Reducing Eddy Current Effects: How Laminated Cores and Reduced Area Help

[jayeshtrivedi]

Dear All,
How laminated core helps in reduction of the eddy current?
How reduction of area is useful in reduction of eddy current?
Thanks.

 

[Baluncore]

Magnetic laminations must be oriented so that conductive material does not act as a large area electrical short circuited turn. The sectional area of lamination penetrated by magnetic field decides the voltage available to drive eddy the currents.

The thickness of laminations is more to do with utilising all the mass of the lamination than with eddy current reduction. The electric and magnetic fields propagate through the insulation between laminations at close to the speed of light. Skin effects on the surface of conductive laminations limit the rate of penetration of the magnetic field. This speed of penetration is very slow and so is measured in metres per second. The thickness of laminations must therefore be selected depending on the frequency of operation, while the orientation of laminations is selected to minimise eddy currents.

 

[jayeshtrivedi]

Hi,

I think am unable to understand the reply, could you please explain in details.

Thanks.

Jayesh Trivedi

 

[Baluncore]

You must read https://en.wikipedia.org/wiki/Eddy_current
then ask more specific questions.

 

[Okefenokee]

Think about drawing circles inside a rectangle without going outside the line. If I have a fairly large rectangle then I can draw some big circles. If I squish the rectangle so that it's more like a plate then I can only draw small circles.

When magnetic fields change in time they cause the electric field to curl up. If this happens in a large conductive mass then there will be a large circular current called the eddy current. If you chop that mass up into plates then their won't be as much room for the current to spin around in each individual plate so the eddy currents will be smaller.