Eddy-current damper

When a conductor moves in a magnetic field, damping forces are generated by eddy currents induced in the conductor. The magnetic damper, with its reliability and thermal stability, has been utilized in various branches of engineering. A recent analysis of it is given by Nagaya and Kojima (1984). 

A schematic of an eddy-current damper is shown in Fig. 10.6. A copper block with resistivity p is under the influence of the magnetic field 6 of a permanent magnet. The relative motion of the magnet and the copper block in the X direction causes a force in the -x direction. By solving Maxwell s equation numerically, Nagaya (1984) calculated the force to be 

10 For example, Lee Spring Company, 1462 62nd Street, Brooklyn, New York 11219. 

While using Eq. (10.36) to calculate the damping constant, the dimensionless parameter Co can be chosen from this chart. (After Nagaya, 1984.) 

---

Fig. 10.6. Eddy-current damper. A magnet is placed against a metal plate of resistivity p. When there is a relative velocity between them, a viscous force occurs. The force constant depends on the strength of the magnetic field and the dimensions of the plate and the magnet. (After Okano et al., 1987.)...

Directional walk of atoms 42 DNA 341 Dominant pole 265 Eddy-current damper 248 Elasticity theory 365—376 Electrochemical tip etching 282—285 Electrochemistry 323... 

There is no permanent flux in this machine, hence, = 0. Further, assuming eddy currents in the rotor, modeled with one equivalent damper winding in each of both the d- and the -axes, results in the BG of Fig. 8.21, again with motor power flow convention. 

---