Electrical drives-universal sources of mechanical energy

Adjustable speed electrical drives are undergoing a transition from DC- to AC-machines, which now affects all applications, from the smallest to the largest power ratings. Macroelectronics and microelectronics are complementary, providing the power and the intelligence for the complex systems. Rapid torque control is the key to all higher level functions in motion control. Its response is limited by the switching frequency of the power converter and the sampling frequency of the digital controller; with servo drives the equivalent lag is of the order of 1 ms, and 10 ms on large drives, thus approaching the ideal of instantaneous torque control