Research On Optical Current Transformer Used To Measurement Small Current

Optical current transformer (OCT) has excellent performance such as good insulation, no saturation, small size and so on, which is considered to be the alternative products of traditional electromagnetic current transformer (CT). The OCT systems are vulnerable to external factors such as temperature, vibration and other effects, leading to unstable operation, poor accuracy, specific performance is the measurement drift over time, mainly due to this, the development of OCT is full of rough for many years.In order to solve the above problems, a new Type of OCT to measure small current is proposed, which is based on the method of comparative measurements, and improving the sensor head of measuring arm, replacing linear current carrying wire by the solenoid to produce a magnetic field. Comparison method of measurement is introduced a reference arm based on the original OCT, with the permanent magnet as a reference magnetic field. Comparing the measurement results of operations of the two sensor arms could eliminate some impacts of external factors. And the current carrying wire of measuring arm can be made to the solenoid to generate a greater magnetic field strength than in the linear wires in a short length. It is possible for OCT to measure small current.First of all, the basic principle of OCT was introduced, and the various parts of the model were analyzed in the perspective of electronic dynamics. Then based on the analysis of the model, together with the solenoid with optical sensor head comparative study of the sensing structure OCT. Then we considered the environmental factors how to affect the OCT mechanism, sensing mechanism and sensitivity of comparative small current. Finally, two key technologies of comparative small current OCT signal demodulation were studied:DC magnetic field demodulation and detection of weak signal communication. Dual-input demodulator DC magnetic field, high-precision capture card and LabVIEW all-digital platform were adopted to detect exchanging weak signals. Thus greatly improving the measurement accuracy and stability of comparative small current OCT.