# Dependence of damping constant on current

1. Sep 16, 2015

### PlickPlock

Using an eddy current brake, one would expect the damping constant $δ$ to increase with the current $I$ supplied to the eddy current brake. My question is, why is $δ$ proportional to $I^2$ and not merely $I$?

The magnitude of the eddy current is $\frac{1}{R}\frac{dΦ}{dt}$, which is why I initially thought $δ$ was proportional to $I$, because the induced current is proportional to $\frac{dΦ}{dt}$.

was what I used as reference; it stated the relation but does not seem to explain why.

2. Sep 17, 2015

### Hesch

The B1-field induced by the brake is proportional to I.
The induced eddy voltage in the disk is proportional to the B1-field.
The induced eddy current in the disk is proportional to the eddy voltage.
The induced B2-field from the disk is proportional to the eddy current.
The braking force is proportional to the magnetic energy density in the airgap = ½*B1*(B20) [ J/m3 ].

That's why.

Last edited: Sep 17, 2015