• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.1610-1615
• /
• 2007

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.1903-1908
• /
• 2008

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 B
• /
• pp.605-608
• /
• 1993

Breakdown characteristics of a small rod-to-rod microairgap has been studied for obtain an optimum breakdown voltage and an airgap spacing to be used as an emission control means by the electrical arc-burning unburnt carbon particulates exhausted from a power station burner. It is found that the breakdown voltage at the rod-to-rod airgap spacing in the rang of $1{\sim}100{\mu}m$ decreased with decrease in the rod-to-rod airgap spacing. And there were no minimum breakdown voltage on a $V_b$-Pd characteristics which is known as the minimum voltage in Paschen's law in air atmosphere. Breakdown voltages of the airgap at the constant airgap spacing were $V_{b-dc}>V_{b-ac}>V_{b-pulse}$, and it was lowest for the pulse voltage applied. As a result, it is found that a pulse power was one of effective power compared with dc or ac to be used as such an unburnt carbon particulate emission control means and the airgap spacing became to several tens ${\mu}m$, then the breakdown voltages were down to several handreds voltages.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 1998년도 추계학술대회 논문집
• /
• pp.129-136
• /
• 1998

The LIM can be used as a transport system with wheel structure. The structural tolerance cause the airgap unbalance and that effects on the LIM performance. The effect of airgap unbalance on the motor performance such as thrust force, velocity and armature current are investigated by using Finite Element Analysis (FEA). From this numerical works, it is known that the airgap unbalance almost does not effect on the motor performance and LIM for transport system is robust to the structural tolerance.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.657-659
• /
• 2001

Prototype DSLPM (Double Side Linear Pulse Motor) has a complicated magnetic circuit to be composed of permanent magnetics and winding. During the fabricating of DSLPM, we found that upper airgap length may be a little different from lower airgap length because of fabrication tolerance and error. So, a little difference of both airgap length have a various effect on the characteristics of DSLPM. Therefore, in this paper, we analyzed the normal force and maximum static thrust force according to the difference of both airgap length on DSLPM with finite element method. Obtained results can be used for design of DSLPM with higher performance.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제52권1호
• /
• pp.1-8
• /
• 2003

Generally, thrust force of double-sided LPM is more powerful than that of single-sided LPM. Also, double-sided LMP can be effectively applied to the high-precision position system with its simple control scheme. However, An equality between two airgap lengths Is a necessary condition for its high performance. If a little difference between two airgaps is existed, unbalanced normal force and undesirable vibration will be generated. Additionally, even though two airgap lengths are absolutely same, undesirable vibration can be generated because the direction of instantaneous normal force on mover is changed according to excitation methods. An effect of inequality of two airgap lengths is presented in this paper. Distribution of airgap permeance vs. relative displacement is analyzed by two dimensional finite element method. Excitation From this results, current waveforms to reduce the undesirable vibration is proposed.

• 대한방사선치료학회지
• /
• 제28권1호
• /
• pp.35-46
• /
• 2016

목 적 : 두경부암의 양성자 치료 시 BoS frame ($Q-fix^{TM}$)을 사용하면 후사방향의 빔 조사 시 couch 와 snout 사이 충돌을 피하면서 Airgap 을 최소화할 수 있다. 이는 couch 에서 BoS frame 을 얼마나 많이 extended 시켰는지가 각 치료 빔 방향의 Airgap (환자와 빔 사출구 거리)을 결정하기 때문이다. 이에 본원에서는 BoS frame의 제한점을 개선하기 위하여 고정장치를 자체 제작하였고, 제작한 고정장치의 유용성을 본 연구를 통해 선량학적으로 평가하고자 한다. 대상 및 방법 : 본원에서 양성자치료를 받은 Brain Cancer환자 3명의 빔 각도 중 후사방향의 빔 6개를 선택하였다. 현재 치료계획 되어 있는 환자를 기존 방식대로 BoS frame만 사용했을 때 각 환자마다 왼쪽후사방향, 오른쪽 후사방향의 빔에서 충돌을 피할 수 있는 snout 위치를 측정하고 이 위치에 따른 Airgap과 Lateral penumbra 영역을 계산하고 DVH값을 분석하였다. 같은 환자의 동일한 빔에서 자체 제작한 BoS frame 고정장치를 사용하여 제조회사에서 권고한 set-up 사항보다 BoS frame을 21 cm superior방향으로 set-up을 진행하였고, 그 후 충돌을 피할 수 있는 snout위치를 측정하고 이 위치에서 Airgap과 Lateral penumbra영역을 계산하고 DVH값을 분석하였다. 결 과 : 자체 제작 BoS frame 고정장치를 사용함에 따라 사용하지 않았을 때 보다 snout 위치 즉 Airgap을 각각 각도별로 5.4 cm ~ 15.4 cm 줄일 수 있었다. Lateral penumbra는 BoS frame 고정장치를 사용하면서 Airgap을 감소시킴에 따라 각도별로 선량분포곡선에서 왼쪽, 오른쪽 부분을 0.1 cm ~ 0.4 cm 감소시킬 수 있었다. 자체 제작한 BoS frame 고정장치 사용함으로써 감소한 Lateral penumbra에 의해 정상조직에 들어가는 선량을 비교해보면 Lt.eyeball, Lt.lens, Lt.hippocampus, Lt.cochlea, Rt.eyeball, Rt.lens, Rt.cochlea, Rt. hippocampus, stem에 들어가는 선량이 0 CGE ~ 4.4 CGE 감소한 것을 알 수 있었다. 결 론 : 두경부암의 양성자 치료 시 자체제작 BoS frame 고정장치를 사용함에 따라 사용하지 않았을 때보다 후사방향의 빔에서 snout 위치를 감소시킬 수 있었고, Airgap을 줄여 결과적으로 Lateral penumbra를 감소시켜 정상조직에 불필요한 선량을 최소화 할 수 있었다. 이에 본 연구를 통해 자체제작 BoS frame 고정장치의 유용성을 선량학적으로 평가한 결과, 후사방향의 빔을 사용하는 두경부암 환자의 양성자 치료 시 유용하게 사용 될 것으로 기대된다. 마지막으로 두경부암 뿐만 아니라 다른 부위 양성자 치료에서도 Airgap을 최소한 할 수 있는 방법을 고안하여 Lateral penumbra를 줄일 수 있는 지속적인 연구가 필요할 것이라고 사료된다.

• Journal of Mechanical Science and Technology
• /
• 제16권12호
• /
• pp.1576-1582
• /
• 2002

Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins which takes place through the motor airgap. When relative misalignment of a rotor in the airgap is introduced during assembly, the dynamic characteristics of the motor system are affected. The rotor-motor system used in a washing machine is modeled using FETM and magnetic forces in a BLDC motor with radial rotor eccentricity are determined analytically The transient whirl responses of a rotor system supported on two roller bearings with relative misalignment in the motor airgap are investigated by considering mechanical and magnetic coupling effects. Results show that rotor misalignment in the airgap considerably affects the vibration of the rotor-motor system.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제51권1호
• /
• pp.1-6
• /
• 2002

Cogging torque is often a principal source of vibration and acoustic noise in high precision spindle motor applications. In this paper, cogging torque is analytically calculated using energy method to show that Fourier spectra of airgap permeance function and airgap MMF function are the most important design parameters to control cogging torque. To control these functions, stator pole shoe pairing and magnet arc design are proposed to minimize cogging torque. As for optimization technique, genetic algorithm is applied to handle trade-off effects of design parameters. Results show that the proposed method can reduce the cogging torque effectively.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집
• /
• pp.1468-1472
• /
• 2009

This paper presents the influence of the airgap tolerance on performance of a linear induction motor. Construction tolerance of the plate affects directly to the cost and performance of the Linear metro. LIM has around 10[mm] large airgap with many restrictions such as construction tolerance, thermal expansion and bend of the reaction plate, abrasion of the wheel, and so on. In order to have steady performance, the airgap should be uniform. But it is impossible to maintain the secondary reaction plate be flat along with the long track. Therefore the influence of the flatness on performance of a LIM should be investigated.