Induction Heating Cooker Research Articles

A Cohort Study on the Use of Commercial Induction Heating Cookers by Pregnant Women and the Birth Weight of Their Infants

A Cohort Study on the Use of Commercial Induction Heating Cookers by Pregnant Women and the Birth Weight of Their Infants

Study of half‐bridge series‐resonant induction cooker powered by line rectified DC with less filtering

AbstractThis paper presents an analysis and design strategy for a half‐bridge series resonant induction heating (HB SR‐IH) cooker powered by a rectified sinusoidal DC. The simplified equivalent circuit of an induction cooker is modelled by a train of rectified sinusoidal DC pulses chopped at the switching frequency. An average root‐mean‐square (RMS) method is proposed to calculate the RMS resonant voltage and current extrapolated to the power line frequency period. The stability of the cooker is achieved by properly setting the damping ratio in the root‐locus plane to keep the system running quasi‐resonantly at the required power. The power control of the SR HB‐IH cooktop is performed by forced commutation above the resonance frequency. A prototype of a 3 kW HB SR‐IH cooker was designed and implemented to validate the estimated results. Various waveforms from low power to high power are discussed and verified by damping ratio control. The SR HB‐IH cooktop achieves a high‐power factor of 0.95 to 0.995 when generating 300W to 3kW due to less filtered DC power. The power quality assessment showed that the total harmonic distortion (THD) of the line current and voltage measured at 3 kW was 4.1% and 3.5%, respectively.

Association Between the Use of Induction Heating Cookers and Delivery Outcomes in Pregnant Women: An Internet-Based Cohort Study.

The number of devices that generate intermediate-frequency electromagnetic fields (IF-EMFs) in the living environment has been increasing. As the public has vague concerns about new devices, it is necessary to clarify the safety of IF-EMFs. Therefore, the present study aimed to examine the possible health effects of IF-EMFs by clarifying the relationship between the use of induction heating (IH) cookers and delivery outcomes. The study participants were pregnant women over the age of 20 years who were registered in panels with an Internet research firm. A total of 8920 pregnant women participated in the baseline survey. Of those who responded to the follow-up survey, 5022 who had a singleton birth were included in the analysis. We then examined the relationship between the use of IH cookers and gestational week at delivery (<37th/⩾37th week) or birth weight (<2500/⩾2500 g) using logistic regression models. No association was found between the use of IH cookers and birth weight, but weak associations were found between the use of stationary- and tabletop-type IH cookers and gestational week at delivery. After all considerations, we determined that the observed increased odds ratio did not indicate an increased risk of premature birth.

Corner coil heating mode improves the matrix uniformity of cooked rice in an induction heating cooker.

Nowadays, an increasing number of people worldwide use induction heating cookers to cook rice for consumption. This work reveals the influence of induction heating cooker heating modes on the quality attributes of cooked rice. Three heating modes, including bottom coil heating mode (mode 1), corner coil heating mode (mode 2), and side coil heating (mode 3), were used. Among the three modes, mode 2 allowed for an intermediate heating rate during rice cooking. For mode 2, the minimized temperature difference between the upper layer (including the central upper layer and peripheral upper layer) and the lower layer (including the central lower layer and peripheral lower layer) can reduce the effect of water absorption time difference on rice quality. Consequently, the rice cooked using mode 2 exhibited improved matrix uniformity, as indicated by the similar moisture content (59.92-61.89%), hardness (15.87-18.24 N), and water mobility (the relaxation time and peak area of the third relaxation peak) of rice samples at four different positions in the pot. The rice cooked by mode 2 showed better texture appearance and a more uniform porous microstructure. Consistently, the cooked rice samples by mode 2 at different positions did not show substantial differences in their starch digestion features.

Load Estimation for Induction Heating Cookers Based on Series RLC Natural Resonant Current

In domestic induction heating applications, cookware can be considered an equivalent load in a series resistor–inductor–capacitor resonant converter. Therefore, the electrical parameters of an equivalent circuit change according to the cookware material, size and the cookware position on the heating coil. This study proposes an online estimation method for detecting the cookware status, determining the material and estimating the equivalent heating resistance of cookware on an induction heating cooker (IHC) for power control. The proposed method could turn off the circuit in abnormal situations such as low equivalent heating coverage rate or non-ferromagnetic cookware and adjust the power in normal situations. In the method, a half-bridge series resonant converter (HBSRC) generates two test patterns with three resonant voltage pulses to detect cookware every 10 ms, only the current feedback information is needed to avoid the calculation loads and times necessary for complex signal operations in software. To verify the proposed method, a digital signal processor based HBSRC with 1000 W was constructed. The maximum errors between the estimated and measured resistance and inductance were 7.14% and 2.91%, respectively. Moreover, power control in emulated user operation reveal that the proposed method and control system can effectively estimate load online to detect cookware status and determine whether to turn off or vary the heating power for an IHC.

Introduction of Induction Heating is too late for older residents with difficulty in handling fire.

ABSTRACT.Handling errors with household flammables, for example pan burning, may result in serious accidents, which may be caused by decreased attention or executive function.Objective:The manuals by several cities simply suggest the use of induction heating (IH) cookers. However, it requires complicated operation of buttons. Furthermore, no previous studies have examined the difficulty of IH operation in older adults.Methods:We examined 166 residents aged 75+ years in Wakuya, consisting 66 Clinical Dementia Rating (CDR) 0 (healthy), 79 CDR 0.5 (very mild dementia), and 21 CDR 1+ (dementia) participants. Based on fire accident, they were classified into “high-risk,” “low-risk,” and “safety” groups. They were asked to actually use an IH as an examination. The participants who passed all procedures were classified as “good users,” and the remaining who failed were classified as “poor users.” Their overall cognitive and executive functions were assessed using the Mini-Mental State Examination (MMSE) and Trail Making Test A and Digit Symbol (DS), respectively.Results:The proportions of “good users” in the CDR 0, CDR 0.5, and CDR 1+ groups were 7 (10.6%), 6 (7.3%), and 0 (0%), respectively. For the CDR 0 and CDR 0.5 group, the good users had higher scores on the MMSE and DS than do the poor users.Conclusions:The introduction of IH is too late for “high-risk group.” Since the IH cooker requires complicated operation of buttons, they may be difficult for older residents to handle. Executive function may be examined for early detection of handling errors with household flammables.

Maternal Use of Induction Heating Cookers During Pregnancy and Birth Outcomes: The Kyushu Okinawa Maternal and Child Health Study.

The effects of exposure to intermediate-frequency electromagnetic fields (IF-EMFs) during pregnancy on birth outcomes are uncertain. We investigated the association between the use of induction heating (IH) cookers, which are major sources of IF-EMFs, during pregnancy and preterm birth (PTB), low birth weight (LBW), small-for-gestational-age (SGA), and birth weight, using data from a prebirth cohort study in Japan. Study participants were 1,565 mothers with singleton pregnancies and the babies born from these pregnancies. We collected the data presented here using self-administered questionnaires. An adjustment was made for maternal age, region of residence, number of children, family structure, maternal education, maternal employment, maternal alcohol intake, smoking during pregnancy, maternal body mass index, baby's sex, and gestational age at birth. IH cooker use during pregnancy was independently associated with a reduced risk of PTB: the adjusted odds ratiowas 0.28 (95% confidence interval: 0.07-0.78). IH cooker use during pregnancy was not associated with LBW, SGA, or birth weight. This is the first study to show that IH cooker use during pregnancy is independently inversely associated with PTB.

Multiphase PFC Rectifier and Modulation Strategies for Domestic Induction Heating Applications

Domestic induction heating appliances have improved the final user experience due to the advantages that this technology offers, such as flexibility, fast heating, cleanness, and safety. Currently, these appliances are implemented using several isolated electronic boards to be able to be powered from one or several mains phases, enabling their use in regions with different connections. In order to enhance this approach, a multiphase power factor correction rectifier is proposed in this article, improving significantly induction heating cookers. The topology is described, and a wide variety of modulation strategies are presented and analyzed, discussing their main advantages and disadvantages according to the conduction mode, operating frequency, switching mode, and control strategy. In order to validate this proposal, an 11 kW and up-to three-phase high power-density converter for domestic induction heating applications is implemented and experimentally analyzed, including its main waveforms and efficiency. Finally, a comparative evaluation is performed to enable the selection of the optimum modulation strategy for each specific application.

Ecological study on the penetration of induction heating cookers and birth outcomes in Japan.

In recent years, equipment that generates intermediate-frequency electromagnetic fields (IF-EMFs) has become increasingly prevalent, and the influence of IF-EMFs on human health is thus attracting increasing attention. The present study was conducted with the aim of analyzing whether there is a relationship between the penetration of induction heating cookers and birth outcomes using an ecological study design at the prefectural level. We created data sets for all 47 prefectures in Japan using previously published statistics. Spontaneous fetal death rate, fetal death rate after 22 weeks of pregnancy, perinatal mortality rate, and proportion of newborns weighing less than 2500 g were used as birth outcomes in correlation analysis. A weak positive association was observed between the penetration of induction heating cookers and the fetal death rate after the 22nd week of pregnancy (r = 0.27, p = 0.07), but it was not statistically significant. In addition, a weak negative association was observed between the penetration of induction heating cookers and the spontaneous fetal death rate (r = −0.27, p = 0.07), but it was not statistically significant. In the present ecological study, no statistically significant association were shown between the penetration of induction heating cookers and birth outcomes. To demonstrate further the safety of induction heating cooker use, observations in epidemiological studies of other designs should be considered.

Spatial-temporal growth model to estimate the adoption of new end-use electric technologies encouraged by energy-efficiency programs

Domestic energy policies destined to foster the use of end-use electric technologies could cause rapid penetration of new residential loads and, consequently, this could cause a significant increase in the demand for electricity in urban areas. This paper presents a spatial-temporal growth model for estimating the adoption of new end-use electric technologies encouraged by energy-efficiency policies. The proposed method consists of three modules: temporal, spatial and grouping. The temporal module calculates by districts or census tracts of a city, the percentage of homes in which residents are prospective buyers of a new end-use electric technology. Then, the spatial module adjusts the calculations made by the temporal module, considering the spatial interactions among the inhabitants of the districts. Finally, the grouping module discovers the low-voltage transformer where the prospective buyers are connected. The results of the proposed model are a spatial database with information related to the percentage of homes in which residents are prospective buyers of a new end-use electric technology, as well as the number of prospective buyers connected to each low-voltage transformer. The results can visualize through thematic maps to identify the districts where the new technology will have faster adoption. The proposed method was employed to estimate the adoption of induction heating cookers in a medium-sized Ecuadorian city. The Ecuadorian government has developed a program of economic subsidies to encourage its population to use this electrical appliance. The results from this application are an important tool to estimate the spatial increase in electricity demand, decide important issues related to the planning of distributed resources, and develop demand-side management programs. Furthermore, the results can be used to evaluate and manage energy policies formulated to achieve environmental and energy goals.

재질 혼합사용 및 턴 수를 고려한 유도가열 밥솥 설계의 필요성

전기를 이용한 가열 방식 중에 유도가열 방식은 다른 가열 방식에 비해 빠른 시간에 높은 효율로 원하는 온도를 얻을 수 있는 방식으로 수 십년 동안 산업 분야, 의료 분야 등에 사용되고 있다. 따라서 성능을 예측할 수 있도록 멀티 코일을 가진 유도가열 열해석이 필요하다. 단순한 형태의 코일이나 피가열체가 아닌 복잡한 형태의 유도 가열 밥솥에 대해 유한요소 해석법을 이용하여 열해석을 수행 하였다. 또한 열해석의 정확성을 입증하기 위해 기존모델에 대한 해석을 진행하여, 해석값과 실험값을 비교 하였고, 열해석 방법이 정확성을 확인하였다. 이 후, 피가열체의 재질 두께 변화와 멀티코일의 턴수 변화에 따른 온도변화를 통해 유도가열 밥솥 설계시 재질 혼용 사용 과 턴 수 최적화의 필요성을 확인하였다.

Urban photovoltaic potential estimation based on architectural conditions, production-demand matching, storage and the incorporation of new eco-efficient loads

The photovoltaic solar potential in an urban sector and the effects produced by the electricity input into a low-voltage grid are determined, the analysis is performed for one year. First, the generation profiles are estimated, assuming the incorporation limits of typical silica panels and using photovoltaic (PV) tiles on roofs as an architectural alternative. Then, the consumer class demand is estimated. Production-demand matching is performed at the load point level to avoid impacts on the grid. A scenario incorporating a new load, induction heating cookers (IHCs) for all residential users, is posed, the use of which coincides with high-radiation hours. Finally, electrical storage is assumed to maximise the PV supply. A 16% coverage with silica PV panels, or 33% with PV tiles, would supply 46% or 39% of the consumption, respectively. With massive incorporation of IHCs and storage, the supply is increased to 73% and 59% of the consumption with silica panels and PV tiles, respectively. An annual consumption reduction of 16 Tn of liquefied petroleum gas is attained in the cases studied. Additionally, it is necessary to redirect the current subsidies for hydro dams and the overall energy sector towards promoting distributed microgeneration.

Improvement of Block IC Preconditioner Using Fill-In Technique for Linear Systems Derived From Finite-Element Method Including Thin Elements

The block incomplete-Cholesky (IC) preconditioner is often used for parallel preconditioner in finite-element method (FEM) supported by distributed computing. When many thin elements are included in an analyzed mesh such as magnetic shielding, the convergence characteristic of preconditioned conjugate gradient method would be deteriorated. At that time, IC preconditioner with fill-in makes the convergence characteristic of linear solver much better. This paper demonstrates the validity of block IC with fill-in on linear systems arising in FEM with many flat elements. First, the ability to improve the convergence property using the fill-in strategy is verified by the simulation of magnetic shielding. Next, the parallelization performance of block IC with fill-in is illustrated by using finite-element mesh of laminated core model and induction heating cooker.

Behavioural phenotypes in mice after prenatal and early postnatal exposure to intermediate frequency magnetic fields

Electromagnetic fields are ubiquitous in the environment. Human exposure to intermediate frequency (IF) fields is increasing due to applications like electronic article surveillance systems, wireless power transfer, and induction heating cooking hobs. However, there are limited data on possible health effects of exposure to IF magnetic fields (MF). In the present study, we set out to assess cognitive and behavioural effects of IF MF in mice exposed during prenatal and early postnatal periods. Pregnant female mice were exposed continuously to 7.5kHz MFs at 12 and 120μT, from mating until weaning of pups. Sham exposed pregnant mice were used as a control group. A behavioural teratology study was conducted on the male offspring at two months of age to detect possible effects on the developing nervous system. Body weight development did not differ between the exposure groups. The exposure did not alter spontaneous motor activity when exploring a novel cage or anxiety in novelty-suppressed feeding or marble burying tests. Improved performance in the Rotarod task was observed in the 12µT group, while the 120μT exposure group swam more slowly than the sham exposed group in the Morris swim navigation task. However, indices of learning and memory (path length and escape latency during task acquisition and search bias during the probe test) did not differ between the exposure groups. Furthermore, the passive avoidance task did not indicate any impairment of long-term memory over a 48h interval in the exposed groups. In a post-mortem histopathological analysis, there was no evidence for an effect of IF MF exposure on astroglial reactivity or hippocampal neurogenesis. The results suggest that the IF MF used did not have detrimental effects on spatial learning and memory or histological markers of tissue reaction. The two statistically significant findings that were observed (improved performance in the Rotarod task in the 12µT group and decreased swimming speed in the 120µT group) are likely to be chance findings, as they do not form an internally consistent, dose-dependent pattern indicative of specific developmental effects.

Behavioral testing of mice exposed to intermediate frequency magnetic fields indicates mild memory impairment.

Human exposure to intermediate frequency magnetic fields (MF) is increasing due to applications like electronic article surveillance systems and induction heating cooking hobs. However, limited data is available on their possible health effects. The present study assessed behavioral and histopathological consequences of exposing mice to 7.5 kHz MF at 12 or 120 μT for 5 weeks. No effects were observed on body weight, spontaneous activity, motor coordination, level of anxiety or aggression. In the Morris swim task, mice in the 120 μT group showed less steep learning curve than the other groups, but did not differ from controls in their search bias in the probe test. The passive avoidance task indicated a clear impairment of memory over 48 h in the 120 μT group. No effects on astroglial activation or neurogenesis were observed in the hippocampus. The mRNA expression of brain-derived neurotrophic factor did not change but expression of the proinflammatory cytokine tumor necrosis factor alpha mRNA was significantly increased in the 120 μT group. These findings suggest that 7.5 kHz MF exposure may lead to mild learning and memory impairment, possibly through an inflammatory reaction in the hippocampus.

OLDER RESIDENTS CANNOT OPERATE WELL THE INDUCTION HEATING (IH) COOKERS DUE TO EXECUTIVE DYSFUNCTION: THE WAKUYA PROJECT

Handling errors with household flammables, such as pan burning, may result in serious accidents. The accidents were caused by a decrease in attention or executive function. The manual for the elderly with dementia of several cities simply suggests the use of Induction Heating (IH) cookers in cases of increased risk of fire. However, the IH cooker contains the complicated button operation and thus may be difficult for older residents to handle. We examined 105 residents aged 65 years or older in Wakuya, northern Japan, consisted of 57 Clinical Dementia Rating (CDR) 0 (healthy), 41 CDR 0.5 (very mild dementia), and 7 CDR 1+ (dementia) participants. The use rate of IH (Induction Heating) appliance was 29% in the CDR 0 group and 24 % of the CDR 0.5 group. We asked the participants to actually use the IH cooker. Using or without the manual of the cooker, the participants who passed all the procedures were classified as “Good Users,” whereas those failed any procedures were classified as “Poor Users.” Their global cognitive and executive functions were assessed using the Mini-Mental State Examination (MMSE), and Trail Making Test A (TMT-A) and Digit Symbol (DS), respectively. The ratio of “Good Users” in the CDR 0, CDR 0.5, and CDR 1+ groups were 23 (40.4%), 7 (17.1%), and 0 (0%), respectively. For the CDR 0 group, the Good Users had higher scores on the MMSE, TMT-A, and DS compared to the Poor Users (p<0.05). As for the CDR 0.5 group, the Good Users showed higher scores on the DS (p<0.05) compared to the Poor Users. Since the IH cooker contains the complicated button operation, they may be difficult for older residents to handle. Executive function may be more likely to be involved in handling errors with household flammables.

Resonant voltage limiting technique of single‐ended resonant inverter for induction heating

Single-ended resonant inverter topology is widely used in domestic induction heating (IH) application due to its concise structure and cost effectiveness. Whereas high resonant voltage caused by the energy transfer between load inductor and resonant capacitor in the IH system may negatively affect the operation of system and long-term reliability. Generally, 1200 V rating IGBT is popularly used for single-ended IH cookers. However, abnormal conditions of AC supply suddenly increases the resonant voltage thereby IGBT can be destructed. Resonant voltage limiting technology is proposed by restricting the maximum current flow to the load inductor in order to relieve the voltage stress across the IGBT. The effectiveness of the proposed method is verified for AC supply distortion by using 1.35 kW single-ended IH system.

Effects of intermediate frequency magnetic fields on male fertility indicators in mice

Human exposure to intermediate frequency (IF) fields is increasing due to new applications such as electronic article surveillance systems, wireless power transfer and induction heating cookers. However, limited data is available on effects of IF magnetic fields (MF) on male fertility function. This study was conducted to assess possible effects on fertility indicators from exposure to IF MF. Male C57BL/6J mice were exposed continuously for 5 weeks to 7.5kHz MF at 12 and 120μT. Sperm cells from cauda epididymis were analysed for motility, total sperm counts, and head abnormalities. Motile sperm cells were classified as progressive or non-progressive. Testicular spermatid heads were counted as well. The body weight development and reproductive tissue weights were not affected. No exposure-related differences were observed in sperm counts or sperm head abnormalities. Proportion of non-motile cells was significantly decreased in the 120µT group, and a corresponding increase was seen in the percentage of motile cells (significant in non-progressive motile cells). In conclusion, no adverse effects on fertility indicators were observed. Increased sperm motility is an interesting finding that needs to be confirmed in further studies.

Analysis and Optimal Design of Induction Heating Cookers

This paper deals with the optimal design of induction heating cooker starting from the analytical analysis of the cooker model. The analytical analysis method is based on the construction of the equivalent circuit of the cooker in which the circuit parameters are calculated from the geometries in a very simple way. By using the analysis method of equivalent circuit, the numerous combinations of primary winding coils for the specific rated power are obtained in fast computation time for a given secondary conductor. Through the calculation procedures, the optimal number of turns and their optimal positions can be obtained with which the cooker provides the highest efficiency at the rated power. The effectiveness and accuracy of the proposed analysis and design are verified through finite element analysis for practical and designed models.

Safety Assessment of Human Exposure to Intermediate Frequency Electromagnetic Fields

SUMMARYThe “intermediate frequency” electromagnetic fields in the context of protecting human exposure have received public concerns in recent years. This is mainly due to the growing emergence of technology or products using those fields, such as induction heating (IH) cookers and wireless power transfer (WPT) systems. This paper reviews the trend of studies and guidelines for human protection related to safety assessment of human exposure to such fields.