Electromagnetic brakes are the brakes working on the electric power & magnetic power. They works on the principle of electromagnetism. These are totally friction less. Due to this they are more durable & have longer life span. Less maintenance is there. These brakes are an excellent replacement on the convectional brakes due to their many advantages. The reason for implementing this brake in automobiles is to reduce wear in brakes as it friction less. Therefore there will also be no heat loss. It can be used in heavy vehicles as well as in light vehicles.

The electromagnetic brakes are much effective than conventional brakes & the time taken for application of brakes are also smaller. There is very few need of lubrication. Electromagnetic brakes gives such better performance with less cost which is today’s need. There are also many more advantages of Electromagnetic brakes. That’s why electromagnetic brakes are en excellent replacement on conventional brakes.

Electromagnetic brakes are of today’s automobiles. A electromagnetic braking system for automobiles like cars, an effective braking system. And, by using this electromagnetic brakes, we can increase the life of the braking unit. The working principle of this system is that when the magnetic flux passes through and perpendicular to the rotating wheel the eddy current flows opposite to the rotating wheel/rotor direction. This eddy current trying to stop the rotating wheel or rotor. This results in the rotating wheel or rotor comes to rest/ neutral.

HISTORY

It is found that electromagnetic brakes can develop a negative power which represents nearly twice the maximum power output of a typical engine, and at least three times the braking power of an exhaust brake. (Reverdin 1994). These performance of electromagnetic brakes make them much more competitive candidate for alternative retardation equipments compared with other retarders. By using by using the electromagnetic brakes are supplementary retardation equipment, the friction brakes can be used less frequently, and therefore practically never reach high temperatures. The brake linings would last considerably longer before requiring maintenance and the potentially “brake fade” problem could be avoided.

In research conducted by a truck manufacturer, it was proved that the electromagnetic brake assumed 80% of the duty which would otherwise have been demanded of the regular service brake (Reverdin 1974). Furthermore the electromagnetic brakes prevents the danger that can arise from the prolonged use of brake beyond  their capability to dissipate heat.

This is most likely to occur  while a vehicle  descending a long gradient at high speed. In A study with a vehicle with 5 axles and weighing 40 tons powered by a powered by an engine of 310 b.h.p travelling down a gradient of 6% at a steady speed between 35 and 40 m.h.p, it can be calculated that the braking power necessary to maintain this speed at the order of 450 hp. The brakes, therefore, would have to absorb 300 hp, meaning that each brake in the 5 axles must absorb 30 hp, that a friction brake can normally absorb with self destruction.

The magnetic brake is well suited to such conditions since it will independently absorb more than 300 hp (Reverdin 1974). It therefore can exceed the requirements of continuous uninterrupted braking, leaving the friction brakes cool and ready for emergency braking in total safety.

The installation of an electromagnetic brake is not very difficulty if there is enough space between the gearbox and the rear axle. If did not need a subsidiary cooling system. It relay on the efficiency of engine components for its use, so do exhaust and hydrokinetic brakes. The exhaust brake is an on/off device and hydrokinetic brakes have very complex control system. The electromagnetic brake control system is an electric switching system which gives it superior controllability.

CONSTRUCTION

The construction of the electromagnetic braking system is very simple. The parts needed for the construction are electromagnetic, rheostat, sensors and magnetic insulator. A cylindrical ring shaped electromagnet with winding is placed parallel to rotating wheel disc/ rotor. The electro magnet is fixed, like as stator and coils are wounded along the electromagnet. These coils are connected with electrical circuit containing one rheostat which is connected with brake pedal. And the rheostat is used to control the current flowing is used to control the magnetic flux. And also it is used to prevent the magnetization of other parts like axle and it act as asupport frame for the electromagnet. The sensor used to indicate the disconnection in the whole circuit. If there is any error it gives an alert, so we can avoid accident.

WORKING PRINCIPLE

The working principle of the electric retarder is based on the electric retarder is based on the creation of eddy currents within a metal discs rotating rotating between two electro magnets, which set up a force opposing the rotation of the discs. If the electromagnet is not energized, the rotation of the disc free and accelerates uniformly under the action of the weight to which its shaft is connected.

When the electromagnet is energized, the rotation of the disc is retarded and the energy absorbed appears as heating of the discs. If the current exciting the electromagnet is varied by a rheostat, the raking force varies  indirect proportion of the value of the current. The development of this invention began when the French company Telma, associated with Raoul Sarazin, developed and marketed several generations of electric brake based on the functioning principle described above. A typical retarder consists of stator and rotor. The stator hold 16 induction coils, energized separately in group of four. The coils are made up of varnished aluminium wire mounted in epoxy resin.

The stator assembly is supported resiliently through anti-vibration mountings on the chasis frame of the vehicle. The rotor is made up of two discs, which provide the braking force when subjected to the electromagnetic influence when the coil are excited. Care fully design of the fins, which are integral to the disc, permit independent cooling of the arrangement.

ADVANTAGES

1. Electromagnetic brakes can develop a negative power which represents nearly twice the maximum power output of a typical engine.

 2. Electromagnetic brakes work in a relatively cool condition and satisfy all

the energy requirements of braking at high speeds, completely without the use of friction. Due to its specific installation location (transmission line of rigid vehicles), electromagnetic brakes have better heat dissipation capability to avoid problems that friction brakes face times the braking power of an exhaust brake.

 3. Electromagnetic brakes have been used as supplementary retardation equipment in addition to the regular friction brakes on heavy vehicles.

 4. Electromagnetic brakes has great braking efficiency and has the potential to regain energy lost in braking.

 5. It’s component cost is less.

DISADVANTAGES

1. The installation of an electromagnetic brake is very difficult if there is

Not enough space between the gearbox and the rear axle.

2. Need a separate compressor.

3. Maintenance of the equipment components such as hoses, valves has to done periodically.

4. It cannot use grease or oil.

APPLICATIONS

1. Used in crane control system.

2. Used in winch controlling.

3. Used in lift controlling.

4. Used in automatic purpose.

The lot’s of new technologies are arriving in world. They create a lot of effect. Most industries got their new faces due to this arrival of technologies. Automobile industry is also one of them. There is a boom in World’s automobile industry. So lot’s of research is also going here. As an important part of automobile, there are also innovations in brakes. Electromagnetic brake is one of them.

A electromagnetic braking for automobiles like cars, an effective braking system. And, by using this electromagnetic brakes, we can increase the life of the braking unit. The working principle of this system is that when the electromagnetic flux passes through and perpendicular to the rotating wheel the eddy current is induced in the rotating wheel or rotor. This eddy current flows opposite to the rotating wheel. This eddy current tries to stop the rotating wheel or rotor. This results in the rotating wheel or rotor comes to rest.