Commutation Principle Research Articles

A 50 kJ Inductive–Capacitive Storage Module With Solid-State High-Power Opening Switch Based on Counter-Current Thyristor

This paper describes a compact high storage density inductive-capacitive storage module. The module is based on high-power opening switches using inverse current commutation with semiconductor devices commutation principle and a high storage density Brooks inductor. These opening switches, being able to switch-OFF pulse currents up to 14.5 kA by the countercurrent subcircuit, make use of the general property of a standard high-power thyristors impedance transition from closing state to blocking state. The experimental results show that with the primary capacitor and counter-current commutation subcircuit charged voltage 3 and 2.5 kV, respectively, the charged current of the Brooks-type inductor is about 14.5 kA, with a charged time of about 4.5 ms. The output peak current of the inductive storage module is about 21 kA. The total stored energy is about 54.9 kJ while the energy density of the inductor is approximately 6.69 MJ/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , which is not including the primary storage and commutation unit.

System Implementation and Testing of the STRETCH Meat Grinder With ICCOS

By applying the principle of inverse current commutation with semiconductor (ICCOS) devices in a slow transfer of energy through capacitive hybrid (STRETCH) meat grinder system, a novel circuit topology called STRETCH meat grinder with ICCOS was proposed by the Tsinghua University in 2013. It can not only raise the amplitude of the opening current, but also reduce the cost of the STRETCH meat grinder circuit obviously by replacing the integrated gate-commutated thyristor (IGCT) with thyristor. This paper discusses the overall design, system implementation, and testing results of a STRETCH meat grinder with ICCOS system with roughly 1-kJ inductive energy. The load is a spiral coil with 1.4-mΩ resistance and 1.4-μH inductance. With closed-loop control strategy, the system detects the charging current of the inductors. When it reaches the designated value, the triggering signal for ICCOS is delivered and after the predefined delay time, the triggering signal for discharging the voltage on the pulseforming capacitor is delivered. The current of the inductors and the load are measured by Rogowski coils. The opening current is 1 kA and the maximum load current is close to 4 kA. All the voltages on the switches are lower than 1 kV. The experimental results are consistent with the simulated ones, which verified the correctness of the theoretical analysis and proved the applicability of the STRETCH meat grinder with ICCOS for larger energy level.

Performance of Induction Heating Power Supply Using Dual Control Mode Pulse-width Modulation–Pulse-density Modulation High-frequency Inverter

This article presents a novel induction heating power supply. The power supply is based on an auxiliary active edge resonant zero-current soft-switching technique. It consists of single-ended push–pull series load resonant inverter. The proposed inverter is cost effective for high-frequency induction heating consumer appliances. The new multi-resonant high-frequency inverter with series load resonance and edge resonance can regulate its high-frequency output power under the constant-frequency zero-current soft-switching commutation principle on the basis of an asymmetrical pulse-width modulation control scheme. The brand-new consumer induction heating product is evaluated and discussed on the basis of simulation and experimental results. To extend zero-current soft-switching operation ranges under a low-power setting as well as improve efficiency, the high-frequency pulse-density modulation strategy is demonstrated for a high-frequency soft-switching inverter. Its practical effectiveness of induction heating power supply is substantially proved from an induction heating application point of view.

Spontaneously spotting and applying shortcuts in arithmetic-a primary school perspective on expertise.

One crucial feature of expertise is the ability to spontaneously recognize where and when knowledge can be applied to simplify task processing. Mental arithmetic is one domain in which people should start to develop such expert knowledge in primary school by integrating conceptual knowledge about mathematical principles and procedural knowledge about shortcuts. If successful, knowledge integration should lead to transfer between procedurally different shortcuts that are based on the same mathematical principle and therefore likely are both associated to the respective conceptual knowledge. Taking commutativity principle as a model case, we tested this conjecture in two experiments with primary school children. In Experiment 1, we obtained eye tracking data suggesting that students indeed engaged in search processes when confronted with mental arithmetic problems to which a formerly feasible shortcut no longer applied. In Experiment 2, children who were first provided material allowing for one commutativity-based shortcut later profited from material allowing for a different shortcut based on the same principle. This was not the case for a control group, who had first worked on material that allowed for a shortcut not based on commutativity. The results suggest that spontaneous shortcut usage triggers knowledge about different shortcuts based on the same principle. This is in line with the notion of adaptive expertise linking conceptual and procedural knowledge.

From Marbles to Numbers—Estimation Influences Looking Patterns on Arithmetic Problems

Flexibly spotting and applying shortcut options in arithmetic is often a major challenge for children as well as adults. Recent work has suggests that children benefit in terms of such flexibility from tasks requiring estimation or other operations with quantities that they cannot easily enumerate. Such tasks often require comparison of quantities by fixation and as such necessitate long-range eye movements, e.g. across the whole screen. We tested whether fixation patterns account for transfer from estimation to arithmetic tasks. Conceivably, participants who first solve estimation tasks are more flexible in spotting and applying shortcuts on later arithmetic tasks, because they stick to scanning the screen with long-range eye movements (which were necessary for solving the estimation task). To test this account, we manipulated the location of the marbles in an estimation task so that one group of participants had to make long-range eye movement, whereas another group did not need long-range eye movements to solve the task. Afterwards participants of both groups solved addition problems that contained a shortcut option based on the commutativity principle. We tested whether shortcut usage and fixation patterns in the arithmetic problems were influenced by the variant of the estimation task provided beforehand. The experiment allowed us to explore whether flexibility in spotting and using arithmetic shortcuts can be fostered by applying a prior task that induces flexible looking patterns. The results suggest that estimation tasks can indeed influence fixation patterns in a later arithmetic task. While shortcut search and application is reflected in fixation patterns, we did not obtain evidence for the reverse influence. Changed fixation patterns did not lead to higher shortcut usage. Thus, the results are in line with top-down accounts of strategy change: fixation patterns reflect rather than elicit strategy change.

A Four-Stage XRAM Generator as Inductive Pulsed Power Supply for a Small-Caliber Railgun

A four-stage XRAM generator is built and then applied to a railgun having a caliber of 15 × 15 mm. The XRAM generator is based on 1-mH Brooks coils and on standard high-power thyristors which are employed as opening switches according to the ICCOS countercurrent commutation principle. The coils of the generator are charged with a current of 10 kA, which corresponds to an energy of 200 kJ. The current is successfully commutated and a pulse with a maximum current of 40 kA is applied to the railgun. Consequently, a projectile with a total weight of 33 g is accelerated to 157 m/s within the railgun length of 2.1 m. The semiconductor switches are exposed to a steep voltage rise due to the muzzle flash when the projectile leaves the railgun without their critical limit being exceeded. Thus, the successful operation of the XRAM generator using semiconductor switches during railgun experiments is demonstrated. Furthermore, we are able to show in a further experiment that the muzzle flash of the railgun can be significantly reduced by switching the XRAM back into charging mode when the projectile leaves the bore. This method also allows the conservation of the energy that remains in the coils after the exit of the projectile from the railgun.

Digital Implementation of PWM Techniques for Two-phase Eight-switch Inverter fed Brushless DC Motor Drives

This paper reports an investigation of pulse width modulation (PWM) techniques for two-phase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan application. The three-phase BLDC motor is widely applied in industry; however, a lower-cost two-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this paper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the drive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electrical-degree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.

Commutation Principle for Variational Problems on Euclidean Jordan Algebras

This paper establishes a commutation result for variational problems involving spectral sets and spectral functions. The discussion takes places in the context of a general Euclidean Jordan algebra.

Thermal Analysis of Interior Permanent-Magnet Synchronous Motor by Electromagnetic Field-Thermal Linked Analysis

This paper reports an investigation of pulse width modulation (PWM) techniques for twophase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan application. The three-phase BLDC motor is widely applied in industry; however, a lower-cost two-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this paper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the drive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electricaldegree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.

Study on Modulation Strategy with Neutral-Point Balancing Control for Three-Level Two Stage Matrix Converter

Aim to the three-level neutral-point potential balancing problem of three-level two stage matrix converter(TLTSMC),which is a new topology from matrix converter family that can synthesis three-level voltage in order to improve output performance in terms of reduced harmonic contents, this paper discussed the operating principles and a space vector modulation strategy with neutral-point potential balancing control for this topology. The method is divided into two control stages. Space vector PWM without zero vectors is used for rectifier stage. The modulation method of inverter stage based on the virtual space vector concept only requires the condition that the flow of neutral-point current equals zero, so the neutral-point balancing problem of this topology is effectively settled. The commutation principle of TLTSMC is analyzed. Finally, the validity and feasibility of this modulation method is tested by simulation and experiment, the result indicates that TLTSMC with the modulation strategy produces better output performance in terms of reduced harmonic contents and is also able to maintain sinusoidal input currents, furthermore, guarantees the balancing of neutral-point potential over the full range of output voltage.

Bidirectional Switch Commutation for a Matrix Converter Supplying a Series Resonant Load

This paper describes a bidirectional switch commutation strategy for a three-phase to two-phase matrix converter supplying a series resonant load. Classical modulation techniques are not applicable because of the needed high output frequencies. This fact, together with the different topology compared to classical three-phase to three-phase matrix converters, makes a new investigation of commutation principles necessary. The paper shows that the three-phase to two-phase resonant matrix converter can be compared with the full-bridge series-resonant converter. Thus, the commutation of the full-bridge series-resonant converter gives the conditions for the bidirectional switch commutation at the matrix converter. One of the main benefits of the derived strategy is the minimization of commutation steps independent of the load current sign.

ICCOS Countercurrent-Thyristor High-Power Opening Switch for Currents Up to 28 kA

Inductive energy storage systems require opening switches which are technically much more difficult to realize than closing switches. Most advanced state-of-the-art semiconductor devices, namely, integrated gate-commutated thyristors, are capable of breaking currents on the order of 4 kA. However, the ISL has developed a high-power opening switch based on standard high-power thyristors and using our so-called inverse current commutation with semiconductor devices (ICCOS) countercurrent commutation principle. These ICCOS opening switches, capable of interrupting pulse currents up to 28 kA, exploit the general property of thyristors, according to which falling short of the holding current puts the device into its blocking state. For this, a well-dimensioned countercurrent pulse is injected, via an elaborate circuit, into the thyristor which is in its conducting state. A 50-muF capacitor is used as the countercurrent pulse source, as well as a fast current-rise thyristor and a fast-recovery diode for the countercurrent subcircuit. The countercurrent energy stored in the dedicated capacitor is not lost in the switching process but fed into the load, in addition to the main-circuit energy. The achieved ICCOS switch-off time is about 30 mus.

Bidirectional Switch Commutation for a Matrix Converter Supplying a Series Resonant Load

This paper describes a bidirectional switch commutation strategy for a three-phase to two-phase matrix converter supplying a series resonant load. Classical modulation techniques are not applicable because of the needed high output frequencies. This fact, together with the different topology compared to classical three-phase to three-phase matrix converters, makes a new investigation of commutation principles necessary. The paper shows that the three-phase to two-phase resonant matrix converter can be compared with the full-bridge series-resonant converter. Thus, the commutation of the full-bridge series-resonant converter gives the conditions for the bidirectional switch commutation at the matrix converter. One of the main benefits of the derived strategy is the minimization of commutation steps independent of the load current sign.

High-power MOSFETs and fast-switching thyristors utilized as opening switches for inductive storage systems

Taking aim at the utilization of inductive storage systems with their manifold advantages for pulsed power applications (e.g., higher energy density, lower operating voltage), this paper focuses on semiconductor devices applied as opening switches in the inductive storage circuit. The devices investigated in this study, unipolar power metal-oxide-semiconductor field-effect transistors (MOSFETs) and bipolar thyristors, represent a wide range of power semiconductor switches. At first MOSFETs are investigated in parallel and series configurations, showing a negligible current imbalance and a symmetrical voltage sharing during switch-off. Furthermore, the maximum peak charge current of a single power MOSFET has been evaluated experimentally and theoretically. Overcoming the problem of a thyristor being exclusively a closing switch, we use a technique, called ICCOS, which is based on the well-known parallel capacitor-current commutation principle. Using this technique we have developed a power switch capable of commutating a peak charge current of 18 kA. The switching performance of such a thyristor configuration is compared to an array composed of numerous MOSFETs.

Comparative Performance Evaluations of IGBTs and MCT incorporated into Voltage-Source Type Single-Ended Quasi-Resonant Zero Voltage Soft Switching Inverter

A cost effective high-efficiency, simple, low noise voltage-source type single-ended quasi-resonant high frequency inverter using a single power semiconductor switching device and its modified circuit topologies are commonly applied for consumer induction heated rice cooker with a warmer function, cooking heater and microwave oven. This paper presents some comparative performance evaluations of each generation IGBT and MCT (MOS Controlled Thyristor) incorporated into the typical voltage-source quasi-resonant inverter operating under zero voltage soft switching transition mode. New generation IGBT has been improved for consumer power applications in order to reduce the conduction loss which is based on the lowered saturation voltage characteristics due to the latest IGBT. The comparative steady-state characteristics of some sample power-semiconductor switching devices of each generation IGBT are demonstrated on the basis of the simplest single-ended quasi-resonant inverter circuit operating under a condition of zero voltage soft switching commutation principle. In addition, the power losses and temperature performance analysis of the latest IGBT are discussed and evaluated as compared with previously-developed IGBTs. Finally, the further reduced saturation voltage and conduction loss characteristics of MCT which are more suitable for consumer utilizations are presented in comparison with the conventional IGBT.

Performance Improvement of Voltage-Fed Three Phase Soft Switching Inverter with a New Resonant DC Link Snubber

This paper presents a voltage source soft switching space voltage vector modulated inverter which incorporates two types of soft commutations; lossless snubber capacitor single operating scheme and active auxiliary resonant DC link snubber scheme. The operating principle of soft commutation is described. In addition, the effectiveness of its improved soft switching scheme is proven on the basis of simulation data.

The Roles of Estimation and the Commutativity Principle in the Development of Third Graders' Mental Multiplication

In this training experiment, pretesting identified 36 third graders (mean age = 8 years 5 months, SD = 4 months) with negligible mastery of multiplication combinations involving factors from 3 to 9. Participants were randomly assigned to 2 groups, which practiced different subsets of combinations, and were then retested. The results were inconsistent with R. S. Siegler's (1988) proposal that item-specific computational practice is necessary to promote changes in error patterns and combination mastery. The results were consistent with the hypotheses that children devise increasingly flexible and accurate estimation strategies and use relational knowledge such as the commutativity principle to master combinations. Because even fast mental-arithmetic errors and correct responses may be due to strategies other than retrieval, researchers need to craft ways of distinguishing between retrieval and nonretrieval strategies.

Zero-voltage switching for three-level capacitor clamping inverter

A zero-voltage switching (ZVS) scheme for a three-level capacitor clamping inverter based on the true pulsewidth modulation (PWM) pole is proposed in this paper. With this scheme, the main switches work with ZVS through the assistance of a small rating zero current switching (ZCS) lossless auxiliary circuitry without imposing any voltage/current spikes on the main devices or any extra control complexities. Consequently, a three-level capacitor clamping inverter system can operate at a promoted switching frequency and becomes more eligible to be considered for high-power advanced applications, for example, in high-speed drives or power active filter areas. In this paper, the main circuit operation issues as regards the clamping voltage stability, damping capacitor stress, and output voltage spectrum are shortly reviewed first, after which the commutation principle, auxiliary circuitry stress analysis, and auxiliary circuitry designing methodology are presented in detail. Experimental results from a 700 V supply 3 kW half-bridge three-level capacitor clamping inverter are demonstrated which conform well to the proposal.

A comparison of load commutated inverter systems for induction heating and melting applications

A comparative analysis of a current source inverter and a voltage source inverter suitable for induction heating and melting applications is presented. Both power supplies considered operate on the principle of load commutation. The comparison is based on criteria such as input power factor, component ratings, maximum and minimum operating frequencies, operation under varying load conditions, inverter starting capability, and system and control simplicity. The voltage source series resonant inverter is found to offer the best overall performance with respect to converter utilization. >

The Development of Counting Strategies for Single-Digit Addition

Over 9 months, structured clinical interviews with 17 kindergartners were used to study (a) the learning of a concrete counting strategy for addition, (b) the transition from concrete to mental counting strategies, and (c) the role of the commutativity principle in developing more economical counting strategies. Kindergartners appear to differ in their readiness to use a concrete strategy. Many children persisted in counting all with objects. The most common sequence of mental counting strategies was counting all starting with the first addend, counting all starting with the larger addend, and then counting on from the larger addend. A knowledge of commutativity does not appear to be necessary to invent counting strategies that disregard addend order.