How Can Eddy Currents Be Used for Energy Recovery in Locomotive Braking Systems?

[Gravitron]

I have read that locomotives use eddy current braking systems, and one article mentioned that this system has also been used to charge batteries in a recovery circuit. However, I can not find details on this idea. From what I understand, the train has conducting discs attached to the wheels, and an electromagnet is charged in close proximity to the disc producing a powerful torque via the eddy currents produced in the disc. How could a system recover electric current from this disc, I thought most if not all the force is converted to heat in the disc. Anyone have any ideas?

Thanks!
G

 

[bjacoby]

I have read that locomotives use eddy current braking systems, and one article mentioned that this system has also been used to charge batteries in a recovery circuit. However, I can not find details on this idea. From what I understand, the train has conducting discs attached to the wheels, and an electromagnet is charged in close proximity to the disc producing a powerful torque via the eddy currents produced in the disc. How could a system recover electric current from this disc, I thought most if not all the force is converted to heat in the disc. Anyone have any ideas?

Thanks!
G

Instead of thinking about "eddy currents" where a conductor moving in a magnetic field creates a circulating current that creates a force opposing the motion make the system more formal. In most "eddy current" systems motion induces a current that flows around in a conductor (in "eddies") and except for the forces created the current is just wasted heating the conductor. But what you are really doing is building a generator that is powering a load so it develops a mechanical force opposing it's mechanical input. In a more formal system we'd use a REAL generator. Now that would be built so as to direct the generated current into external wires rather than just round and round in the conductive parts. And then as a load you might use a large resistor, but better would be a bank of batteries that need charging! Hence if you want to slow the train (or Toyota Prius) you hook the battery pack to the generators on the wheels which provide a slowing torque and at the same dime produce an electric current which is charging the batteries. This way much of the energy needed to slow the vehicle is save to be used again in speeding it back up! Clever!

 

[Gravitron]

Instead of thinking about "eddy currents" where a conductor moving in a magnetic field creates a circulating current that creates a force opposing the motion make the system more formal. In most "eddy current" systems motion induces a current that flows around in a conductor (in "eddies") and except for the forces created the current is just wasted heating the conductor. But what you are really doing is building a generator that is powering a load so it develops a mechanical force opposing it's mechanical input. In a more formal system we'd use a REAL generator. Now that would be built so as to direct the generated current into external wires rather than just round and round in the conductive parts. And then as a load you might use a large resistor, but better would be a bank of batteries that need charging! Hence if you want to slow the train (or Toyota Prius) you hook the battery pack to the generators on the wheels which provide a slowing torque and at the same dime produce an electric current which is charging the batteries. This way much of the energy needed to slow the vehicle is save to be used again in speeding it back up! Clever!

Yes I see, but what I'm trying to understand is this... In the example, the train uses a solid conducting disc attached to the wheels. how would you capture the electricity from a disc like this. I can understand using a series of coils arranged in a circular fashion around the wheel, with a commutator/brush to connect the ends of the coils, but how would you do this in a solid disc? The disc is uniform, so where would you tap the disc to capture the electrical energy? Would you simply place a brush at the perimeter and the center of the disc?

Thanks!

 

[Bob S]

Read about regenerative and rheostatic braking in diesel-electric and electric locomototives at:

http://en.wikipedia.org/wiki/Dynamic_braking

Bob S

 

[sardar]

lad to hear that you are interested in eddy currents and their applications in braking systems. Eddy currents are a phenomenon that occurs when a conductor, such as a metal disc, is exposed to a changing magnetic field. The changing magnetic field induces a circulating electric current within the conductor, which in turn produces its own magnetic field. This interaction between the induced magnetic field and the original magnetic field creates a force that opposes the motion of the conductor, resulting in the braking effect.

In the case of locomotives, the conducting discs attached to the wheels are used as part of an eddy current braking system. As you mentioned, an electromagnet is charged in close proximity to the disc, and the resulting eddy currents in the disc create a powerful braking force. This force is then converted to heat in the disc, which dissipates into the surrounding environment.

However, it is possible to recover some of this heat energy and convert it back into electric current using a recovery circuit. This is achieved by using a device called a rectifier, which can convert the alternating current (AC) produced by the eddy currents into direct current (DC). The DC current can then be stored in batteries or used to power other systems on the train.

It is worth noting that not all of the braking force can be recovered in this way, as some of it will still be lost as heat in the disc. But by incorporating a recovery circuit, some of the energy that would otherwise be wasted can be reused, making the braking system more efficient.

I hope this helps to clarify the concept of using eddy currents for both braking and energy recovery in locomotives. I encourage you to continue exploring this fascinating topic and perhaps even conduct your own experiments to further understand the principles at work.