Design and Development of DSP based Control Card for Regenerative AC Drives

Abstract

AC drive widely used to control the speed of AC motor. In certain cases where AC drive regenerate energy due to this DC link capacitor voltage exceed to the specified level very rapidly because of small capacitor value. One of the technique to limit this voltage value is the dynamic braking where switch transfer the excess regenerative current to the resistor which generates the heat and wastage of energy. Instead of these in regenerative braking the energy is transfer to the ac mains to be used at later. During regenerative braking motor acts as a generator. The motoring and generating action can be explain by torque and speed curve relation. In first and third quadrant where speed and torque are in same direction so motor operated in motoring action and power flows from ac mains to the motor (motoring) and in second and fourth quadrant where speed and torque are in opposite direction so power flows from motor to ac mains (generating). The control of the DC link capacitor voltage during regeneration that can be done by DSP. The application areas of the project are locomotives, downhill conveyors, elevators, cranes etc.