• Journal of international Conference on Electrical Machines and Systems
• /
• v.1 no.2
• /
• pp.105-110
• /
• 2012

This paper designs the high-efficiency and the low-cost drive system of the smallsize electric vehicles (EVs). The power circuit for driving the dc motor is designed by considering both the cost and efficiency. In order to reduce the conduction loss of MOTFET and diode for controlling an armature voltage, some MOSFETs and diodes at the armature are in parallel connection. An operating sequence for both the field current and the armature voltage according to the accelerator pedal angle is suggested for changing smoothly the rotating direction of dc motor. Through the simulation studies, the performances of the proposed methods are verified.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1994.11a
• /
• pp.143-146
• /
• 1994

In older to investigate the properties of electric conduction in low density polyethylene(LDPE) for power cable, the thickness of specimen was the 30, 100($\mu\textrm{m}$) of LDPE. The experimental condition for conductive properties was measured until the breakdown occurs at temperature ranges from 30 to 110[$^{\circ}C$] and in the electric field of 1 to 5 ${\times}$10$^2$[Mv/m]. As for increase of temperature, the current density of LDPE was increased with constant ratio in low field, but changes with exponential function in high field. The tunnel current of pre-breakdown region is shifted toward low field as much as thermal excitation energy.

• Electrical & Electronic Materials
• /
• v.7 no.2
• /
• pp.138-144
• /
• 1994

Electrical conduction phenomena of $C_{22}$-quinolium(TCNQ) Langmuir- Blodgett(LB) films are reported through a study of current-voltage(I-V) characteristics along a perpendicular direction. The I-V characteristics were investigated by applying a step or a pulse voltage to the specimen as well as changing temperatures in the range of 20-250[.deg. C] It show an ohmic behavior in low-electric field, and a nonohmic behavior in high-electric field. This nonohmic behavior has been interpreted in terms of a conduction mechanism of space-charge limited current and Schottky effect. When the electric field is near the strength of 10$_{6}$ V/cm, there occur anomalous phenomena similar to breakdown. When step or pulse voltage is applied, the breakdown voltage shifts to the higher one as the step or pulse time width becomes shorter. To see the influence of temperature, current was measured as a function of temperature under the several bias voltages, which are lower than that of breakdown. It shows that the current increases to about 103 times near 60-70[.deg. C], and remains constant for a while up to around 150[.deg. C] and then suddenly drops. We have also performed a DSC(differential scanning calorimetry) measurement with $C_{22}$-quinolium(TCNQ) powder in the range of 30-300[.deg. C]. These results imply that the anomalous phenomena occuring in the high electric field are caused by the electrical and internal thermal effect such as a joule heating.ating.

• The Journal of Korean Physical Therapy
• /
• v.18 no.4
• /
• pp.19-26
• /
• 2006

Purpose: This study aimed the effects of percutaneous electric nerve stimulation (PENS) applied to different parts of the streptozotocin-induced diabetic rats on the change of glucose and nerve. Methods: rats (ten weeks old) were selected as the subjects; the normal group was five rats, and the diabetes induction group II, III and IV were five rats, respectively, which were randomly sampled from the twenty-five streptozotocin-administered rats with more than $240\;d{\ell}/m{\ell}$ of blood sugar. For PENS, electric current with 2 Hz of stimulation frequency and $200\;{\mu}s$ of pulse duration was applied to the subjects for fifteen minutes a day, six days a week, for three weeks. Calculation of glucose and weight, and nerve conduction test were conducted forty-eight hours and three weeks after streptozotocin administration, respectively. Results: As for change of glucose and weight, the group III with stimulation to the acupoints and the group IV with stimulation to non-acupoints showed significant differences from the control group II (p<0.05). As for MNCV (motor nerve conduction velocity), the group III with stimulation to the acupoints showed significant differences from the group IV with stimulation to non-acupoints and the control group II (p<0.05). Conclusion: PENS had the effects of inhibiting increase of glucose, change of weight and decrease of nerve conductive function between the distal and proximal ends of the peripheral nerve in the STZ-induced diabetic rats.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.6
• /
• pp.44-51
• /
• 1999

The electrical conduction mechanism of high dielectric $(Ba,Sr)TiO_3$ (BST) thin film capacitor, which is the promising cell capacitor for high density DRAM, was investigated in low field region (<0.2MV/cm). It is known that the current in the low field region consists of dielectric relaxation current and leakage current. The current-time (I-t) measurement technique under the constant voltage was used for extracting successfully each current component. The conduction mechanism of the BST capacitor was deduced from the dependency of the current on the measurement temperature, strength of electric field, the polarity of applied electric field and post annealing process. From these results, it was suggested that the dielectric relaxation current and the leakage current are originated from the redistribution of internally trapped electron by hopping process and Pool-Frenkel conduction mechanism, respectively. It was also concluded that traps causing these two current components are due to oxygen vacancies within the BST film.

• Design & Manufacturing
• /
• v.16 no.2
• /
• pp.46-52
• /
• 2022

As the consumer market in the eco-friendly vehicle industry grows, the demand for water pump in a electric car parts market. This study intend to propose a mathematical model that can verify the effect of improving thermal properties when a non-conductive cooling filler liquid is introduced into an electric vehicle water pump. Also, the pros and cons of the immersion cooling method and future development way were suggested by analyzing the cooling characteristics using on the derived analysis solution. Thermal characteristics analysis of electric water pump applied with non-conductive filler liquid was carried out, and the diffusion boundary condition in the motor body and the boundary condition the inside pump were expressed as a geometric model. As a result of analyzing the temperature change for the heat source of the natural convection method and the heat conduction method, the natural convection method has difficulty in dissipating heat because no decrease in temperature due to heat release was found even after 300 sec. Also, it can be seen that the heat dissipation effect was obtained even though the non-conductive filling liquid was applied at the 120 sec and 180 sec in the heat conduction method. It has proposed to minimize thermal embrittlement and lower motor torque by injecting a non-conductive filler liquid into the motor body and designing a partition wall thickness of 2.5 mm or less.

• Korean Journal of Materials Research
• /
• v.20 no.5
• /
• pp.271-277
• /
• 2010

In this paper two aspects of the percolation and conductivity of carbon black-filled polyethylene matrix composites will be discussed. Firstly, the percolation behavior, the critical exponent of conductivity of these composites, are discussed based on studying the whole change of resistivity, the relationship between frequency and relative permittivity or ac conductivity. There are two transitions of resistivity for carbon black filling. Below the first transition, resistivity shows an ohmic behavior and its value is almost the same as that of the matrix. Between the first and second transition, the change in resistivity is very sharp, and a non-ohmic electric field dependence of current has been observed. Secondly, the electrical conduction property of the carbon black-filled polyethylene matrix composites below the percolation threshold is discussed with the hopping conduction model. This study investigates the electrical conduction property of the composites below the percolation threshold based on the frequency dependence of conductivity in the range of 20 Hz to 1 MHz. There are two components for the observed ac loss current. One is independent of frequency that becomes prevalent in low frequencies just below the percolation threshold and under a high electrical field. The other is proportional to the frequency of the applied ac voltage in high frequencies and its origin is not clear. These results support the conclusion that the electrical conduction mechanism below the percolation threshold is tunneling.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.4
• /
• pp.593-600
• /
• 2016

The solar array regulator for low earth orbit satellites controls a operating point of solar array for suppling electric power to the battery and the other units. Because the control object is reversed, the new approach for large and small signal analysis is needed despite using buck-converter for power stage. In this paper, the steady state analysis of solar array regulator is performed in continuous conduction mode and discontinuous conduction mode, and the border condition for each mode is established. Also, the small signal model of solar array regulator is established in discontinuous conduction mode. Experiments are carried on in worst condition which the solar array regulator can face with discontinuous conduction mode. The results show that the solar array regulator is in stable.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1213-1215
• /
• 1997

In order to investigate the electrical characteristics due to the BTA(Benzotriazole) additive in the transformer, the electrical characteristics of the transformer oils contained benzotriazole as an anti-static agent for streaming electrification is studied by measuring the electric conduction. As a result of the electrical conduction characteristics, it is confirmed that the conduction current of virgin specimen is more higher than that of specimen contained the BT A 10[ppm] over 35[$^{\circ}C$], but that of specimen contained the BT A 10[ppm] over 50[$^{\circ}C$] is increased.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.2
• /
• pp.625-633
• /
• 2015

The effect of altitude on thermal conduction, surface temperature, and thermal radiation of partial arc was investigated on the basis of molecular gas dynamics to facilitate a deep understanding of the pollution surface discharge mechanism. The DC flashover model was consequently modified at high altitude. The validity of the modified DC flashover model proposed in this paper was proven through a comparison with the results of high-altitude simulation experiments and earlier models. Moreover, the modified model was found to be better than the earlier modified models in terms of forecasting the flashover voltage. Findings indicated that both the thermal conduction coefficient and the surface thermodynamics temperature of partial arc had a linear decrease tendency with the altitude increasing from 0 m to 3000 m, both of which dropped by approximately 30% and 3.6%, respectively. Meanwhile, the heat conduction and the heat radiation of partial arc both had a similar linear decrease of approximately 15%. The maximum error of DC pollution flashover voltage between the calculation value according to the modified model and the experimental value was within 6.6%, and the pollution flashover voltage exhibited a parabola downtrend with increasing of pollution.