• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2001.02a
• /
• pp.72-75
• /
• 2001

The persistent current mode operation of HTS coils is one of the key technologies required for very high-field MRI magnets composed of LTS and HTS coils. But to date, the fabrication of persistent current mode system using HTS is not investigated well. In this paper, we fabricated the magnet and PCS using by BSCCO-2223 tape and jointed them with solder. The current decay behavior of the circuit was measured in liquid nitrogen by monitoring the magnetic field in the centre of magnet with a Hall sensor. To enhance the characteristic of persistent current mode system, superconducting joint method should be investigated.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.5
• /
• pp.450-454
• /
• 2003

This paper proposes a new driving scheme for single-phase SRM. The driving scheme is very simple and inexpensive. By use of this scheme, simple power devices based on low switching losses enable to high efficiency SRM drive. Starting, One of the main problem in single-phase SRM is overcame by a new starting algorithm with one hall sensor and a parting magnet. The proposed single phase SRM has a high efficiency and robust drive characteristics compared to that of a universal motor.

• Journal of Sensor Science and Technology
• /
• v.20 no.1
• /
• pp.25-29
• /
• 2011

This paper describes the design and analyses of vibration driven electromagnetic energy harvester with high power generation which is suitable for supplying power generator from human body motion. The proposed harvester consists of magnet, coil, and SM (Soft magnetic Material). In order to generate more induced voltage, the SM to concentrate flux lines from end of magnetic poles was arranged into insert moving magnet. Each model was designed and analyzed by using ANSYS software to simulation. The maximum power is generated when load resistance of $1303\;{\Omega}$ is equal to coil resistance. The generated maximum power of for harvesters with SM is $677.85\;{\mu}W$ and 5.46 times higher than without SM at 6 Hz vibration frequency.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.992-994
• /
• 2004

In this paper, hybrid electromagnets using NdFeB permenant magnet are designed by 3-dimensional finite element analysis. Four hybrid magnets levitate the carrier of which total weight including control circuits and battery is 14[kg]. The nominal air gap length of the hybrid magnet is 3[mm]. The control circuit consists of DSP, 4-quadrant chopper, and gap sensor as feedback sensors. As a result, some experimental results for the magnetic levitation control by PI feedback control theory are shown.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.3
• /
• pp.1241-1250
• /
• 2018

Parallel three-phase voltage source inverters in a direct connection configuration are widely used to increase system power ratings. A zero-sequence circulating current can be generated according to the switching method; however, the zero-sequence circulating current not only distorts current, but also reduces the system reliability and efficiency. In this paper, a model predictive control scheme is proposed for parallel inverters to drive an interior permanent magnet synchronous motor with zero-sequence circulating current suppression. The voltage vector of the parallel inverters is derived to predict and control the torque and stator flux components. In addition, the zero-sequence circulating current is suppressed by designing the cost function without an additional current sensor and high-impedance inductor. Simulation and experimental results are presented to verify the proposed control scheme.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.4
• /
• pp.456-463
• /
• 2018

With the development of weapon systems by mounting various sensors, it makes important to analyze the precise functioning of sensor to external environment. In the case of small arms with magnetic sensor, the malfunction of small arms might be caused by strong external magnetic fields. In this study, the effects of magnetic sensor on external magnetic fields were analyzed, and optimal magnetic shield and shield structure were designed through M&S. In addition, the magnetic-shielding effectiveness of magnetic sensor in small arms was verified with commercial shielding materials. As a result, it was demonstrated that the Fe-Cu-Si-Nd-B with the structure of multi-layer metallic shields was shown the magnetic-shielding effectiveness of 83 % for an external permanent magnet and 19 % for an alternating magnetic field of 180 dBpT at 60 Hz, respectively.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.44 no.4 s.316
• /
• pp.42-47
• /
• 2007

To reduce the chattering errors of reed switch sensors in the automatic remote measurement of water meter a reed switch sensor was analyzed and improved. The operation of reed switch sensors can be described as a mechanical contact switch by approximation of permanent magnet piece to generate an electrical pulse. The reed switch sensors are used mostly in measurement application to detect the rotational or translational displacement. To apply for water flow measurement devices, the reed switch sensors should keep high reliability. They are applied for the electronic digital type of water flow meters. The reed switch sensor is just mounted simply on the conventional mechanical type flow meter. A small magnet is attached on a pointer of the water meter counter rotor. Inside the reed sensor two steel leaf springs make mechanical contact and apart repeatedly as rotation of flow meter counter. The counting electrical contact pulses can be converted as the water flow amount. The MCU sends the digital flow rate data to the server using the wireless communication network. But the digital data is occurred difference or won by chattering noise. The reed switch sensor contains chattering error by it self at the force equivalent position. The vibrations such as passing vehicle near to the switch sensor installed location causes chattering. In order to reduce chattering error, most system uses just software methods, for example using filter algorithm and also statistical calibration methods. The chattering errors were reduced by changing leaf spring structure using mechanical characteristics.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.5
• /
• pp.329-335
• /
• 2008

Recently, super high-speed motor drives have been available due to the development of power electronics technology And they are used in various fields of industry because of their advantages. This paper describes the control algorithm for a permanent magnet synchronous motor(PMSM) drive at the speed of 118,000r/min using DSP and IGBT inverter. Hall sensors are implemented to measure the rotor position and speed, and a speed observer is used to reduce the performance deterioration caused by the low resolution of hall sensors. To enhance the output power capacity in the high-speed operating region, a flux weakening controller which also can work as an anti-wind up controller is used. Computer simulations and experiments are peformed to validate the proposed method.

• Journal of Advanced Navigation Technology
• /
• v.17 no.5
• /
• pp.524-544
• /
• 2013

In this paper, A tow system of miniature establishes each motor to individual 1C1M methods to control for a permanent magnet synchronous motors (PMSM) is constructed. You assume that is wiring having had the ability that can all absorb regenerative power which occurred when permanent magnet synchronous motors(PMSM) brake is all used to it, and to occur about agreement use scope expansion my electricity. To regenerative braking power securities of a PMSM and to stop of the bronzes my a control security, and that the electricity as you apply to vector control method and an speed sensor of controller to microprocessor, And you studied to speed, motor electricity energy control method to the algorithm and you brake a revival by regenerative braking power securities of a permanent magnet synchronous motors. It is proposed that motor control method to the algorithm you brake a revival by electricity braking power securities, you do to simulations regarding a momentum load and experiment.

• Korean Journal of Heritage: History & Science
• /
• v.54 no.1
• /
• pp.206-219
• /
• 2021

The warming of the climate is increasing the damage caused by termites to wooden buildings, cultural properties and houses. A group removal system can be installed around the building to detect and remove termite damage; however, if the site is not visited regularly, every one to two months, you cannot observe whether termites have spread within, and it is difficult to take prompt effective action. In addition, since the system is installed and operated in an exposed state for a long period of time, it may be ineffective or damaged, resulting in a loss of function. Furthermore if the system is installed near a cultural site, it may affect the aesthetic environment of the site. In this study, we created a detection system that uses wood, cellulose, magnets, and magnetic sensors to determine whether termites have entered the area. The data was then transferred to a low power LoRa Network which displayed the results without the necessity of visiting the site. The wood was made in the shape of a pile, and holes were made from the top to the bottom to make it easier for termites to enter and produce a cellulose sample. The cellulose sample was made in a cylindrical shape with a magnet wrapped in cellulose and inserted into the top of a hole in the wood. Then, the upper part of the wood pile was covered with a stopper to prevent foreign matter from entering. It also served to block external factors such as light and rainfall, and to create an environment where termites could add cellulose samples. When the cellulose was added by the termites, a space was created around the magnet, causing the magnet to either fall or tilt. The magnetic sensor inside the stopper was fixed on the top of the cellulose sample and measured the change in the distance between the magnet and the sensor according to the movement of the magnet. In outdoor experiments, 11 cellulose samples were inserted into the wood detection system and the termite inflow was confirmed through the movement of the magnet without visiting the site within 5 to 17 days. When making further improvements to the function and operation of the system it in the future, it is possible to confirm that termites have invaded without visiting the site. Then it is also possible to reduce damage and fruiting due to product exposure, and which would improve the condition and appearance of cultural properties.