8.2 Dynamic characteristics Ë 273Fig. 8.13:Corrected levitation force average in each steady velocity.
caused by energy loss due to field perturbations was only about 5% and only happens
at speeds below 60 km/h. Between 60 and 238 km/h during speed-up or speed-down,
the whole levitation performance of the HTS Maglev seemed not to be affected.
To compare the speedup history effect, more dynamic levitation measurements
under direct speedup were carried out to understand how the levitation forces
performed without the force relaxation duration. Because the shielding current in
the inner region gradually attenuates in an applied field perturbation according to
theE-Jcharacteristic of the bulk, it causes an irreversible energy loss so that the
varying field would intensify the attenuation of the levitation forces (as shown in
Fig. 8.14). The four force averaged curves located below the static force relaxation
curve can be classified into two groups according to their test velocity. At the same
velocity, the force attenuation showed a similar saturation tendency, no matter which
Fig. 8.14:Averaged levitation force curves in different measurement cases.