Eddy Current Dynamometer

Eddy Current Dynamometer:

The working principle of eddy current dynamometer is shown in the figure below. It consists of a stator on which are fitted some electromagnets and a rotor disc made of copper or steel and coupled to the output shaft of the engine. When the rotor rotates, eddy currents are produced in the stator due to magnetic flux set up by the passage of field current in the electromagnets. These eddy currents are dissipated in producing heat so that this type of dynamometer requires some cooling arrangement. The torque is measured exactly as in other types of absorption dynamometers, i.e., with the help of a moment arm. The load in internal combustion engine testing is controlled by regulating the current in the electromagnets.

The following are the main advantages of eddy current dynamometers:

High brake power per unit weight of dynamometer.

They offer the highest ratio of constant power speed range (up to 5 : 1).

Level of field excitation is below 1% of total power being handled by the dynamometer. Thus, they are easy to control and operate.

Development of eddy current is smooth hence the torque is also smooth and continuous under all conditions.

Relatively higher torque under low-speed conditions.

It has no intricate rotating parts except shaft bearing.

No natural limit to size, either small or large.