In induction cap sealing, power is transferred to thin Al foil(s) traveling beneath an energized coil-head to create a hermetically sealed bond between the foil and the rim of a plastic/glass container. The distribution of transferred power on foil plays crucial roles for quality of sealing, sealing range, productivity, and energy efficiency. It is particularly difficult to seal moving containers using foils with a large diameter. Achieving desired heat distribution by thermal conduction on a thin foil is difficult. The problem gets aggravated when several large containers reside beneath the coil-head. The effective load resistance could go beyond its limiting value, resulting reduction in coil current. Corresponding reduction in power density in foil could result undersealing. To resolve the problems of sealing continuously fed large-mouth containers (foil diameter >= body diameter), this article proposes a novel coil-head to take care of energy distribution electromagnetically. It achieves sealing of large containers without any feeding constraints and inherently avoids overload condition. The coil enhances the efficiency of energy utilization and productivity. The coil-head is experimentally validated by sealing containers using foils with a diameter range 35-140 mm. Its superior field distribution is also verified. Even after transferring less power, the foil area sealed/second is drastically increased.

The cost of energy is one basic input that needs to be reduced optimally. Excess energy use makes multi-dimensional impact on energy cost and environment. Energy cost could be reduced by several means such as increasing the energy efficiency, productivity, quality of end products, etc. This article highlights that if the energy need of processes is met in electrical domain, power electronics (PE) can help optimize the energy use at multiple stages of energy delivery mechanism such as at source, during power conditioning, during its transmission to or distribution in load. Like in electric vehicle (EV), it should be utilized at the load end efficiently and environment-friendly manner. This article elaborates that the same can be achieved through use of domain specific efficient PE converters. This practical article details with three examples involving different application domains where different avenues for improvement are explored. First, the article details how a change in energy source for a process brings large benefits. In the second, it covers how PE controls the energy utilization in the load to boost the energy efficiency in the process. Thirdly, it details that proper choice of power converter for dynamic power flow control boosts energy efficiency to reduce the energy cost.

In industry, for superior utilization of large capital equipment, a single large-current high-power converter is desired to convert electrical energy to a controlled high-intensity heat source to cater to the dynamic requirement of several welding methods (e.g., welding, hard-facing, gouging, weld overlay, etc.). The dynamic process behavior of multi-input minimally semiautomatic or single-input manual processes could follow either constant voltage (CV) or constant current (CC) arc type. Due to completely different type of arc or load characteristics, this article proposes a de-coupled control approach to guide the power source to independently take care of each arc type. It proposes feedforward control for CV arc type and robust second order sliding mode control (SOSMC) approach for dynamically uncertain CC arc type for manual welding. It further highlights that low-loss resonant or soft-switching topologies are less compatible for decoupled control of high-power loads with wide range impedance characteristics. For desired energy efficiency of a full-bridge DC-DC converter for arc welding, this article details that robustness features of SOSMC could be used for superior component engineering that incur low power loss. Finally, this article completely validates the proposed idea in a 1000A power converter for both CC and CV arc types.

Volume and share of electronic retail (e-tail) business are growing rapidly and this rapid growth was accelerated further due to COVID-19. More e-tailing businesses have increased last-mile delivery operations. To handle this growth, last-mile operators are facing huge challenges due to the complexity of last-mile operations. The last-mile is not only challenging but also critical to e-tailers, customers, society, and the environment. Hence a study of the current body of knowledge on the last-mile of business-to-customer (B2C) e-tailer has become necessary for e-tailers now. This study attempts to review the research done on this important subject and find possible research opportunities that could benefit e-tailers appreciably. The study deciphers critical factors and solutions related to the last-mile. A research framework is also proposed. Practitioners may pay more attention to the implementation and adoption of alternate last-mile delivery arrangements. The challenges and effects of the last-mile offer some directions to researchers.

One large-current high-power full-bridge DC-DC converter is often used to cater several multi-characteristic welding loads. The load could be a welding arc or a conductive molten flux. The contour of operating point (voltage-current) of each load type is different. The converter often operates under complex light-load conditions. The design of such high power continuous-duty converter needs to meet three objectives – desired control performance, high across-the-load efficiency, and superior thermal management. To address the thermal issues, this article proposes to use parallel-connected converter modules. It helps distribute the power loss over larger component base; increased surface area would assist the heat removal process. For high operating efficiency, this article proposes superior component engineering in each module. And, for high across the load efficiency, this article proposes to enable or disable an efficient converter module based on the current demand. It means each converter module is equipped to feed the connected load in stand-alone mode. For reduction of power loss, this article elaborates the role of each critical component. The distribution of heat loss would be optimally shared if the current sharing by converter modules is equal, but it needs to be compatible to the dynamic behavior of multi-input process loads. This research proposes and practically validates that single PWM-controller driven parallel-connected converter-modules are not only compatible to process dynamics, the idea would achieve proper current sharing among similar components.

In medium to high-frequency power transformers, apart from minimizing the power loss in the core and copper, the design of its thermal circuit plays an important role in containing the temperature rise in different parts. It is extremely complex because there exist multiple loss centers with different heat removal characteristics. Moreover, the power loss is concentrated around a small core volume and the rest of it is available for convection and radiation. This article proposes to use a hybrid core configuration to improve the heat removal feature of the transformer. This article establishes through practical validation of suitability, i.e., the magnetic compatibility of cores in the hybrid magnetic circuit. It further explores the application prospect of the proposed concept where the thermal performances have been compared using different core types in two different application domains. In the first case, the core could always remain energized to its rated value, and in the second design, both the windings could always draw their respective rated current.

The design of medium- to high-frequency power electronics transformer aims not only to minimize the power loss in the windings and the core, but its heat removal features should also allow optimal use of both core and copper. The heat removal feature (e.g., thermal conduction) of a transformer is complex because there exist multiple loss centers. The bulk of total power loss is concentrated around a small segment of the core assembly where windings are overlaid. The primary winding is most constrained thermally. For superior use of core and copper, the temperature rise in different segments of the transformer should be well below their respective safe operating limits. In practice, cores of same soft-magnetic materials are traditionally used. To achieve superior temperature profile and for better long-term performance, this article proposes to use the mixed-core configuration. The new core(s) would replace the parent ones from the segment where windings are laid. The characteristic features of new cores would share increased burden of heat removal from the transformer. To obtain the qualitative insight of magnetic and thermal performance, the proposed mixed-core transformer would be thoroughly validated practically in two different high-power applications. In the first case, the core is always energized to its rated value, and in the second one, windings are always energized at respective rated current capacity.

Due to its non-contact mode of power transfer, the induction heating principle is favorably used in the packaging industry for sealing of wide range plastic and glass containers. In cap sealing, the power transferred to thin aluminum foil is used to create a bond between the foil and the lip of the bottle. The process ambiance for sealing bottles containing different types of products could be different. Dust prone environment prevailing for sealing coffee, nutraceuticals, several pharma products, etc. recommends the use of an air-tight enclosure. Likewise, to avoid water particles entering the enclosure during its frequent cleaning of exterior surfaces, packaging solutions for the dairy industry need water-tight enclosures. The process ambiance and nature of products are such that those power controllers would increasingly be housed in IP 65 enclosures. The air movement inside i.e., the free convection is restricted. To make the controller inherently self-cooled, this research proposes to make the internal convection effective by creating requisite buoyant force through proper choice of power converter topology where component engineering would also play important role. This article details that the choice of topology should not only reduce the power loss, it would also be useful for loss distribution. It further details that the choice of components is critical to ensure effective internal air movement for reliable operation of the controller. The proposed idea has been validated by designing a 1.5 kW, 47 kHz power controller housed in a zero ventilated enclosure that also includes the coil head.

In a full bridge DC-DC converter (FBDC) the transformer is a major component for controlled power delivery to secondary side isolated DC loads. Its excitation characteristics is nonlinear and it suffers from a serious problem called magnetic saturation. The power loss in it and also in power switching devices connected at its primary are calculated based on the assumption that the DC flux in core is considered zero. Inverter topology often influences the parametric design of transformer. This article elaborates, with detailed practical validation, that the transformer could influence on choice of suitable control function and its gain values. For that, two popular control functions i.e., proportional plus integral (PI) and second order sliding mode control (SOSMC) would be elaborated here. The approach of controller design for PI and SOSMC is different. Collective approach of gain selection in PI results conservative values of its two gains. On the other hand, two gains in SOSMC are purely based on worst-case process behavior, value of each gain is large. For compatibility study of both control functions in FBDC, nonlinear, extremely dynamic, wide range and diverse arc welding process would be considered as load. Experimental results suggests that SOSMC generates superior control performance in terms of robustness features and control response. Still, as this article further establishes with requisite practical validations, that non-linear magnetic circuit could act as a hindrance for effective utilization of capacity of FBDC based on high-gain fractional order SOSMC function.

In full-bridge dc–dc converter, the transformer is used to provide requisite voltage translation and safety isolation. For control of secondary-side variable(s) the control-actuation takes place at its primary. Converter's thermal deign presumes that the average flux in core in an integral switching-cycle is zero and the magnetizing current is negligible to ensure optimum core loss and, particularly, power loss in primary switching devices at turn- off would be optimally small. The choice of control function should not disturb this basic precondition. Though, proportional plus integral control is mostly used, complex super twisting control (STC) is being rigorously tried as an apt alternate. The selection of its two gains is based on worst-case dynamic process behavior. This article addresses that such process-behavior-based gain-selection may not work well, particularly, when the actuation is through a transformer having nonlinear excitation characteristics. Using practical approach, this article elaborates that an optimally designed transformer, driven by high-gain STC, introduces dc bias in core leading to higher switching losses, poor operating duty-cycle of the system and the worst is, it could drive the transformer to saturation inviting reliability issues. The article further details with practical results an alternate high-gain control function for a high-frequency full-bridge dc–dc converter that generates superior effectiveness.

High-power high-frequency air-cooled induction heating transformers, mostly used as current multiplier and isolation purposes, are custom designed. For their reliable performance and long life, the thermal evaluation at rated load is necessary. Creating an equivalent load as test facility for reliability testing of such type of transformer is difficult. Characteristics of such loads drastically change after Curie temperature. Moreover, prolonged heating could increase the nearby ambient temperature and, more importantly, the traditional heat run test wastes large amount of energy. Whenever the coil is energized, windings of transformer draw respective rated current; even at no load condition the copper loss is at rated value. While both windings drawing rated current at desired frequency, using the concept of localized eddy current loss as well as excess eddy current loss, this article proposes a novel method to inject requisite core loss to the magnetic circuit to emulate the characteristics of full load condition but the power drawn from the transformer would be zero. The proposed idea would be validated where only 200W resonant inverter would be used to inject power loss equivalent to full-load condition of 30 kW transformer to emulate the heat run test

Advancements of power electronic technologies result in significant improvement in efficiency of power delivery to applications that consume or feed electrical energy to a grid. A transformer is an integral part of the power delivery process. Transformers used for power delivery must be efficient, compact and of low cost, and more importantly, they should be compatible with the connected source such as a power inverter. For a desired power density, the transformer design involves optimization of its electrical and magnetic circuits permitted by the thermal limits of core and copper. The limit of the magnetic circuit is indirectly linked to the winding design. Better use of core influences the design of the electrical circuit as well. Therefore, proper choice of core material and geometry is very important design consideration. This article reviews the domain of soft magnetic materials suitable for handling large electrical power from grid frequency to high-frequency applications. The paper covers different examples and elaborates the role of a transformer for one specific application. Review of transformer design considerations used in different applications, which are categorized based on their load characteristics, is a novelty of this work.

This article presents a grid integrated single-stage solar photovoltaic system supported with a battery energy storage to charge the battery of an electric vehicle. An efficient energy management system based on the state of charge, generated SPV power, and total load demand is designed for battery energy storage. Each connected EV can choose to operate either in grid-to-vehicle or vehicle-to-grid mode without affecting the DC link voltage. Deficient power is taken from the grid and surplus SPV power is fed into the grid at unity power factor, where the grid-connected converter control plays a significant role. Sliding mode control (SMC) with an improved reaching law is implemented for DC link voltage and grid-connected converter current control. Model uncertainties and mismatched disturbances are estimated using a nonlinear disturbance observer (NDO). The NDO based SMC is compared with conventional SMC and linear PI control under various transient scenarios. The Lyapunov candidate function determines the stability of the proposed control system. The simulation results prove the robustness of NDO-SMC based control of grid-connected converter under varying irradiance and load requirements.

Optimal design of transformer for high-frequency high-power applications involves proper choice of number of primary and secondary turns of proper conductor area in windings as well as configuring those conductors to influence not only the copper loss but also the functioning of power converter. The design of magnetic circuit, however, depends on choice of cores with proper magnetic and thermal features. Traditionally, cores of same soft-magnetic materials are used. Nowadays, several types of soft magnetic materials are available possessing different magnetic, electric and thermal conduction features. For high power transformers several cores are stacked. To improve the power handling capability, this article proposes to use flux integrators of different materials to generate superior power loss and heat removal characteristics. The idea would be practically validated through design and testing of transformer for 25 kW induction heating applications.

Arc welding is an indirectly controlled process where the electrical variables of arc are controlled to create joints of requisite mechanical and metallurgical characteristics after maintaining workable environment for the welder. Constant voltage arc types are mostly used in industry because they are energy efficient, more productive and welder friendly, these processes could be easily automated. However, the nature of arc types for CV processes appears drastically different for different metal transfer modes, input conditions, and process settings. The nonlinear arc itself poses as altogether different loads to power controller. Moreover, the process consists of several dynamic activities, each having different response time, their interaction with control variables add extra burden to controller. To simplify controller design, the input conditions of the process are defined in such a way that minimally defined two-input process could be controlled by controlling two independent dynamic activities. To meet that purpose with increased robustness this article proposes to use two independent easily implementable yet superior SOSM controllers—one for control of arc and another for control of wire feed speed. Robust control of wire feeding would reduce disturbance burden on the arc controller. The approach would be experimentally validated by practically designing both controllers along with creating requisite joints for wide range use suitable for ready-to-use in industrial applications.

In induction heating applications, active and passive power components play important roles for proper functioning of the power controllers. For suitability study, the characterization of active power components is well defined and documented. Characterization of capacitors is also well defined. They are commercially available as well. High-frequency power magnetic components, such as transformers and inductors, are not readily available. For better power density and reliable operation of controllers, their qualitative evaluation is necessary. The parametric set to define the suitability of finished high-frequency magnetic components is large and wide, have multiple and complex heat sources. For input materials, multiple choices are available. Two main ingredients in high-frequency magnetic components are the magnetic core and litz-wire conductor. This article, using inherent features of ZVZCS SRI topology, explores practical methods to validate the optimal design of the high-frequency power transformer for induction heating applications. The method is able to evaluate the usable current density of the litz wire conductors as well as the upper limit of usable flux density of nanocrystalline cores.

GMAW is multi-input indirectly controlled process where electrical variables of arc are controlled to create joints of requisite mechanical and metallurgical features. In popular short-circuit mode of droplet transfer, joint quality, weld spatters, fumes and arc radiation are of concern. They also affect productivity, environment around welder, etc. In depth research on these issues resulted in sharp improvement on qualitative aspects of welding, by adopting a novel droplet transfer mechanism where there is paradigm shift of executing the transfer process. It moves from explosive electromagnetic force driven to surface tension transfer approach. This article discovers that these innovative control solutions possess features that have close resemblance of perfect demonstrations on utility of event triggered control approach in complex practical domain. The triggering mechanism for control actuation is reactive. Introduction of more events has helped improve on clarity in process behavior. The control actions are more definite and adverse contributions of disturbances like weld pool oscillations are avoided. And, now, the control of multi-event process is managed by single input i.e. the welding current. This article details that SOSM controller would be apt for fast reactive control actions. It also outlines a basic design approach for event-triggered SOSM controller along with a few experimental results.

Arc welding process involves high-intensity moving energy source in the form of electric arc. For creating joint, the heat source moves along the line of joint being created on the workpiece. Control of automatic (zero human assistance) or semi-automatic (manual movement of heat source) arc welding processes could require not only feeding of electrode material at constant rate but also the movement of electrode tip, often, more controlled motions. Due to superior control and actuation features the axial field pancake PMDC motors are more suitable. Due to their small value of armature time constant, when driven by PWM controller at moderate frequency, the armature current tends to be discontinuous. It allows the back-EMF be sampled for speed feedback and with proper power converter configuration and control the power factor could as well be improved. This article proposes a design of single-stage power controller for controlled and accurate movements of electrode tip sensorless and achieves multiple features such as improved power factor, reduced stress on components, reduced component count, high reliability, reduced current surge at start, longer life of magnets. It also details practical implementation of the idea and demonstrates the advantages claimed.

High power transformers used in induction heating are traditionally conduction-cooled, they are poorly coupled and efficiency is not great. Unlike other power electronics applications, in induction heating, the electrical circuits of transformer are always loaded with rated current, the magnetic circuit is loaded when heating of job taking place. Copper loss is always at peak and core loss is load dependent. There is hardly any work reported on optimizing such critical component. For its optimization, there needs to be a paradigm shift in design approach. The article proposes that the starting point of design is to optimize its energy efficiency by minimizing its no-load loss i.e. the total copper loss and make it air-cooled. For constant current windings it is natural to minimize the length of litz-wire conductors used, it puts constraints on magnetic circuit where the core is forced to operate at high flux density. The transformer would be inherently compact. For such configuration the core material plays an important role. For choice of suitable core to reliably operate at large flux density, this article comparatively studies different soft magnetic materials for practical design of extremely efficient (99.78%) transformer for induction heating.