Baylor Elmagco Eddy Current Brake, Model Installation, Operation and Maintenance Manual. 1. Manual No. 3′ NATIONAL. Baylor elmagco eddy current brake, model maintenance instructions. I hope this link helps. It explained the concept very well. Eddy current brake – Wikipedia.
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An eddy current brakealso known as an induction brakeelectric brake or electric retarderis a device used to slow or stop a moving object by dissipating its kinetic energy as heat.
However, unlike friction brakesin 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 hrake an elmgaco force between a magnet and a nearby conductive object in relative motion, due to eddy currents induced in the conductor through electromagnetic induction.
A conductive surface moving past a stationary magnet will have circular electric currents called eddy brske induced in it by the magnetic fieldas described by Faraday’s law of induction.
By Lenz’s lawthe circulating currents will create their own magnetic field which opposes the field of the magnet. Thus the moving conductor will experience a drag force from the magnet that opposes its motion, proportional to its velocity. The kinetic energy of the moving object is dissipated as heat generated by the current flowing through the electrical resistance of the conductor.
In elmagcp eddy current brake the magnetic field may be created by a permanent magnetor an electromagnet so the braking force can be turned on and off or varied elmavco varying the electric current in the electromagnet’s windings. Another advantage is that since the brake does not work by frictionthere are no brake shoe surfaces to wear out, necessitating replacement, as with friction brakes. A disadvantage is that since the braking force is proportional to relative velocity of the brake, the brake has no holding force when the moving object is stationary, as is provided by static friction in a friction brake, so in vehicles it must be supplemented by a friction brake.
Eddy current brakes are used to slow high-speed trains and roller coastersas a complement for friction elmagck in semi-trailer trucks elmaggco help prevent brake wear and overheating, to stop powered tools quickly when power is turned off, and in electric meters used by electric utilities. An eddy current brake consists of a conductive piece of metal, either a straight bar or a disk, which moves through the magnetic field of a magnet, either a permanent magnet or an electromagnet.
When it moves past the stationary magnetthe magnet exerts a drag force on the metal which opposes its motion, due to circular electric currents called eddy currents induced in the metal by the magnetic elmqgco. Note that the conductive sheet is not made of ferromagnetic metal such as brae or steel; usually copper or aluminum are used, which are not attracted to a magnet.
The brake does not work by the simple attraction of a ferromagnetic metal to bgake magnet. See the diagram at right. It shows a metal sheet C moving to the right under a magnet.
The magnetic field B, green arrows of the magnet’s north pole N passes down through the sheet. Since the metal is moving, the magnetic flux through sheet is changing. At the part of the sheet under the leading edge of the magnet left side the magnetic field through the sheet is increasing as it gets bdake the magnet. From Faraday’s law of inductionthis field induces a counterclockwise flow of electric current I, redin the sheet.
Baylor Elmagco Eddy Current Brake – Rebuilt
This is the eddy current. In contrast, at the trailing edge of the magnet right side the magnetic field through the sheet is decreasing, inducing a clockwise eddy current in the sheet. Another way to understand the action is to see that the free charge carriers electrons in the metal sheet are moving to the right, so the magnetic field exerts a sideways elmmagco on them due to the Lorentz force.
The mobile charge carriers in the metal, the electronsactually have a negative charge, so their motion is opposite in direction to the conventional current shown. Due to Ampere’s circuital laweach of these circular currents creates a counter magnetic field blue arrowswhich due to Lenz’s law opposes the change in magnetic field, causing a drag force on the sheet which is the braking force exerted by the brake.
At the leading edge of the magnet left side by the right hand rule the counterclockwise current creates a magnetic braie pointed up, opposing the magnet’s field, causing a repulsive force between the sheet and the leading edge of the magnet. In contrast, at the trailing edge right sidethe clockwise current causes a magnetic field pointed down, in the same direction as the magnet’s field, creating an attractive force between brke sheet and the trailing edge of the magnet. Both of these forces oppose the motion of the sheet.
The kinetic energy which is consumed overcoming this drag force is dissipated as heat by the currents flowing through the resistance of the metal, so the brkae gets warm under the magnet.
The braking force of an eddy current brake is exactly proportional to the velocity Vso it acts similar to viscous friction in a liquid. The braking force decreases as the velocity decreases. When the conductive sheet is stationary, the magnetic field through each part of it is constant, not changing with time, so no eddy currents are induced, and there is no force between the magnet and the conductor.
Thus an eddy current brake has no holding force. Disk electromagnetic brakes are used on vehicles such as trains, and power tools such as circular sawsto stop the blade quickly when the power is turned off.
A disk eddy current brake consists of a conductive non- ferromagnetic metal disc rotor attached to the axle of the vehicle’s wheel, with an electromagnet located with its poles on each side of the disk, so the magnetic field passes through the disk. The electromagnet allows the braking force to be varied. When no current is passed through the electromagnet’s winding, there is no braking force. When the driver steps on the brake pedal, current is passed through the electromagnet windings, creating a magnetic field, The larger the current in the winding, the larger the eddy currents and the stronger the braking force.
Power tool brakes use permanent magnetswhich are moved adjacent to the disk by a linkage when the power is turned off. The kinetic energy of the vehicle’s motion is dissipated in Joule heating by the eddy currents passing through the disk’s resistance, so like conventional friction disk brakes, the disk becomes hot. Unlike in the linear brake below, the metal of the disk passes repeatedly through the magnetic field, so disk eddy current brakes get hotter than linear eddy current brakes.
Japanese Shinkansen trains had employed circular eddy current brake system on trailer cars since Series Shinkansen. However, N Series Shinkansen abandoned eddy current brakes in favour braje regenerative brakessince 14 of the 16 cars elmgaco the trainset used electric motors. In regenerative brakes, the motor that drives the wheel is used as a generator to produce electric current, which can be used to charge a battery, so the energy can be used again.
Most chassis dynamometers and many engine dynos use an eddy-current brake as a means of providing an electrically adjustable load on the engine. They are often referred elmagck as an “absorber” in such applications.
Inexpensive air-cooled versions are typically used on chassis dynamometers, where their inherently high-inertia steel rotors are an asset rather than a liability. Conversely, performance engine dynamometers tend to utilize low-inertia, high RPM, liquid-cooled configurations.
Eddy Current Brakes
Downsides of eddy-current absorbers in such applications, compared to expensive AC-motor based dynamometers, is their inability to provide stall-speed zero RPM loading or to motor the engine – for starting or motoring downhill simulation.
Also, since they do not actually absorb energy, provisions to transfer their radiated heat out of the test cell area must typically be provided.
Either a high-volume air-ventilation or water-to-air heat exchanger adds additional cost and complexity. In contrast, the high-end AC-motor dynamometers cleanly return the engine’s power to the grid. Linear eddy current brakes are used on some vehicles that ride on rails, such as trains.
They are used on roller coastersto stop the cars smoothly at the end of the ride. The linear eddy current brake consists of a magnetic yoke with electrical coils positioned along the rail, which are being magnetized alternating as south and north magnetic poles.
This magnet does not touch the rail, but is held at a constant small distance from the rail of approximately 7 mm the eddy current brake should not be confused with another device, elmagfo magnetic brake, in wide use in railways, which exerts its braking force by friction of a brake shoe with the rail.
It works the same as a disk eddy current brake, by inducing closed loops of eddy current in the conductive rail, which generate counter magnetic fields which oppose the motion of the train.
The kinetic energy of the moving vehicle is converted to heat by the eddy current flowing through the electrical resistance of the rail, which leads to a warming of the rail. An bdake of the linear brake is that since each section of rail passes only once through the magnetic field of the brake, in contrast to the disk brake in which each section of the disk passes repeatedly through the brake, the rail doesn’t get as hot as a disk, so the linear brake can dissipate more energy and have a higher power rating than disk brakes.
The eddy current brake does not have any mechanical contact with the rail, and thus no wear, and creates no noise or odor. The eddy current brake is unusable at low speeds, but can nrake used at high speeds both for emergency braking and for regular braking. The TSI Technical Specifications for Interoperability of the EU for trans-European high-speed rail recommends that all newly built high-speed lines should make the eddy current brake possible.
The first train in commercial circulation to use such a braking system has been the ICE 3. Modern roller coasters also use this type of braking, but in order to avoid the risk posed by potential power outagesthey utilize permanent magnets instead of electromagnets, thus not requiring any power supply, however, without the brae to adjust the braking strength as easily as with electromagnets. In physics education a simple experiment is sometimes used to illustrate eddy currents and the principle behind magnetic braking.
When a strong magnet is dropped down a vertical, non-ferrous, conducting pipe, eddy currents are induced in the pipe, and these retard the descent of the magnet, so it falls slower than it would if free-falling. As one set of authors explained. But this implies that the moving magnet is repelled in front and attracted in rear, hence acted upon by a retarding force.
In typical experiments, students measure the slower time of fall of the magnet through a copper tube elmago with a cardboard tube, and may use an oscilloscope to observe the pulse of eddy current induced in a loop of wire wound around the pipe when the magnet falls through. From Wikipedia, the free encyclopedia. Canadian Journal of Physics. American Journal of Physics. Activities for the undergraduate laboratory”.
European Journal of Physics. Brake van Diesel brake tender Diesel electric locomotive dynamic braking Electronically controlled pneumatic brakes Electro-pneumatic brake system on British railway trains Emergency brake train Retarder Dowty retarders. Retrieved from ” https: Brakes Electromagnetic components Electrodynamics Railway brakes Physics experiments. Commons category link is on Wikidata.
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