• Proceedings of the KIEE Conference
• /
• 2001.10a
• /
• pp.337-339
• /
• 2001

High speed brushless permanent magnet (PM) machines are a key technology for electric drives and motion control systems for many application, since they are conductive to high efficiency, high power density small size and low weight. Proposed slotless PM machine is constructed without stator winding slots. Its stator magnetic material is in the form of a ring and winding have a toroidal configuration and its rotor consists of a 4-pole Halbach array or radially magnetized PM rotor.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.10
• /
• pp.1371-1376
• /
• 2014

In this paper, 4-phase switched reluctance motor(SRM) with 8-stator and 6-rotor pole structure is proposed for a high speed fan with a low voltage. The air blower has unidirectional rotation characteristics and requires a low torque ripple and noise as well as high efficiency. To achieve the requirements, voltage and current according to loading condition of limited specification is considered. Design process is to select the bore diameter, pole arc, york of stator and rotor to get a high torque and efficiency. To verify the validity of the proposed structure, finite element method(FEM) is employed to get the performances. And the converter for the proposed SRM is employed a 1.5q power converter for cost effectiveness. Prototype SRM is manufactured and tested, and the test results show this design is within the specification and good for the air blower applications.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2000.11c
• /
• pp.784-791
• /
• 2000

To improve the uniformity of slurry spreading and to reduce the odor problem, a hose slurry spreader was developed, which spread the slurry near to the surface of the soil. First, the uniformity of slurry spreading was investigated. The best result of 8.1 ％ CV was obtained at the rotor speed of 250 rpm than any other speeds for the swine slurry, which contains 13.6% of dry matter. In case of dairy cattle slurry, which contains 8.2% of dry matter, the uniformity has the best result of CV 7.2% by high rotor speed of 330 rpm. A high speed of rotor has built a sufficient pressure in the distributor and discharged a uniform quantity of slurry through the hoses. Therefore, in practical use one should work with rotor speed over 300 rpm to maximize the uniformity of slurry spreading. Second, odor test was done with the swine slurry. While the conventional spreader shows ∑ value 440, the hose slurry spreader and its combination of disk harrow show ∑ value 258 and 184 respectively. With the air dilution sensual test and a 3-point odor bag, the conventional spreader shows 66.9 or 35.4 point and by the hose slurry spreader is 9.7 or 11.1 point. So, the developed spreader was found to have a greater effect on the reduction of odor problem. Finally, it is recommended to spread certain amount of the slurry for paddy field equivalent to the chemical fertilizer based on the N-content. It means 22 tons of swine slurry per ha. Since most of the livestock farms possess less arable land, a system of linking farms is necessary to utilize the slurry crossover the farms. The cost of slurry utilization including filling, transport spreading and brokerage is 3200-6800 Won/㎥ in accordance with the transport distance.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.4E
• /
• pp.37-44
• /
• 1996

To get accurate vibration analysis of rotor-bearing systems, finite element models of high speed rotating shaft, unbalance disk, and fluid film journal bearing are developed. The study includes the effects of rotary inertia, gyroscopic moment, damping, shear deformation, and axial torque in the same model. It does not include the axial force effect, but the extension is straighforward. The finite elements developed can be used in the analysis design of any type of multiple rotor bearing system. To show the accuracy of the models, numerical examples are demonstrated.

• Proceedings of the KIEE Conference
• /
• 1998.07a
• /
• pp.269-271
• /
• 1998

Reluctance Synchronous Motors(RSM) with new rotor shape are considered in this paper. Since the stator of a RSM is similar as that of an induction motor, attention is focused here on the rotor structure. We have designed the parameter of RSM and analyzed the characteristics of the electromagnetic energy conversion.

• Journal of Power Electronics
• /
• v.18 no.3
• /
• pp.714-722
• /
• 2018

This paper presents a wide-range speed control scheme of brushless DC (BLDC) motors based on a hall sensor with separated low- and normal-speed controllers. However, the use of the hall sensor signal is insufficient to detect motor speed in the low-speed region because of low sensor resolution and time delay. In the proposed method, a micro-stepping current control method according to the torque angle variation is presented. In this mode, the motor current frequency and rotating angle are determined by the reference speed without the actual speed fed by the hall sensor. The detected torque angle is used to adjust the current value in a limited band to control the current value in accordance with the load. The torque angle is detected exactly at the changing point of the hall sensor signal. The rotor can follow the rotating flux with the variable torque angle. In a normal speed range, the conventional vector control scheme is used to control the motor current with a PI speed controller using the hall sensor. The torque characteristics are analyzed on the basis of the back EMF and current shape. To adopt the vector control scheme, the continuous rotor position is estimated by the measured speed and hall sensor position. At the mode changing point between low and normal speed range, the proper initial current command and reference rotor position are calculated. The calculated current command can reduce the torque ripple during transient mode. The proposed method is simple but effective in extending the speed control range of a conventional BLDC motor with hall sensor without the need for a high-resolution encoder. The effectiveness of the proposed method is verified by various experiments on a practical BLDC motor.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.6
• /
• pp.519-529
• /
• 2010

In the present study, unsteady calculations have been performed to simulate flows around a UH-60A full configuration including main rotor, fuselage, and tail rotor. A flow solver developed for helicopter aerodynamic analysis was used for the simulation of the complete helicopter in high-speed and low-speed forward flight. Unsteady vibratory loads on the main rotor blades were compared with flight test and other calculated data for the assessment of the present flow solver. Aerodynamic interaction of the three components of the helicopter was investigated by comparing with the results of main-rotor-alone, main rotor and fuselage, and tail-rotor-alone configurations. It was found that the existence of the fuselage has an effect on the normal force distribution of the main rotor by varying downwash distribution on the rotor disc, and tip vortices trailed from the main rotor strongly interact with the tail-rotor.

• Composites Research
• /
• v.14 no.3
• /
• pp.77-89
• /
• 2001

Since the critical whirling vibration frequency of high speed built-in type motor spindle systems is dependent on the rotor mass of the built-in motor and the spindle specific bending modulus, the rotor and the shaft were designed using magnetic powder containing epoxy and high modulus carbon fiber epoxy composite, respectively. In order to increase the amount of the magnetic flux of the composite squirrel cage rotor of an AC induction motor, a steel core was inserted into the composite rotor. From the magnetic analysis, the optimal configurations of steel core and conductor bars for the dynamic characteristics of the rotor system were determined and proposed. The temperature dependence of composite squirrel cage rotor materials was investigated by various experiments such as TMA, DMA and VSM.

• Journal of Aerospace System Engineering
• /
• v.13 no.5
• /
• pp.39-48
• /
• 2019

The turbulent flow in the rotor-stator mixer is based on shear characteristics generated by the interaction of the stator with the rotor rotating at high speed. In this study, the flow characteristics analysis of the unsteady state generated by the interaction of the rotor and the stator in the prototype model of the emulsion-fuel related mixer development was performed with the MRF and SMM by applying the ANSYS FLUENT $k-{\varepsilon}$ (RKE) turbulence model. The behavior and shear characteristics of the flow particles generated at the interface between the designed rotor and stator, and trends such as velocity distribution and turbulence eddy dissipation, were predicted and verified using the CFD analysis.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.3
• /
• pp.286-293
• /
• 2004

This paper presents the result of a study on the starter control for a turbo generator. Because a starter in gear box type turbo-generator system is composed of gearbox and brush DC motor, it should be replaced with High Speed Generator(HSG)) in HSG type Turbo-generator. There-ore, it is necessary to design a new starting algorithm and starter. In gearbox type system, brush DC motor is rotated to the designed speed using low voltage-high current battery power. After brush DC motor speed is increased to several times by gearbox, gas turbine engine can be rotated to designed starting speed. If we implement a starter with High Speed Generator(HSG), it is necessary to drive high-speed generator to high-speed motor. High-speed generator with permanent magnet on rotor has a low leakage inductance fur driving high-speed rotation, and it is necessary high DC link voltage for inverter when High-speed generator is driven to high speed. This paper presents result of development of the boost converter for converting high voltage DC from low battery voltage and design of the inverter for controlling a high frequency current to be injected to motor winding. Also, we show performance of the designed starter by driving the turbo generator.