In a power converting apparatus which converts AC power into DC power, an inverter circuit including at least one series-connected single-phase inverter is connected in a downstream of a stage in which an AC input is rectified in series therewith. In the downstream stage of the inverter circuit, there are provided a smoothing capacitor connected via a rectifier diode and a short-circuiting switch for bypassing the smoothing capacitor. The short-circuiting switch is set to an ON state only in each of short-circuiting phase ranges of which midpoint matches each of zero-crossing phases and an output of the inverter circuit is controlled by using a current command so that a DC voltage of the smoothing capacitor follows a target voltage and an input power factor is improved.

Power converting apparatus

A power conversion device includes a power switching circuit that supplies AC voltages generated between switching elements operating as upper arms and switching elements operating as lower arms, and a control circuit that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements by a PWM method in a first operational region in which frequency of an AC power to be outputted is low, and that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements at timings based upon the phase of the AC power to be outputted in an operational region in which the frequency of the AC power to be outputted is higher than in the first operational region.

Power Conversion Device

A vacuum insulated switchgear comprising a vacuum container accommodating at least a pair of movable contacts and a pair of fixed contacts, wherein the movable contacts are capable of taking three positions, the switchgear being a double-break three-position type switch having breaking and disconnecting functions.

Vacuum insulated switchgear

The continuous development of the voltage-source-converter-based multiterminal high-voltage direct-current transmission system has led to a great need for dc circuit breakers to isolate short-circuit faults in the dc side. The operating time of dc breakers is mainly dependent on the mechanical contacts separation time. In this paper, three key units of the ultra-fast operating mechanism, including drive unit, buffer unit, and holding unit were investigated. A prototype of the 40.5-kV ultra-fast vacuum switch has been developed where the Thomson-coil actuator (TCA) is used to fulfill the function of the drive unit and the buffer unit, and a bistable spring mechanism is used as the holding unit. The state equations of the bidirectional TCA used as the drive unit and buffer unit in the operating process are completed based on the equivalent circuit method and finite-element method. The experimental and simulation results of the prototype are compared and they are in good agreement as expected. Therefore, the mathematical model is verified. The factors that influence the drive unit and the buffer unit performances are discussed. The achieved operating time of the prototype is about 2.3 ms.

Research on Operating Mechanism for Ultra-Fast 40.5-kV Vacuum Switches

This paper presents the test results of an ultrafast (less than 2 ms) medium-voltage hybrid dc circuit breaker prototype that consists of three switching devices: a 15-kV silicon carbide (SiC) emitter turn-off thyristor as the main breaker (MB), a fast acting mechanical switch, and a commutating switch (CS) to quickly divert the primary current to the MB for arcless interruption. The hybrid dc circuit breaker prototype can interrupt a circuit in less than 2 ms in dc power systems up to 10 kV, such as in electric ships. The ultrafast operations and extremely low loss can effectively limit the fault current level and switching transients in all medium-voltage systems, and can provide intelligent and fast protection function for smart power distribution and critical loads in a modernized grid. The design considerations of the three switching devices of the hybrid dc circuit breaker are presented. This paper focuses on the ultrafast mechanical switch and the testing of the hybrid dc circuit breaker, while a companion paper addresses the high-voltage solid-state main switch and the low-voltage solid-state CS.

A Medium-Voltage Hybrid DC Circuit Breaker—Part II: Ultrafast Mechanical Switch

A fast changeover from one power system to another in the event of an irregularity in the power source system substantially reduces operating costs by minimizing a power loss in switches during conduction, dispenses with a cooling device for cooling a thyristor switch, and implements the thyristor switch in a compact and low-cost design. The power supply system for a load includes one switching apparatus for connecting a load to one power source system, and another switching apparatus for connecting the load to another power source system. Each of the switching apparatus includes a pair of thyristors connected in anti-parallel and a mechanical switch connected in parallel with the thyristor pair. The thyristor pairs and the mechanical switches are controlled so that the mechanical switches conduct a load current when the load is supplied with power from the one power source system in a steady power supply state. The thyristor switches conduct the load current during a power source changeover time within which the load is disconnected from one power source system and connected to the other power source system, and do not conduct the load current during the steady power supply state.

Electric power supply system for load

A tank filled with an insulating gas accommodates insulator tubes incorporating vacuum-valve breakers for individual phases One end of each insulator tube is fixed to the inside of the tank Each vacuum-valve breaker is installed generally on a common longitudinal axis with the relevant insulator tube in such a manner that its movable electrode rod is directed toward the fixed end of the insulator tube The insulator tube has as its integral part a bus line fixing portion projecting in a direction intersecting the longitudinal axis of the insulator tube from the proximity of its end opposite to the fixed end to support a bus-side conductor in an insulated fashion

Metal-enclosed switchgear

This paper presents a design and testing of a new high-speed electromagnetic driving mechanism for a high-voltage vacuum circuit breaker (VCB). This mechanism is based on a high-speed electromagnetic repulsion and a permanent magnet spring (PMS). This PMS is introduced instead of the conventional disk spring due to its low spring energy and more suitable force characteristics for VCB application. The PMS has been optimally designed by the 3D nonlinear finite-elements magnetic field analysis and investigated its internal friction and eddy-current effect. Furthermore, we calculated the dynamic of this mechanism coupling with the electromagnetic field and circuit analysis, in order to satisfy the operating characteristics—contact velocity, response time, and so on, required for the high-speed VCB. A prototype VCB, which was built based on the above analysis, shows sufficient operating performance. Finally, the short circuit interruption tests were carried out with this prototype breaker, and we have been able to verify its satisfying performance. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 34–40, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20398

Development of a high-speed electromagnetic repulsion mechanism for high-voltage vacuum circuit breakers

Electromagnetic field analysis coupled with motion using the tableau approach has been applied to high-speed circuit breakers of eddy current repulsion mechanisms. This breaker has an opening time of 1 ms and break time less than 1 cycle (20 ms). The driving part of the breaker is composed of electromagnetic repulsion mechanisms and disk springs with nonlinear characteristics. The mechanisms are composed of two fixed coils and one repulsion plate. A numeric experiment has been applied to investigate the dynamic behavior of the electromagnetic repulsion mechanism using the equivalent circuit method. Calculation results were in good agreement with both measurement results and calculation results by FEM on an experimental model. In addition, repulsive forces depending on material conductivities have been researched. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 8–16, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20149

https://onlinelibrary.wiley.com/doi/pdf/10.1002/eej.20149

Electromagnetic analysis coupled with motion for high‐speed circuit breakers of eddy current repulsion using the tableau approach

Electromagnetic field analysis coupled with motion using the tableau approach has been applied to high speed circuit breakers of eddy current repulsion mechanisms. This breaker has an opening time of 1ms and a break time less than 1 cycle (20ms). The driving part of the breaker is composed of electromagnetic repulsion mechanisms and disk springs with nonlinear characteristics. The mechanisms are composed of two fixed coils and one repulsive plate. A numeric experiment has been applied about the dynamic behavior of the electromagnetic repulsion mechanism using the equivalent circuit method. Calculation results were good agreement with both of measurement results and calculation results by FEM on an experimental model. In addition, repulsion forces depending on material conductivities have been researched.

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Kenichi Koyama

Papers

Electric power supply system for load

Metal-enclosed switchgear

Development of a high-speed electromagnetic repulsion mechanism for high-voltage vacuum circuit breakers

Electromagnetic analysis coupled with motion for high‐speed circuit breakers of eddy current repulsion using the tableau approach

Electromagnetic Analysis Coupled with Motion for High Speed Circuit Breakers of Eddy Current Repulsion using the Tableau Approach