The superconducting magnet which is installed on a maglev vehicle suffers a disturbance of magnetic fluctuation from the ground coils. This magnetic disturbance has a frequency widely ranging from 0Hz to several hundred Hz which is proportional to the speed of maglev vehicle. We constructed the facilities which can simulate an actual electro-magnetic disturbance on the magnet in running and exercised electro-magnetic vibrating tests. It was revealed that an extreme increase of heat load on the inner vessel of the energized magnet was caused at a particular frequency. The initial amount of the heat load in these phenomena surpassed the capacity of the refrigerator installed in the tank of the superconducting magnet. So we have investigated into the causes of these phenomena and performed an experiment for confirming the effect of the improvement in a new setup. As a result, we could identify broadly three factors of heating and now we have good prospects of largely suppressing the heating by reducing the disturbance through the folded arrangement of the ground coils and structural improvement of the magnet. This paper describes the heating phenomena of a magnet under the electro-magnetic disturbance and the improvement for suppressing them as well as the historical background of maglev development.
High rigidity type superconducting magnet (SCM) is developed and tested by electromagnetic vibration simulator which simulate the actual running condition. To reduce the increase of heat load by the vibration of cryostat, several kind of design concepts are chosen. It is recognized by the experiment result that the most effective design concept is to increase the characteristic frequency in twisting mode of inner vessel with the high rigidity outer vessel.
Superconducting magnets on Maglev trains vibrate due to harmonic ripples of electromagnetic flux generated by ground coils. Heat load caused by vibration in the magnet, made in 1990, amounted to several tens of watts in the electromagnetic vibration test. This was mainly because AC loss was induced in the helium vessel housing the superconducting coil, due to relative vibration between the aluminum thermal shield and the coil. The heat load caused by vibration should be strictly restricted to less than 4W due to limited cryogenic refrigeration capacity. The heat load has been tested using electromagnetic flux ripples for a superconducting magnet model of one coil which corresponds to 1/4 of an actual magnet. The flux ripples simulate the 6th harmonic of the actual ground levitation coil. Some ideas to reduce the heat load were tried for the magnet model, such as high resistance thermal radiation shield, high rigidity of vacuum vessel, high purity copper plating on the helium vessel. As a result, these ideas were effective, and the maximum heat load due to vibration was restrained to less than 4W per magnet for one coil magnet model.
Superconducting magnets (SCM) for Maglev Trains are vibrated by several mechanical and electro-magnetic disturbances. The main disturbance is the vibration caused by the magnetic field fluctuation, which arises from the ground coils. Heat load and vibration characteristics under these conditions have been evaluated by electro-magnetic disturbance tests which are to simulate actual running conditions. Through the electro-magnetic disturbance tests with an initial type SCM which was made in 1990 on an experimental basis, it became clear that the heat load was more than several 10W under a specific frequency, which exceeded the cryogenic refrigeration capacity. As the result of the analysis of heat load and vibration of the SCM, it was estimated that the heat load was caused by the eddy current which was due to the relative vibration between the radiation shield plate (aluminum) and the inner vessel under the magnetic flux of the SCM. The mechanism of heat load generation by the vibration between the radiation shield plate and the inner vessel, and a method of reducing heat load are discussed here.
It is revealed that much heat is generated not only by the eddy current due to the relative displacement between the conducting elements in the magnet, but also by the mechanical vibrating deformation of a superconducting coil. We measured the characteristics of heating by the mechanically vibrating superconducting coil in resonance using the oil servo actuator. As a result of these experiments, the following facts are made clear: (1) The heat generated in a vibrating superconducting coil is larger in the twisting configuration than in the bending one under the vibrating mode. (2) The characteristics of the increment in heating in the vibrating coil under the energizing and the de-energizing state were almost the same. We cite as the factor in heating phenomena of the mechanical excitation the frictional heat between the fasteners and a superconducting coil. And the size of the displacements in these frictional parts are supposed to be the order of several micrometers. We intend to make further analysis of the factor of heating from now on.
Superconducting magnets which are installed on a Maglev vehicle vibrate under the influence of various disturbances in running. Main disturbance is the harmonic ripples of electromagnetic flux generated by ground coils. To estimate the influence of the harmonic flux ripples, the facilities called an electromagnetic vibration simulator were constructed. Heat load in some magnets, made in 1980's, extremely increased on the high frequency region in the electromagnetic vibration test. We have investigated the cause of these phenomena from various aspects, and made short superconducting magnet models containing a single superconducting coil and superconducting magnets with high rigidity having different internal structures for testing various ideas to reduce the heat load. As a result, we have obtained good results. Then we have started on production of the new superconducting magnets for Yamanashi test line. Here is an outline of the new magnets.
A basic understanding of the copper oxide high-Tc superconductors is reviewed. Crystal structures of the oxide superconductors are described in terms of their basic structures of Cu-O plane. Electric properties are closely related with the carrier concentration in the system, and a model for the electronic structures of the oxide superconductors is shown. The role of Cu-O plane is discussed for a design of a new layered copper oxide high-Tc superconductors by employing the block layer model.