During its early years in the 1960s, AC drives had rather small solid-state components; this meant that the amount of current AC drives could supply to the electric motor was quite limited.  This usually limited the size of the electric motor that could be controlled by a frequency and they were not commonly used.  However, when larger transistors became available in the 1980s, AC drives allowed the largest electric motors to have their speed controlled.  Some of the earliest AC drives used linear amplifiers to control all aspects of the drive.  Jumpers and dip switches were used to provide ramp-up (acceleration) and ramp-down (deceleration) features by switching larger or smaller resistors into circuits with capacitors to create different slopes.

These days AC drives have developed into perhaps the most common type of output or load for a control system.  Because applications are more complex, AC drives have the ability to control the speed of the electric motor, the direction which the motor shaft is turning, the torque the electric motor provides to a load and any other motor parameter that can be sensed.  Modern AC drives have a variety of parameters that can be controlled by numbers programmed into it or downloaded from another microprocessor-controlled system such as a programmable controller (PLC).  AC drives are also available in smaller sizes that are more cost-efficient and take up less space.