Eddy currents are setup in any metallic block which is in the vicinity of changing magnetic fluxes. These primarily cause heat losses, and in certain cases causes damping of the relative motion between the metallic block (where the currents are induced) and the magnet producing the field.To reduce these effects, we use two strategies:-
- Laminating the metallic core, that is to be in the vicinity of changing magnetic flux.
- By drawing teeth along the piece of metal.
I fail to understand how these would reduce the eddy losses? The reason cited in the first case is the eddy current path will be blocked by the laminations. But from what I see, laminations just make the eddy currents go in smaller circles, and the path length traversed by the eddy currents are actually more than in the case without laminations, and therefore the resistance should increase, and the power losses should increase!
In the second case, the reason cited is the reduction in the area of the eddy current loops and hence a smaller magnetic moment for damping.($\vec \mu=I\vec A$)But again, although the area of each eddy current loop has decreased, but then individual loops in different "teeth" can produce individual moments, and the net area being same, the net moment will still be equal producing similar deacceleration!