Origin and development of bearingless motor;
After Ferrari and Tesla invented the multiphase AC system, in the mid-1980s of 19, Dovoro Volschi invented the three-phase asynchronous motor. Asynchronous motors don't need brushes and commutators, but bearing maintenance is still a difficult problem when they run at high speed for a long time.
After World War II, the development of DC magnetic bearing technology made it possible for the motor and transmission system to run without contact, but the cost of this transmission system was very high, because ferromagnetic objects could not be stably suspended in a constant magnetic field. The invention of active magnetic bearing solved this problem. However, using active magnetic bearings to support rigid rotors requires the application of control forces in five degrees of freedom. Magnetic bearings are bulky, complex and costly.
In the second half of the 20th century, in order to meet the development and utilization of nuclear energy, it is necessary to produce enriched uranium by ultra-high speed centrifugal separation, and magnetic bearings can meet the support requirements of high-speed motors, so Europe began to study various schemes of magnetic bearings. 1975, Herman applied for a bearingless motor patent, in which the relationship between the number of motor windings and the number of magnetic bearing windings was proposed as 1. With Herman's proposal, it was impossible to manufacture bearingless motors at that time.
With the further improvement of magnetic properties of magnetic materials, it has laid a strong competitive position for permanent magnet synchronous motors. At the same time, with the application of bipolar transistor, combined with the lossless switching circuit proposed by Beringer, a new generation of high-performance power amplifiers can be manufactured to meet the requirements of bearingless motors. 1985 or so, the appearance of power switching devices and digital signal processors with fast and load capacity makes the vector control technology of AC motor proposed for more than 20 years practical, thus solving the digital control problem of bearingless motors. Based on these scientific and technological advances, bickel of Swiss Federal Institute of Technology made the bearingless motor for the first time in the late 1980s.
Almost at the same time as bickel, Japanese A.Chiba realized the bearingless technology of reluctance motor for the first time in 1990.
1993, R.Schoeb of Zurich Federal Institute of Technology realized the bearingless technology of AC motor for the first time.
The key breakthrough in the practical application of bearingless motor is the development of bearingless permanent magnet synchronous slice motor by Baleta of Zurich Federal Institute of Technology in 1998. The simple structure of the motor greatly reduces the cost of the control system and has great application value in many fields.
In 2000, S.Sliber of Zurich Federal Institute of Technology developed a bearingless single-phase motor, which took a step forward in the research history of bearingless motor, reduced the cost of control system, and made the practical application of bearingless motor not only imaginable, but also economical. Bearingless motors are as simple as those supported by mechanical bearings, and the electrical control system is not complicated. It is also economical to use bearingless motors in many fields.