Design of a CT-Based Energy Harvesting Circuit for Three-Phase AC Motors

This paper presents a current-transformer (CT) based energy harvesting circuit which powers a sensor board used for three-phase AC motors. The design is based on a Texas Instruments reference design with some modifications to suit the customer’s requirement. In this design, three-phase current transformers with delta-connected secondary coils are used to harvest energy from the magnetic field surrounding the input line currents. A backup battery is used for cold starting the circuit as well as to provide power backup when there is not enough energy harvested by the current transformers. The practical test results match the simulated test results where the energy harvesting board was able to harvest 5V/1.75W from three phase 10A input line currents or from 0.85A line currents with 12 primary turns on the current transformers