Showing papers by "Jin Hur published in 2014"

Design and Optimization of Neodymium-Free SPOKE-Type Motor With Segmented Wing-Shaped PM

Abstract: This paper proposes a new design of SPOKE-type PM brushless direct current (BLDC) motor without using neodymium PM (Nd-PM). The proposed model has an improved output characteristic as it uses the properties of the magnetic flux effect of the SPOKE-type motor with an additional pushing assistant magnet and subassistant magnet in the shape of spoke. In this paper, ferrite PM (Fe-PM) is used instead of Nd-PM. First, the air-gap flux density and backelectromotive force (BEMF) are obtained based on the field model. Second, the analytical expressions of magnet field strength and magnet flux density are obtained in the air gap produced by Fe-PM. The developed analytical model is obtained by solving the magnetic scalar potential. Finally, the air-gap field distribution and BEMF of SPOKE-type motor are analyzed. The analysis works for internal rotor motor topologies. This paper validates results of the analytical model by finite-element analysis for wing-shaped SPOKE-type BLDC motors.

Finite-Element Analysis of the Demagnetization of IPM-Type BLDC Motor With Stator Turn Fault

Abstract: This paper investigates the dynamic demagnetization characteristics of an interior permanent magnet (PM) brushless dc motor with a stator turn fault (STF). A new algorithm, which is a finite-element method combined with a line voltage equation of the motor, is developed to analyze demagnetization under dynamic and transient states and considers an STF. The input current, circulating current, magnetic distribution characteristic, and operating property of the PM, including the irreversible demagnetization in the fault state, are analyzed using this algorithm by considering the magnetic saturation effect. The feasibility of the proposed method confirmed from the analysis results is verified via an experiment. Through this fault analysis, we can accurately check the fault phenomena and healthiness of a PM motor against the demagnetization fault for fault prevention.

Transient Analysis of Irreversible Demagnetization of Permanent-Magnet Brushless DC Motor With Interturn Fault Under the Operating State

Abstract: We investigated the irreversible demagnetization of a permanent-magnet (PM) brushless dc motor under an interturn fault condition. For the transient analysis, we developed a finite-element method-based demagnetization algorithm in the operating state, taking into account the circulating current flowing in the shorted turns and the freewheeling current flowing in the diode. We analyzed the magnetic distribution property, input current, circulating current, and demagnetization characteristic of the PM using this algorithm. The analysis results from the demagnetization algorithm were verified by dynamic fault experiments.

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

Abstract: 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.

Diagnosis Technique Using a Detection Coil in BLDC Motors With Interturn Faults

Abstract: Interturn faults (ITFs) cause significant changes in the electrical and magnetic characteristics of motors. In particular, ITFs can be the cause of serious distortions in the magnetic field of an air gap. Therefore, we develop a system matrix with an ITF for FEM simulation, which considers the nonlinearity of the ITF. Using the analysis of the magnetic characteristics of the detection coil from the FEM results, a circuit that employs the proposed diagnosis algorithm is shown to detect the phase and the location of a fault.

Quasi-Zero Torque Pulsation of Surface Permanent Magnet Synchronous Motor for Ship Gyro Stabilizer by Pole/Slot Number and Air-Gap Designs

Abstract: This paper deals with the reduction of torque pulsation including torque ripple and cogging torque in surface PM brushless ac motors. The fractional combination and air-gap shape design by shaping the PM and stator core are studied to reduce torque pulsation. Torque ripple reduction is achieved by adjusting the magnetic flux density in air-gap contour by cutting magnet outer shape. Quasi-zero torque pulsation in this paper means the ripple ratio to average torque <;0.5%. The magnetic field and torque characteristics are analyzed by 2-D finite element analysis and prototype to validate is manufactured and measured.

Design and analysis of modified spoke type BLDC motor using a ferrite permanent-magnet

Abstract: This paper proposes a new design of a spoke-type permanent magnet brushless direct current (BLDC) motor that are using a ferrite permanent magnet (Fe-PM), not Neodymium permanent magnet (Nd-PM). At this study, in order to proposed this design, the important factors are length, thickness of the Fe-PM and angle of between the interior permanent magnets. By changing the angle between the permanent magnets, we can maximize the usage of permanent magnets and more concentrate the flux. Also, through a rotor surface structure alteration, we can reduce cogging torque and torque ripple. By adjusting them, we are presented new-type Fe-PM motor. Results showed that compared to two models which are surface permanent magnet motor (SPM) and Spoke-type ferrite permanent magnet motor using the finite element analysis (FEA).

Optimization of Magnetic Flux-path Design for Reduction of Shaft Voltage in IPM-Type BLDC Motor

Abstract: In this paper, we propose a method for suppressing shaft voltage by modifying the rotor shape and the permanent magnets in interior permanent magnet type high voltage motors. The shaft voltage, which adversely affects the bearing by occurring bearing current, is induced by parasitic components and the leakage flux in motor-driven systems as well as inherent linkage flux between main magnetic flux and shaft according to rotor configuration. Thus, shaft voltage should be analyzed and considered under inverter-driven and non-inverter-driven conditions because inherent linkage flux can analyze under non-inverter-driven condition. In this study, we designed re-arrangement magnet and re-structuring rotor to minimize the shaft voltage. In addition, we optimized the proposed models. The shaft voltage suppression effect of the designed model was validated experimentally and by comparative finite element analysis.

Study of Hybrid-Type Field Coil for Superconducting Rotating Machines

Abstract: This study examines a hybrid-type superconducting field coil that exploits the advantages of a permanent magnet and an electromagnet-type coil to mitigate the weaknesses of a conventional superconducting field coil with a power supply. The hybrid-type superconducting field coil proposed in this study can be applied to improve the performance of conventional superconducting rotating machines. One of the biggest problems of conventional superconducting power generators is the large fluctuation in the output voltage due to the fluctuation in the load. However, the hybrid-type superconducting field coil can be applied to superconducting power generators to stably control the electromotive force of the field and to effectively reduce the fluctuation in the output voltage. This study uses a high-temperature superconductor (HTS) 2G wire to manufacture a test model for the innovative superconducting field coil. A proof-of-principle test using the finite element method was conducted, and the performance of the coil was verified through an experiment.

Design and Analysis of a Permanent-Magnet-Assisted Switched Reluctance Motor

Abstract: A permanent-magnet-assisted switched reluctance motor (SRM) having small excitation poles, where phase coils are concentrically wound on the poles and thin permanent magnets are inserted inside the poles, is proposed in this paper. The insertion of permanent magnets into the stator excitation poles has a significant influence on positive torque improvement leading to a boost in efficiency. Three key design parameters such as the thickness of permanent magnets, space between two adjacent permanent magnets, and the width of stator excitation poles are determined during a design procedure in terms of the enhancement of positive torque. Step-by-step design modification and a comparison between the proposed permanent-magnet-assisted SRM and no-permanent-magnet SRM have been conducted by means of static torque comparison along with dynamic performance. The first prototype from steel laminations up to its physical assembly has been constructed.

Design of an portable emergency power supply with multi input sources

Abstract: This paper presents design guideline of portable emergency power supply with multi input and output requirements. The available structures which satisfy design considerations are proposed and analyzed. Based on the chosen structure, suitable topology and controller of each part applied to charge a battery in a wide range of input condition. In addition, system operation algorithm is proposed according to input and battery voltage condition. The verification of designed prototype for portable emergency power supply is carried out by experiment results in various operation modes.

Inter-turn fault tolerant control system in brushless DC motor by using yoke winding

Abstract: A fault tolerant control is mightily important in industrial and electrical vehicles. A shutdown of these motors should not happen due to its direct relationship to enormous loss to life and property, even if inter-turn fault of a winding occur. This paper proposed an inter-turn fault (ITF) tolerant control system using new-design brushless DC (BLDC) motor, which has teeth and yoke winding connected in parallel for fault tolerant control. The special point of new-design BLDC motor is that back electromotive force of teeth and yoke winding have nearly similar value and phase. In addition, we used a fault detection using input impedance algorithm. It can distinguish the ITF condition using variation of input impedance, which is obtained by monitoring of input voltage and current. After that, a fault tolerant control can prevent the spread of the fault by cutting off the three-phase winding and maintain partial output characteristics in proposed BLDC motor. The system has a special advantage that can use existing inverter without additional control device. Finally, we analyzed characteristics of the ITF tolerant control system in proposed BLDC motor using finite element method.

Permanent Magnet Eddy Current Analysis of SPM Synchronous Motors according to Magnet Shapes

Abstract: This paper presents the comparison study of permanent magnet (PM) eddy current of concentrated winding type surface permanent magnet synchronous motor (SPMSM) with different rare-earth magnet shapes. The fractional slot winding having 10 poles and 12 slots is studied. The PM eddy current is analyzed to compare for each shape by 2 dimensional (2D) finite element analysis (FEA). The eddy current and their loss of particular position of PM as well as their distributions are displayed for each model. The effect of partly enlarged air-gap made by PM shape to PM eddy current is compared.

Optimal DC-link voltage balancing control for 3-level half-bridge series resonant DC-DC converter

Abstract: In this paper, optimal DC-link voltage balancing control for 3-level half-bridge series resonant DC-DC converter is proposed. The proposed converter can minimize switching frequency variation according to load and improve overall efficiency for a wide range of loads. However, the performance of proposed converter can be lowered by DC-link voltage unbalance. For figuring out voltage unbalance problem, three types of balancing strategies, PWM off, semi-HB, and direct conversion are proposed. The characteristics of these strategies are explained and compared in the aspect of balancing period, output voltage ripple, transient time, and efficiency. The validity of proposed converter is verified through simulation and experimental results.