Mathematical modeling and experimental validation of an eddy current brake with permanent magnets

Magnetic brakes are devices used in rotating systems to apply a resisting torque to the machine. The most common configuration relies on electromagnetic induction, which generates eddy currents in a rotating component, typically a disk. The torque can be adjusted by controlling the electric current in the electromagnet coils. In contrast, brakes that use permanent magnets produce a constant torque, which depends solely on the distance between the magnets and the rotating part. Although electromagnetic brakes have been extensively studied, permanent magnet brakes are less explored. There are relatively few studies that provide mathematical models capable of accurately predicting the braking torque in line with experimental results. This work contributes to the field by bringing a different approach to model the system. The NdFeB (Neodymium–Iron–Boron) magnets are modeled using an equivalent coil circuit, and the generation of eddy currents is described based on electromagnetic theory to calculate the induced magnetic field in the disk. The model also incorporates the effect of torque saturation at high rotational speeds. The numerical predictions of the braking torque are compared with experimental measurements obtained from a test bench. Tests were conducted at various rotational speeds and with different gaps between the magnets and the rotating element. The results show a strong correlation between the model and the experimental data, confirming the accuracy of the model.