Stray Inductance Research Articles

Accurate Power Circuit Loss Estimation Method for Power Converters With Si-IGBT and SiC-Diode Hybrid Pair

An accurate power circuit loss estimation method has been developed for designing power converters with hybrid pairs of silicon (Si) insulated-gate bipolar transistor (Si-IGBT) and silicon carbide (SiC) Schottky barrier diode/SiC p-i-n diode. An analytical model of the switching losses of the hybrid pairs is proposed to achieve high accuracy and short calculation time. The nonlinearity of the device parameters and the stray inductance in the circuit are considered in the model. For the accurate power loss calculation, an empirical parameter extraction method is introduced for extracting device parameters. The calculated circuit power losses are compared with measurement results, and good agreements are confirmed. By using the proposed method, the power loss of a power converter utilizing 4.5-kV Si-IGBT/SiC-p-i-n-diode hybrid pairs is estimated to investigate the upper limitation of the switching frequency.

Analysis of Output Pulse of High Voltage and Nanosecond Blumlein Pulse Generator

A high voltage and nanosecond Blumlein pulse generator has been developed to produce an output pulse whose voltage level is greater than 250 kV and pulse duration 5 ns. The generator consists of various components such as a charging circuit, a pulse transformer, and a spark gap switch. As a heart of the generator, a Blumlein pulse forming line has been constructed in the cylindrical form using three cylindrical aluminum electrodes that are placed concentrically. Unlike the ideal Blumlein line, the output pulse of an actual Blumlein line may be affected by stray inductances and capacitances of switching and charging components, thereby degrading the performance of the generator. In this paper, PSPICE simulations have been performed to examine effects of stray inductances and capacitances on waveforms of output pulses. Simulation results show that the pulse waveform is significantly distorted mainly by the stray inductance of the spark gap switch.

Characterization and Experimental Assessment of the Effects of Parasitic Elements on the MOSFET Switching Performance

This paper presents a comprehensive study on the influences of parasitic elements on the MOSFET switching performance. A circuit-level analytical model that takes MOSFET parasitic capacitances and inductances, circuit stray inductances, and reverse current of the freewheeling diode into consideration is given to evaluate the MOSFET switching characteristics. The equations derived for emulating MOSFET switching transients are assessed graphically, which, compared to results obtained merely from simulation or parametric study, can offer better insight into where the changes in switching performance lie when the parasitic elements are varied. The analysis has been successfully substantiated by the experimental results of a 400 V, 6 A test bench. A discussion on the physical meanings behind these parasitic effect phenomena is included. Knowledge about the effects of parasitic elements on the switching behavior serves as an important basis for the design guidelines of fast switching power converters.

Analysis and minimisation of DC bus surge voltage for electric vehicle applications

In electrical vehicle driving systems, the DC bus usually shows large surge voltages because of the presence of loop parasitic inductance and hard-switching operations of voltage source inverters. The unexpected transient overvoltage mostly accounts for switching devices failures. To guarantee system reliability, high-voltage-rating insulated-gate-bipolar-transistors (IGBTs) are commonly used in practical systems to accommodate potential surge voltages. This eventually results in the increase of power loss and system cost. A comprehensive study is presented in this study to minimise the surge voltage across the DC bus. It starts with a surge voltage model indicating that the commutation loop inductances and the switching dynamics are two critical contributors to voltage spikes. An optimal design approach to lower the stray inductance of the connecting busbar is presented. Considering the characteristics of electric vehicle (EV) inverters controlled by space vector modulation, a slew-rate limiter strategy is proposed to minimise the surge voltage. The low inductance busbar design and control strategy are validated by simulation and experimental test.

An Investigation Into the Effects of the Gate Drive Resistance on the Losses of the MOSFET–Snubber–Diode Configuration

This paper presents an investigation into the effects of the gate drive resistance on the losses of the MOSFET–snubber–diode (MSD) configuration commonly used in many power converters. An analytical loss model that takes the circuit stray inductances, MOSFET parasitic capacitances and inductances, and reverse current characteristic of the freewheeling diode into consideration is derived to describe the interactions among the MOSFET, snubber, and freewheeling diode during the switching transients. Two possible turn-ON switching situations, determined by the gate drive part and the power part, respectively, are distinguished in the analysis. It is then used to study the effects of the stray inductances, gate drive resistance and snubber on the switching behaviors, power loss distribution, and voltage stress on the MOSFET in the entire MSD configuration. A sequence of steps will be given to illustrate how an optimal combination of the gate drive resistance and snubber capacitance is determined, in order to minimize the overall loss of the MSD configuration for a maximum permissible voltage stress on the MOSFET. The loss model and method of determining the gate drive resistance and snubber capacitance are evaluated by comparing the theoretical predictions with the experimental results of a 400V, 6A test bench. The performances of the MSD configuration with different types of freewheeling diodes will be studied.

Research of MEDM Pulse Power Based on the Non-Resonant Natural Oscillation

Aiming to discharge feebly, improving the frequency of MEDM power pulse is an ideal choice. But due to the influence of power resistor, capacitor, inductor with stray capacitance and stray inductance, increasing the higher pulse power frequency met bottleneck. Through the analysis of MEDM discharging circuit and routes, this paper puts forward the theory of not using components, but depending on the natural oscillation of MEDM machine tools and connection line to make MEDM pulse power. Through theoretical calculation and simulation, the oscillation period of discharging circuit can be controlled in 1.5ns, and the pulse width can be less than 750 Ps. It provides theoretical support for making picosecond pulse power and nanometer manufacturing with MEDM.

Design of Wiring Structure by Considering Bus Bar Inductance

Recently, high-switching-frequency and high-di/dt switching operation of inverters has been studied for the purpose of finding a way to reduce the size and weight of LC filters. In power electronic circuits, the stray inductance of the bus bar between a DC capacitor and power devices may cause an overshoot voltage and electromagnetic interference (EMI) noise for high-di/dt switching operation. Therefore, it is necessary to design the bus bar structure while considering the minimization and optimization of the bus bar inductance value. Generally, the bus bar inductance is analyzed by using 3D finite element method (FEM), but it takes a long time to construct analytical models and to perform the analysis. This paper proposes an improved calculation method for a medium-voltage inverter, based on the partial inductance calculation method. In addition, the wiring structure is designed by considering the stray inductance with using an inductance-mapping method.

Practical exercises for learning to construct NMR/MRI probe circuits

AbstractNine sets of laboratory exercises are designed to acquaint the student with many aspects of NMR/MRI probe resonant circuits. These include demonstrations of stray inductance and capacitance, matching a resonant circuit to 50 Ω, inductive coupling, doubly resonant circuits, loading effects of tissue, and radiation from the probe circuit. Many of the exercises are for the bench, but some are performed in an NMR system. The exercises should lead to an understanding of, as well as some intuitive knowledge about, basic NMR/MRI probe circuits. © 2012 Wiley Periodicals, Inc. Concepts Magn Reson Part A 40: 1–13, 2012.

A ns-μs duration, millitesla, exponential decay pulsed magnetic fields generator for tumor treatment

In order to research a new tumor treatment method using exponential decay pulsed magnetic fields (EDPMF), we developed a EDPMF generator by means of the integration of pulsed power technology and modern power electronics technology. After charging a capacitor with a high voltage dc power supply, EDPMF was generated inside the Helmholtz coils by means of discharging the capacitor through a switch to the discharge resistor. After a brief introduction of basic principle of EDPMF generator, steep pulse formation circuit and Helmholtz coils, two main parts of EDPMF generator, were discussed in detail, especially on design techniques. A height-adjustable platform was designed inside the Helmholtz coils. Cell solution and little animals could be treated on this platform. The peak value, width and repeat rate of the output EDPMF waveform could be adjusted independently in the range of 0 - 1 mT, 160 ns-55 μs and 1 Hz-1 kHz, respectively. The rise time of the output EDPMF waveform was shortened to 70-220 ns by means of choosing quickly operating switch and reducing circuit stray inductance. Magnetic field distribution uniformity was improved via designing better geometrical structure of Helmholtz coils. This was proved by finite element simulation and measurement. Cell experiment in vitro was performed by exposing human liver cancer cells (Hep-G2) to pulsed magnetic field (0.8 mT, 55 μs, 15 Hz) using this generator and the result showed that proliferation of cancer cells in treated group was significantly (P<;0.01) inhibited. This suggests possible clinical application using this kind of EDPMF for local tumor treatment.

Research and development of UHV AC transformer and shunt reactor

SUMMARYThe Jingdongnan‐Nanyang‐Jingmen UHV AC Pilot Project has already been put into service in China. In this paper, insulation level of power transformer and shunt reactor for 1000 kV power transmission project in China are introduced. UHV AC transformer and shunt reactor structures are given. Key technologies, including cooling type, regulating method for UHV AC transformer, pattern of outgoing line, and noise controlling, are discussed. Besides, due to the high voltage class, high capacity, and super size of UHV power transformer, the size of its test circuit is correspondingly enlarged, the impacts of stray inductance and capacitance will be more intense consequentially, thus in factory test including lighting impulse test, switching impulse voltage test, short‐duration induced AC voltage test at 500 kV side, and long‐duration induced AC voltage test with partial discharge measurement are presented. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Development of Embedded Heatsinking Layers for Compact Arrays of X-Ray TES Microcalorimeters

Transition-edge sensor microcalorimeter arrays in compact geometries and large formats experience local heating from bias power and x-ray hits that must be dissipated in the frame. For devices on solid, non-perforated silicon substrates, we have introduced an underlying embedded copper heatsinking layer to enhance the ability of the frame to remove this heat. In particular, such a layer can mitigate thermal crosstalk between nearby pixels within the array. Further improvements in array performance, such as decreased magnetic field sensitivity and stray inductance, are possible by turning the heatsinking layer into a superconducting ground plane. In this presentation, we report on the development of heatsinking layers consisting of a 1-2 μm thick high-quality copper layer which is sandwiched between two thin refractory metal-based diffusion barriers. These diffusion barriers are designed to avoid copper migration into the surrounding material over time, especially during our high temperature TES fabrication process which takes place in excess of 400°C . A 0.3-0.5 μm thick PECVD SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> cover layer isolates the heatsinking layer from the detector circuit. We present first results on our attempt to tailor the materials forming the diffusion barrier to fabricate both well defined superconducting ground planes and non-superconducting layers with the desired barrier characteristics.

Power Electronics-A Continuing Challenge

The age of power semiconductors began when thyristors made their first appearance. They gradually replaced the saturable inductors that were used so far for switched power conversion. The problems related to the nonlinearities of magnetic amplifiers were then easily overcome by naturally commutated thyristor converters. Even so, constructing a line-controlled thyristor converter was still a laborious task. Implementing a current control ler, for instance, required us to design and assemble an analog signal amplifier using many discrete transistors, those novel electronic components. Offset and drift of an amplifier varied with temperature, requiring repeated manual adjustments. Little did we know about parasitic capacitances or stray inductances. Hence, what was meant to be a dc amplifier tended to operate as a high-frequency oscillator.

Multiphase Multilevel Modular DC–DC Converter for High-Current High-Gain TEG Application

This paper presents a high-efficiency zero-current-switching (ZCS) switched-capacitor (SC) dc-dc converter for high-current high-voltage-gain TEG application. Compared with the traditional hard switching SC circuits, the proposed circuit achieves ZCS for all the switches, thus minimizing the switching loss and electromagnetic interference noise. The huge electrolytic capacitor bank existing in the hard switching SC circuit, which is used to reduce the voltage ripple and achieve high efficiency, is eliminated. The low-capacitance ceramic capacitor is utilized instead. Different from other ZCS SC circuits that insert a magnetic core, the proposed circuit utilizes stray inductance that is present in the circuit to achieve ZCS, thus leading to small-size, low-cost, and high-reliability features. The proposed circuit also owns continuous input current and low-output-voltage ripple features. Therefore, the power loss related to the input capacitor can be minimized. By using the proposed topology, high-efficiency and high-power-density SC dc-dc converters could be made for high-current and high-voltage-gain application. Simulation and experimental results are given to demonstrate the validity and features of the proposed topology.

Passive protections against breakdowns between accelerating grids in SPIDER experiment

In the SPIDER experiment a ITER-like full size plasma source will be realized with the target to extract a Dˉ beam of 70 A and then to accelerate it to 100 keV energy. The reduction of the effects due to the frequent breakdowns between the accelerating grids is needed, because of grids damage due to energy deposition by arcing and strong electromagnetic noise (EMI) emission. The solution proposed is a comprehensive design of the circuit. Two passive components are installed: a Damping Resistor and an Output Filter in series to the Power Supplies. Then a doubled screened structure will be adopted for the 30 m long – 100 kV Transmission Line TL, which connects the Ion Source and Acceleration Power Supplies to their loads: the Inner Screen will be connected to the reference ground (the vessel) by a resistive link, the Outer Screen acting as a low-impedance ground. Finally, a Distributed Core Snubber DCS (magnetic snubber) will be installed onto the TL, aimed to increase the damping of the oscillations due to the stray inductances and capacitances. The DCS is composed of 10 magnetic alloy cores and is equipped by a biasing circuit to enhance the flux swing in unsaturated condition during the breakdown. A detailed model of the circuit is developed to evaluate the passive components parameters for protection against breakdown, in which all the magnetic and capacitive couplings between components are modeled as well as the magnetic core snubber saturation.

New sample cell configuration for wide-frequency dielectric spectroscopy: DC to radio frequencies

A new configuration for the sample cell to be used in broadband dielectric spectroscopy is presented. A coaxial structure with a parallel plate capacitor (outward parallel plate cell: OPPC) has made it possible to extend the frequency range significantly in comparison with the frequency range of the conventional configuration. In the proposed configuration, stray inductance is significantly decreased; consequently, the upper bound of the frequency range is improved by two orders of magnitude from the upper limit of conventional parallel plate capacitor (1 MHz). Furthermore, the value of capacitance is kept high by using a parallel plate configuration. Therefore, the precision of the capacitance measurement in the lower frequency range remains sufficiently high. Finally, OPPC can cover a wide frequency range (100 Hz-1 GHz) with an appropriate admittance measuring apparatus such as an impedance or network analyzer. The OPPC and the conventional dielectric cell are compared by examining the frequency dependence of the complex permittivity for several polar liquids and polymeric films.

Modification of the Maxwell–Wien Bridge for Accurate Measurement of a Process Variable by an Inductive Transducer

The small inductance of an inductive transducer generally linearly changes with a process variable, but their measurement by the usual inductive bridge circuit like the Maxwell bridge, the Maxwell-Wien Bridge, the Hay bridge, etc., suffers from errors due to the effect of the stray capacitance between bridge nodal points and the ground and the stray inductance on the inductive coil, respectively. The conventional Wagner-Earth technique is not suitable for continuous measurement. In this paper, a modified operational-amplifier-based Maxwell-Wien bridge measurement technique has been proposed in which the effect of stray capacitance and inductance is minimized. In the first phase of the experiment, the bridge performance has been studied with a known variable inductor, and in the second phase, the same experimentation was done by replacing the variable inductor with an inductive coil having an adjustable core position for the measurement of displacement. The linear characteristics over a wide range of displacement with good repeatability, linearity, and variable sensitivity have been described.

Study on Influence of Stray Inductance in Micro EDM Using Electrostatic Induction Feeding Method

In the micro EDM method by electrostatic induction feeding, a pulse generator is coupled to the tool electrode by a capacitor, since the negative influence of the stray capacitance in the circuit can be eliminated, and the discharge energy per pulse can be minimized, thereby realizing discharge craters of nanometer order. However, there is still the stray inductance in the discharge circuit, other than the stray capacitance. In this study, in order to examine the influence of the stray inductance, experimental investigation was conducted.

On Dynamic Effects Influencing IGBT Losses in Soft-Switching Converters

Two different dynamic effects influencing the insulated gate bipolar transistor (IGBT) losses in soft-switching converters are demonstrated. The first one, the Dynamic tail-charge effect shows that the tail charge is dependent not only on the absolute value of the current at turn-off, but also on the dynamics of the current. This effect may have a significant impact on the optimization of zero-current-switching converters. The Dynamic conduction losses originate from the conductivity modulation lag of the IGBT. It is shown by experiments that the on-state losses depend on the operating frequency. Different methods to accurately determine the on-state losses are evaluated. It was found that the best method is an indirect measurement, where the stray inductance is identified by the use of an oscillating circuit. The experiments are performed under a sinusoidal current excitation at a fixed amplitude (150 A) for different frequencies (up to 104 kHz). The switching devices used are IGBT modules rated 300-400 A/1200 V in a bridge-leg configuration. From the experiments performed, it is found that IGBTs of a modern punch-though (PT) designs have the lowest losses in the series-loaded resonant converters studied in this paper.

Practical Design Guidelines of qZSI Based Step-Up DC/DC Converter

Practical Design Guidelines of qZSI Based Step-Up DC/DC ConverterThis paper presents some design guidelines for a new voltage fed step-up DC/DC isolated converter. The most significant advantage of proposed converter is voltage buck-boost operation on single stage. The most promising application for proposed converter is in the field of distributed power generation e.g. fuel cells or photovoltaic.The most sensitive issues - such as power losses caused by high currents in the input side of converter and high transient overvoltages across the inverter bridge caused by stray inductances were discussed and solved. The proposals and recommendations to overcome these issues are given in the paper. The Selection and design guidelines of converter elements are proposed and explained.The prototype of proposed converter was built and experimentally tested. Some results are presented and evaluated.

Designing an Adjustable Wide Range Regulated Current Source

LLC resonant converter has been used widely as dc-dc converter for achieving constant dc voltage. In this paper, an LLC resonant converter, by adding an inductance to its conventional topology and considering the rectifying stage stray inductances, is proposed for an adjustable wide range regulated current source (20-200 Adc) for using as ion implanter's filament power supply. The additional inductor increases output current adjustment range and efficiency, especially at light loads. Transformer's leakage inductances and rectifying stage stray inductances have been considered. Because of these inductances, the rectifier stage always works in continuous conduction mode, and its conduction angle is forced to be larger than ?, and peak current of the rectifier stage and the output capacitor have been reduced effectively. Switching losses and electromagnetic interference noises have been reduced as well due to zero-voltage switching at the primary and secondary sides of the converter, and zero-current switching at its secondary side. Soft switching is achieved for all power devices under all operating conditions. A developed prototype of the converter has been tested under different load (2.5-12.5 m?) and input voltage conditions (320-370 V dc) with maximum efficiency of 87%. Experimental results confirm high performance of the designed adjustable and regulated current source even under the worst-case conditions.