Abstract: The performance of an eddy current brake is controlled by controlling the magnetic flux in its housing by changing the energizing voltage of the energizing coil of the brake in accordance with a signal obtained by comparing a signal representative of the desired brake performance with a signal representative of the actual magnetic flux measured in the housing at a location of substantially homogeneous flux distribution. The desired performance signal may be a signal representative of the difference between a desired rotational speed signal and the actual rotational speed signal, or it may be a signal representative of the difference between a desired torque signal and an actual torque signal. The desired performance signal may also be a signal representative of the difference between a signal obtained by comparing desired and actual rotational speed signals with a signal representative of actual torque. A Hall generator is used to measure actual flux.