How Eddy Currents Produce Attractive Electromagnetic Forces-Maglev

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Discussion Overview

The discussion revolves around the mechanisms of attractive electromagnetic forces in maglev systems, particularly focusing on the role of eddy currents. Participants explore the differences between attractive and repulsive magnetic suspension systems, with an emphasis on understanding how eddy currents can contribute to attraction in electromagnetic systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in visualizing how eddy currents can produce attractive forces, noting that their understanding primarily revolves around repulsive systems.
  • Another participant mentions that they have only encountered repulsive maglev systems and requests references for attractive systems.
  • A participant cites the German Transrapid system as an example of attractive forces but claims that lifting does not involve eddy currents.
  • One participant references a website that discusses eddy currents in the context of attractive electromagnetic suspension, but expresses uncertainty about its validity and notes inconsistencies in explanations across different sources.
  • Another participant suggests that the presence of iron in the undercarriage and train electromagnets leads to magnetic attraction, questioning the role of alternating current in lifting magnets and mentioning the use of eddy currents in other applications like distance sensors and braking.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the mechanisms of attraction in maglev systems. There are competing views regarding the role of eddy currents and the specifics of how attractive forces are generated.

Contextual Notes

There are limitations in the discussion regarding the clarity of the mechanisms involved in attraction, the dependence on specific definitions of magnetic forces, and the unresolved nature of how alternating current interacts with the system.

Who May Find This Useful

Individuals interested in maglev technology, electromagnetic systems, and the principles of eddy currents may find this discussion relevant.

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How Eddy Currents Produce Attractive Electromagnetic Forces--Maglev

Hello, I am working on a paper about maglev systems and am trying to describe attractive electromagnetic suspension systems, but I am having a little trouble exactly visualizing how this works, which from what I have read is due to magnetic fields through eddy currents. In repulsive electrodynamic suspensions systems, this all makes a lot of sense to me. The changing magnetic field runs through the surface of the tracks and sets up eddy currents that oppose the time-changing flux, which in turn create a magnetic field of their own. The result of the two magnetic fields is magnetic repulsion, due to the magnetic pressure between the two systems.

But how can eddy currents be used to explain the attraction. When I draw the diagrams of magnetic fields going through a conductor, I am only able to figure out a way to draw them such that the induced magnetic field is repulsive. Can anyone help me see how they can be attractive as well? Thank you!
 
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I may have lead a sheltered life but I have only heard of repulsive maglev systems. Do you have a reference?
 


I was reading through several websites, though this is the one that mentioned an eddy current for attractive EMS:
http://www.hk-phy.org/energy/transport/trans_phy02_e.html

I can't vouch for the validity, and it seems like every website explains it a little differently, but the website's second diagram is good, and it is one I have seen on many sites. All in all, I am just having difficulty explaining the mechanism for induction. Anybody have a better idea than I at how the alternating current in the undercarriage of the train attracts the guideway (rail)?
 


If I understand it correctly, there is iron in the undercarriage (as well as in the train electromagnets). So its a "simple" case of magnetic attraction.
I found no mention of AC for the lifting magnets. AC lifting magnets might not work with the propulsion system.
Eddy currents are used for distance sensors (according to your link, which I do not like very much) and for braking.
 

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