Showing papers by "Jin Hur published in 2017"

Mitigation Method of the Shaft Voltage According to Parasitic Capacitance of the PMSM

Abstract: This study proposes the shaft voltage mitigation method according to change in parasitic capacitances of a permanent magnet synchronous motor. To consider the shaft voltage reduction in the initial motor design process without any filter, the parasitic capacitances affecting the shaft voltage are calculated using the motor geometry parameters. Then, the shaft voltage is analyzed according to change in parasitic capacitances using the equivalent circuit model and the torque characteristic is also analyzed to effectively mitigate the shaft voltage. As a result, the rotor-to-winding is determined as an appropriate parameter to mitigate the shaft voltage among the parasitic capacitances, because it affects the shaft voltage and does not affect the output torque. Finally, the shaft voltage mitigation method according to variation of rotor-to-winding capacitance is verified by experiment.

Detection Technique for Stator Inter-Turn Faults in BLDC Motors Based on Third-Harmonic Components of Line Currents

Abstract: Among the methods for detecting stator inter-turn faults, the techniques that use the harmonic characteristics have been researched in induction motors with distributed windings. However, it is questionable that the techniques are available to apply in permanent magnet machines with concentrated windings and different control methods. First of all, this study analyzes the harmonic components of line current in a brushless dc (BLDC) motor, including the issues such as supply imbalance and inherent structural asymmetry, through the developed finite-element analysis and experiment under different operating conditions. As a result, the third harmonic in negative frequency (–3f) is suitable as a fault detector because it is free from those issues. Finally, in BLDC motors with 120° conduction in a six-step operation, the faults can be detected by determining whether or not the third harmonics exist at the incipient state.

Dynamic Characteristic Analysis of Irreversible Demagnetization in SPM- and IPM-Type BLDC Motors

Abstract: In this study, the dynamic characteristic analysis algorithm is developed for the irreversible demagnetization. The conventional static characteristic analysis of irreversible demagnetization considers only the d -axis magnetic flux components. However, the accuracy of this method is limited in its analysis of the characteristics of the irreversible demagnetization when the motor is rotating. Therefore, we have developed a dynamic characteristic analysis algorithm for irreversible demagnetization. Using the developed algorithm, static and dynamic characteristic analysis of irreversible demagnetization is compared for interior- and surface-type permanent magnets brushless dc motor. Finally, we propose a maximum current limit for motor designs to reduce the impact of irreversible demagnetization.

Optimization Design of PMSM With Hybrid-Type Permanent Magnet Considering Irreversible Demagnetization

Abstract: This paper proposes optimization design of permanent-magnet synchronous motor (PMSM) using hybrid-type permanent magnet (PM) considering irreversible demagnetization. Here, the hybrid-type PM is defined as using both of neodymium PM (Nd-PM) and ferrite PM (Fe-PM) in a rotor. First, irreversible demagnetization of Fe-PM occurring by reversed magnetic field of Nd-PM is analyzed by using a finite-element method, when a rotor is inside or without a stator in order to improve reliability of PMSM using hybrid-type PM. Second, the optimized design considering demagnetization phenomenon is suggested for analyzing exactly output characteristics of the motor using hybrid-type PM. Finally, the prototypes based on proposed design are developed for evaluating the performance and demagnetization phenomenon through experiment.

Improvement in Stability and Operating Characteristics of HTS Coil Using MIT Material

Abstract: This paper proposes a new method of achieving electrical stability and controllability of a high-temperature superconductor (HTS) coil. The proposed method applied a material with a metal-insulator transition (MIT) property to the turn-to-turn resistance of an HTS coil. As a result, the turn-to-turn resistance remained at the insulator level in the normal state, thus removing delay during charging and discharging. During transient state, the turn-to-turn resistance dropped to the metal level, and current bypass occurs similar to that in a noinsulation coil, thus preventing the coil from burning out. The validity of the MIT characteristic and the proposed method were verified through experiments.

Optimized design of PMSM with hybrid type permanent magnet for improving performance and reliability

Abstract: This paper proposes optimized design of permanent magnet synchronous motor (PMSM) using hybrid type permanent magnet (PM) for improving the output characteristics and reliability. Here, the hybrid type PM is defined as using both of neodymium permanent magnet (Nd-PM) and ferrite permanent magnet (Fe-PM) in a rotor. First, the optimized design of PMSM considering magnetic equivalent circuit is suggested for reducing total reluctance value of Nd-PM and Fe-PM to increase the performance of motor. As a result, parallel configuration of reluctance factors is helpful for increasing output characteristics, and it is analyzed by using a finite element method (FEM). Secondly, irreversible demagnetization of Fe-PM occurring by reversed magnetic field of Nd-PM is analyzed, in two cases of a rotor exists with and without a stator in order to improve reliability of PMSM using hybrid type PM. Finally, a prototype based on proposed design is developed for evaluating the enhanced performance.

Pseudo-sensorless control of PMSM with linear hall-effect sensor

Abstract: For the control of electric motors, conventional inverters have utilized position and current sensors, but they undesirable in terms of cost and maintenance effort. For this reason, approaches without the sensors are developed by applying back electromotive force or signal injection-based method which also has some problems related to the the deterioration of control performance in low speed range or cross-saturation and secondary saliency, respectively. To overcome the above-mentioned problems, this study proposes a pseudo-sensorless driver with linear hall sensors that conduct the function of position sensor by measuring the edge-field of permanent magnets. The harmonic components of measured signals are eliminated by adaptive notch filter and phase-locked loop for obtaining accurate rotor position, and then the signals are again synchronized with the fundamental wave of current in stationary reference frame which is used for vector control. The outstanding features of proposed method are simplicity and proper controllability in wide speed range at minimal cost.

Analysis of cogging torque and torque ripple according to unevenly magnetized permanent magnets pattern in PMSM

Abstract: This paper presents analysis of cogging torque and torque ripple according to unevenly magnetized magnet patterns in permanent magnet synchronous motor. In previous studies it has confirmed that non-uniformly magnetized permanent magnet causes unexpected increase of cogging torque and torque ripple because of slot harmonic components. However, these studies investigated insufficient number of irregular magnet patterns to accurately grasp the tendency about the effect of uneven magnetized magnet of rotor on torque ripple. In this study, various uneven magnet patterns were investigated using finite-element method and verified with the experimentation. As a result, it is proved that the unexpected increase of cogging torque and torque ripple can be reduced when the total sum of magnetic flux of N poles and S poles are equal, even if a few magnets are magnetized non-uniformly.

Shaft-to-frame voltage mitigation method by changing winding-to-rotor parasitic capacitance of IPMSM

Abstract: Common-mode voltage (CMV) by switching pattern of space vector pulse width modulation (SVPWM) excites parasitic capacitance coupling in interior permanent magnet synchronous motor (IPMSM), and it finally causes shaft voltage. Among all parasitic capacitances, winding-to-rotor parasitic capacitance has the greatest effect on the shaft-to-frame voltage. In the study, mitigation method of a shaft-to-frame voltage is proposed by changing the winding-to-rotor parasitic capacitance. Specifically, modified winding shape is utilized for mitigate the shaft-to-frame voltage by suppressing the stator winding-to-rotor capacitance. In addition, electromagnetic shield is applied to suppress the effect of the end winding-to-rotor parasitic capacitance on the shaft-to-frame voltage.

Shaft-to-frame voltage suppressing approach by applying eletromagnetic shield in IPMSM

Abstract: As the common-mode voltage generated by the pulse width modulated inverter excites the parasitic capacitance coupling between the winding, stator, rotor, and bearing, shaft voltage occurs between the shaft and the grounded motor frame. Thus, this study proposes the shaft voltage suppression approach by applying a cylindrical copper shield surrounding the shaft in an interior permanent magnet synchronous motor. The cylindrical copper shield can suppress the shaft voltage by cancellation of the parasitic capacitance between the end winding and the rotor (a part of the winding to rotor capacitance).

Simplified equivalent model of PMSM with inter-turn fault

Abstract: An inter-turn fault significantly affects the electromagnetic properties in electric machines, and its propagation may quickly lead to the shutdown of the machines within a few seconds. To build the prediction or detection techniques of the fault, a fault analysis should be carried out. Generally, most faults are analyzed by a method using negative-sequence components obtained from symmetrical coordinate transformation. However, the method is complex and required many parameters. Therefore, this study proposes a simplified d-q equivalent circuit model of permanent magnet synchronous motor with an inter-turn fault. By already reflecting the negative-sequence components in d-q direct quadrate current equations derived from finite-element method in advance of a final model construction, the simplified model does not require the separation of positive and negative sequence components. As a result, the model can rapidly examine the influence of the fault due to its simplicity and fast response. The model is verified by numerical analysis, simulation, and experiment.

Design technique for PMSM with hybrid type permanent magnet

Abstract: This paper proposes a design technique of permanent magnet synchronous motor (PMSM) using hybrid type permanent magnet (PM) to consider simple structure and irreversible demagnetization. Here, the hybrid type PM is defined as using both of neodymium permanent magnet (Nd-PM) and ferrite permanent magnet (Fe-PM) in a rotor. For developing a competitive motor in terms of performance per manufacturing cost, firstly, the hybrid type PMSM is suggested by designing simple configuration considering magnetic property of Nd-PM and Fe-PM. Secondly, in this study, irreversible demagnetization of Fe-PM occurring by reversed magnetic field of Nd-PM is analyzed, when a rotor exists with and without a stator, and based on this analysis, a technique for avoiding the irreversible demagnetization phenomenon is proposed in order to improve reliability of hybrid type PMSM. Finally, the prototype based on proposed design is developed for evaluating the performance and demagnetization phenomenon through experiment.

Apparatus and Method for monitoring demagnetization of permanent magnet motors

Abstract: An apparatus for diagnosing a demagnetization state of a permanent magnet motor according to an embodiment of the present invention includes: a back electromotive force measuring unit which measures a back electromotive force of a permanent magnet; a Fourier transform unit which performs fast Fourier transform of the back electromagnetic force; and a demagnetization state diagnosing unit which diagnoses the demagnetization state of the permanent magnet by using a predetermined value and a harmonic back electromagnetic force in which the fast Fourier transform is performed. Accordingly, the present invention can accurately determine the irreversible demagnetization of the permanent magnet motor.

Simplified equivalent model of PMSM for analyzing influence of inter-turn fault on motor characteristics

Abstract: To analyze the influence of an inter-turn fault on electric machines, each sequence component is required through symmetrical coordinate transformation. Generally, the fault significantly affects the negative-sequence components. However, the method using symmetrical sequences is complicate and requires many parameters. Therefore, this study proposes a simplified d-q equivalent circuit model of a permanent-magnet synchronous motor with the fault by already reflecting negative-sequence components in d-q current equations obtained by finite-element analysis. Because the simplified model does not need to distinguish positive and negative sequence components, it has a fast response speed. In particular, the detection techniques using motor current signature analysis, the proposed model can be usefully used. Due to these benefits, the proposed model help to develop the detect techniques and confirm the effect of the fault on motors, rapidly. The model is verified by numerical analysis, simulation, and experiment.

Distortion voltage compensation in field-weakening region of IPMSM

Abstract: An optimal field weakening (FW) control for interior permanent magnet synchronous motor (IPMSM) considering the nonlinearities of IPMSM and inverter is presented in this paper. Nonlinearities of inverter cause distortion voltage (DV) which considerably affects the efficiency of IPMSM in FW region. In FW operation, the efficient utilization of available voltage is extremely important. Typically, in conventional FW control the ideal reference voltage is used as a feedback voltage. However, due to DV the actual voltage is not same as reference voltage. In addition, in high speed, the nonlinear characteristics of IPMSM, due to saturation and cross magnetization degrade the motor performance. Thus, under such circumstances tracking the optimal FW operating point became challenging. This paper proposes a hybrid FW control method to compensate the dead time effect and inverter voltage drop considering the nonlinear parameter of IPMSM. The compensated input phase voltage allow us to track the optimal operating point for IPMSM and enable us to achieve an accurate and optimal field weakening operation, which improves torque and speed capability in the flux-weakening region. The significance of the proposed method is verified by simulation and experiment.

Rotor and permanent magnet-type motor including same

Abstract: A rotor and a permanent magnet-type motor including the same are disclosed. The rotor comprises: a rotary shaft insertion hole for inserting a rotary shaft thereinto; a rotor iron core having a plurality of permanent magnet insertion holes, which are continuously formed therein, are maintained in a V shape by being spaced from the rotary shaft insertion hole, and have each of V-shaped frames forming a zigzag shape by including at least two curves; and a plurality of permanent magnets inserted into the plurality of permanent magnet insertion holes.