Conventional condition monitoring of electrical machinery is conducted by measuring signals such as currents and vibrations outside the motor. Wireless sensors now provide a means of accessing and measuring useful signals inside the motor where the phenomena responsible for failure occur. These sensors are capable of not merely sensing, but also processing, storage and eventually communication. Since all these activities require power that is supplied conventionally by batteries, the useful life of the sensor node is limited by the life of the battery. This paper describes the design of an energy scavenger capable of collecting energy from the fringing field in a three-phase induction motor. The field in the magnetic filed is converted to electrical energy for use in intelligent wireless sensor nodes. The alternating magnetic field in a three phase induction motor is first measured by the hall-effect sensors. A coil wound on a ferrite core harvests the leaked energy. The experimental results are compared to the theoretical calculations of induced voltage. The paper describes results from tests conducted with a prototype coil that is used to power wireless sensor nodes in a motor running at full speed.

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