force while giving higher thrust than the former. The simulation and experimental results validate the research theory.

Affected by the end effect, the inductances of the slot-less tubular permanent magnet synchronous linear motor (TPMSLM) are unbalanced. This paper reports the research on the inductance unbalance and the thrust ripple characteristics for the slot-less TPMSLM, and it presents an optimization scheme adopting modular structure with a three-segment primary component. The inductance unbalance characteristic is obtained and quantitatively investigated based on the finite element models. The causes of the self-inductance unbalance and the mutual-inductance are explained, respectively, and the difference between the two unbalances are quantitate investigated. Then, the thrust ripple is specifically analyzed by establishing the voltage and thrust models according to the laws of the inductance unbalance. Thus, the theoretical connection between the inductance unbalance and the thrust ripple has been established. Moreover, the inductance and thrust ripple characteristics of the modular motor are discussed and compared with those of the conventional motor. The prototypes of the conventional motor and the modular motor are developed to verify the findings of the research. At last, corresponding conclusions obtained by the comparison of modular motor with conventional motor are drawn.