Ten years past and many years of advancement ahead

摘要

Ten years ago we were celebrating the 100th anniversary of the birth of the efficient speed control of electric motors pioneered by Harry Ward Leonard. Much had changed in those 100 years with the introduction of solid state switches replacing multiple motors and the microprocessor and ASIC replacing carbon resistor stacks. As well as the significant component changes, the functionality of the drive had developed. It was a speed controller. By 1995 it was, in some applications, a process controller with many drives offering PID control. Whilst the functionality had broadened, the core motor shaft control performance had improved and induction motors were being harnessed in demanding applications ranging from printing and elevators to machine tool spindles. This was achieved by the use of vector control based on rotating reference frame algorithms. Some drive manufacturers created confusion in the market by offering 'voltage vector' technology. Thankfully that 'marketing' has now gone.