Electrodynamic forces in induction heating of bimetallic plates with planar circular coils

Contents The paper deals with the calculation of the electrodynamic forces acting on a planar circular coil placed over a bimetallic plate.The analysis is carried out with reference to the induction heating of plates of magnetic and non-magnetic materials.

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Elektrodynamische Kräfte bei Induktionsheizung einer Bimetallplatte durch ebene kreisförmige Spule

Übersicht Die vorliegende Arbeit beschreibt die Berechnung der elektrodynamischen Kräfte zwischen einer Bimetallplatte und einer darüber befindlichen ebenen kreisförmigen Spule.Die Analyse ist mit Bezug auf die Induktionsheizung der magnetischen und nicht magnetischen Platten durchgeführt.

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Symbols J ₀,J ₁ Zero and first order Bessel functions of the first kind - H ₀,H ₁ Zero and first order Struve functions - Legendre gamma function - r, ,z cylindrical coordinates - R _i ,R _e inner and outer radii of the inductor coil - h distance between the inductor coil and the surface of the metal plate - s _i thickness of the i-th layer of the plate - =2f angular frequency - ₀ permeability of free space - _i , _i resistivity and relative permeability of the material of the i-th layer of the plate - penetration depth of the induced currents in the i-th layer - N number of turns of the inductor coil - sinusoidal current in the inductor - magnetic potential vector - magnetic flux density - F _z time average value of the force acting on the coil - P _z (r,h) time average value of the pressure acting on the coil at radiusr. Work supported by the C.N.R. (National Research Council)     

Analytical calculation of circular diagram of large induction motor

The analytical calculation of a circular diagram of a large induction motor carried out based on load testing at undervoltage requires no graphic constructions and permits one to calculate the operating performances and maximal torque with acceptable accuracy.     

无线充电系统实际Litz线绕平面线圈高频电阻分析与计算

线圈高频电阻的计算对无线充电系统线圈的优化设计至关重要.实际工程一般采用Litz线来绕制线圈以减小趋肤和邻近损耗,但由于扭绞工艺的影响,实际Litz线的电阻值介于理想Litz线和平行束导线之间.本文首先详细分析Litz线电阻的组成与影响因素;其次,提出采用理想Litz线和平行束导线的电阻来拟合实际Litz线电阻的计算方...     

感应加热电源锁相电路分析与设计

感应加热电源在工作中由于负载谐振频率的波动,要求逆变器触发频率能同步负载谐振频率的变化,即要求锁相频率范围覆盖负载谐振频率波动的范围。分析了感应加热电源的锁相工作原理,给出了CD4046芯片为核心的锁相电路和频率参数计算。企业生产实践证明该锁相电路工作可靠,锁相频率范围较宽,能满足加热不同规格产品的需要。     

A three-dimensional temperature field calculation for a transformer-type heating element

A mathematical model for calculating the temperature field of a transformer-type heating element with a spatial pole core using the finite element method is described. A computer simulation program of the three-dimensional temperature field is developed, and calculation results for a transformer of 25-kW capacity are given.     

感应加热电源频率跟踪控制的研究

为减小逆变器功率器件的开关损耗,提高装置输出效率,应该控制逆变器的工作频率实时跟踪负载谐振频率,确保开关器件工作在零电压零电流开关(ZVZCS)状态。介绍了在感应加热电源中采用TMS320F2812实现超音频频率跟踪的数字锁相环(DPLL)方法,给出了实现DPLL的算法。并对基于该芯片的DPLL频率跟踪控制的原理进行了分析。最后给出了相应的仿真波形和感应加热电源样机的实验波形,验证了该方法的正确性。     

Application of the evolution strategy to optimize multistep field plates for high voltage planar pn-junctions

Contents The blocking capability of a high voltage planar pn-junction, equipped with a five-stepped field plate and a channelstopper is optimized. The breakdown voltage of the optimized structure is 92% of the bulk breakdown voltage (2000 volts). The structure without field plate reaches only 21% of the bulk breakdown voltage. It is shown, how the optimization procedure can be carried out almost automatically taking advantage of the evolution strategy. The method is demonstrated and the benefits are elaborated in comparison to the conventional optimization procedure.

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Anwendung der Evolutionsstrategie zur Optimierung mehrstufiger Feldplatten für hochsperrende planare pn-Übergänge

Übersicht Die Blockierfähigkeit eines hochsperrenden planaren pn-Übergangs mit einer fünfstufigen Feldplatte und einer Stoppzone wird optimiert. Die Durchbruchspannung der optimierten Struktur beträgt 92% der Volumendurchbruchspannung (2000 Volt). Ohne Feldplatte erreicht die Struktur nur 21% der Volumendurchbruchspannung. Es wird gezeigt, wie durch Nutzung der Evolutionsstrategie das Optimierungsverfahren nahezu selbständig durchgeführt werden kann. Die Methode wird vorgestellt und die Vorteile gegenüber dem konventionellen Optimierungsverfahren werden präsentiert.

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Dedicated to Prof. Dr.-Ing. Manfred Stiebler on the occasion of his 60th birthday     

Mathematical modeling of induction heating units for moving round billets

The paper considers the question of constructing interrelated nonlinear electromagnetic and thermal models of processes arising when the moving steel round billets undergo thermal heating. The peculiarities of the effect of temperature on physical parameters are described.     

感应加热电源PDM波形的频率谱分析

脉冲密度调制(PDM)技术可用于调节感应加热电源的输出功率,其主要优点在于能够保证感应加热电源逆变器开关器件始终工作在零电压或零电流开关状态,然而PDM控制的负载电流波形含有多种谐波,分析了各种PDM波形的频率谱,得出了调制比D、负载的时间常数t和PDM序列长度T与PDM波形频率谱的关系。分析表明均匀脉冲密度调制技术控制脉冲序列对称性良好,产生的谐波最少。     

A degeneracy study in the circulant and bordered-circulant approach to birdcage and planar coils

A method for finding closed-form solutions for the normal mode frequencies of systems with circulant symmetry was investigated. This method is particularly useful for questions of degeneracy that arise when one considers parallel imaging techniques like SENSE and SMASH in MRI. It is applicable to systems that include birdcage coils as well as planar coils with the appropriate rotational symmetry. A proof is given that complete degeneracy of all normal mode frequencies is impossible when all mutual inductive couplings are included. We tested the method against measurements made on a planar coil array and on an 8-element birdcage coil. The inclusion of the co-rotating end-ring mode changes the fundamental symmetry of the system from circulant to 'bordered circulant.' Closed-form solutions for the normal mode frequencies of a bordered circulant system are also given.     

A degeneracy study in the circulant and bordered-circulant approach to birdcage and planar coils

A method for finding closed-form solutions for the normal mode frequencies of systems with circulant 2pi/2 symmetry was investigated. This method is particularly good for questions of degeneracy that arise when one considers parallel imaging techniques like SENSE and SMASH in MRI. It is applicable to systems that include birdcage coils as well as planar coils with the appropriate rotational symmetry. A proof is given that complete degeneracy of all normal mode frequencies is impossible when all mutual inductive couplings are included. We tested the method against measurements made on a planar coil array and on an 8-element birdcage coil. The inclusion of the co-rotating end-ring mode changes the fundamental symmetry of the system from circulant to "bordered circulant". Closed-form solutions for the normal mode frequencies of a bordered circulant system are also given.     

Mathematical model for calculation of the heat-hydraulic modes of heating points of heat-supplying systems

The mathematical model and calculation method of the thermal-hydraulic modes of heat points, based on the theory of hydraulic circuits, being developed at the Melentiev Energy Systems Institute are presented. The redundant circuit of the heat point was developed, in which all possible connecting circuits (CC) of the heat engineering equipment and the places of possible installation of control valve were inserted. It allows simulating the operating modes both at central heat points (CHP) and individual heat points (IHP). The configuration of the desired circuit is carried out automatically by removing the unnecessary links. The following circuits connecting the heating systems (HS) are considered: the dependent circuit (direct and through mixing elevator) and independent one (through the heater). The following connecting circuits of the load of hot water supply (HWS) were considered: open CC (direct water pumping from pipelines of heat networks) and a closed CC with connecting the HWS heaters on single-level (serial and parallel) and two-level (sequential and combined) circuits. The following connecting circuits of the ventilation systems (VS) were also considered: dependent circuit and independent one through a common heat exchanger with HS load. In the heat points, water temperature regulators for the hot water supply and ventilation and flow regulators for the heating system, as well as to the inlet as a whole, are possible. According to the accepted decomposition, the model of the heat point is an integral part of the overall heat-hydraulic model of the heat-supplying system having intermediate control stages (CHP and IHP), which allows to consider the operating modes of the heat networks of different levels connected with each other through CHP as well as connected through IHP of consumers with various connecting circuits of local systems of heat consumption: heating, ventilation and hot water supply. The model is implemented in the Angara data-processing complex. An example of the multilevel calculation of the heat-hydraulic modes of main heat networks and those connected to them through central heat point distribution networks in Petropavlovsk-Kamchatskii is examined.     

Characteristics of an induction motor with reduced turns of terminal coils

The use of PWM inverters with high switching characteristics for the adjustable speed drive system causes an overvoltage with steep‐fronted waveform on the motor terminals. As this steep‐fronted transient voltage in inverter drive loads heavily on the terminal coils of motor winding, the insulation failure in the motor winding occurs mostly on the terminal coils. Therefore, it is reasonable to reduce the turns of terminal coils only and to increase the dielectric strength of interturn insulation. This paper presents a comparison of measured characteristics of normal induction motors and induction motors with reduced turns of terminal coils and also a comparison of the results measured and calculated by equivalent circuit. The appropriate rate of reduced turns of terminal coils is about 20%. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 49–56, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10093     

Stochastic controlled system intended for induction heating of high-speed tubular billets

Statistical and spectral analyses of longitudinal distribution of tubular billet heating temperature caused by rolling process have been carried out. The transfer functions of the electric heating channel (EHC) of an induction pusher-type furnace (IPF) are revealed. A mathematical model is developed in Simulink environment. The processes of tubular billets heated in an IPF are analyzed for the case where the output temperature is distributed stochastically in a longitudinal direction.     

双定子笼型感应电动机的数学模型及性能计算

对双定子笼型感应电动机建立了数学模型,进行了性能分析与计算,利用Ｃ＋＋语言编制了计算机辅助设计程序,并设计与试制了两台２２ｋＷ、６极的模型机,通过实验证明了理论分析与计算的正确性。     

A new concept for finite element simulation of induction heating ofsteel cylinders

This paper presents a new algorithm for finite element simulation of induction heating of steel cylinders. Such cylinders have been installed as calender rolls in the Calcoil system for paper plants. This algorithm is used in place of the preprocessor module in EMRC NISA II software. A special preprocessing program has been designed for modeling of a typical section of the cylinder. Computed results are compared to infrared measurements of a laboratory model of a calender roll and, finally, the possibilities of utilizing and developing the algorithm are discussed     

感应加热用传导冷却YBCO高温超导磁体的热稳定性实验研究

与传统的高频交流感应加热技术相比,高温超导直流感应加热技术能够大幅度提升低电阻率、非铁磁性金属材料的透热处理加工效率。在高温超导感应加热系统中,超导磁体的热稳定性是保证系统安全稳定运行的关键。本文对传导冷却YBCO高温超导磁体进行通流实验,通过布置在磁体不同位置的多个温度传感器来监测各部分的温度情况,以温度能否在安全范围内趋于平稳作为判定条件研究超导磁体的热稳定性。同时,本文还研究了磁体载流的幅值与上升速率对磁体温升的影响。结果表明,高温超导磁体在传导冷却条件下,其长期安全稳定运行电流值的安全裕度因子选择通常比浸泡冷却式磁体略低,对于运行的实验磁体,安全裕度因子可取为0.65;传导冷却磁体远端导热性能差,可通过增加导冷点以及改善传热的方式来弥补冷却不均的缺陷;在磁体能够稳定运行的一定范围内,电流不同的上升速率对最终温升无明显影响。本文的研究成果将为今后大型传导冷却超导磁体的热稳定性分析与安全运行提供有价值的参考。