Eddy Current Dynamometer

The Eddy Current Dynamometer is Bi-directional, Dry-gap Type. In a dry gap unit, the only resistance to movement of the rotor is that of bearing friction and the small effect of windage. With zero excitation, an almost no-load condition can be achieved over the entire speed range.
The construction comprises of a thin spoked steel rotor revolving in a casing that houses the field coil and the heat exchanger. When excitation current is generated in the coil, a magnetic flux is developed. An equal and opposite magnetic field is induced in the heat exchanger walls facing the rotor. This field is pulsating corresponding to the RPM of the rotor. The changing field produces Eddy Currents in the heat exchanger walls that oppose the excitation field and thus causing retarding action to be imposed on the rotor. The magnetic flux lines developed in the rotor can be kept to a minimum thickness, resulting in a low moment of inertia.