Ki-Doek Lee

Parameter Design of IPMSM With Concentrated Winding Considering Partial Magnetic Saturation

The interior permanent magnet synchronous motor (IPMSM) is usually applied to the traction motor in the hybrid electric vehicle and the electric vehicle due to its high-power density and wide speed range. In this paper, the IPMSM with concentrated winding for a 110 cc electric motorcycle is introduced. Its design was improved for high efficiency and a wide speed operation range. The output characteristics were also analyzed according to the partial magnetic saturation of the shoe and web in many variables. Because partial magnetic saturation affects the harmonics and the eddy current loss of the permanent magnet, it was confirmed that the output characteristics of the motor significantly changed. As a result, the new shape and the design parameters for which the partial magnetic saturation was considered were obtained. Higher level efficiency and a wider operating range than with the base model were confirmed.

Torque Density Elevation in Concentrated Winding Interior PM Synchronous Motor With Minimized Magnet Volume

Permanent magnet (PM) synchronous motors (PMSMs) have been used to drive a number of vehicles. They have high torque density, high efficiency, and a wide speed range. However, the high cost of PMs is disadvantageous. This paper presents a technique for increasing the torque density by modifying the shape of the PMs and minimizing the magnet volume. The PM characteristics such as flux density, demagnetizing force, PM energy product, and the air-gap flux density are represented by a lumped magnetic equivalent circuit when the thickness and width of the PM are increased for the same volume but with different shapes. The torque, torque ripple, core loss, magnet loss, and efficiency of three interior (IPMSM) models designed by the proposed method are compared by finite element analysis. In addition, the demagnetization of the PM due to high temperature, maximum torque load angle, and an adverse field is analyzed. Finally, the analysis result is compared with that of the experiment to verify the proposed model.

Inductance Calculation of Flux Concentrating Permanent Magnet Motor through Nonlinear Magnetic Equivalent Circuit

In order to design a permanent magnet synchronous motor (PMSM), the inductance must be computed. In this paper, the flux concentrating PMSM (FCPMSM) is introduced. Calculating the inductance is difficult because of the complex structure of the rotor. Because the rib and the bridge consist of an iron core, they have nonlinear characteristics. In order to obtain the effective value of the inductance, nonlinear characteristics must be considered in a magnetic equivalent circuit (MEC). In this paper, to calculate the inductance of an FCPMSM, the relative permeance of the rotor was analyzed. Then, the dq-axis MEC, including the nonlinear magnetic reluctance, was created using the flux line. Finally, we verified the validity of the proposed inductance calculation method by comparing the results between the finite-element method and the proposed method.

Inductance Calculation in IPMSM Considering Magnetic Saturation

The design of a motor with a large armature reaction, such as the electric vehicle traction motor, can be implemented using a trial-and-error method based on the finite element method (FEM). The base model-design method that uses conventional magnetic equivalent circuits is quite inaccurate. To avoid such inaccuracy, this study proposes a method that accurately calculates the inductance values at a practical operating point considering the control issue. To achieve this objective, the flux linkage due to the current phase angles in each section is modeled using magnetic equivalent circuits. The result is used to calculate the inductance, assuming relative permeance waves. Finally, the validity of this study is verified by FEM simulation and testing.

A Performance Study on a Permanent Magnet Spherical Motor

To realize the multi-Degree-of-Freedom (multi-DOF) movement, researches on spherical motor have been conducted in many countries. The Spherical motor has a 3-DOF, whose shaft can not only rotate as rotary motor but also tilt in the 2-DOF space. Researches on spherical motor will greatly contribute to 3-DOF systems, because spherical motor can reduce the size and weight of 3-DOF systems. This paper studies a new type of spherical motor that has rotating coils and tilting coils. Also, the current function depending on shaft angles is proposed. Finally, the torque is calculated corresponding to different shaft angles and rotating speeds. Moreover, these performances are validated via experiments.

NE-Map-Based Design of an IPMSM for Traction in an EV

Th\s paper proposes a novel plot called an NE-Map that has two axes representing the no-load electromotive force (EMF) and the number of windings per slot. The NE-Map is applied to the design of an interior permanent magnet synchronous motor. Here, the design of the rotor is implemented using a magnetic equivalent circuit. In addition, the phase currents and current phase angles are estimated by considering the maximum torque per ampere and the flux weakening control method, and a stator is designed using this estimation. As these processes are presented in terms of the values of the EMF and the number of windings per slot, this representation allows for the verification of the relationship among the motor parameters and the determination of the final model by reflecting the design constraints. This process is applied to the design of a traction motor in hybrid EVs, and its validity is verified by comparison with finite element analysis and test data.

Method for Analyzing Vibrations Due to Electromagnetic Force in Electric Motors

In this paper, a method for predicting vibrations due to an electromagnetic force from among the other types of vibrations that occur in an electric motor is proposed. Among electromagnetic forces, the forces applied in the radial direction were separated into their spatial and temporal harmonic components for developing the vibration-prediction method. Each separated radial force densities acts as a vibration source and generates vibrations combined with the mechanical characteristics of the motor. The separation of vibration sources makes it possible to predict the magnitude of the vibration velocity occurring in the motor. This enables optimal motor design considering vibration. To this end, a description explaining the characteristics of electromagnetic vibrations that occur in an eight-pole nine-slot permanent magnet synchronous motor has been provided in this paper as an example. In addition, the proposed method was verified by comparing the obtained vibration velocity with that obtained through electromagnetic-vibration coupled analysis.

A Study on the Compensation of the Inductance Parameters of Interior Permanent-Magnet Synchronous Motors Affected by the Magnet Size

Interior permanent-magnet synchronous motors (IPMSMs) produce both magnetic and reluctance torques. The reluctance torque is due to the difference between the d- and q-axis inductances based on the geometric rotor structure. The steady-state performance analysis and precise control of the IPMSMs greatly depend on the accurate determination of the parameters. The three essential parameters of the IPMSMs are the armature flux linkage of the permanent magnet, the d-axis inductance, and the q-axis inductance. In the basic design step of an IPMSM, the inductance parameters are very important for determining the motor characteristics, such as the input voltage, torque, and efficiency. Thus, it is very important to accurately estimate the values of the motor inductances. The inductance parameters of IPMSMs have nonlinear characteristics along the magnet size because the iron core is saturated by the magnet and armature reaction fluxes. In this study, the inductance parameters were calculated using both the magnetic-equivalent-circuit method and the finite-element method (FEM). Then the calculated parameters were compensated by the saturation coefficient function, which was also calculated via the magnetic-equivalent-circuit method and FEM.

A Study on Driving Simulation and Efficiency Maps with Nonlinear IPMSM Datasets

Hybrid electric vehicles have attracted much attention of late, emphasizing the necessity of developing traction motors with a high input current and a wide speed range. Among such traction motors, various researches have been conducted on interior permanent-magnet synchronous motors (IPMSMs) with high power density and mechanical solidity. Due to the complexity of its parameters, however, with nonlinear motor characteristics and current vector control, it is actually difficult to accurately estimate the base speed within an actual operating speed range or a voltage limit. Moreover, it is impossible to construct an efficiency map as the efficiency differs according to the control mode. In this study, a simulation method for operation performance considering the nonlinearity of IPMSM was proposed. For this, datasets of various nonlinear parameters were made via the finite-element method and interpolation. Maximum torque-per-ampere and flux-weakening control were accurately simulated using the datasets, and an IPMSM efficiency map was accurately constructed based on the simulation. Lastly, the validity of the simulation was verified through tests.

Current Control Method of WRSM in High-speed Operation Range

This Paper analyzes the characteristics of the WRSM in high-speed operation range. To verify the control characteristics of various WRSM models, the relative position of the central point of current limit circle and voltage limit ellipse is defined as M value and 3 models according to M max value are designed through inductance change. Through the designed models, the current control method of 3-variables control for maximum power especially in high-speed operation range is presented.