Longer Service Life Research Articles

Investigation of medium-term self-healing performance of strain-hardening cementitious composites incorporated with colloidal nano silica

• Colloidal nano silica (CNS) improved the mechanical performance of the cementitious composite. • The regaining of the mechanical performance of the pre-damaged sample was improved by CNS. • The addition of CNS improved the hydration degree and pozzolanic reaction. In this research, the properties of the colloidal nano silica-incorporated strain-hardening cementitious composite (SHCC) were investigated. Specifically, mechanical properties and medium-term (three months) self-healing performance were evaluated through various testing methods. The critical mechanical behaviors, including compressive, tensile, flexural properties, and bonding strength were assessed. The results indicated that the incorporation of colloidal nano silica (CNS) can effectively improve the mechanical properties of SHCC. Both non-destructive and destructive testing methods were implemented to monitor the medium-term self-healing performance of the SHCC with various CNS incorporation ratios. The SHCC samples were pre-cracked and placed under two separate environmental conditions during the healing period. It was found that the incorporation of the CNS can effectively improve the regaining of the mechanical performance of the SHCC within one season (three months) after subjected to damage. The thermal gravity analysis (TGA) and scanning electron microscope (SEM) were conducted to understand the hydration conditions of each sample. It is summarized that the CNS incorporation ratio between 0.3 and 0.6 percent would be optimal for SHCC to reach excellent mechanical properties and self-healing performance. This study provides insight for the design of the high-performance cementitious composite with longer service life by enhancing the self-healing efficiency.

MICROSTRUCTURE AND TRIBOLOGICAL PERFORMANCE OF SELF-LUBRICATE CLADDING PRODUCED BY TUNGSTEN INERT GAS AND MICROWAVE HYBRID HEATING TECHNIQUES

The wear reduction of moving components is highly desirable because wear limits their reliability and service life, mainly at elevated temperatures. This study produced thick clads of NiCrSiB/WC/MoS2/BaF2 by tungsten inert gas (TIG) and microwave hybrid heating (MHH) cladding techniques, which were compared for microstructural and high-temperature tribological properties. The clad samples were subjected to sliding contact using a pin on disc tribometer at 200∘C, 400∘C, 600∘C under 20 and 40[Formula: see text]N load. The worn surface was analyzed using FESEM, XRD and three-dimensional (3D) profilometer. The experimental results revealed a significant effect of the TIG current and MHH exposure time on the microhardness value, which predominantly depends on the morphological characteristics. The average hardness of TIG clads was found to be 1.2 times higher than the MHH clad. Because of the MoS2 and BaF2 encapsulation, the continuous lubricant layer formation compensated for improved wear resistance with good reliability and longer service life. This work provides significant insights into the wear behavior of TIG and MHH clads at elevated temperatures and the prospective applications in turbines, where inadequate wear resistance of titanium alloy is the major concern for its use.

Wear Mechanism and Life Map Construction of Nitride Coatings on Different Substrates

The sliding wear and failure behaviors of CrN and AlTiN coatings on high speed steel (HSS) and cemented carbide (WC-Co) were investigated on a reciprocating test machine under different normal forces (30–120 N). The wear mechanism was explored based on the analysis of coefficient of friction (CoF), wear and damage of coating. Then, the coating service life maps were established and the factors affecting the coating life were explored. The results indicated that the bonding strength of coatings to the WC-Co substrate were larger than those to the HSS substrate. The CoFs of CrN fluctuated during the wear process, while CoFs of AlTiN coatings were closer to those of the uncoated substrates. The wear depths of coated samples were smaller than those of uncoated substrates. The wear depths were small when the coatings worked and then increased with the number of cycles and the normal forces. For the CrN coatings, they had longer service life under smaller normal forces than under the large forces. Under small forces, an adhesion layer derived from the wear debris was formed on the coating surface to reduce the wear at the beginning of the test, after that the main failure mechanism was abrasive wear and delamination. Under large forces, the main failure mechanism was spallation. For the AlTiN coatings, the main failure mechanism was spallation on the HSS substrate; however, on the WC-Co substrate it was adhesive and abrasive wear. The coatings (CrN and AlTiN) on WC-Co had longer service life under various normal forces than on the HSS. CrN coating has the better wear-resistance than AlTiN coatings.

Risk-Based Operation and Maintenance Planning of Steam Turbine with the Long In-Service Time

In order to ensure the safety of power generation in Poland and to maintain energy production from coal-fired units with the long in-service time, it is required to develop a strategy for the further operation of the conventional power plants in conditions of increased flexibility. The presented research focuses on the critical component of the steam turbine, which is the high-pressure rotor. The methodology of the forecasting of crack propagation and growth of life-consumption processes was described, and the probability of a failure in subsequent years was estimated. The development of the identified phenomena depends mainly on the stress increases during start-ups; therefore, these increases were determined to ensure the safety of the turbine’s operation during the assumed period of operation (13 years). The permissible stress for rotor central bore (threatened with crack propagation) was 220 MPa for start-ups which were not carried out “on demand”, and for heat grooves (threatened with life-consumption processes) it was 420 MPa or 210 MPa, depending on the initial wear level of the material. An algorithm for online stress monitoring was presented, taking into account the variability of the heat transfer coefficients. The compiled method can be transformed into a real-time stress level control system. As a result, it is possible to obtain the desired increase in stress during start-up. For a longer service life (20 years), a method of selecting the optimal time interval to carry out preventive actions based on a risk analysis was additionally delineated. The optimal year to perform repair was between the 14th and 15th year of operation. The developed research allows presenting a strategy for further operation and maintenance (O&M) of the turbine, which can be adapted to a real unit.

Diagnostic of Combined Mechanical and Electrical Faults in ASD-Powered Induction Motor Using MODWT and a Lightweight 1-D CNN

The early fault detection in the rotary electrical machines,such as induction motors (IMs), has been growing in modern industry. IMs have been widely used in industrial applications due to its easy installation, reliability, and low cost. However, the increasing usage of IMs also increases the need for timely maintenance in order to ensure their operation and a longer service life. This article proposes a new diagnosis methodology based on maximal overlap discrete wavelet transform and a lightweight 1-D convolutional neural network (CNN) architecture, in order to detect mechanical and electrical faults and their combination, in adjustable speed drive (ASD)-powered IMs. Specifically, single and combined faults were studied from the next: Outer raceway bearing (mechanical), turn-to-turn short-circuit, and phase-to-ground short circuit (electrical). The presented study was developed using current signals acquired from stators of IMs of 1 hp. The current signals are measured at powered conditions introduced by a power grid with a constant frequency at 60 Hz, and an ASD at three different frequencies. The proposed diagnostic methodology reaches more than 99% of accuracy.

The Cavitation Characteristics of High Speed Centrifugal Pumps With Different Impeller Types

Addressing the cavitation prevention requirements for a longer service life of the high-speed centrifugal pump in the temperature control system of aerospace, the effect of blade inlet width on cavitation performance is studied on the premise of consistency of impeller outlet diameter D2, impeller outlet width b2, volute inlet diameter D3, pump interface and other structural parameters. Therefore, the corrected coefficient k1 of blade inlet exclusion coefficient is introduced; four groups of centrifugal impellers with inlets of different geometric structures blades are put forward. To begin with, based on the D# pump performance test and Pumplinx simulation, the cavitation performance of high-speed pump with four different groups of impellers is studied under five working conditions of negative inlet pressure (Pj=(−20, −30, −40, −50, −60)kPa) on the premise that energy characteristics agree well with cavitation performance. According to the results, when Pj drops from −50 kPa to −60 kPa, the cavitation perform changes the most significantly. This indicates that the method of twisting the centrifugal impeller of the suspended forward-extended blade shows a significant effect in preventing cavitation performance under such working conditions of high speed and negative pressure. Its application in aerospace power systems can effectively reduce the impact of low pressure in the system and significantly improve the cavitation performance.

Performance Evaluation of Rice-husk Ash Based Bacterial Concrete

The performance evaluation of bacterial concrete made with Rice Husk Ash (RHA) is presented in this paper. Concrete is the most widely used construction material on the planet, and because of its longer service life than other building materials, it is sometimes viewed as indestructible. Continuous exposure to harsh weathering, on the other hand, causes an increase in concrete porosity and, as a result, a reduction in mechanical properties. The effect of concrete permeability on porosity and porosity connection. Microbial concrete, which uses microorganisms to increase the durability and life of the concrete, has been presented. These bacteria are employed to precipitate calcium carbonate in concrete, which is extremely desired because the calcite precipitation caused by microbial activity is pollution-free and natural. Rice husk is used to substitute fine aggregate in concrete mixes of 0, 5, 10 and 15.

FACTORS OF MARGIN BONE STABILITY AROUND IMPLANTS: LITERATURE REVIEW

Implant-supported dentures are increasingly used in dental practice since last century. The purpose of this review is to assess the effect of the transmucosal surface of restorations and implants on peri-implant tissues.
 Factors that affect bone loss around implants can be divided into local, systemic and social. Local factors include implant geometry, occlusal loading, and biological aspects. Biological factors include peri-implantitis, poor bone quality, surgical implant placement procedure, early implant loading, and poor osseointegration. Among other factors that can lead to bone loss, systemic factors (patient age, general condition, genetic predisposition) as well as social factors (socioeconomic status of the patient, oral hygiene, drug use) play an important role.
 The article compares and discusses the properties of different materials. The advantages, disadvantages and biomechanical concept of different implant-abutment connections are presented. The location of the connections relative to the bone level and the effect of the micro-gap between the abutment and the implant are described. The article focuses on the following issues:
 
 exposure to the material from which the implants and abutment are made, with an emphasis on titanium alloys and zirconium dioxide;
 implant systems, which are classified according to their location in relation to the level of the bone;
 type of connection between implants and abutments: external (external hexagon), internal (internal hexagon and octagon) and their modifications, such as conical (Morse taper);
 the influence of the precision of abutments to the implants` connection;
 type of fixation;
 features of transmucosal surfaces;
 biological factors around the implant-abutment joint.
 
 Scientists and manufacturers offer advanced solutions that reduce the number of complications and ensure a longer service life of implants-supported restorations. With proper procedures and the right selection of systems and tools, you can reduce bone loss and preserve soft tissue. Finding a balance between function and aesthetics in implant rehabilitation is a crucial issue.
 The use of solutions aimed at achieving the expected result in each individual patient, which allow individual consideration of the above risk factors for marginal bone loss, will probably become a standard part of the examination at the preoperative stage of treatment.

Susceptibility to Expansive Reactions of a Greener UHPC: Micro to Macro-Scale Study

Nowadays, in Europe, several infrastructures, such as bridges, viaducts, and maritime structures, are in an advanced state of degradation. Therefore, novel repair/rehabilitation techniques are sought. Recent advances in ultra-high-performance fibre-reinforced cement-based composites (UHPFRC) represent a significant step towards resilient structures. In addition to their remarkable mechanical properties (compressive strength > 150 MPa), they present extremely low permeability and, as a premise, very high durability. Despite their relatively high cost, UHPFRC can be a competitive solution for rehabilitation/strengthening applications where smaller volumes are needed. UHPFRC applied in thin layers (with or without reinforcement) can replace carbonated and/or cracked concrete acting as a protective watertight and/or strengthening layer. The structural capacity increases (stiffness, ultimate strength), and the durability is expected to improve significantly while keeping cross-sectional dimensions. Additional advantages are expected, such as reduced intervention time, fewer maintenance routines, reduced life-cycle cost, and longer service life. Although much of the focus on UHPFRC has centred on mechanical and/or structural performance, durability is inevitably linked with mechanical properties. The current work evaluated the durability of non-property and greener UHPC concerning expansive reactions, alkali-silica reactions and expansion due to external sulphates, by macro and micro-scale integrative study. Linear expansion tests were performed in UHPC specimens according to ASTM C 1260 and LNEC E−364. At the macro level, no deleterious expansion due to ASR or external sulphate occured. Expansion due to ASR was 0.0018% after 14 days of immersion in an alkali-rich environment, and no expansion was recorded regarding sulphate attack. However, SEM analysis reveals reactive products of ASR and sulphate attack, namely, ASR gel and ettringite, respectively, in UHPC specimens.

Characterisation of modified asphalt mixtures with lignin of pinus and eucalyptus woods

ABSTRACT Lignin is a natural polymer that has antioxidant properties. However, a supplied lignin’s physical, chemical, and rheological behaviour will differ from the source. Thus, the objective of this work was to investigate the mechanical performance of asphalt mixtures produced with asphalt binders modified by lignins at the contents of 0, 3, 6, and 9%, from pinus and eucalyptus sawdust. The mixtures were evaluated by performing the Splitting Tensile Strength Test, Lottman, Resilient Modulus, and Dynamic Modulus. The results pointed to lignin, both tested, as a good natural polymer due to the increase in resilience of the asphalt mixtures and reduction of susceptibility to moisture for the proposed contents. Therefore, it is suitable for field use. Lignin can be identified as a residual modifier that can provide longer service life to asphalt coatings, presenting itself as an alternative modifier to the synthetic elastomeric polymers. The addition of 3% pinus lignin presented the best mechanical performance, followed by the addition of 9% eucalyptus lignin.

Enhanced blue-light excited cyan-emitting persistent luminescence of BaLu2Al2Ga2SiO12:Ce3+, Bi3+ phosphors for AC-LEDs via defect modulation

Alternating current light-emitting diodes (AC-LEDs) have received significant attention from both academia and industry due to their remarkable benefits of more compact volume, cheaper manufacturing cost, greater energy usage efficiency, and longer service life. One of the most significant challenges for AC-LEDs is the flicker effect, which is mainly caused by the unavoidable 5–20 ms dimming time. Aiming to reduce the flicker effect, we designed a series of excellent blue-light excited cyan-emitting persistent luminescence (PersL) phosphors BaLu2Al2Ga2SiO12:Ce3+, Bi3+ via defect engineering of co-doping Bi3+. Interestingly, we found that co-doping Bi3+ not only effectively enhanced the PersL intensity, but also regulated the PersL lifetime of this phosphors. As the Bi3+ co-doping concentration increases to 0.01, the τ80 value (the time when the PersL intensity decreases to 80% of the initial intensity) increases from 0.24 to 19.61 ms, which proves to be effective in compensating the flicker effect of AC-LEDs. A new method of generating white light emission during the dimming time through adding the blue-light excited cyan PersL phosphor to the original orange-red PersL phosphor was proposed and an AC-LED lamp with a decreased percent flicker of 48.15% was fabricated, which is significantly better than the other currently reported AC-LED devices based on PersL phosphors. These results demonstrate that BaLu2Al2Ga2SiO12:Ce3+, Bi3+ might be an attractive material for low-flicker AC-LEDs.

Multi-Objective Optimization Design of Ladle Refractory Lining Based on Genetic Algorithm.

Genetic algorithm is widely used in multi-objective mechanical structure optimization. In this paper, a genetic algorithm-based optimization method for ladle refractory lining structure is proposed. First, the parametric finite element model of the new ladle refractory lining is established by using ANSYS Workbench software. The refractory lining is mainly composed of insulating layer, permanent layer and working layer. Secondly, a mathematical model for multi-objective optimization is established to reveal the functional relationship between the maximum equivalent force on the ladle lining, the maximum temperature on the ladle shell, the total mass of the ladle and the structural parameters of the ladle refractory lining. Genetic algorithm translates the optimization process of ladle refractory lining into natural evolution and selection. The optimization results show that, compared with the unoptimized ladle refractory lining structure (insulation layer thickness of 0 mm, permanent layer thickness of 81 mm, and working layer thickness of 152 mm), the refractory lining with insulation layer thickness of 8.02 mm, permanent layer thickness of 76.20 mm, and working layer thickness of 148.61 mm has the best thermal insulation performance and longer service life within the variation of ladle refractory lining structure parameters. Finally, the results of the optimization are verified and analyzed in this paper. The study found that by optimizing the design of the ladle refractory lining, the maximum equivalent force on the ladle lining, the maximum temperature on the ladle shell and the ladle mass were reduced. The thermal insulation performance and the lightweight performance of the ladle are improved, which is very important for improving the service life of the ladle.

Full Life-Cycle Optimal Battery Scheduling for Maximal Lifetime Value Considering Degradation

The dilemma between battery operating revenue and aging has not been addressed appropriately by previous studies. This paper presents a co-optimization method of battery full life-cycle scheduling and lifespan for its maximal lifetime value, involving usage limits, nonlinear aging characteristics, and time-value-of-money effects. The resulting dispatch model consists of numerous large-scale non-convex nonlinear programming (NLP) problems with the nonlinearity appearing in the equality constraint, which cannot be solved efficiently through conventional methods. Thus, we design an exact and fast solution approach including the equivalent problem transformation, a modified pegging algorithm, and a novel acceleration algorithm. The proposed methods are illustrated and validated by numerical tests using real historical data from Pecan St. Project. Test results suggest that it is not the case that the longer service life, the more battery lifetime profits can be generated. The proposed scheduling method can improve the lifetime profits than the conventional methods. For a battery with a 15-year design life, the optimal scheduling and lifespan with a 5-day resolution can be obtained within half an hour.

Performance Evaluation and Prediction of Preservation Asphalt Overlay in Louisiana

The Louisiana Department of Transportation and Development (LaDOTD) has been using thin asphalt overlay (2 in.) as a preservation technique for asphalt-surface pavements. Although LaDOTD has specified the triggers for its application, it was not always applied on the recommended timing. It is unclear how the application timing affects the overlay performance. Additionally, no studies have been conducted to determine optimal application timing for the overlay and predict its performance using the available tools such as AASHTOWare Pavement Mechanistic-empirical design (Pavement ME) software. The objectives of the study are (1) to evaluate field performance of the preservation asphalt overlay and develop performance prediction models, (2) to determine optimal application timing for the overlay, and (3) to investigate if Pavement ME models are able to predict performance of the overlay by modifying model coefficients. To achieve the objectives, 33 preservation asphalt overlay projects were selected, and their performance was evaluated and predicted, then the optimal application timing was investigated based on the benefit and cost analysis. The results indicate that 58% of the preservation asphalt overlays had 10–20 years’ service life, and 42% had 7–10 years’ service life in relation to Pavement Condition Index threshold of 70. Additionally, good precondition or flexible base (asphalt concrete or unbounded base) can result in a longer service life in the overlay. It is also found that an average value of optimal timing of the next overlay application is the 9th year after construction. Finally, the rehabilitation models of asphalt overlay in Pavement ME software could be used for preservation asphalt overlay by modifying model coefficients.

An Overview of Self-Healable Polymers and Recent Advances in the Field.

The search for materials with better performance, longer service life, lower environmental impact, and lower overall cost is at the forefront of polymer science and material engineering. This has led to the development of self-healing polymers with a range of healing mechanisms including capsular-based, vascular, and intrinsic self-healing polymers. The development of self-healable systems has been inspired by the healing of biological systems such as skin wound healing and broken bone reconstruction. The goal of using self-healing polymers in various applications is to extend the service life of polymers without the need for replacement or human intervention especially in restricted access areas such as underwater/underground piping where inspection, intervention, and maintenance are very difficult. Through an industrial and scholarly lens, this paper provides: a) an overview of self-healing polymers; b) classification of different self-healing polymers and polymer-based composites; c) mechanical, thermal, and electrical analysis characterization; d) applications in coating, composites, and electronics; e) modeling and simulation; and f) recent development in the past 20 years. This review highlights the importance of healable polymers for an economically and environmentally sustainable future, the most recent advances in the field, and current limitations in fabrication, manufacturing, and performance.

Numerical Analysis of a Small Pneumatic Hammer Performance Based on Evaluation Method of Friction Force

Mechanical power loss in pneumatic hammers comes from the friction between parts in relative motion, and wear is among the failure mechanisms of the top hammer. Therefore, it is important for high performance and a longer service life of pneumatic hammers to reduce the friction force between parts in relative motion. This study presented a novel approach to quantitatively determine the friction force and consider it in the simulation model of pneumatic hammer. First, the friction force between piston and cylinder in a small pneumatic hammer was measured using an experimental setup at different inlet pressures. We could find from the experimental result that the friction force was about 0.8 N under the horizontal installation when there was no pressure supply, but it increased significantly, was 20 times greater than that without pressure supply, due to aerodynamic action by compressed air leaked from the annular gaps between the cylindrical matching surfaces of the components. In addition, it increased from 10.27 to 16.7 N due to an increase in inlet pressure and mechanical power loss in the pneumatic hammer that was about 10% of impact energy. Then, numerical analysis for a small pneumatic hammer performance was performed by a model considered the friction force using AMESim software. Finally, it can be seen from the simulation results that the proposed approach could significantly reduce the error between the simulated and the measured values for the impact energy because of ignoring the friction force. This approach will be used to predict service life of piston and find a low friction piston of pneumatic hammer in practical engineering.

Feasibility and optimal sizing analysis of stand-alone hybrid energy systems coupled with various battery technologies: A case study of Pelee Island

Selection of the best component arrangement and sizing measurement for hybrid energy systems (HES) is vital to provide a reliable, consistent, and cost-effective energy supply. This study investigates a techno-economic feasibility analysis of stand-alone HES on Western side of Pelee Island, Canada, whose load is 2426 kWh/day. Several hybridization cases, including diesel (DG), wind (WT), and solar (PV) energy generation, coupled with converters (CNV) and four different battery-electric storage technologies, are explored for technical and economic suitability. The battery architectures involve Scenario I: 1 kWh Lead Acid (LA), Scenario II: 1 kWh Li-Ion, Scenario III: 100 kWh Li-Ion, and Scenario IV: 2.5 kWh PowerSafe (SBS). The results favored the Scenario II solution: 152 kW PV module, 200 kW DG, 190 kW CNV when integrated with 853 kWh Li-Ion battery which has the lowest NPC and LCOE by $3.67M and 0.321$/kWh, respectively. Fuel price and solar irradiance of LA-based systems are more sensitive to renewable fraction and less sensitive to LCOE.1 kWh Li-Ion battery-based hybrid options maintain their lowest LCOE and NPC over variation of fuel price, irradiance, and required load. Unmet load comparison reveals that PV/WT/DG/100 kWh Li-Ion and PV/WT/2.5 kWh SBS, respectively, are the most and least reliable hybrid cases. When comparing storage throughput, it is expected that 100 kWh Li-Ion batteries would be more efficient and have a longer service life than 2.5 kWh SBS batteries.

Stiffness optimization and reliable design of a hip implant by using the potential of additive manufacturing processes

BackgroundDue to the steadily increasing life expectancy of the population, the need for medical aids to maintain the previous quality of life is growing. The basis for independent mobility is a functional locomotor system. The hip joint can be so badly damaged by everyday wear or accelerated by illness that reconstruction by means of endoprostheses is necessary.ResultsIn order to ensure a high quality of life for the patient after this procedure as well as a long service life of the prosthesis, a high-quality design is required, so that many different aspects have to be taken into account when developing prostheses. Long-term medical studies show that the service life and operational safety of a hip prosthesis by best possible adaptation of the stiffness to that of the bone can be increased. The use of additive manufacturing processes enables to specifically change the stiffness of implant structures.ConclusionsReduced implant stiffness leads to an increase in stress in the surrounding bone and thus to a reduction in bone resorption. Numerical methods are used to demonstrate this fact in the hip implant developed. The safety of use is nevertheless ensured by evaluating and taking into account the stresses that occur for critical load cases. These results are a promising basis to enable longer service life of prostheses in the future.

USING NANOCLAY HYDROPHILIC BENTONITE AS A FILLER TO ENHANCE THE MECHANICAL PROPERTIES OF ASPHALT

Higher traffic loads on the wheels, increased traffic volumes, and exposure to changing weather conditions result in increasing the road stresses and strains, putting the paving layers in danger of degradation such as fatigue, stripping, cracking, and rutting. A tremendous number of studies and trials have been conducted to modify asphalt to have a longer service life, less maintenance, be cheaper, and be more environmentally friendly. Recently, nanotechnology has proven very beneficial in all industries, including asphalt. It can be used to enhance the asphalt's mechanical properties. Using nano clay in asphalt is expected to improve the mechanical properties and the service life of the asphalt. So the main objective of this study is to investigate the performance of nano clay hydrophilic bentonite in improving the physical characteristics of asphalt concrete. This study uses nano clay with various replacement ratios as fillers to the ordinary used limestone filler in asphalt concrete. The used replacement percentages were (0%, 20%, 40%, 60%, 80%, and 100). The experimental tests that were conducted in this study include Marshall Stability (MS), Marshall Flow (MF), voids in mineral aggregate (VMA), theoretical maximum specific gravity (Gmm) and air voids (AV).The results showed a noticeable enhansment in the behavior of the asphalt mix with increasing the replacement percentage by nanoclay. Also, it was found that the 60% replacement rate by nanoclay has the highest Marshall stability with an increase of 93%, also the lowest flow with a decrease of 25% compared to the control asphalt mix.

Transient optimization control strategy of hybrid capacity regulating transformer

In order to overcome the problems of the traditional capacity regulating transformer, this paper presents a hybrid capacity regulating transformer(HCRT) that uses anti-parallel thyristors instead of mechanical switches. Advantages of presented HCRT are there is no arc in such transformer, faster response speed and longer service life. Taking into account of the characteristics of the semi-controllable thyristor, this paper proposes a transient optimization control strategy to avoid internal short circuit and load voltage loss in HCRT. After receiving the capacity regulating command which is the delay time calculated by the parameters of transformer, the closing time of the switch group is controlled, therefore, the continuity of the magnetic flux and load voltage in each phase in the process of capacity regulating is ensured. Finally, the simulation results of comparative experiments are provided to illustrate the advantages and effectiveness of the proposed method. Meanwhile, the experimental results obtained on the prototype of HCRT are provided to verify the effectiveness of transient optimization control strategy for HCRT.