Doubly Salient Permanent Magnet Motor Research Articles

Electromagnetic Characteristics Analysis and Torque Ripple Reduction for Doubly Salient PM Machine

In this paper, the air-gap field modulation analysis and torque ripple reduction method for doubly salient permanent magnet motor (DSPMM) are presented. Based on the flux linkage distributions in the motor, the equivalent magnetic circuit models for permanent magnet (PM) and armature winding excitations are built, respectively. The air-gap magnetomotive forces (MMFs) caused by PM MMF and armature MMF can be obtained by combining the air-gap permeance and equivalent magnetic circuit models. The electromagnetic properties of the DSPMM are investigated from the perspective of air-gap field modulation principle. It is revealed that multiple field harmonics contribute to torque generation, and the torque ripples of the DSPMM are mainly caused by the cogging torque. To reduce the torque ripples, the 5th or 7th harmonic currents can be injected into the armature winding to compensate the cogging torque, and their analytical formulas will also be given. The finite element simulations and experiments are carried out to verify the results of theoretical analysis and the effectiveness of the proposed control method.

Torque Ripple Mitigation of T-3L Inverter Fed Open-End Doubly-Salient Permanent-Magnet Motor Drives Using Current Hysteresis Control

A torque ripple mitigation and current hysteresis control for T-type three level (T-3L) inverter fed open-end doubly-salient permanent-magnet motor (DSPM) drives is proposed in this paper. The structure, principle, and characteristics of the DSPM are studied and analyzed and a T-3L inverter fed open-end three-phase DSPM drive configuration is proposed in this paper. Then, this paper introduces a novel commutation strategy to reduce the torque ripple during phase commutation. Furthermore, the multi-loop hysteresis current controller and DC-link voltage balancing algorithm are presented. The effectiveness of the proposed control schemes is verified by both simulation and experimental results.

Principle and Analysis of Doubly Salient PM Motor With Π-Shaped Stator Iron Core Segments

This paper investigates a novel three-phase doubly salient permanent magnet (DSPM) motor. Because of the adoption of Π-shaped stator iron core segments, the asymmetrical magnetic circuit among different phases occurring in conventional DSPM motors with E-shaped stator iron core segments can be avoided, so that balanced and sinusoidal three-phase PM flux linkage and no-load electromotive force (EMF) can be achieved. First, based on a 12/7 stator/rotor pole combination, the operation principle of Π-core DSPM motor is discussed using the least magnetic reluctance principle. Then, the general airgap field modulation theory is extended to the Π-core DSPM motor for explaining its operation principle further and armature winding connection. The finite element analysis is used to validate theoretical analysis, as well as to calculate its electromagnetic performances. The results show that the 12/7-pole Π-core DSPM motor possesses higher average torque output capability and lower torque ripple compared with the 12/8-pole E-core counterpart. Finally, a 12/7-pole Π-core DSPM motor is built and tested so as to experimentally verify the theoretical analysis.

Novel Stator Design of Double Salient Permanent Magnet Motor

This paper presents a novel double salient motor design in which the permanent magnets are implanted in the stator to provide additional magnetic flux sources for enhancing its performance and reducing the inherent cogging torque. The feasible cones method is adopted to calculate the dimensional sizes of the proposed short flux path motor. The assembled stators concept is employed to design the magnetic flux paths of the double salient permanent magnet (DSPM) motor and also transfer the heat generated by the windings outside the motor. Due to the nonlinear properties of the doubly salient structure, this paper utilizes both magnetic circuit analysis and finite element analysis to evaluate different operating characteristics of the designed DSPM motor. Experimental data are provided to verify the proposed design.

A New Linear Double Salient Permanent Magnet Motor with Complementary Winding

In this paper, two novel structures of linear double salient permanent magnet (LDSPM) motor having magnets and armature windings in primary are proposed and compared. Firstly, the design principles of both motors are presented. Then, for a fair comparison, two motors are designed based on the same primary dimensions including the slot area, teeth number, pole pitch, permanent magnet volumes and coils number per phase, while the stator pole pitch and the primary structure are different. Finally, the configurations and static characteristics of both motors are critically compared based on finite element (FE) analysis. The results indicate that the proposed topology can avoid the asymmetry of back-EMF waveforms and reduce cogging force and thrust force ripple. Also, the proposed primary permanent magnet linear motors are suitable for the longer stator application such as urban rail transit (URT).

New fault-tolerant flux-mnemonic doubly-salient permanent-magnet motor drive

By incorporating the flux-mnemonic concept into the hybrid-field doubly-salient permanent-magnet (DSPM) motor structure, the resulting flux-mnemonic DSPM motor not only offers efficient online air-gap flux control, but can also flexibly operate as a DSPM motor when the PMs are magnetised or a switched reluctance (SR) motor when the PMs are demagnetised. The key of this study is to artfully utilise these modes of operation for the proposed flux-mnemonic DSPM motor drive. Namely, the motor drive works in the DSPM mode during open-circuit fault, and changes to the SR mode during short-circuit fault. Both computer simulation and experimental results are given to verify the validity of the proposed fault-tolerant flux-mnemonic DSPM motor drive.

Remedial Brushless AC Operation of Fault-Tolerant Doubly Salient Permanent-Magnet Motor Drives

The doubly salient permanent-magnet (DSPM) machine is a new class of stator-PM brushless machines, which inherently offers the fault-tolerant feature. In this paper, a new operation strategy is proposed and implemented for fault-tolerant DSPM motor drives. The key is to operate the DSPM motor drive in a remedial brushless ac (BLAC) mode under the open-circuit fault condition, while operating in the conventional brushless dc mode under normal condition. Both cosimulation and experimental results confirm that the proposed remedial BLAC operation can maintain the average torque, reduce the torque ripple, and retain the self-starting capability under the open-circuit fault.

Design of Doubly Salient Permanent Magnet Motors With Minimum Torque Ripple

This paper presents a design approach for doubly salient permanent magnet (DSPM) motors, aiming to minimize the torque ripple. The key is to propose the design criteria that the reluctance of all magnetic paths is the same, and the armature windings can be artfully connected to compensate the variation of self-inductance. Based on these criteria, the magnetic characteristics become symmetric, and the variation of self inductance is suppressed. Thus, the resulting torque ripple can be minimized. By using the time-stepping finite element method, the proposed DSPM motor and the existing DSPM motor are quantitatively compared in terms of their back-EMFs, self-inductances, and torque ripples, hence confirming the validity of the proposed design approach.

Analysis of Fault-Tolerant Performance of a Doubly Salient Permanent-Magnet Motor Drive Using Transient Cosimulation Method

Doubly salient permanent-magnet (DSPM) motors offer the advantages of high power density and high efficiency. In this paper, it is examined that the DSPM motor is a new class of fault-tolerant machines, a potential candidate for many applications where reliability and power density are of importance. Fault analysis is performed in a DSPM motor drive, including internal and external faults. Due to the fact that the experimentation on a true motor drive for such a purpose is impractical because of its high cost and difficulty to make, a new cosimulation model of a DSPM motor drive is developed using coupled magnetic and electric circuit solvers. Last, to improve the performance of a DSPM motor drive with an open-circuited fault, a fault compensation strategy is proposed. Simulation and experimental results are presented, showing the effectiveness of the proposed cosimulation method and the high performance of the fault-tolerant characteristic of DSPM motor drives.

Performance Prediction of Multiphase Doubly Salient Permanent Magnet Motor Having Nonuniform Air Gap

This paper presents the effects of nonuniformity of the air gap on various performance characteristics of a multiphase doubly salient permanent magnet motor (DSPM). A 6/4 DSPM configuration is analyzed with the help of two-dimensional finite element analysis to predict the effects of three important air gap nonuniformities viz. 1) relative eccentricity between the stator and rotor axes; 2) concentricity error on one half of the rotor; and 3) an elliptical rotor. It is observed that a relative eccentricity up to 20% of air gap has no appreciable effect on the static torque characteristics of the DSPM, above which the permanent magnet torque increases due to reduced air gap, thereby increasing the unbalanced magnetic pull. Therefore, about 20% tolerance in air gap can be allowed for relative eccentricity errors. In case of the concentricity error on one half of the rotor, this tolerance is from -10% to plusmn15% of the air gap, whereas the corresponding limits in the elliptical rotor case are plusmn15% of the air gap

Design of permanent magnets to chaoize doubly salient permanent magnet motors for electric compaction

This article proposes and implements a class of chaotic motors for electric compaction. The key is to develop a design approach for the permanent magnets (PMs) of doubly salient PM (DSPM) motors in such a way that chaotic motion can be naturally produced. The bifurcation diagram is employed to derive the threshold of chaoization in terms of PM flux, while the corresponding phase-plane trajectories are used to characterize the chaotic motion. A practical three-phase 12∕8-pole DSPM motor is used for exemplification. The proposed chaotic motor is critically assessed for application to a vibratory soil compactor, which is proven to offer better compaction performance than its counterparts. Both computer simulation and experimental results are given to illustrate the proposed chaotic motor.

Torque Ripple Minimization of Four-Phase Doubly Salient Permanent Magnet Motors Using Two-Phase Operation

Owing to the nature of salient poles in both the stator and rotor, doubly salient permanent magnet (DSPM) motors suffer from severe torque ripples. In this paper, a new operation mode is proposed and analyzed, namely the use of two-phase operation to minimize the torque ripple of a four-phase DSPM motor. Both theoretical analysis and computer simulation are given to illustrate the proposed two-phase operation. Finally, experimental results are provided for verification.

Effects of inter-turn fault in phase winding on the performance of multi-phase doubly salient motors

This paper presents the results of a 2-D Finite element analysis carried out on switched reluctance motor and doubly salient permanent magnet motor (DSPM) to study the effects of inter-turn fault in phase winding on the average torque, ripple torque, and the phase inductance. It is shown that the DSPM has an inherent advantage of partial withstand to inter-turn faults.

FE analysis of multiphase doubly salient permanent magnet motors

This paper presents the results of two-dimensional (2-D) finite-element analysis (FEA) carried out on 8/6 and 6/4 doubly salient permanent magnet (DSPM) motors to arrive at the magnet leakage factor and the flux density ratios of various parts of the motors so as to aid the designers of this newer motor. The two permanent magnets being kept embedded in the stator halves along with the typical doubly salient structure of the DSPM motor causes more leakage of the magnet flux. After extensive FEAs of the two configurations of the motors, it is observed that a magnet leakage factor of 1.32 is giving the correct results for use in conventional designs of this motor. Based on the optimum designs of the two motors, the flux densities in the airgap, rotor yoke, rotor pole, and stator yoke can be 1, 0.5, 0.9, and 0.5 times the flux density considered for the stator pole, which will normally be just above the knee-point value of the B-H characteristics of the core material used.

Torque Ripple Minimization of Doubly Salient Permanent-Magnet Motors

Due to the nature of salient poles in both the stator and rotor, the doubly salient permanent-magnet (DSPM) motor suffers from severe torque ripples. In this paper, the torque ripple of DSPM motors is analyzed, and the torque ripple factor is newly derived. A new approach, namely the conduction angle control, is proposed to minimize the torque ripple. Moreover, the genetic algorithm is employed to optimize the corresponding control angles. Computer simulation and experimental results are given to verify the proposed approach.

Slanted and saw-toothed stator poles for improved performance of doubly salient permanent magnet motor

This paper presents the results of extensive finite element analyses conducted on doubly salient permanent magnet motor (DSPM) for improving the torque characteristics by novel methods; namely (i) slanted stator pole and (ii) saw-toothed stator pole. In the first method, stator poles are given a slant at the pole face; the slant in a direction opposite to the rotation of the motor has resulted in 7.33% and 71.45% increase in the average and maximum torques, respectively, when compared with the motor with original stator poles. With appropriate saw-tooth shaped stator poles, various permanent magnet torque and static torque profiles can be achieved.

Control and operation of a new 8/6-pole doubly salient permanent-magnet motor drive

This paper proposes a new 8/6-pole doubly salient permanent-magnet (DSPM) motor drive, which offers the advantages of higher power density, higher efficiency, and wider speed range. The corresponding control and operation of the motor drive are presented. A variable proportional-integral (PI) controller combined with bang-bang control for the DSPM motor drive is developed. Two operation modes, namely, four-phase and two-phase operation modes, are proposed for the 8/6-pole DSPM motor drive. The drive system is implemented and tested. The results show that the developed control scheme can operate the DSPM motor properly, and the DSPM motor drive offers high efficiency over wide power range and good dynamic performance. Furthermore, the two-phase operation mode of the 8/6-pole DSPM motor offers the possibility of eliminating the torque ripple of the motor drive.

New split-winding doubly salient permanent magnet motor drive

A new split-winding doubly salient permanent magnet (DSPM) motor drive is proposed. This DSPM motor drive offers the advantages of high power density, high efficiency, and wide speed range. The corresponding operation, analysis, implementation, and experimentation are successively presented. Finally, experimental results are used to confirm that the proposed DSPM motor drive offers high efficiency over a wide output power range, exhibits good dynamic performance, and extends the constant-power operation range significantly.

New Methods of Measuring Inductance of Doubly Salient Permanent Magnet Motors

The inductance characteristic of doubly salient permanent magnet (DSPM) motors is the basis of design, analysis, and control of the motor. Due to the nonlinearity and doubly salient structure of the motor, this characteristic is a function of not only the rotor position, but also the strengthening and weakening actions of the armature flux to the permanent magnet (PM) flux, which makes the measurement of inductance difficult. This article proposes new methods for the measurement of the motor inductance for any rotor positions and level of excitation. The methods are applied to the two newly proposed DSPM motors and the results are compared with those obtained by finite element analysis. It is shown that the proposed peak value method can correctly reflect the influence of the strengthening and weakening actions of the armature flux to the PM flux on the inductance of DSPM motors.

Analysis and control of novel split-winding doubly salient permanent magnet motor for adjustable speed drive

In this paper, a novel split-winding doubly salient permanent magnet (DSPM) motor is proposed and the theoretical and experimental studies on the magnetic field, static characteristics and control strategy of this motor are carried out. The steady-state and dynamic models are presented and the output power equation is derived. The feasibility of extending the operation range of the DSPM motor by using split-windings is proved. The finite element method is used to analyze the magnetic field, in which the leakage flux outside the stator circumference is taken into account. Based on the operation principle and the static characteristics of the motor, the control strategy and scheme are developed and implemented in a microcomputer-based controller. According to the features of the 4-phase 8/6-pole DSPM motor, a half-bridge power converter without neutral is adopted to reduce the number of power devices and to eliminate the problem of voltage unbalance in the split capacitors. The experimental results on the prototype machine not only verify the theoretical analysis, but also show that the proposed DSPM motor drive possesses good steady-state and dynamic performances, offering high efficiency over wide power range, and that the split-winding topology can effectively extend the operation range of the DSPM motor.