Eiichi Mukai

Measurement Test of Phase Difference in a High Tc Superconducting Magnet

An excitation test of an experimental superconducting magnet constructed using a high Tc superconductive wire (HTSW) was carried out. From the observation of the voltage and the current waveforms in the superconducting magnet, it was confirmed that the phase difference considerably approximated 90deg. Moreover, the phase difference in the experimental superconducting magnet was measured using the proposed electronic circuit. As a result, it was clarified that its proposed electronic circuit for phase difference measurement had relatively high accuracy

Reduction of steady-state impedance in magnetic shielding type superconducting fault current limiter

A magnetic shielding type superconducting fault current limiter (MSFCL) has undesirable leakage impedance and thus the voltage drop relating to the leakage impedance occurs in the steady-state operation (the standby condition of a fault). Therefore, in this paper, a divided MSFCL model is proposed to reduce the value of the leakage impedance in the steady-state operation. The divided model of MSFCL was actually constructed. Then, some experiments were carried out to demonstrate the advantage of the divided model. We confirmed the advantage of the divided model of the MSFCL through these experiments.

Study on generation of harmonic voltage using synchronous machine with d-axis and q-axis harmonic field windings - part 2

We investigated the harmonic voltages generated by a synchronous machine adding d- and q-axis harmonic field windings to reduce the harmonics in a power line. First, electronic circuits such as a frequency multiplier, band-pass filter, and phase shifter were newly designed and made to carry out the experiment. Next, an experimental circuit, for which an AC voltage of frequency 6f synchronized to the power line voltage of frequency f could be obtained, was constructed to examine the generation of harmonic voltage in more detail. Finally, an experiment involving the generation of harmonic voltage was performed using an experimental synchronous generator with harmonic windings in the d- and q-axis. In this paper, the experimental results on the generation of harmonic voltage by the synchronous machine are presented.

Load variation characteristic of magnetically levitated vehicle with hybrid magnets

This paper reports the experimental results of the load variation characteristics of a magnetically levitated vehicle with hybrid magnets, which we studied in place of street cars and conveyor systems. Magnetically levitated systems have the following advantages: no bearings, no wheels, no noise, no air pollution and low maintenance. We propose new constructive electromagnets and magnetic rails. The magnetically levitated part must be cordless and the power source has involve Ni-MH AA size rechargeable batteries. As a experimental result, the number of dry cell batteries is increased with increasing load.

Characteristics of a magnetically levitated vehicle using a small number of dry cell batteries

An experimental vehicle of 20kg was magnetically levitated using a small number of dry-cell batteries, which consisted of 10 Ni-MH cells of 1900mAh in series. The magnets were activated sequentially, because the internal resistance of the batteries suppressed the maximum current. The vehicle was kept levitating for about 2 hours and was stable against disturbance due to instantaneous external force.

Study on reduction of steady-state impedance in magnetic shielding type superconducting fault current limiter

A magnetic shielding type superconducting fault current limiter (MSFCL) has undesirable leakage impedance and thus the voltage drop relating to the leakage impedance occurs in the steady-state operation (the standby condition of a fault). Therefore, this paper proposes a divided MSFCL model to reduce the value of the leakage impedance in the steady-state operation. The four-divided model of MSFCL was actually constructed. Then experiments were carried out to demonstrate the advantage of the divided model. Moreover, the divided model was compared with a non-divided model with the same turns of the coils. We confirmed the advantage of the divided model through these experiments.