Ik-Sang Jang

Proposal of Improved Winding Method for VR Resolver

The variable reluctance (VR) resolver is generally used instead of an optical encoder as a position sensor on motors for hybrid electric vehicles or electric vehicles owing to its reliability, low cost, and ease of installation. The commonly used conventional winding method for the VR resolver has disadvantages, such as complicated winding and unsuitability for mass production. This paper proposes an improved winding method that leads to simpler winding and better suitability for mass production than the conventional method. In this paper, through the design and finite element analysis for two types of output winding methods, the advantages and disadvantages of each method are presented, and the validity of the proposed winding method is verified. In addition, experiments with the VR resolver using the proposed winding method have been performed to verify its performance.

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.

Design of Novel Overhang Structure for Separated Pole-Piece Type Ferrite Magnet Motor

A separated pole-piece type ferrite magnet motor (FMM) is a novel type of motor that can maximize reluctance torque and reduce leakage flux by separating the pole pieces and the web. However, when this type of motor has a short stack length and a large area of pole pieces, the leakage flux in the axial direction has significant influence on the motors performance. A rotor overhang structure is one of the most crucial design parameters that compensate for the side effects of leakage flux. A conventional overhang structure increases magnetic torque but raises the level of induced voltage. This limits the operation speed range. To overcome such problems, this paper presents a novel multilevel overhang structure. Based on the unique structure of the separated pole-piece type FMM, the overhang length of the pole pieces was set to be shorter than the other parts of the rotor. It was observed that the operating speed range was widened, and more reluctance torque was generated, compared to motors with conventional overhang structures. The proposed overhang structure was optimized by 3-D finite element analysis, and the model was validated by comparing the actual experimental results with its predicted performance.

Robust Zero Power Levitation Control of Quadruple Hybrid EMS System

This paper presents the improved zero power levitation control algorithm for a quadruple hybrid EMS (Electromagnetic Suspension) system. Quadruple hybrid EMS system is a united form of four hybrid EMS systems one on each corner coupled with a metal plate. Technical issue in controlling a quadruple hybrid EMS system is the permanent magnets equilibrium point deviation caused by design tolerance which eventually leads to a limited zero power levitation control that only satisfies the zero power levitation in one or two hybrid EMS system among the four hybrid EMS system. In order to satisfy a complete zero power levitation control of the quadruple hybrid EMS system, the proposed method presented in this paper adds a compensating algorithm which adjusts the gap reference of each individual axe. Later, this paper proves the stability and effectiveness of the proposed control algorithm via experiment and disturbance test.

Output Characteristics of IPMSM According to Pole-Slot Combinations

Due to the depletion of energy and other environmental problems, a trend emerges wherein engine cars are likely replaced by hybrid cars and electric cars. A military engine truck must be replaced by a hybrid truck because it needs an improved starting performance, high power supply, and low noise operation corresponding to environmental preservation. When the traction motor is designed, the selection of pole-slot (p-s) combinations becomes extremely difficult due to the combined influences characterizing a motor. Thus, the inverter specifications are considerably related to the selection of pole-slot combinations. This paper now introduces IPMSMs(interior permanent magnet synchronous motors) for traction motor applying hybrid Humvee. Four models with constraint conditions are dealt with in the analysis of characteristics based on the pole-slot combinations. According to the analysis of finite elements method (FEM) and the inverter specifications, the pole-slot combination suited the traction motor for hybrid Humvee. Afterwards, the results were compared with each other.