3.6 Permanent magnet Maglev Ë 73benefits, including low-noise operation, the ability to operate in challenging terrain
with steep grades and tight turns, all-weather operation, low maintenance, rapid
acceleration, and the potential for high speed.
The levitation system uses a vehicle mounted on PM of double Halbach arrays. The
orientations of the magnetization of the magnets in the Halbach arrays are arranged
to concentrate the field lines below the array while nearly canceling the field above
the array. This results in a system which requires no active magnetic shielding of the
passenger compartment. In a double Halbach array, the strong sides of two Halbach
arrays oppose each other with the track between the double Halbach array. The
track and vehicle chassis cross-section, as well as the magnetic configuration of the
double Halbach array are shown in Fig. 3.3. The dotted lines show the position of
the surface of the levitation track position. The guidance force is provided passively by
the propulsion magnets (on the vehicle) interacting with the laminated iron core of the
LSM winding (on the track). The Inductrack systems of the PM-EDS require the vehicle
to travel at a certain speed of roughly around 100 km/h, to produce strong enough
repulsive magnetic forces for levitation.
The test track is full scale, 120 m in length, with a 50-m radius curve. The track
was completed in November 2004. A passive secondary suspension system provides
damping and improves the passenger ride quality. Testing with chassis weight up to
10,000 kg, a speed of 10 m/s, air gaps up to∼30 mm, and acceleration up to 2.8 m/s^2
has been achieved [71].
Hoburg [74] studied the distribution of the magnetic field in the coach of a Maglev
vehicle based on Halbach arrays. The results showed that the magnitude of the
magnetic field due to superimposed fields from the propulsion, upper levitation, and
lower levitation magnets were about 1.5 gauss at floor level, 0.5 gauss at seat level, and
0.2 gauss at head level over the area of the passenger compartment.
Cho et al. [75] analyzed the characteristics of an electrodynamic suspension PM-
EDS device with a PM Halbach array system. In order to validate the characteristic
analysis scheme for PM-EDS devices, the dynamic performance was tested using
a high-speed rotary-type dynamic test facility with linear peripheral speed up to
250 km/h. A comparison was made between the analysis and the experimental results
to demonstrate the design considerations of PM-EDS device for high-speed Maglev.
Fig. 3.3:Halbach arrays of General Atomics [71]. The
dotted lines show the surface of the levitation track
position.