EDDY CURRENT BRAKES PDF
Keywords: Magnetic brakes; eddy-current magnetic brakes; optimum control. friction, an eddy-current braking system transforms the kinetic energy of the. Get More Information about Eddy Current Brakes PDF Download by visiting this link. Eddy current is the swirling current produced in a. An eddy current braking experiment was conducted to study the behaviour of three different materials to be used as brake disc which are aluminium, copper and zink. A few graph been presented in this paper to show the best material to be used as the brake disc for electromagnetic.
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Eddy Current Brakes - Free download as Word Doc .doc), PDF File .pdf), Text File .txt) or read online for free. The document reports the progress of Team 16's Eddy Current Brake design. experimentation resulting in optimized eddy current brake/motor configuration. International Research Journal of Engineering and Technology (IRJET) e-ISSN: Volume: 03 Issue: 04 | Apr ppti.info p-ISSN:
Optical tachometer. A list of all necessary elements follows: Many changes in this list are possible. For instance, any of the dc variable power sources can be replaced by a fixed source combined with a rheostat, the angular speed can be measured by stroboscopic techniques, etc.
Eddy Current Brakes Seminar Report pdf
This section describes several kinds of measurements that can be carried out with the proposed experimental setup. In all cases typical results are included. Braking time of the disc: First of all, the time necessary for the disc to completely stop from a fixed initial angular speed when the motor is turned off can be measured as a function of the excitation intensity.
We must keep in mind that the larger the excitation intensity is selected, the larger the voltage applied to the motor must be to achieve that initial speed. Figure 3 shows how larger excitation intensities make the braking time shorter as a result of more powerful eddy currents.
Error bars have been set to 0.
However, the results plotted in figure 3 are not suitable for verifying this fact, due to the lack of a known model for the internal braking torque acting on the motor.
Therefore, the result of this first experiment cannot be numerically tested. Figure 3. Braking time for the copper disc versus excitation intensity.
The initial speed of the disc was set to rpm.
Eddy current losses versus angular velocity: Then the voltage supplied by the power source of the motor must be varied in order to select various angular speeds.
Then the power dissipated only by eddy currents is simply: Standard error analysis techniques have been used to calculate error bars, assuming uncertainties of 0.
Eddy current losses versus excitation intensity: Equation 1 states that Pe is proportional to the square of the excitation intensity in the coil.
The excitation intensity was fixed to 3. An example to test the proportionality between Pe in the copper disc and I 2 ex. The angular speed was fixed to rpm. Above figure shows a set of typical results. It appears that the proportionality between Pe and I 2 ex does not hold, especially at low intensities.
Nevertheless, we must recall that the core of the electromagnet is made of iron, i.
In fact, it would be interesting to use a coil alone as a truly linear source of magnetic field. Unfortunately, the absence of a ferromagnetic core results in low magnetic fields and therefore Pe becomes too low to be measured with conventional ammeters and voltmeters.
To carry out such a test, both rotation speed and excitation intensity must be fixed, and the power consumed by the motor with each of the discs attached to it must be calculated. Pe is estimated by subtracting from this power the power consumption of the motor alone turning at the same angular speed better, a non-conducting disc equal in size to the conducting ones should have been used, but the difference is negligible.
Eddy Current Brakes
Table 1 shows the results. The angular speed and the excitation intensity were fixed to rpm and 3. Tabulated resistivities were extracted from a general reference , and exact coincidence with those of the sample discs cannot be guaranteed, especially in the case of alloys.
As we can see, results for aluminium, copper and brass show a reasonable agreement with equation 1. The case of steel, however, is clearly anomalous because of its ferromagnetic behaviour.
The time variation of the magnetic field applied on every point of the disc results in hysteresis loops creating an additional braking effect superimposed to eddy current torque see, for example, . This is probably the main reason for the high total losses observed in steel. From the above it may be deduced that: As we have seen, our experimental setup allows students to investigate one of the most outstanding aspects of eddy currents, namely their dissipated power.
Simple tests to measure Pe and to study its functional dependence on the velocity, the sources of the magnetic field and the sample resistivities have been carried out. The results show a reasonable but not indisputable agreement with theoretical predictions.
Nevertheless the author believes that the experiments deal with concepts, instruments and measurement techniques with high didactic value for the students, regardless of whether the agreement between theory and experiments is good or poor. Flag for inappropriate content. Related titles. Jump to Page. Search inside document. Here, we investigate the potential for this type of frictionless braking and the phenomenon behind this effect.
A typical school math problem involving two trains and distance, rate, and time is so classic that it has become a TV trope. But textbook authors and television writers may need to update some details as new developments in transportation technology emerge. For instance, high-speed commercial trains often travel at an average speed of mph, shaving a lot of time off the journey.
So, future train math problems may need to factor in much higher speeds and use two cities that are farther apart. The Shanghai magnetic levitation train, the fastest commercial high-speed electric train in the world. Image by Andreas Krebs — Own work.
If a traditional train would travel at mph using mechanical brakes, the brakes might not stop it in time — or at all. The faster a train moves, the harder the friction brakes have to work to dissipate the kinetic energy, which means the brakes run a greater risk of wearing out altogether. To combat this, many trains use dynamic braking that reduces wear and tear, but the friction-based components can still fail.
When the vehicle has the means, regenerative braking is preferred. For this type of frictionless braking, a linear motor or generator converts kinetic energy back into electric energy, which, at a later stage, can be reused for acceleration.
Less energy efficient but still better than mechanical braking is the use of eddy current braking. With eddy current braking, all generated electric energy is converted directly into heat.
Since the energy conversion takes place without mechanical contact, these systems tend to be much more robust than friction-based systems. This is the case for magnetically levitating maglev vehicles, such as the Shanghai maglev and a Japan Railway train that set a record-breaking top speed of mph.
One design developed and tested by a German railway company uses a linear array of eight electromagnets fitted between the wheels, at a distance of about 7 mm from the rail. Train operators can turn on these magnets when they want to slow down, which causes the magnets to generate a magnetic field that expands into the rail.
Because the rail is stationary, it will experience a concentrated magnetic field moving in at high velocity, and strong eddy currents will develop. These eddy currents are a result of the rail resisting the enforced change in magnetic flux: They flow in such a direction that the rail generates its own magnetic field, which tries to counteract expel the applied one. The two magnetic fields repel each other and a braking force results — meaning the train will come to a frictionless stop.
Advantages of this type of frictionless braking include being finely controlled, relatively inexpensive, and free of pollution and noise. This causes skidding and wear and tear of the vehicle.
And if the speed of the vehicle is very high, the brake cannot provide that much high braking force and it will cause problems. It is an abrasion-free method for braking of vehicles including trains. It makes use of the opposing tendency of eddy current. Eddy current is the swirling current produced in a conductor, which is subjected to a change in magnetic field. Because of the tendency of eddy currents to oppose, eddy currents cause energy to be lost. More accurately, eddy currents transform more useful forms of energy such as kinetic energy into heat, which is much less useful.Then the following proportionality law holds: The time variation of the magnetic field applied on every point of the disc results in hysteresis loops creating an additional braking effect superimposed to eddy current torque see, for example, .
Also a time dependent study was done to show the development of the same eddy currents in the disc with deceleration. The inside surface of the drum is acted upon by the linings of the brake shoes. When disc rotates a flux change occur in the section of the disc passing the poles of stator. In many applications, the loss of useful energy is not particularly desirable.
But there are some practical applications.
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