Design and Construction of a Brushless Permanent Magnet Servomotor for Direct-Drive Application

The feasibility and design of permanent magnet servomotors for direct-drive application at a power level near 10 kW at 270 r/min are investigated. Such applications imply low-speed machines with a great amount of iron and permanent magnet material. The compromise between the specific energy and the cost of magnets is one of the usual guides for designing such motors. The performance of an actual prototype shows that the use of low-cost ferrite material associated with a proper flux-concentration structure of a magnetic circuit is especially interesting at this power level. The design procedure is presented with a prediction of the performance based on field calculations, which can be compared with experimental results of generator operation. The motor can be used in several brushless configurations. An evaluation of the performance, in each case, according to the kind of static converter and control strategy is presented. Several improved models and computer simulations are used. The adaptation of the rotor damper circuits to the supply is also discussed.