Analysis of the Thermal Limits of Conventional Eddy Current Brakes based on a Thermal 1d-Model

Abstract

This article describes the thermal limits of conventional eddy current brakes with an eddy current element with homogeneous material density. Eddy current brakes are wear-free, but have a low power density compared to friction brakes. Most conventional eddy current brakes on the market or in other publications run at a speed of less than 3000 rpm. The objective of this work is to evaluate the maximum speed and theoretical power density of eddy current brakes of the references shown in this work. The maximum speed is limited by the maximum allowable temperature and the maximum allowable load on the rotor due to centrifugal forces. Therefore, the maximum speed and maximum power density are approximated with a transient thermal model after evaluating the maximum speed at 20 degrees Celsius for different applications. Prior to this, the geometry data of the eddy current brakes are evaluated and the torque-speed curves are fitted using a model-based approach to approximate the torque at higher speeds. The highest power density electrically excited eddy current brake studied in this work would have a maximum power density of 4kWk$\text{g}^{-1}$ and the permanent magnet excited eddy current brake of about 15 kWk$\text{g}^{-1}$