Current Sensor Based On Giant Magnetostrictive Material And Fiber Bragg Grating

With the fast developments of the industry,agriculture,transportation,and national defense,the power industry plays an increasingly important role in people's living.However,higher requests are put forward to electric detection.The traditional current sensors can't meet the requirements of recent industrial technology development and the power failures are appearing frequently with the increase of the electricity consumption.The optical current sensor can make up for the shortcomings of the traditional current sensors,and this field has been extensive researched.The optical current sensors have become a hot research field of current measurement.Fiber Bragg grating(FBG) is one of the most rapidly developed optical passive devices in recent years.FBG has the features of low cost,light weight,small size, anti-electromagnetic interference and can realize the distributed measured,so it has been widely applied in communication and sensing fields,especially in the field of current sensing.Various structures of fiber Bragg grating current sensors are emerging constantly.This essay reviewed the present situation of FBG current sensors,compared and analyzed their developments and existing problems.Based on this research,this paper proposed a new optical current sensor composed by combining FBG with the giant magnetostrictive material(GMM) Terfenol-D.The Terfenol-D rod was elongated in the magnetic field,and the strain caused the change of the optical parameters of FBG, which was stuck on the material along the axial direction.Thereby the center wavelength of FBG was shift.In certain biased magnetic field,the relationship between the measured current and the wavelength shift is linear.So the value of the current which produced the magnetic field can be got through measuring the center wavelength shift.The main research works are as following:1.The optical properties and sensing principles of FBG was studied,and the FBG temperature and stress model was established.2.The magnetostrictive phenomena,mechanism and material characteristics of the magnetostrictive material was studied.Compared the GMM Terfenol-D with other magnetostrictive material,Terfenol-D was chosen as sensor medium.The whole scheme of FBG current sensor based on GMM was designed on this basis.3.The magnetostriction coefficient of GMM was measured by the resistance strain gauges.The prestressed device was designed according to the characteristics of magnetostrictive materials.The effect of prestress impact on the properties of magnetostrictive materials was analyzed from the theory and the experiments.4.The silicon plate magnetic core coils which were used to change the measured current into magnetic field were designed and made.The magnetic field generated by one circle of great electric current was simulated by many circles of little current.5.The FBG current sensing system,including the sensing head,magnetic circuit, light path was designed and the bias magnetic field was designed and optimized.6.The data measurement of FBG current sensor was completed and analyzed.