H. Tsukiji

Tests of disk type magnetic flux pump with the ability of high voltage output

Using a superconducting magnetic flux pump, thick power leads for a superconducting magnet could be replaced with thin string leads to excite the excitation magnet of the superconducting flux pump. We have developed a new type of flux pump with high-voltage output to shorten the charge and discharge time of the load magnet. The test of the pump with four stacked disks as the exciter for the load magnet has been carried out. This disk type flux pump yielded 70 mV of voltage across its terminal and 10 A of current through a 85 mH load magnet which was the field winding of 20 kVA class fully superconducting generator within 12 seconds. This output voltage of the new flux pump is about 10 times larger than that of our previous work. Moreover since it is easy to stack disks for a superconducting flux pump, the high-voltage exciter for a 1 H class superconducting magnet could be expected to be made easily.

Recovery time of superconducting non-inductive reactor type fault current limiter

A superconducting fault current limiting device for electric power systems has been investigated to determine its feasibility. A noninductive reactor type fault current limiter has been constructed using a metal superconductor. Two bifilar wound solenoids were connected in antiparallel or antiseries. On each connection, a fault current limiting test was performed by suddenly short-circuiting a resistive load. The recovery (normal-to-superconductive state transition) time after the current limiting mode has been studied using a small-scale model of a fault current limiter for an LV power distribution line. The results reveal that the current limiter could be operated under a repetitive fault current accident which was removed within a few cycles of the limiting mode. The recovery time is a function of the dissipated energy under current limiting mode. Test results are presented.

Electrical characteristics of fully superconducting synchronous generator in persistent excitation mode

A brushless-excited superconducting generator with a superconducting dynamo, i.e., a magnetic flux pump, has been fabricated. Concurrently, a fully superconducting generator in which both armature and field coils are made of superconductors has been investigated. The authors describe the experimental machine model and the test results on electrical characteristics. >

Output power limit of 200 MW class brushless superconducting generator excited with magnetic flux-pump

A study on excitation system would be important to enhance potentials of superconducting AC generators. The authors have fabricated a 20 kW class fully superconducting machine with the brushless excitation system which consists of a magnetic flux-pump. By many tests of power generation using this machine, they have investigated theoretically and experimentally the feasibility of the brushless superconducting generator and magnetic flux-pump. Based on these results, this paper proposes the conceptual design and electric characteristics of a practical scale flux pump for an exciter system of a 200 MW class superconducting generator (Super-GM). Furthermore, the paper presents a comparison of output power limits for such as different excitation methods; a persistent field current mode and a conventionally adjusting field current mode.

Turn off trigger energy characteristics of the superconducting power electronics device (S-PED)-in case of type d

S-PED means a superconducting power electronics device. We made some thermally controlled S-PED which is a normally-on device. They work up to 100 Hz as a full wave rectifier. For the power supply of superconducting magnets, the flux pump can be used as SPEED (superconducting power electronics excitation device). In this paper, we describe the turn off characteristics of one of the S-PED (type d). The relations between generated resistance, gate-trigger energy and channel current were obtained.

Fabrication and excitation testing of a fully superconducting brushless generator with magnetic flux pump

Development of a highly efficient excitation system is important in enhancing the potential of superconducting ac generators. A new conceptual design in which electricity is generated with a brushless exciter system using a superconducting dynamo (the magnetic flux pump) has been proposed. Research on a fully superconducting generator using both a superconducting armature and a superconducting field winding has been under way for the past 7 years. In this paper an experimental model of the machine is described and test results on brushless excitation with the magnetic flux pump, with the machine operating as a fully superconducting brushless generator with an estimated capacity of 20 kVA, are presented.

Fully Superconducting AC Generator with Brushless Excitation System

A study on efficient excitation system must be important to enhance the potential of superconducting AC generators further. After the first successful demonstration in a feasibility of magnetic-flux pump based brushless excitation system suitable for superconducting generators in 1983 [1], we have been constructing a testing machine able to generate actual electric power. Concurrently with it, we have been studying a fully superconducting generator with both of armature and field coils made of superconductors.

Current status of superconducting synchronous motor in Saga University

Since there are no iron cores in the rotor and stator windings of superconducting synchronous motors, some reactances are intrinsically smaller than those of conventional motors. Low synchronous reactance would be expected to improve the torque-ampere ratio stability and the overload capacity of superconducting machines. Two types of 30 kVA synchronous motors, such as rotating armature and rotating field types, have been constructed. The rotating armature type motor had been fabricated and tested. The results show the difficulty of holding a stator cryostat in a low-heat leak condition. The low synchronous impedance requires some control of the armature current and/or the motor field current. The rotating field type motor encountered balancing problems due to the triple-pipe configuration of the helium supplier in the torque tube.