• Journal of Power Electronics
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• v.1 no.1
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• pp.36-47
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• 2001

The carrier-based space vector pulse width modulation(SVPWM), which is considered as highly simple and efficient PWM technology, can be also used in multilevel inverters. The method was originally designed for the two-level inverter and developed to the diode clamped multilevel inverter structure. however it may be noted that it also cause bad switch utilization in cascaded multilevel inverter. This paper introduces an improved carrier-based SVPWM scheme, which is fully suitable for cascaded multilevel inverter topologies because it can achieve the optimized switch utilization through the redistribution of the triangular carrier waves considering leg voltage redundancies while having the advantages of the conventional carrier-based SVPWM. Using simulation and experimental results, the superior performance of new PWM method is shown.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9A
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• pp.1359-1371
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• 1999

In this paper, we propose an efficient explicit rate (ER) feedback switch algorithm for available bit rate (ABR) flow control. In order to improve the disadvantages of existing ER feedback switch algorithms with congestion avoidance, the proposed scheme adjusts the target utilization dynamically according to the queue length and its growth rate. also, we investigate the performance of the proposed switch algorithm and compare it with ERICA and NIST switches using simulation. Simulation results show that the proposed switch algorithm can control the cell emission rate of a source rapidly according to variations of available link bandwidth by using dynamic adaptation of target utilization. It also exhibits a better performance than the existing ER feedback switches in terms of queue length and link utilization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1148-1159
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• 1997

In the broadband integrated service digital networks (B-ISDN), ATM switches hould be abld to accommodate diverse types of applications ith different traffic characteristics and quality ddo services (QOS). Thus, in order to increase the utilization of switches and satisfy the QOS's of each traffic type, some types of priority control schemes are needed in ATM switches. In this paper, a nonblocking input and output queueing ATm switch with capacity C is considered in which two classes of traffics with different loss probability constraints are admitted. 'Partial push-out' algorithm is suggested as a loss priority control schemes, and the performance of this algorithm is analyzed when this is adopted in input buffers of the switch. The quque length distribution of input buffers and loss probabilities of each traffic are obtained using a matrix-geometric solution method. Numerical analysis and simulation indicate that the utilization of the switch with partial push-out algorithm satisfying the QOS's of each traffic is much higher than that of the switch without control. Also, the required buffer size is reduced while satisfying the same QOS's.

• Journal of the Korea Computer Industry Society
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• v.2 no.4
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• pp.547-564
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• 2001

In this paper a simulation has been performed to compare and evaluate the performance between the EPRCA(Enhanced Proportional Rate Control Algorithm) and EMRCA(Explicit Max_min Rate Control Algorithm) switches. The variation of the ACR at the source end system, the queue length, the utilization rate of the link bandwidth and the share fairness at the transient and steady states are used as the evaluation criteria for the simulation. The EMRCA switch is more stable than the EPRCA switch and reduces its buffer size. Also, it achieves a higher utilization rate of the link bandwidth than the EPRCA switch. The hardware complexity of the EMRCA switch is significantly lower than the EPRCA and other rate-based switches. Since it eliminates the necessity of the floating-point operation for calculation of the MACR(Mean Allowed Cell Rate) at the switch.

• Journal of Power Electronics
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• v.16 no.1
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• pp.173-181
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• 2016

In this paper, a new technique for harmonic optimization in cascaded H-bridge 7-level inverters is proposed. The suggested strategy is based on minimizing an objective function which simultaneously optimizes the converter utilization and Total Harmonic Distortion (THD). The Switch Utilization Ratio (SUR) is formulized for both the phase and line-line voltages of a 7-level inverter and is considered in the final objective functions. Based upon the SUR formula, utilization ratio enhancement will reduce the value of feeding DC links, which improves the efficiency and lifetime of the circuit components due to lower voltage stresses and losses. In order to achieve more effective solution in different modulation indices, it is assumed that the DC sources can be altered. Experimental validation is presented based on a three-phase 7-level inverter prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.10-18
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• 2016

In this study, an efficient clamp is proposed to reduce the switch voltage stress of a forward converter. The proposed clamp consists of a conventional LC snubber, a tertiary winding, and a diode. When the switch is turned OFF, the magnetizing inductor energy of the transformer is recovered directly into the flyback output, which is the tertiary winding and diode network, instead of circulating in the LC snubber. Therefore, switch voltage stress and circulating current caused by the magnetizing inductor energy are reduced. This condition improves the efficiency of the forward converter with limited switch voltage stress. A theoretical analysis and the design guidelines of the proposed converter are provided. Experimental results are also reported.

• Transactions on Electrical and Electronic Materials
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• v.14 no.3
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• pp.116-120
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• 2013

This paper proposes a novel RF MEMS dc-contact switch with stiff membrane on a quartz substrate. The uniqueness of this work lies in the utilization of a seesaw mechanism to restore the movable part to its rest position. The switching action is done by using separate pull-down and pull-up electrodes, and hence operation of the switch does not rely on the elastic recovery force of the membrane. One of the main problems faced by electrostatically actuated MEMS switches is the high operational voltages, which results from bending of the membrane, due to internal stress gradient. This is resolved by using a stiff and thick membrane. This membrane consists of flexible meanders, for easy movement between the two states. The device operates with an actuation voltage of 6.43 V, an insertion loss of -0.047 dB and isolation of -51.82 dB at 2 GHz.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1533-1536
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• 2001

This paper considers the TMN system for management of public ATM switching network which has the four-level hierarchical structure consisting of one network management system, a few element management system and several agent-ATM switch pairs, respectively. The effects of one TMN command on the local call processing performance of the component ATM switch an analyzed using Jackson's queueing model. The TMN command considered is the permanent virtual call connection, and the performance measures of ATM switch are the utilization, mean queue length and mean waiting time for the processor interfacing the subscriber lines and trunks directly, and the call setup delay of the ATM switch.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.303-309
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• 2009

Switched Reluctance Motor(SRM) has become popular for industrial application, particularly for low medium drives due to the advantages of SRM over the other ac motors: SRM can be manufactured with low cost because it has a simple structure. But, asymmetric bridge converter that generally is used for driving requires two discrete switching devices and freewheeling diodes per phase, and cause the SRM drives to be complicated and to increase the cost of overall system. Therefore, this paper suggests a new type of 4-switch converter for SRM. 4-switch converter topology is studied to provide a possibility for the realization of low cost 3-phase SRM drive system. For effective utilization of the developed system, a new current control algorithm is designed and implemented to produce the desired dynamic performance. With the developed power conversion circuit and control scheme, it is expected that the proposed system can be widely used in commercial applications with reduced system cost.

• Proceedings of the KIEE Conference
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• summer
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• pp.354-356
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• 2004

This paper is the transient analysis for choosing the optimal SCR ratings of AC3 utilization category testing equipment(AC3 TE) used for electrical durability test for magnetic switch according to IEC60947-4 Annex B by utilizing EMTP -ATPDraw. Magnetic contactor closes and opens the motor load with ON/OFF switch of electronic contactor. It is also used for protecting and controlling the load. Magnetic contactor detects the over-current flow in the load with a over-current relay and disconnects the load by opening its control power. The key cost of AC3 TE is the SCR ratings. The more decreases SCR ratings, the more decreased the cost is, but it is impossible to ensure the reliability. On the other hand, the more increases SCR ratings, the more increased the cost is. Thereupon, in this paper after the testing circuit is simulated by using EMTP-ATPDraw the SCR ratings will be applied in order to guarantee the testing reliability of PT&T(Power Testing and Technology institute in LG Industrial Systems Co.,Ltd.).