The development is described of a new range of eddy-current dynamometers with capacity ranging from 70 kW at up to 12000 rev/mm to 500 kW at up to 4500 rev/min. These are dry-gap, homopolar, disc-type inductor machines in which the excitation coils and water-cooled lossplates are stationary and only a toothed steel member rotates. A design analysis procedure is presented which was used in the development, taking due account of eddy-current penetration and lossplate thickness, magnetic circuit saturation, temperature variations and end effects. Some fundamental points are made concerning conditions at maximum torque, and the performance of machines having two loss members in a single field system is analysed. Measured and computed performance of representative machines under operational conditions show good agreement.