Magnetic Float Liquid Level Detection Method for High-Temperature Superconducting Flux-Pinning Maglev System

High temperature superconducting (HTS) flux-pinning maglev system uses the flux-pinning characteristics of HTS bulk to achieve self-stable levitation, but the superconductivity of HTS bulk depends on low temperature maintained by liquid nitrogen. It can be seen that the real-time detection of liquid nitrogen level is an essential safety detection in the HTS flux-pinning maglev system. However, the liquid nitrogen level measurement of Dewar is limited by many conditions, such as small available size of Dewar, small liquid nitrogen capacity, low temperature characteristics of liquid nitrogen, etc. These conditions require the liquid level detection system to be able to withstand low temperature, have sufficient identification accuracy and have no significant impact on the cold insulation performance of Dewar. All of these bring difficulties to the design of real-time liquid level detection in the maglev system. Based on the structural characteristics of Dewar, a new type of magnetic float liquid level detection device is studied in this paper. The device can realize liquid nitrogen level detection function and low-level alarm function. Its technical principle is to use Hall sensor array to detect the position of the magnetic float in real time, and transmit the data to the onboard computer for data storage and data monitoring. The experimental results show that the proposed liquid nitrogen level detection method can meet the requirements of liquid nitrogen level detection and alarm with certain accuracy, and will not bring additional heat leakage to affect the Dewar performance.