Researchers at the Hong Kong Polytechnic University have developed an electrical current sensor designed to power itself with harvested energy while monitoring electrical equipment.
Similar to a thermometer that measures temperature, the 1-milimeter-thick smart sensors are made from rare earth multiferroics with giant magnetoelectric properties and are capable of recognizing changes in electrical currents within electrical equipment such as electrical cables, conductors, junctions and bus bars. The sensors work by detecting magnetic fields generated by electricity and converting them into electrical voltage signals, explains Professor Derek Siu-wing Or of the Department of Electrical Engineering at The Hong Kong Polytechnic University, adding that the amplitude of the converted signals is linearly proportional to the magnetic fields, while the frequencies directly follow the magnetic fields.
The sensors are particularly unique, says Or, because they do not need the additional power supplies or signal conditioners often required by traditional current sensors. The elimination of these requirements means that the smart sensors do not have power cords and electronic active components, and can therefore be used for early fault detection in a variety of difficult-to-reach environments.
“Our smart sensors are essentially simple, totally passive and capable of producing large and clear output voltage signals 2,000 times higher than [that of] traditional current sensors. This passive and self-sustainable nature allows real-time, nonstop monitoring of the ‘health’ of electrical equipment, including those carrying high voltages, heavy currents and/or strong electromagnetic fields,” Or said.
‘“These smart sensors can [also] be tailored to harvest electromagnetic radiations emitted by the electrical equipment being monitored and turn them into useful electrical energy. The stored electrical energy can be used to power up microcontrollers, displays [and] wireless transmitters, further advancing the smart sensor technology toward ‘energy-harvesting smart wireless sensors’.”
The smart sensors are currently being tested in electrical traction systems on trains in Hong Kong and Singapore in order to provide in-situ monitoring of traction conditions and detect electrical faults that may bring train services to a halt. Or and his colleagues plan to continue to enhance the sensors’ harvesting capability and improve their sensitivity and reliability.
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