The principles of electromagnetic induction are applied in many devices and systems, including induction cookers, transformers and wireless energy transfer;however, few data are available on resonance in the electromo...The principles of electromagnetic induction are applied in many devices and systems, including induction cookers, transformers and wireless energy transfer;however, few data are available on resonance in the electromotive force (EMF) of electromagnetic induction. We studied electromagnetic induction between two circular coils of wire: one is the source coil and the other is the pickup (or induction) coil. The measured EMF versus frequency graphs reveals the existence of a resonance/anti-resonance in the EMF of electromagnetic induction through free space. We found that it is possible to control the system’s resonance and anti-resonance frequencies. In some devices, a desired resonance or antiresonance frequency is achieved by varying the size of the resonator. Here, by contrast, our experimental results show that the system’s resonance and anti-resonance frequencies can be adjusted by varying the distance between the two coils or the number of turns of the induction coil.展开更多
We derive a general form of the induced electromotive force due to a time-varying magnetic field. It is shown that the integral form of Faraday's law of induction is more conveniently written in the covering space...We derive a general form of the induced electromotive force due to a time-varying magnetic field. It is shown that the integral form of Faraday's law of induction is more conveniently written in the covering space. Thus the differential form is shown to relate the induced electric field in the nth winding number to the (n+1)th time-derivative of the magnetic field.展开更多
In order to survive in this modern world, electricity is an essential thing. Electricity allows us to power the technology we use every day. Without electricity, people can’t imagine their lives. As a developing coun...In order to survive in this modern world, electricity is an essential thing. Electricity allows us to power the technology we use every day. Without electricity, people can’t imagine their lives. As a developing country, Bangladesh still lacks electricity every day. The electricity supply to the rural areas is very poor. It is known that energy can be converted from one form to another form. As noise is </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> energy, it can also be converted into various forms of energy. Noise can be represented as a sound </span><span style="font-family:Verdana;">that</span><span style="font-family:Verdana;"> is loud or unpleasant and causes disturbances such as street traffic sounds, construction sounds, airports</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> etc. Using a suitable transducer, noise (sound) energy can be transferred into a viable source of electricity generation. This can be accomplished by employing a transducer and converting noise-induced vibrations into electrical energy. Our main goal is getting enough energy, reducing the pressure of the main grid of electricity and decreasing fossil fuel imports. This paper presents the design and investigation of an energy harvesting system from noise. In this paper, an application is designed to get energy from noise by using a speaker as a transducer. Voltage has been stepped up by using a transformer, a diode which gives DC value which can be tapped into a battery and provide energy from the battery when it is needed. The embedded device was initially tested by clapping hands and tested further by using car horns. The vibrations created by car horns and other noises have been converted into electrical energy through the principle of electromagnetic induction. In total, the application produced optimal results of 0.5</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:Verdana;">1.0 volts which were stepped up using a transformer while maintaining the whole system being low cost and user-friendly.展开更多
针对电磁发射领域短初级直线感应电机(short primary linear induction motor,SPLIM)的纵向端部效应引起的感应电势不对称现象,首先基于一维场理论分别对正序和负序电流激励条件下的SPLIM气隙电磁场进行推导及计算分析,得到气隙电磁场...针对电磁发射领域短初级直线感应电机(short primary linear induction motor,SPLIM)的纵向端部效应引起的感应电势不对称现象,首先基于一维场理论分别对正序和负序电流激励条件下的SPLIM气隙电磁场进行推导及计算分析,得到气隙电磁场解析表达式,并将其计算与有限元计算值比较,结果表明,解析计算值与有限元结果精度相当。然后给出基于气隙磁密和绕组分布函数的感应电势计算方法,同时给出对称电压激励条件下初级绕组感应电势的计算流程,并通过有限元和试验进行验证。在以上分析基础上,将气隙磁密分解为基本行波磁密、入端正向行波磁密、出端反向行波磁密3部分,深入分析感应电势不对称机理以及感应电势不对称随系统设计变量变化规律。提出的基于磁密分解和绕组函数计算感应电势的方法,可为此类电机的设计、分析、控制提供一种新的思路。展开更多
For doubly-fed induction generator(DFIG)-based wind turbines(WTs),various advanced control schemes have been proposed to achieve the low voltage ride through(LVRT)capability,whose parameters design is significantly re...For doubly-fed induction generator(DFIG)-based wind turbines(WTs),various advanced control schemes have been proposed to achieve the low voltage ride through(LVRT)capability,whose parameters design is significantly reliant on the rotor electromotive force(EMF)of DFIG-based WTs.However,the influence of the rotor current on EMF is usually ignored in existing studies,which cannot fully reflect the transient characteristics of EMF.To tackle with this issue,this study presents a comprehensive and quantitative analysis of EMF during grid faults considering various control modes.First,the DFIG model under grid faults is established.Subsequently,the transient characteristics of EMF are analyzed under different control modes(that is,rotor open-circuit and connected to converter).Furthermore,the EMF transient eigenvolumes(that is,accessorial resistance item,transient decay time constant,and frequency offset)are quantitatively analyzed with the typical parameters of MW-level DFIG-based WT.The analysis results contribute to the design of the LVRT control scheme.Finally,the analysis is validated by the hardware-in-the-loop experiments.展开更多
文摘The principles of electromagnetic induction are applied in many devices and systems, including induction cookers, transformers and wireless energy transfer;however, few data are available on resonance in the electromotive force (EMF) of electromagnetic induction. We studied electromagnetic induction between two circular coils of wire: one is the source coil and the other is the pickup (or induction) coil. The measured EMF versus frequency graphs reveals the existence of a resonance/anti-resonance in the EMF of electromagnetic induction through free space. We found that it is possible to control the system’s resonance and anti-resonance frequencies. In some devices, a desired resonance or antiresonance frequency is achieved by varying the size of the resonator. Here, by contrast, our experimental results show that the system’s resonance and anti-resonance frequencies can be adjusted by varying the distance between the two coils or the number of turns of the induction coil.
文摘We derive a general form of the induced electromotive force due to a time-varying magnetic field. It is shown that the integral form of Faraday's law of induction is more conveniently written in the covering space. Thus the differential form is shown to relate the induced electric field in the nth winding number to the (n+1)th time-derivative of the magnetic field.
文摘In order to survive in this modern world, electricity is an essential thing. Electricity allows us to power the technology we use every day. Without electricity, people can’t imagine their lives. As a developing country, Bangladesh still lacks electricity every day. The electricity supply to the rural areas is very poor. It is known that energy can be converted from one form to another form. As noise is </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> energy, it can also be converted into various forms of energy. Noise can be represented as a sound </span><span style="font-family:Verdana;">that</span><span style="font-family:Verdana;"> is loud or unpleasant and causes disturbances such as street traffic sounds, construction sounds, airports</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> etc. Using a suitable transducer, noise (sound) energy can be transferred into a viable source of electricity generation. This can be accomplished by employing a transducer and converting noise-induced vibrations into electrical energy. Our main goal is getting enough energy, reducing the pressure of the main grid of electricity and decreasing fossil fuel imports. This paper presents the design and investigation of an energy harvesting system from noise. In this paper, an application is designed to get energy from noise by using a speaker as a transducer. Voltage has been stepped up by using a transformer, a diode which gives DC value which can be tapped into a battery and provide energy from the battery when it is needed. The embedded device was initially tested by clapping hands and tested further by using car horns. The vibrations created by car horns and other noises have been converted into electrical energy through the principle of electromagnetic induction. In total, the application produced optimal results of 0.5</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:Verdana;">1.0 volts which were stepped up using a transformer while maintaining the whole system being low cost and user-friendly.
文摘针对电磁发射领域短初级直线感应电机(short primary linear induction motor,SPLIM)的纵向端部效应引起的感应电势不对称现象,首先基于一维场理论分别对正序和负序电流激励条件下的SPLIM气隙电磁场进行推导及计算分析,得到气隙电磁场解析表达式,并将其计算与有限元计算值比较,结果表明,解析计算值与有限元结果精度相当。然后给出基于气隙磁密和绕组分布函数的感应电势计算方法,同时给出对称电压激励条件下初级绕组感应电势的计算流程,并通过有限元和试验进行验证。在以上分析基础上,将气隙磁密分解为基本行波磁密、入端正向行波磁密、出端反向行波磁密3部分,深入分析感应电势不对称机理以及感应电势不对称随系统设计变量变化规律。提出的基于磁密分解和绕组函数计算感应电势的方法,可为此类电机的设计、分析、控制提供一种新的思路。
基金Supported in part by the National Natural Science Foundation of China under Grant 51907072in part by the Fundamental Research Funds for the Central Universities under Grant 2021XXJS004。
文摘For doubly-fed induction generator(DFIG)-based wind turbines(WTs),various advanced control schemes have been proposed to achieve the low voltage ride through(LVRT)capability,whose parameters design is significantly reliant on the rotor electromotive force(EMF)of DFIG-based WTs.However,the influence of the rotor current on EMF is usually ignored in existing studies,which cannot fully reflect the transient characteristics of EMF.To tackle with this issue,this study presents a comprehensive and quantitative analysis of EMF during grid faults considering various control modes.First,the DFIG model under grid faults is established.Subsequently,the transient characteristics of EMF are analyzed under different control modes(that is,rotor open-circuit and connected to converter).Furthermore,the EMF transient eigenvolumes(that is,accessorial resistance item,transient decay time constant,and frequency offset)are quantitatively analyzed with the typical parameters of MW-level DFIG-based WT.The analysis results contribute to the design of the LVRT control scheme.Finally,the analysis is validated by the hardware-in-the-loop experiments.