Induction motors connected with a three-phase AC system may malfunction due to reverse phase or open phase faults. Conventional overcurrent relays and overheating relays are used to prevent such accidents; however, their drawbacks include a low response speed and false operation. Therefore, in this study, a digital relay for the reverse-open phase was designed and fabricated. This relay can detect the reverse phase and open phase faults and send a trigger signal to the control circuit. The proposed relay was developed based on a microcontroller. The detection times of the reverse phase and open phase were verified as 320ms and 80ms, respectively. Compared with conventional relays that only protect the motor from one type of fault, the proposed relay can detect both, reverse phase and open phase faults. In addition, the fault detection, identification criterion, and trigger signal patterns can be modified by programming according to the requirements of users.
In this study, novel ultrasonic rotary motor of hexadecagon shape stator was proposed. Statorof the hexadecagon ultrasonic motor was composed of an elastic ring and ceramics. The elastic ring hadsixteen sides and sixteen angular points. Eight ceramics were attached on the outer surface of the eightsides of the ring. When rotor of cylindrical shaft was inserted inside of the ring stator, central lines of thesixteen sides of the stator hold the shaft by the slight pressures(frictions). This slight pressure was apreload of the motor and it could be controlled by radius and thickness of the ring. When two sinusoidalvoltages which have 90 degree phase difference were applied to each four ceramics, elliptical displacementsof inner surface of the ring were obtained. These elliptical displacements of the inner surface rotated theshaft rotor through the frictions. The proposed hexadecagon ultrasonic motor was designed and analyzedby using the finite element method (FEM), depending on materials of the elastic ring. Based on the FEMresults, one model of motor which showed maximum displacement at contact points was chosen andfabricated. And characteristics of the motor were compared with simulated results. When the motor wasfabricated with these results, EL20ET0.5CT0.5CW2 model showed 115[rpm] speed about input voltage of60[Vrms] at 65.6[kHz]. And the maximum torque of 6[gfcm] was obtained. From these results, thehexadecagon shaped ultrasonic motor can be used to actuator for optical device which needs detailedposition control. Also it can be used to medical and portable device by reducing size and weight.
This paper tried to develop a BLDC electric motor securing the 800 W-level watertight structure for driving the outboard motor. For this purpose, this paper developed a high-efficient controller-integrating BLDC electric motor system for underwater propulsion and designed and developed a triple watertight structure. Besides, this study developed a outboard motor integrating motor, propeller and controller based on the production of a controller for BLDC motor which can the speed control by selecting low-voltage, high-current power element. The characteristics of developed outboard motor were 24 V input voltage, over 800 W motor output, and max. 3,000 rpm motor, and 84.9% motor efficiency,and the developed outboard motor could secure the watertight structure in 5 m in water depth.
A variety of diagnostic tests are widely applied in the field in industry to evaluate the condition of high voltage (HV) motor stator insulation. In this paper, the influence of temperature on the stator insulation diagnostic tests such as the insulation resistance, AC current, dissipation factor, and partial discharge measurements are studied and reported. The tests are performed with the HV motor stator winding temperature set between 40℃ to 80℃ in 10℃ intervals. It is shown that the AC current, dissipation factor, and partial discharge magnitude steadily increase with temperature, which suggests that temperature must be taken into account in the interpretation of the test results.
Diagnostic tests were performed on two high voltage (HV) motor stator windings. These tests included the measurement of insulation resistance, polarization index, AC current, dissipation factor (tanδ) and partial discharge (PD) magnitude. Surface contamination of HV motor stator windings has an effect on the AC current and tanδ. When the stator windings were finished cleaning and insulation reinforcement, the increase rate of AC current (ΔI) and dissipation factor (Δtanδ) were very small compared to those before cleaning. However, the PD magnitude remained the same. These tests show that cleaning and insulation reinforcement of HV motor stator windings can reduce the insulation failure.
To assess the condition of stator insulation, nondestructive and overpotential tests were performed on four high voltage motors. The stator windings under these tests have nominal ratings of 6.6 kV. After completing nondestructive tests, the AC overvoltage applied to the stator windings was gradually increasing until insulation failure in order to obtain the breakdown voltage. No. 1, No. 2, No. 3 and No. 4 of 6.6 kV motors failed near rated voltage of 18.4 kV, 19.8 kV, 19.7 kV and 21.7 kV, respectively. The breakdown voltage of four motors was higher that expected for good quality coils(14.2 kV) in 6.6 kV motors. Almost all of failures were located in a line-end coil at the exit from the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of AC current, dissipation factor(tanδ) and partial discharge magnitude.
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The Correlation Analysis Between Insulation Diagnosis and Breakdown Testing Hee-Dong Kim, Ja-Young Koo, Jun-Ho Kwak, Hyungchul Kim Journal of Electrical Engineering & Technology.2025; 20(8): 5659. CrossRef
When the high voltage motor fails in power plants, there will be an occurrence where the generator`s output would be reduced or the generators would trip. Despite of these effects, the causes of deterioration of the high voltage motor is very seldom investigated. In this paper, the collected data which tested in the field over 10 years have been treated statistically, and analyzed to correlate the insulation deterioration of high voltage motor and installation environment, number of start/stop, and service life. Moreover, the proper period of insulation test is developed to map out maintenance strategy and reduce maintenance costs.
A Rotationally Asymmetric Reluctance Machine With Improved Torque Density Cahya A. Harianto, Scott D. Sudhoff IEEE Transactions on Energy Conversion.2013; 28(1): 62. CrossRef
Improving Sensitivity of the Pyroelectric Infrared Flame Detector Hyun Seon Song, Yeu Yong Lee Journal of the Korean Institute of Illuminating and Electrical Installation Engineers.2015; 29(4): 77. CrossRef
Driving Characteristics of a Simple Square-Frame Ultrasonic Motor J.W. Kim, C.H. Park, S.S. Jeong, M.H. Kim, T.G. Park, H.H. Chong Applied Mechanics and Materials.2011; 110-116: 210. CrossRef
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