Influence of Thermal Phenomena on the Characteristics of Selected Electronics Networks

This paper presents the results of investigations on the influence of thermal phenomena—self-heating in semiconductor devices and mutual thermal couplings between them—on the characteristics of selected electronics networks containing bipolar transistors (BJTs) or insulated gate bipolar transistors (IGBTs). Using the authors’ compact electrothermal models of the transistors mentioned above, the non-isothermal DC and dynamic characteristics of these devices and selected networks with these devices are calculated. Their selected characteristics are compared with the measurement results. The waveforms of currents in the considered networks are also determined taking into account thermal phenomena. Discrepancies between the obtained calculation and measurement results and the calculation results obtained without thermal phenomena are indicated. In particular, attention is paid to cooling conditions at which the networks under consideration may be damaged due to thermal phenomena.

Sensorless Control of Voltage Peaks in Class-E Single-Ended Resonant Inverter for Induction Heating Rice Cooker

Single-ended (SE) resonant inverters are widely used as power converters for high-pressure rice cooker induction, with 1200 V insulated-gate bipolar transistors (IGBTs) being used as switching devices for kW-class products. When voltage fluctuations occur at the input stage of an SE resonant inverter, the resonant voltage applied to the IGBT can be directly affected, potentially exceeding the breakdown voltage of the IGBT, resulting in its failure. Consequently, the resonant voltage should be limited to below a safety threshold—hardware resonant voltage limiting methods are generally used to do so. This paper proposes a sensorless resonant voltage control method that limits the increase in the resonant voltage caused by overvoltage or supply voltage fluctuations. By calculating and predicting the resonance voltage through the analysis of the resonance circuit, the resonance voltage is controlled not to exceed the breakdown voltage of the IGBT. The experimental results of a 1.35 kW SE resonant inverter for a high-pressure induction heating rice cooker were used to verify the validity of the proposed sensorless resonant voltage limiting method.

The Influence of Soldering Profile on the Thermal Parameters of Insulated Gate Bipolar Transistors (IGBTs)

The effect of solder joint fabrication on the thermal properties of IGBTs soldered onto glass-epoxy substrate (FR4) was investigated. Glass-epoxy substrates with a thickness of 1.50 mm, covered with a 35 μm thick Cu layer, were used. A surface finish was prepared from a hot air leveling (HAL) Sn99Cu0.7Ag0.3 layer with a thickness of 1 ÷ 40 μm. IGBT transistors NGB8207BN were soldered with SACX0307 (Sn99Ag0.3Cu0.7) paste. The samples were soldered in different soldering ovens and at different temperature profiles. The thermal impedance Zth(t) and thermal resistance Rthof the samples were measured. Microstructural and voids analyses were performed. It was found that the differences for different samples reached 15% and 20% for Zth(t) and Rth, respectively. Although the ratio of the gas voids in the solder joints varied between 3% and 30%, no correlation between the void ratios and Rth increase was found. In the case of the different soldering technologies, the microstructure of the solder joint showed significant differences in the thickness of the intermetallic compounds (IMC) layer; these differences correlated well with the time above liquidus during the soldering process. The thermal parameters of IGBTs could be changed due to the increased thermal conductivity of the IMC layer as compared to the thermal conductivity of the solder bulk. Our research highlighted the importance of the soldering technology used and the thermal profile in the case of the assembly of IGBT components.

Accurate Circuit-Level Modelling of IGBTs with Thermal Phenomena Taken into Account

This paper proposes a new compact electrothermal model of the Insulated Gate Bipolar Transistors (IGBT) dedicated for SPICE (Simulation Program with Integrated Circuit Emphasis). This model makes it possible to compute the non-isothermal DC characteristics of the considered transistor and the waveforms of terminal voltages and currents of the investigated device and its internal temperature at transients. This model takes into account the nonlinearity of thermal phenomena in this device. The form of the formulated model is described and the problem of estimating its parameter values is discussed. The correctness of the proposed model was verified experimentally both at DC operation and at transients. The obtained results are compared to the results of computations performed with the use of the classical literature model. A very good agreement between the results of measurements and computations performed with the new model is obtained at different cooling conditions and in a wide range of changes of parameters characterising the electrical excitation of the tested device.

Paralleling insulated-gate bipolar transistors in the H-bridge structure to reduce current stress

In this study we present the new power electronic circuit implementation to create the arbitrary near-rectangular electromagnetic pulse. To this end, we develop a parallel- Insulated-gate bipolar transistors (IGBT)-based magnetic pulse generator utilizing the H-bridge architecture. This approach effectively reduces the current stress on the power switches while maintaining a simple structure using a single DC source and energy storage capacitor. Experimental results from the circuit characterization show that the proposed circuit is capable of repeatedly generating near-rectangular magnetic pulses and enables the generation of configurable and stable magnetic pulses without causing excessive device stresses. The introduced device enables the production of near-rectangular pulse trains for modulated magnetic stimuli. The maximum positive pulse width in the proposed neurostimulator is up to 600 µs, which is adjustable by the operator at the step resolution of 10 µs. The maximum transferred energy to the treatment coil was measured to be 100.4 J. The proposed transcranial magnetic stimulator (TMS) device enables more flexible magnetic stimulus shaping by H-bridge architecture and parallel IGBTs, which can effectively mitigate the current stress on power switches for repetitive treatment protocols.

Enhancing the Performance of DFIG Wind Turbines Considering Excitation Parameters of the Insulated Gate Bipolar Transistors and a New PLL Scheme

The major aim for achieving the successful synchronization of a wind turbine system to the grid is to mitigate electrical and mechanical stresses on the wind generator. During transient state, the gearbox, shaft, and rotor of the wind generator could be damaged due to mechanical stress. The rotor and stator windings of the wind generator, including its insulation, could be affected. This paper undertakes an extensive analysis of the effects of the excitation parameters of the power converter Insulated Gate Bipolar Transistors (IGBTs), on the transient state performance of the Doubly Fed Induction Generator (DFIG), considering different scenarios. The optimal excitation parameters of IGBTs were used for further analysis of the wind generator, considering a new Phase-Locked-Loop (PLL) scheme. The PLL computes the phase displacement of the grid required to achieve orientation and synchronization control. Consequently, it helps in preventing power system distortion due to stator-grid interphase. This paper proposes a new approach that integrates PLL control strategy and a Series Dynamic Braking Resistor (SDBR) to augment the fault ride through capability of a variable speed wind turbine that is DFIG-based. The SDBR helps the post fault recovery of the wind generator. Simulations were run in Power System Computer Aided Design and Electromagnetic Transient state Including DC (PSCAD/EMTDC) to examine severe fault conditions, and to test the robustness of the controllers employed. The results show that the proposed hybrid control strategy aids the fast recovery of the DFIG wind generator variables during fault conditions.