High frequency heating methodseddy current heating. This paper is intended to provide insight into these phenomena so that improved high frequency. Induction heating is an accurate, fast, repeatable, efficient, noncontact technique for heating metals or any other electricallyconductive materials. Saturated low frequency eddy current slofec reliable tank. Hysteresis and eddycurrent losses of a transformer. An induction heating system consists of an induction power supply for converting line power to an alternating current and delivering it to a workhead, and a work coil for generating an. What are the applications of high frequency eddy current. Losses in high speed permanent magnet machines used in liping. Nondestructive techniques based on eddy current testing. Among other things, it explains i why eddy current. Both induction heating and eddy current testing work with coils, generators. Created onapril 10, 2019last updated onapril 10, 2019byelectricalvoice you are here. Pdf electromagnetic induction is characteristic of generating heat directly within the.
Denale david taylor research center metals and welding division annapolis md, 214025067 single frequency phase analysis eddy current techniques have limited potential for inspections for surface cracking in inhomogeneous. High frequency heating steel pipe with induction heating equipment. Effect of increasingly high frequency on induction heating. Encyclopedia article about eddy current heating by the free dictionary.
The heat in the material to be heated is produced by eddy currents. The mathematical methods employed in solving the relevant problems are. At high frequencies, the induced eddy currents are concentrated at the inside and outside surfaces of the tubings. High frequency eddy current heating is frequently used for forging and annealing. In the case of induction heating, an iron shaft is placed as a core of an induction coil. This skin effect forces the alternating current to flow in a thin layer towards the surface of the workpiece. How amount of heating is controlled in high frequency eddy. A large amount of heat is produced at the outermost part of the shaft by the eddy current when the high frequency current is passed. For the induction heating process to be efficient and practical, certain relationships of the frequency of the electromagnetic field that produces the eddy.
Applications of high frequency eddy current technology for material characterization of thin coatings 186 fig. At higher frequencies, this heating is caused by molecular dipole rotation within the dielectric. These high frequency effects are caused by the magnetic field resulting from current flow in transformer windings and circuit wiring. At two standard depths of penetration 2d, the eddy current density has decreased to 1e squared or. Eddy current technology incorporated built the worlds first portable, multi frequency eddy current instrument complete with a. Within these ranges there are specific frequencies allocated for industrial, scientific and medical uses, the socalled ism. Apr 30, 2015 the heating effect originates from the transformation of electric energy into heat energy and is used in induction heating devices, like some cookers and welders.
It is recommend that this frequency and 2 times this frequency be mixed for a support plate cancellation when performing eddy current inspections of heat exchanger tubes with the given alloy and wall thickness. Eddy current losses in transformer windings and circuit wiring. Typically, the instruments are designed for manual handling of a singe coil sensor. The object is often called a work piece, and the heating coil a work coil.
These eddy currents are beneficial in the case of induction heating because they flow inside the material and produce i2r losses which causes the material to heat up. Handle lightweight and durable, suitable for prolonged use, a variety of tip to choose from. By doing so alternating magnetic field is set up, eddy currents are induced in the metal piece and heating is. The highfrequency eddy current technology is a suitable inspection. Simultaneous injection multi frequency eddy current instruments are recommended for heat exchanger tube inspections. If you cannot read the numbers in the above image, reload the page to generate a new one. Kulkarni, aissms college of engineering, pune universitypune, maharashtra, india l.
Microcomputer control, pushbutton thermostat, digital temperature calibration, and automatic sleep and automatic shutdown. High frequency eddy current heating electrical engineering. Infrared heating this is the most inefficient method of electric heating. Power loss due to eddy currents is eddy current loss and appears in the form of heat. High frequency heating in which special high frequency generators is essential, e. Early detection of these defects in production lines can save large sums of money in the metal industry.
High frequency induction heating is widely used for quick heating of conductive material. When attempting to locate flaws, a frequency is often selected which places the expected flaw depth within one standard depth of penetration. All rdo induction model lfihfi induction heating systems are equipped with diagnostic limit indicators for voltage, power, frequency and current, along with trip indicators for frequency, current, over temperature, doorcabinet interlock and water pressure. Mosfet based high frequency inverter for induction heating. Induction heating ih is a noninvasive heating technology 1 based on inducing an alternating magnetic field in a media to be heated fig. Home electric heating what are the applications of high frequency eddy current heating. Because temperature distribution of the heated body is governed by the.
Induction heating an overview sciencedirect topics. These indicators are located on the front panel for ease of diagnostic control. However, there are some uses of this eddy current like in induction heating. The requirements for capacitors used in high power induction heating are perhaps the most demanding of any type of capacitor. So by controlling the amount of eddy current we can control the temperature of the material. These are limited by laminations in the stator and rotor. This data is referenced to an encoded position and time and. The impedance of an eddy current probe may be affected by the following factors. However, an eddy current brake cannot provide a holding torque and so may be used in combination with mechanical brakes, for example, on overhead cranes. Pdf computational study of electromagnetic fields, eddy.
Home electric heating how amount of heating is controlled in high frequency eddy current heating. For high power induction heaters, the drive coils are hollow with liquid cooling. Multiple frequency eddy current techniques simply involve collecting data at several different frequencies and then comparing the data or mixing the data in some way. High frequency eddy current heating, temperature and return temperature and speed, to achieve leadfree soldering. Eddy currents are induced in the heating element by electromagnetic induction, the. Better control of depth is attained through induction heating, since the high frequency eddy currents responsible for heating are localized in the surface of the workpiece by the skin effect. Highfrequency eddy current an overview sciencedirect. All ferromagnetic materials may realise very strong internally induced magnetic fields when excited by an externally applied magnetic field and is called electromagnetic induction and is primarily how all transfo. The process relies upon a material characteristic known as electromagnetic induction. In this technique, a coil also called probe or sensor is excited with sinusoidal alternating current frequency, f, 50 hz5 mhz, 100 ma. Aug 30, 2015 electrical heating part 07 high frequency heating methods dielectric heating sir james alfred ewing coined the word hysteresis sir james alfred ewing bon on 27th march 1855 he.
Eddy current losses losses caused by unintended current flow in the rotor and the stator. High frequency induction heating model hfi power supplies. Since there is no contact with a brake shoe or drum, there is no mechanical wear. Induction heating is heating conductive metals with no physical contact, by using high frequency electricity. The dc voltage is converted again into a high frequency ac voltage by a classd inverter. Low frequency eddy current testing for subsurface cracks in aluminum aircraft supports n. Handbook induction heating eddy current paper ibg eddy current. Why does higher frequency cause higher eddy current losses in. Red hot bolt, run time of about 1 minute, about 120 khz. Defined by faradays law, within an idealized, long solenoid, the absorbed power density in tissue due to eddy currents is. Low frequency probes eddy current probes techna ndt. Dielectric heating, also known as electronic heating, radio frequency heating, and high frequency heating, is the process in which a radio frequency rf alternating electric field, or radio wave or microwave electromagnetic radiation heats a dielectric material.
Definitions and data tables for eddy current testing. Applications of high frequency eddy current technology for. Non destructive testing eddy current testing, wirbelstrom. This eddy current generates joule heating, and a heat loss of the electromagnetic energy eddy current loss will be caused. Sep 09, 20 in addition to this, the high frequency used in induction heating applications gives rise to a phenomenon called skin effect.
High frequency induction heating equipment performs heating by utilizing the two heating principle, namely hysteresis loss and eddy current loss. At three depths 3d, the eddy current density is down to only 5% of the surface density. Principle ec testing works on the principles of electromagnetic induction. We have the most extensive experience, and we develop the highest quality ect inspection products. Mitigation of eddy current heating during magnetic. Large currents are forced through the object which is to be heated.
High quality eddy current testing solutions for complete inspections. Mosfet based high frequency inverter for induction heating equipment using matlab simulink environment prof. High frequency heating methodseddy current heating akash. Eddy current testing is an inspection method that can be used for a variety of purposes including the detection of cracks and corrosion, material and coating thickness measurement, material identification and, in certain materials, heat treatment condition. Swami aissms college of engineering, pune universitypune, maharashtra, india abstract. An induction heater consists of an electromagnet and an electronic oscillator that passes a high frequency alternating current ac through the electromagnet. Lowering the frequency allows the eddy currents to penetrate deeper into the material. Heat exchanger assemblies are often a collection of tubing that have support brackets on the outside. The skin effect increases the effective resistance of the metal to the passage of the large current. What is induction heating and how do induction coils work. Principle of highfrequency induction heater unit micro. Pdf frequency optimization for eddy current thermography. Frequency frequencies typically used for eddy current testing range from 100 hz to 4 mhz. Thermal magnetic characteristic for high frequency induction.
The frequency applied in dielectric heating is very high in the range of 10 to 50 khz, but the efficiency of this system is low about 50%. The depth of penetration is dependent of test drive frequency, the test materials conductivity and magnetic permeability. Hysteresis and eddycurrent losses of a transformer lamination viewed as an application of the poynting theorem by john barranger lewis research center summary an energyloss equation is developed based on the poynting theorem. Skin effect the tendency for current in an ac circuit to flow on the outer edges of the conductor resulting in increased resistance. A practical discussion of its uses and limitations in high. Eddy current analysis of induction heating by boundary element. The data described in this section, which were introduced by locally heat treating the. Why does higher frequency cause higher eddy current losses. Basics of induction heating technology radyne corporation. Zetec is the industry leader for costeffective eddy current testing ect in complex applications. The heat in the disc can be increased by increasing the coil current, increasing the number of turns, frequency of supply, close spacing between the coil and work, using higher permeability magnetic material and higher electrical resistivity of the disc. Pdf effect of heating of steel tubes by induction at high frequency. Typically, the material to be heated is ferromagnetic and conductive and, consequently, induced currents, also called eddy or foucault currents, cause the material to be heated by joule effect. A step by step guide to performing a high frequency eddy current ndt inspection on aluminium aluminum.
Ether nde are a dedicated manufacturer of eddy current ndt equipment and accessories including a vast range of ec weld probes, et weld probes and ect weld probes and are the go to company for all your eddy current ndt solutions. It is proportional to the square of the current flow. The definition of microwave usually is between 500 mhz and 5 ghz. An interstitial heater, made of an electrically conductive tube with a. The optimum frequency of carbon steel pipe weld coating is verified. High frequency eddy current testing, material characterization, coating condition, thin. An example of where a multi frequency eddy current inspection is used is in heat exchanger tube inspections. Typical induction heating applications involve a drive coil with high currents at some kilohertz khz frequency and a conductive target object placed inside or near the drive coil to induce currents and create heat figure 1. The articles to be heated are placed within a high frequency current carrying coil, alternating magnetic field is set up, eddy currents are induced in the article and heating is, therefore, affected fig. While a significant improvement over conventional magnetic particle inspections, the eddy current method as it was developed in these programs is limited to use for inspections of pipelines from the outside surface.
In order to reduce eddy current loss, a sheet thickness on a. Eddy current testing is one of the most extensively used nondestructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. The eddy current test does detect fine differences in microstructure with high sensitivity. Our low frequency eddy current probes include spot bridge, ring bridge, spot reflection, ring reflection, sliding, and pencil probes.
Each individual coil produces a signal relative to the phase and amplitude of the structure below it. Series resonant induction heater uzzors2k hobby projects site. If a defect appears in the effective area, the eddy current have to take a different way, this changes the impedance of the coil and the operator see the changes on his screen z1z2. It has received notable attention from the meat industry, and has shown great potential to be used as an alternative to conventional steam and hot. Feb 28, 2011 eddy current testing is a versatile technique that makes possible the hot eddy current testing of semifinished products such as wires, bars and tubes at temperatures of up to 1,200 c 59,75 and at production speeds of up to 150 ms. The depth of penetration of the eddy currents is dependent upon frequency. The resistance felt by the eddy currents in a conductor causes joule heating and the amount of heat generated is proportional to the current squared. Since the sensitivity of an eddy current inspection depends on the eddy current density at the defect location, it is important to know the strength of the eddy currents at this location. In addition to this, the high frequency used in induction heating applications gives rise to a phenomenon called skin effect. Lower and higher frequencies are used with many specialapplication eddy current instruments. Coreless induction furnace principle your electrical guide. The capacitor bank used in the tank circuit of an induction heater must carry the full current that flows in the work coil for extended periods of time. The high frequency current carrying coil is known as heater coil or work coil, the material which is to be.
Introduction the conductive strip grating is a periodic planar arrangement of conductive strips with a long length and small thickness. Eddycurrent heating article about eddycurrent heating by. Eddy current brakes use the drag force created by eddy currents as a brake to slow or stop moving objects. Yihua 900h 100w high frequency eddy current heating. There is little wastage of heat in eddy current heating as heat. Dielectric process heating uses the frequency range from about 5 mhz to 5 ghz with radio frequency, rf, being normally defined as being less than 100 mhz. Thermal magnetic characteristic for high frequency induction heating analysis article in journal of applied physics 9110. Induction heating occurs when an electrical current eddy current is induced into a workpiece that is a poor conductor of electricity. Highfrequency current definition of highfrequency current. Recent progress of high silicon electrical steel in jfe steel.
Eddy currents are electric currents inducted by transformer action in the material. Vfd losses in efficiency are as follows ir losses heating is the largest loss caused by resistance to current flow in the motor winding and rotor bars. Eddy current array testing, or eca, is a technology that provides the ability to simultaneously use multiple eddy current coils that are placed side by side in the same probe assembly. Multifrequency eddy current testing of ferromagnetic welds. Classd inverters take the energy from the mains voltage. Eddy current losses are much more important than hysteresis losses in induction heating. Jul 29, 2015 a step by step guide to performing a high frequency eddy current ndt inspection on aluminium aluminum.
Proximity effect the tendency for current to flow in other undesirable patterns loops or concentrated distributions due to the presence of magnetic fields generated by nearby conductors. The metal to be heated is placed within a high frequency current carrying coil. Experimental studies of eddy current testing have emerged as an important approach alongside numerical modelling. Eddy current loss can also be divided into classical eddy current loss and excess eddy current loss for a more accurate analysis. The frequency is selected by the operator and is determined by several factors. Nondestructive techniques are used widely in the metal industry in order to control the quality of materials. Induction heating is the process of heating an electrically conducting object usually a metal by electromagnetic induction, through heat generated in the object by eddy currents. Skin depth frequency table eddy current technology. For example, a 9010 cuni tube with a wall thickness of 0. When attempting to inspect the full wall thickness of the tubing, the signal from the mounting bracket is often troublesome.
Slofec is a trademark acronym for saturated low frequency eddy current. The drawings below represents schematically how does eddy current works. Highfrequency eddy current an overview sciencedirect topics. The coil red causes a magnetic field, which initiate eddy current.
Eddy current heating for hyperthermia cancer treatment city, of hope. Krause department of physics, royal military college of canada, kingston, on, k7k 7b4. Inspecting heat exchangers in various industries eddy. The high level of frequency employed in the process of induction heating produces skin effect that makes the alternate current flow in the direction of the work piece. Because of skin effect associated with alternating current, high frequencies tend to keep the eddy currents circulating near the surface. The process of boronizing of the surface layers of carbon steels under induction high energy treatment at frequency 440 khz in a range of specific power from 1. As their name implies, they appear to flow around in swirls on eddies within a solid mass of material. This paper focus on investigating the defect signal characteristics of carbon steel pipe weld coating inspection using different frequency eddy current testing.
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