382 Ë 10 HTS Maglev launch technology
Fig. 10.8:Profile of the magnetic field generated by the superconducting bulk magnet at different
excitation current [30].
systems to improve the potential performance. The advantage of this HTS motor
technology that it can decrease the volume and weight of the motor, as well as
increasing its efficiency and force density [29].
A single domain melt-textured cylinder YBa 2 Cu 3 O 7 bulk with a height of 18 mm
and diameter of 30 mm was used in our experiment [30]. An NdFeB permanent magnet
with the same dimensions was also employed. The electromagnetic forces between the
HTS bulk magnet and the 3-phase copper windings were measured by a self-developed
HTS Maglev measurement system SCML-02 [19] (see Section 5.3). The sample was
magnetized by the field-cooling method. The magnetization field was generated by
a field control system consisting of a magnet power supply and an electromagnet
in series with charging currents ranging from 0 to 60 A. Since the charging currents
had a linear relationship with the DC magnetic fields produced, the corresponding
magnetization fields ranged from 0 to 0.922 T. The flux curves were obtained with a
gauss meter.
The flat 3-phase copper windings were excited by a variable-voltage and variable-
frequency (VVVF) power source with a frequency range from 5 to 400 Hz to produce the
sinusoidal traveling field with wavelength휆=42 mm. The waveform of the traveling
magnetic field is represented with the magnetic flux densityBin the following
expression
Btrx(x,t)=Bmxsin 2 휋−^2 휋
휆x,Btrz(x,t)=Bmzcos 2 휋−2 휋
휆x,(10.1)
where (2휋/휆)xis the space-phase훼and 2휋ftis the time-phase훽.BmxandBmz
are the maximum value of the magnetic flux density along thex-axis andz-axis,