Wojciech Mysiński

Currently, manufacturers of power-electronic components are trying to introduce the silicon carbide (SiC) technology in their products and MOSFET transistors made with this technology are available on the market. They are characterised by a significantly higher operating frequency, reaching even 100 kHz and low switching losses. The application of this type of devices causes high voltage gradients at the inverter output, which can lead to increased inverter electromagnetic disturbances. This article presents test results and a high-frequency analysis, allowing for a preliminary evaluation of the use of SiC transistors in inverters in the context of electromagnetic compatibility.

Electrical discharge machining is a process of machining a work-piece to a desired shape by using the eroding effect of electric spark discharges. A gap width controller is one of the key components of each electrical discharge machine. It is gap width controllers that mainly determine the machining speed and accuracy. This article describes a gap width controller based on fuzzy logic. The control algorithm operates according to the number of short circuits, open circuits and normal pulses that occur within a control period. A specially developed PC application allows for accessing and modifying electrical discharge machining parameters.

Producers of power electronics components are currently introducing silicon carbide (SiC) to their products and MOSFET transistors made with this technology, working at a wide voltage and current range, are affordable. They are distinguished by high frequency of operation, reaching 100 kHz and low switching losses. Silicon carbide technology allows to build power converters, which are characterized by high efficiency, smaller dimensions, smaller passive components and higher thermal tolerance in comparison with traditional technology (Si). The aspect of the electromagnetic compatibility of SiC technology converter was analyzed in the article. Determined levels of interferences generated by the converter into the supply grid in the range of harmonics and inter-harmonics were presented. Measurement results of electromagnetic conducted disturbances were presented. Increased levels may make it difficult to fulfil standard requirements and may adversely affect the operation of devices connected to the same supply network. Additionally, conducted disturbance levels at converter output have also been analyzed, of which increase may lead to problems in providing the so-called inner compatibility of the tested circuit or may be a source of radiated electromagnetic emission. The results of tests and analysis, presented in the article, conducted for wide frequency range, allow to evaluate the silicon carbide (SiC) technology application for a converter in the EMC scope.

As new power transistors, such as SiC Mosfets, are being increasingly used in power electro- nics systems, it has become necessary to use special drivers. This article compares the parame- ters of SiC Mosfet, Si Mosfet, and IGBT gate circuits. Differences are discussed with reference to the ways in which these transistors are controlled. Gate circuit parameters of SiC transistors differ slightly from those of common Mosfet or IGBT transistors, and in order to be able to fully utilise the capabilities of these new devices, it is necessary to employ appropriate drivers. This article discusses one such driver for SiC transistors.

The article presents Middlebrook’s method, which allows one to obtain the frequency analysis of  power electronic circuits based on time analysis. The authors carried out their simulations in LTspice. The article discusses selected examples of circuits, such as an active filter, a resonant RLC circuit and a Buck-Converter with a correction circuit. An important advantage of Middlebrook’s method is that it allows for the determination of the amplitude and phase characteristics for nonlinear circuits, as opposed the common .AC method. Simulation tests of non-linear circuits indicate that, in order to obtain correct results using Middlebrook’s method, the values of input signals need to be selected very carefully