Interior Permanent Magnet Motor Research Articles

Development of a High Power Density Motor Made of Amorphous Alloy Cores

In this paper, the development of a permanent-magnet (PM) motor made of amorphous alloy (AA) core is presented. The motor is rated as 20 kW, and base speed is 2500 r/min. A massive produced interior PM motor used in electric vehicle traction application is chosen as the baseline motor. An optimization software package built based on Matlab platform is used to design the stator made of AA, while the rotor is preliminary designed with the help of analytical formulation aiming at lowest core loss in stator teeth and finally tuned by finite-element analysis. The optimized AA motor is 31% smaller in volume than the baseline motor while keeping the continuous power rating unchanged, which means 45% more in power density. To validate the mathematical model beneath the optimization software package, two prototype motors have been manufactured. The first motor is the AA motor, optimized in this paper, and the second motor has exactly the same lamination shape and structural design of motor 1 but its material is nonoriented silicon steel like the baseline motor, instead of AA. The test result show the efficiency of motor 1 is higher than the baseline motor in full speed range, and motor 2 is badly behaved in terms of efficiency. The observation from the test proves that simply replacing the silicon steel with AA does not work under all circumstances, and the optimization experience gained for the AA cannot be used directly in designing a silicon steel motor.

Self-Commissioning of Interior Permanent- Magnet Synchronous Motor Drives With High-Frequency Current Injection

In this paper, a simple and robust method for parameter estimation at rotor standstill is presented for interior permanent magnet (IPM) synchronous machines. The estimated parameters are the stator resistance through dc test, the dq inductances using high-frequency injection, and the permanent magnet flux by means of a closed-loop speed control maintaining rotor stationary. The proposed method does not require either locking the rotor or additional/special power supplies. The validity of the suggested method has been verified by implementation on two IPM motor prototypes. Finally, the estimated parameters have been compared against results obtained through finite-element simulations and with machine magnetic characterization, separately performed, to validate the method's effectiveness. Saturation and cross-saturation effects are taken care of through amplitude modulation and cross-axis current application, respectively.

Investigation of Magnet Arrangements in Double Layer Interior Synchronous Permanent Magnet Motor over Wide-Speed Range for Electric Vehicle Applications

In this paper, the magnet arrangement for a manufactured Double Layer Interior Synchronous Permanent Magnet Motor (DLISPMM) for Electric Vehicle (EV) applications is investigated. In a first step, the manufactured motor is optimized for its nominal condition, by using a particular design of experiment (DOE) method. In a second step, a comparative analysis for the two types of DLISPMMs for a wide speed range operation is performed, by using a parametric Finite Element (FE) model, for calculation of the main machine characteristics, in conjunction with a convenient dynamic model, considering magnetic saturation, for implementation of field weakening control. The initial linear and the final, considering magnetic saturation, dynamic models are evaluated. Finally, the initial and final designs are compared in terms of the main operating characteristics for both nominal low speed and high speed field weakening operation.

Evolutionary Optimization of a Fractional Slot Interior Permanent Magnet Motor for a Small Electric Bus

Fractional Slot Concentrated Winding (FSCW) Interior Permanent Magnet (IPM) motors constitute a favorable choice for electric vehicle applications due to their inherent advantages of high efficiency and performance, field weakening capability and permanent magnet effective shielding from eddy currents. In this paper, an IPM motor with buried sinusoidal magnets for a small electric bus is optimized in terms of both efficiency and performance. The overall magnet volume and the corresponding iron bridge width are maintained within specified borders, thus enabling adequate field weakening and permanent magnet shielding margins. In the optimization process a single-objective Differential Evolution (DE) algorithm is utilized, showing great convergence characteristics.

Rotor-Dynamic Characteristic Evaluation of Interior Permanent Magnet Motor using Finite Element Method

Dynamic characteristics of a critical speed of the rotor components at interior permanent magnet motor were evaluated using one-dimensional (1D) and three-dimensional (3D) finite element methods. Critical speed of the rotor wasinvestigated in the Campbell diagram, which shows the relationship between natural frequency and rotational velocity of the system when the motor is not in operation. The 1D finite element analysis shows that there are two modes which are close to the design frequency of 300 Hz i.e. mode 1 and 2. However the critical rotational velocity in both modes are still far above the maximum velocity design of 6,000 rpm. Validation using 3D finite element analysis demonstrated that all modes were still above the designed frequency and did not find any critical speed below 6,000 rpm. It can be concluded that the critical speed of the rotor of IPM motor is still outside the system resonance region, and can be operated safely.

Topology design method of flux barrier in IPM motor by means of genetic algorithm implemented by multistep procedure

This study derives a high performance flux barrier for an interior permanent magnet (IPM) motor using binary-based topology optimization (TO). TO has a higher degree of optimization than size or shape optimization. An IPM motor has many design parameters including the current phase angle, core shape of rotor and stator, and magnet position and shape. The flux barrier in an IPM motor plays a particularly important role, influencing several characteristics. We apply TO, using a multistep genetic algorithm, to the rotor core in order to determine a flux barrier with the highest torque performance.

Efficiency Improvement for Concentrated Flux IPM Motors for Washing Machines

Concentrated flux interior permanent magnet (CFIPM) motors have the advantage that their utilization of flux linkage is more efficient than that of general IPM motors and CFIPM motors are suitable for washing machine motors, which demand low-speed, high-torque specifications. However, low efficiency occurs in the low-speed high-torque mode considering the high-speed operation for spin mode. This paper proposes a magnet overhang structure between the rotor core that reduces leakage flux and improves efficiency for a CFIPM in wash mode. Optimization of the 3D design of magnet overhang structures is performed to improve the efficiency with the same quantity of permanent magnets. The validity of the optimal design is experimentally verified through the fabrication of prototypes.

Analysis and Design of a Multi-Layered and Multi-Segmented Interior Permanent Magnet Motor by Using an Analytic Method

Although demand for the multi-segmented and multi-layered (MSML) interior permanent magnet (IPM) motor is high, the analytic method for this motor has not yet been proposed. The finite element method has been used in the analysis and design of the MSML IPM motor, even though it takes much time to perform. To solve this problem, the correct and rapid analytic analysis method for the MSML IPM motor is proposed in this paper. This method is called the MCC method because it is the combination of the Magnetic equivalent circuit, Conformal mapping to consider slotting effect, and Concentration flux of IPM. Furthermore, the feasibility of the optimization of the MSML motor by using the proposed MCC method is verified in this paper.

Critical Criteria for Successful Synchronization of Line-Start IPM Motors

In this paper, the critical criteria for successful synchronization of line-start interior permanent magnet (IPM) motors are studied for different loading conditions. An approximate solution technique based on average torque analysis is developed for determining the critical slip and the critical inertia of a line-start IPM motor for steady state and dynamic high inertial loads. Transient analysis of a 1-hp three-phase four-pole line-start IPM motor is conducted to determine the accuracy of the proposed criteria. Experimental investigations are carried out for the same 1-hp laboratory IPM motor. Analytical, simulation, and test results are presented. There is close agreement between analytical, simulation, and experimental results, which validates the accuracy of the proposed criteria.

Peak Power Improvement of Interior Permanent Motor for Electrified Vehicles

The capabilities of peak power and continuous power are the main concerns for electrified vehicles. To achieve good acceleration on uphill climbing, improved peak power density is necessary. The motor?s peak power is determined by the maximum allowable temperature of the motor package. If the temperature at peak output power can be kept low, then a higher peak power is achieved. The major purpose of thermal management is to control both the heat generation and dissipation. Therefore, to maximize the interior permanent magnet (IPM) motor peak power capability, the losses or heat generation among the various key components, such as the windings, stator core, and ?magnets, should be reasonably distributed.

Comparison of Finite-Element-Based State-Space Models for PM Synchronous Machines

An interior permanent-magnet (PM) motor is modeled by a combined analytical–numerical approach, in which the relationships between the stator currents and flux linkages are identified with static finite-element (FE) analysis. In addition to the previous approaches using the current space vector as the state variable, new models are also developed using the flux-linkage space vector, which leads to more convenient time-integration of the voltage equations. In order to account for the zero-sequence effects in delta connection, the models also include either the zero-sequence flux or current as an additional state variable. Finally, the possibilities of deriving the required quantities as partial derivatives of the magnetic field energy are discussed. The energy-based approaches avoid inaccuracies related to torque computation and thus allow better satisfying the power balance in the state-space model. We show the ability of the developed state-space models to predict the currents and torque equally to a nonlinear time-stepping FE model with much less computational burden. The results are validated by means of measurements for a prototype machine in both star and delta connections. In addition, we also demonstrate the effect of the zero-sequence current on the torque ripple in case of a delta-connected stator winding.

Design of a Low-Torque-Ripple Fractional-Slot Interior Permanent-Magnet Motor

Despite a strong nonlinear behavior and a complex design, the interior permanent-magnet (IPM) machine is proposed as a good candidate among the PM machines owing to its interesting peculiarities, i.e., higher torque in flux-weakening operation, higher fault tolerance, and ability to adopt low-cost PMs. A second trend in designing PM machines concerns the adoption of fractional-slot (FS) nonoverlapped coil windings, which reduce the end winding length and consequently the Joule losses and the cost. Therefore, the adoption of an IPM machine with an FS winding aims to combine both advantages: high torque and efficiency in a wide operating region. However, the combination of an anisotropic rotor and an FS winding stator causes some problems. The interaction between the magnetomotive force harmonics due to the stator current and the rotor anisotropy causes a very high torque ripple. This paper illustrates a procedure in designing an IPM motor with the FS winding exhibiting a low torque ripple. The design strategy is based on two consecutive steps: at first, the winding is optimized by taking a multilayer structure, and then, the rotor geometry is optimized by adopting a nonsymmetric structure. As an example, a 12-slot 10-pole IPM machine is considered, achieving a torque ripple lower than 1.5% at full load.

Ant colony optimization for the topological design of interior permanent magnet (IPM) machines

Purpose – The purpose of this paper is to apply an Ant colony optimization approach for the solution of the topological design of interior permanent magnet (IPM) machines. Design/methodology/approach – The IPM motor design domain is discretized into a suitable equivalent graph representation and an Ant System (AS) algorithm is employed to achieve an efficient distribution of materials into this graph. Findings – The single-objective problems associated with the maximization of the torque and with the maximization of the shape smoothness of the IPM are investigated. The rotor of the device is discretized into a 9×18 grid in both cases, and three different materials are considered: air, iron and permanent magnet. Research limitations/implications – The graph representation used enables the solution of topological design problems with an arbitrary number of materials, which is relevant for 2 and 3D problems. Originality/value – From the numerical experiments, the AS algorithm was able to achieve reasonable shapes and torque values for both design problems. The results show the relevance of the mechanism for multi-domain topology optimization of electromagnetic devices.

Optimal shape design of flux barriers in IPM synchronous motors using the phase field method

Purpose– The purpose of this paper is to present an optimization method for flux barrier designs in interior permanent magnet (IPM) synchronous motors that aims to produce an advantageous sinusoidal flux density distribution in the air-gap.Design/methodology/approach– The optimization is based on the phase field method using an Allen-Cahn equation. This approach is a numerical technique for tracking diffuse interfaces like the level set method based on the Hamilton-Jacobi equation.Findings– The optimization results of IPM motor designs are highly dependent on the initial flux barrier shapes. The authors solve the optimization problem using two different initial shapes, and the optimized models show considerable reductions in torque pulsation and the higher harmonics of back-electromotive force.Originality/value– This paper presents the optimization method based on the phase field for the design of rotor flux barriers, and proposes a novel interpolation scheme of the magnetic reluctivity.

Effect of Si Content on Iron Loss of Electrical Steel Sheet Under Compressive Stress

The magnetic properties of nonoriented electrical steel sheets under compressive stress were investigated. Iron loss under compressive stress decreases with an increase of Si content. In particular, a 6.5% Si steel sheet shows an extremely low deterioration ratio of iron loss under compressive stress. Furthermore, the deterioration ratio of a 6.7% Si steel was negative. These results were explained well by magnetostriction. The deterioration ratio of iron loss under compressive stress decreases with a decrease of magnetostriction. To evaluate the effect of magnetostriction on iron loss in a motor, interior permanent magnet motors were made using 3.0%, 6.5%, and 6.7% Si steel sheets. In the motor using 3.0% Si steel, the iron loss was increased after the heat shrinking. On the contrary, in the motor using 6.5% Si steel, the iron loss showed a little change after heat shrinking and in the motor using 6.7% Si steel, the iron loss decreased after the heat shrinking.

Comparison of the Fault Characteristics of IPM-Type and SPM-Type BLDC Motors Under Inter-Turn Fault Conditions Using Winding Function Theory

In this paper, the characteristics of brushless dc (BLDC) motors were compared and analyzed according to the types and control methods under the inter-turn fault (ITF) condition. The shorted windings produced by the ITF were modeled by the winding function theory (WFT) based on the distributed constant circuit method. We also introduced the inductance calculated by the WFT to the voltage equation and analyzed the effect of the ITF using the characteristics of the input and output parameters. The increase rate of torque ripple, increase rate of input current, and the circulating current of the surface permanent-magnet (PM) and interior PM motors under healthy and ITF conditions were compared to determine which motor type is more efficient in preventing the ITF. We also analyzed the fault characteristics by applying the advanced angle control. In this paper, the analysis results are validated by the finite-element method and experiments.

Study of Dynamic Simulation on Driving System and Modeling Motor for Electric Drive Application of Armored Vehicles

Establish an IPM(Interior Permanent Magnet) motor mathematic model based on saturated inductance parameters. This model aimed at the traction motor of electric drive system of a certain armored vehicle. Driving control system was established on SIMULINK platform, and the consequence was analyzed.

Topology Optimization of Rotor Core Combined With Identification of Current Phase Angle in IPM Motor Using Multistep Genetic Algorithm

This paper derives an effective shape of the flux barrier in an interior permanent magnet (IPM) motor. IPM motors generally have many design parameters such as the current phase angle, shape of the rotor and stator's iron core, and shape and position of the magnet. The flux barrier plays an important role in controlling torque characteristics. We apply topology optimization (TO) to the rotor core using a multistep genetic algorithm to determine an effective flux barrier. Furthermore, we extend the TO to combinatorial optimization for considering its effect on the current phase angle. Thus, a reasonable flux barrier with an optimal phase angle is determined.

Topology Optimization Method Based on On–Off Method and Level Set Approach

This paper proposes a two-step method for topology optimization, in which after global search is performed by the on-off method, and then local search is carried out by the level set approach. The genetic and gradient-based algorithms are employed for the former and latter optimizations, respectively. This present method is applied to two numerical examples; topology optimizations of a magnetic shield system and interior permanent magnetic motor. It is shown that this present method can find solutions with better performances in comparison with the conventional on-off method.

Magnetic and Structural Finite Element Analysis of Rotor Vibrations Due to Magnetic Forces in IPM Motor

We present a method to analyze magnetically induced rotor vibrations in an interior permanent magnet motor by simultaneously considering the excitation of radial, tangential, and axial magnetic forces and the gyroscopic effect. We show that the magnetic forces acting on rotor poles are multiples of the half slot harmonic originating from A+A-B-B+C+C- winding as well as slot harmonics. We determine the equivalent friction forces of ball bearings and apply them to the structural finite element model to prevent numerical divergence of angular velocity of the rotor. The results of simulation show that rotor vibrations are mainly affected by the slot harmonics of the magnetic forces, and it was validated by the experiments measuring rotor vibrations with an accelerometer and a slip ring.