A non-invasive electric current sensor employing a modified shear-mode cymbal transducer

• This paper presents a non-invasive current sensor consisting of a modified shear-mode cymbal transducer and a Halbach array.
• The Halbach array generates concentrated magnetic field on the electric wire, leading to an enhanced magnetic force on the array.
• The magnetic force is further amplified by the cymbal transducer which works in shear mode.
• The sensitivity of the sensor is improved due to the enhancement effect of the magnetic force resulting from the Halbach array and the amplification effect of the cymbal transducer.

This paper presents a non-invasive sensor for electric current monitoring in electric power grid. The sensor consists of a modified shear-mode cymbal transducer and a Halbach array attached on the transducer. The Halbach array generates concentrated magnetic flux density on the side where the electric wire is placed and lowers the magnetic field on the other side. The wire experiences an enhanced Ampere force when energized, and the resulting reaction force of the Ampere force is further amplified by the cymbal transducer. The transducer works in shear mode and produces a voltage proportional to the applied electric current. At low frequencies, the sensor exhibits a flat voltage response. The non-resonant sensitivity of the sensor reaches ∼6.98 mV/A over the frequency range of 10–80 Hz with a separating distance of d = 3.0 mm. The average sensitivity is 6.97 mV/A with high linearity at the power-frequency of 50 Hz, and a small current step change of 0.05 A can be clearly distinguished.