In order to select the best AC drives for a given AC motor, a complete analysis of application categories is required.  Multi-axis controllers are used to control and monitor multiple, independent axes of motion.  Motor speed controllers are application-specific and used to control machines such as conveyors.  Digital motion control hardware and software for the coordinated multi-axis control of industrial robots and robotic systems are utilized by robotic motion controllers.  Servo amplifiers are electronic modules that convert low level analog command signals to high power voltages and currents, while inverter drives convert AC power inputs to DC power outputs.  High frequency drives supply power to AC motors at frequencies that are much higher than those used in standard-power applications.  Regenerative drives support motor braking, while variable speed drives support speed control and adjustment.  AC drives using microcontrollers, silicon controlled rectifiers (SCR), digital signal processors (DSP), and pulse width modulation (PWM) is also available.