Eddy current brakes use the drag force created by eddy currents as a brake to slow or stop moving objects. Eddy current inspection ection transformer analotransformer analo g when two coils are coupled by a magnetic field, they are subject to yp w e wo co s e coup ed by g e c e d, ey e subjec o the effects of a mutual inductance. Eddycurrent clutches consist of a field, ta chometer, and eddycurrent control. This paper analyzed the eddy characteristics of the coaxial cylindrical magnetic coupler by using the finite element method, and simulated the impact of eddy currents on magnetic field. Consistent performance requires identification of the eddy current probe parameters which characterize performance. Eddy currents also called foucaults currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to faradays law of induction.
Coupled electromagnetic and thermal analysis of ferrite. Comparison of eddy current distributions and lorentz forces calculated by fem top. The two major parts of the eddycurrent clutch are the drum assembly and the output rotor and shaft assembly. Eddy current clutch working, application, advantages and. The coupling currents can be reduced by reducing the area of the loop reducing the enclosed magnetic. After the motor has reached its target speed, its controller engages the eddy clutch. Openloop control consists of manual variation of the field coil voltage to. Design optimization of an axialfield eddycurrent magnetic coupling. Eddy current methods have been utilized for more than 100 years as a means for detecting and characterizing. Modelassisted eddy current inspection for enhanced. This paper presents an approach for quick calculation of steadystate and transient performances of an axialfield eddycurrent coupling. Coupling of finite and boundary elements for transient.
Consequently, the coupling currents and the corresponding coupling current losses, can be much larger than the eddy current losses. Eddy current clutches or eddy current slip coupling are available in a broad range of sizes and speed up to thousands of kilowatts in both vertical and horizontal configurations. The subject is presented under the following headings. A mixedfem and bem coupling for a threedimensional eddy. This invention relates to shaft mounted eddy current drives or clutches and more particularly to the general type of drive in which a magnetic body is rotatably mounted on a driven shaft mounted hub. The eddy current block models the effect of eddy currents by generating a magnetomotive force mmf that opposes changes in the magnetic flux.
Advantages of the eddy current method high testing speed high test throughput easy to automate 100% testing objective results evaluation high reproducibility documentation and recording of test results no contamination by coupling liquids areas of application for the eddy current method eddy current testing for safe components 100. Indeed, these currents are exactly the same as the. Since there is no contact with a brake shoe or drum, there is no mechanical wear. The variable speed output shaft is rotated by the constant speed a. An eddy current drive, also known generically as a magnetic drive, eddy current clutch or magnetic clutch, is an electromechanical variable. The eddy current coupling usually consists of three basic members. Fast iterative solution of eddy current problems by a 3 d. Study on the eddy current loss characteristic of the. If a flaw in the conductive material disturbs the eddy current circulation, the magnetic coupling with the probe is changed and a defect signal can be read by measuring the coil impedance variation.
With the new tx series, waycon is introducing a fully digital device incorporating usb, can and a highspeed analogue interface. In addition, the block models parasitic effects using a series reluctance and a parallel leakage permeance. Therefore, the voltage output from the eddy current should be out of phase to the h oscillation because dhdt should change the phase by 90 deg with respect to that of the h oscillation. Tech talk february 2011 eddy current drives holland industrial. Modelling and design of an eddy current coupling for slip. They are an adjustable speed drive and provide soft starting capability. The attempt at a solution can anyone tell me two types of eddy current couplings. Gear coupling selection procedure table 1 torque and horsepower ratings standard selection method the standard selection method can be used for most motor, turbine, or engine driven applications.
This results in a high degree of cushioning between the drive system and load, permitting longer life for the machinery involved. Steadystate and transient performance of axialfield eddy. Dynamatic dcd drives eddy current drive by drive source international, inc. Basic characteristics of eddy current testing using. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed. Eddy current clutches and brakes heat up considerably due to the development of eddy currents with increasing rpm with temperature increase the value of the torque attainable decreases considerably. Eddy current, magnetic coupling, analytic thermal and magnetic model. Voltage and current intensity when one wants to couple the eddycurrent problem with a circuit problem, one has to consider, as the only external. Baylor elmagco eddy current brake, model 7838 installation, operation and maintenance manual 1.
Pdf a general analytical model of permanent magnet eddy. Bei designs ultrasonic and eddy current nondestructive evaluation systems for a variety of material applications including composite materials, metals, ceramics, particulate filled polymeric materials, and other complex material systems of interest. Eddycurrent coupling as an industrial variablespeed. An eddy current drive system consists of ac motor and eddy current coupling, a control and operators control station. The centaflexa rubber elements are available in various. Eddy current probes are particularly suitable devices for.
Eddycurrent inspection is very good for detecting fibers and fiber content because the fibers. A symmetric coupling of methods of finite and boundary elements for numerical solution of transient eddy current problems is described. Fast iterative solution of eddy current problems by a 3 d hybrid approach coupling the cell and the boundary element methods f. When starting eddy current clutch operates at 100% slip allow the driver motor to accelerate. The eddy current torque coupling converts energy into heat. Eddycurrent inspection of advanced composite materials appears to overcome some of the difficulties typical of ultrasonic inspection. An eddy current brake, also known as an induction brake, electric brake or electric retarder, is a device used to slow or stop a moving object by dissipating its kinetic energy as heat. The electromagnetic coupling occurs between the eddy current coil and.
The accuracy of an eddy current inspection depends in large part on the performance of the eddy current probe. Us3064149a us711953a us71195358a us3064149a us 3064149 a us3064149 a us 3064149a us 711953 a us711953 a us 711953a us 71195358 a us71195358 a us 71195358a us 3064149 a us3064149 a us 3064149a authority us united states prior art keywords magnets permanent eddy current flux permanent magnet prior art date 19570201 legal status the. Eddy current drives, also known generically as magnetic drives, eddy current clutches or magnetic clutches are driven at constant speed by an ac motor and utilize a simple electromagnetic device to control torque and speed to the driven load. Available formats pdf please select a format to send. Eddy current techniques in ndeeddy current techniques in. In eddy current clutches and brakes the temperature coefficient of the copper is. A general analytical model of permanent magnet eddy current couplings article pdf available in ieee transactions on magnetics 501. Workbench coupling maxwell 3d eddy current calculates losses and couples directly to ansys thermal maxwell 3d electrostatic calculates capacitances between winding and core maxwell 3d eddy current calculates r,l vs. The single flexing coupling is for use in the case where shafts are supported by three bearings. In addition, this paper calculated eddy current power.
The body contains or supports an electric coil fed through slip rings from a relatively stationary brush holder assembly. The coupling shown in the diagram on the right above is suitable for use in cases subject to great radial loads. This motion determines an electric field in the conductor that induces eddy currents. Eddy current couplings and brakes thyssenkrupp magnettechnik. Eddy current inspection methods university of houston. A mixedfem and bem coupling for a threedimensional eddy current problem volume 37 issue 2 salim meddahi, virginia selgas. Ts file contains the coupling interaction from the 3d em simulation. Coupling of finite and boundary elements for transient eddy current problems. To connect the servomotor used in nc machine tools with the ball screw, an exceptional usage of the coupling as shown in the. Pec signals are known to possess a broad frequency spectrum enabling them to penetrate into different depths and to provide information about the geometry of the test piece being evaluated.
Results show the effec tiveness of the proposed methodology. Watercooled couplings wcs couplings eddy current coupling. For example, carboncarbon material can be inspected using eddycurrents without making the sample wet or using any acoustic coupling substances. Pulsed eddy current pec sensing is considered as the most versatile member of the family of eddy current ec nondestructive evaluation nde techniques. Baylor elmagco eddy current brake, model 7838 installation. When inspecting products with a uniform cross section, an eddy current signal is produced when the leading end or trailing end of the product approaches the test coil. They can be induced within nearby stationary conductors by a timevarying magnetic field created by an. Using magnetic resonant coupling, the edm slit signal increased 1. When a magnetic metal part is placed in an eddy current. Mounted on the end of motor shaft 10 extending into coupling housing 7 and adapted for rotation therewith is an eddy current coupling inductor member 27 which, in accordance with one aspect of the invention, comprises an imperforate hub and web portion 28 which supports one end of an eddy current inductor drum 29 which concentrically overlies. The eddy current principle of torque transmission features no direct physical contact between the constant speed and output members. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. Homework statement i have a really simple question, state two types of eddy current couplings and state a flexible coupling, but ive been googling it for the last half an hour and cant find an answer.
Basic eddy current concepts, eddy current generation and distribution, coilspecimen coupling factors, specimens magnetic and electrical effects, and basic electrical concepts related to eddy current testing. Coupling of finite and boundary elements for transient eddy current problems dalibor lukas1. Us3064149a controllable flux permanent magnet systems. In eddy current clutches and brakes the temperature coefficient of the copper is considered along with the temperature coefficient of the magnet. Box elder innovations offers their expertise in solving your nde and sensor measurement needs.
Eddy current devices have a straightline torquespeed characteristic, with the torque increasing linearly with the speed by virtue of the fact that the induced currents vary in magnitude with the speed of the rotating field. This method of varying speed only reduces the speed of the driven load, which is different than. In eddy current test systems where encircling coils are used, coupling efficiency is referred to as. The eddy current coupling as claimed in one of the preceding claims, wherein the magnetic. There is no mechanical linkage between input and output members of the drive. Detecting microstructure and flaws in composites using. 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. Introduction the working principle of eddycurrent couplers relies on the interaction between a conductor in motion with respect to a magnetic field. Eddycurrent, coupling systems, finite element, electromagnetism 1. The drive unit consists of an ac induction motor driving the input member or fan pole assembly of the magnetic drive. Modelassisted eddy current inspection for enhanced detection sensitivity in cfrp. The eddy current coupling and control unit of load car offered should be well. The axialradial screwing connection for the centaflexa, unique in this market, eases the assembly significantly.
In this study the possibility of using an eddy current coupling as the slip. Pulsed eddy current sensing for critical pipe condition. This is an essential step in modelling of electromagnetic forming of metalic sheets. However, unlike friction brakes, in which the drag force that stops the moving object is provided by friction between two surfaces pressed together, the drag force in an eddy current brake is an. The unbounded domain is discretised by means of finite.
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