A modern AC motor drive is a very intelligent system which covers a wide range of different electro technical apparatus and a wide scope of electrical engineering skills. A modern AC motor drive consists of four closely acting main parts: the AC machine, the power electronics, the motor control algorithm and the control hardware, i.e. the signal electronics. The advances in semiconductors and microelectronics have made the rapid development of AC motor drives possible. Semiconductors used in the switching converters provide the electric energy processing capability and microcontrollers and digital signal processors provide the data processing power for complex control algorithms.