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In a hard switched mosfet based converter, turn-on energy losses is predominant in the total switching loss. At higher junction temperature the turn-on energy loss further increases due to the reverse recovery effect of the complementary mosfets body diode in a half-bridge configuration. Estimation of the switching loss under different operating conditions at an early design stage is essential for optimizing the thermal design. Analytical switching loss models available in literature are generally used for estimating the switching losses due to its accuracy and simplicity. In this article, the inaccuracy in the reported loss models due to non-inclusion of temperature-dependent reverse recovery characteristics of body diode, is investigated. A structured method to determine the temperature-dependent switching loss of a SiC mosfet in a half-bridge is presented. A simple methodology has been proposed to analyze the carrier lifetime's temperature dependencies of a SiC mosfets body diode. Device parameters from a $\text{1.2}\,\text{kV}/36\,\text{A}$ SiC mosfets datasheet are used for developing the loss model and experimental validation of the model. [ABSTRACT FROM AUTHOR]

This article puts forward a high repetition rate and high-voltage resonant pulse generator for plasma-assisted milling. This circuit uses only one semiconductor switch with an antiparallel diode and works in the resonant mode with the help of a resonant inductor, a resonant capacitor, and a pulse transformer to generate high-voltage pulses. An equivalent circuit of the proposed topology considering parasitic elements is established. Based on the equivalent circuit, the working principle of the pulse generator is analyzed in detail. In order to verify the theoretical analysis and circuit operation, a laboratory prototype with a 150-V dc input is implemented. The pulse repetition rate can be adjusted from 5.32 to 18.90 kHz, and the peak output voltage correspondingly varies between 8.84 and 11.7 kV. The pulse generator is used to drive a dielectric barrier discharge plasma-assisted milling chamber. Experimental results show that the pulse generator can work stably. [ABSTRACT FROM AUTHOR]

This letter proposes a harmonic mitigation strategy to cancel out current harmonics induced by the front-end rectifiers in multidrive systems, which consist of diode rectifiers, silicon-controlled rectifiers (SCR), and boost converters in the dc-link. The proposed strategy is a combination of a new dc-link modulation scheme with a phase-shifted current control enabled by the SCR. The dc-link current modulation scheme is implemented by adding and subtracting specific modulation levels, which makes the total currents drawn from the grid “multilevel,” resulting in an improved current quality. Simulations and experiments have validated the effectiveness of the proposed harmonic mitigation solution for multidrive systems. [ABSTRACT FROM PUBLISHER]

One of the most important power quality issues is related to current harmonics generated by nonlinear loads such as diode and thyristor front-end rectifiers. Well-established solutions to overcome this problem, such as active power filters (APFs), have the required high power rating components as a major disadvantage. An alternative, called hybrid power filter (HPF), mixes low power rating active filters with passive filters. Unfortunately, many of these HPF topologies have, as a common disadvantage, a great number of passive components and/or transformers. Based on this fact, new concepts of HPFs, consisting of small-rated inverters and $LC$ filters, have been introduced with wide acceptance. The advantage comes from the fact that these HPFs are connected to the grid without any matching transformer. Recently, some topologies based on dual-converter configurations have been shown to be very attractive, where the APF (or HPF) must deal with highly nonlinear loads with high values of $di/dt$ and supplying the reactive power together with harmonic compensation. On the other hand, the drawback of dual converters is the high number of switch devices. Therefore, this paper proposes a transformerless HPF based on a new six-switch two-leg inverter with an enhanced harmonic compensation capability. Aside from presenting a reduced number of switches when compared with dual topologies, the proposed solution is capable of providing fully compensation even for loads with high harmonic content. Experimental results are presented for an HPF inverter prototype in order to demonstrate that the harmonic compensation performance meets the IEEE 519 standard. [ABSTRACT FROM PUBLISHER]

In variable-speed drives systems, diode rectifiers and thyristor rectifiers are often used as the front-end circuit for ac-dc conversion. The advantages of the conventional rectifier are its simplicity and high reliability. The drawbacks include the harmonic current distortion and the lack of re-generation capability. In recent years, industries adopt the transistor-based active front-end (AFE) technologies to accomplish high power factor operation and re-generation capability. However, the cost of AFE is much higher than the conventional diode/thyristor front-end. Besides, the AFE is often less reliable than the diode/thyristor front-end under utility transients. In this paper, an IGBT-based auxiliary converter (AXC) system is proposed. The AXC operates as a shunt active filter to compensate the harmonic current of the rectifier when the load consumes power. When the dc load regenerates, the AXC system can channel the re-generation energy back into the utility system. The combination of the diode rectifier and the AXC can accomplish unity power factor operation and re-generation, but it also causes circulating current between the AXC and the rectifier, which leads to higher operational losses and higher noise level. The mechanism of the circulating current is analyzed in this paper, and solutions are also presented. Computer simulation and field test results are presented to validate the performance of the proposed AXC system. [ABSTRACT FROM AUTHOR]

This paper presents an innovative method for reducing current distortion on the ac side of six-pulse parallel-connected ac/dc rectifiers. The principle of the method is to modify the current waveforms on the dc side of the rectifier by using two self-commutated switches (insulated-gate bipolar transistors). It is demonstrated that accurate shaping of currents on the dc side achieves low distortion levels in currents IA, IB, and IC on the ac side. The effectiveness of the method is confirmed by laboratory recordings, which are related to steady-state and transient studies. [ABSTRACT FROM AUTHOR]

The results of numerical modeling of the stationary nonisothermal current-voltage ( I-U) characteristics of forward-biased high-voltage diodes and thyristors in the interval of current densities J ∼ 200–500 A/cm2 revealed an N-S transition in the shape of these curves and a hysteresis in the constant current source regimes. It is established that the mechanism of these phenomena is related to a temperature-induced decrease in the coefficient of ambipolar diffusion under the conditions of enhanced recombination. Devices with such I-U characteristics can be irreversibly switched by short current pulses from stable states on the working branch to the states with high heat evolution, which leads to a risk of thermal breakdown. [ABSTRACT FROM AUTHOR]

High-voltage 4H-SiC bipolar devices, including rectifier diodes, bipolar junction transistors, and thyristors are discussed. The results of experimental and theoretical studies of the steady-state and transient characteristics of these devices are presented. Specific features of device operation, related to the specific electronic properties of silicon carbide and SiC-based p–n structures, are analyzed. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

In power stations and substations of electric power companies, power semiconductor devices such as diodes and thyristors have been used in control power supplies and emergency power supplies since the 1970s. Such equipment is designed on the assumption that power semiconductor devices are semipermanent, since their service life is much longer than that of capacitors and resistors. Therefore, it is hard to find studies that have systematically examined the long-term reliability of semiconductor devices. Such studies are very important from the viewpoint of ensuring reliability and improving the renewal period by proper equipment maintenance. This paper discusses the long-term reliability of power semiconductor devices used in power station rectifiers and substation rectifiers. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 67–75, 2001 [ABSTRACT FROM AUTHOR]

Discusses a study which fabricated light-triggered eight-kilovolts thyristors with an integrated breakover diode. Design considerations for amplifying gate structure; Experimental details of the study; Determination of the doping profiles; Values for the minimum light power necessary to turn on the thyristor.

The article presents a new method for reducing harmonics of rectifier circuits by switching taps of interphase reactor. The tap-change circuit is very simple and the addition of it only slightly increases the site and cost of the circuit. Nevertheless, it reduces the harmonic content remarkably as shown in the article. The performances of the three-tap rectifier circuit are discussed in detail in this paper. The proposed scheme is applicable not only to the thyristor rectifier but also to the diode rectifier. In the future, it would be applied further to inverters and cycloconverters.