IEEE Electrification - December 2021 - 63

landing (i.e., no suspension available at low speed). Moreover,
the large levitation height of the Inductrack EDS makes it
incompatible with linear propulsion, which means that the
linear motor has to be separate and act over another track
surface. If one decides to make the propulsion external
instead of on board the capsule, the linear synchronous
motor (LSM) is considered the most energy-efficient solution.
However, the LSM favors electromagnetic suspension (EMS),
as these technologies can be integrated with each other. This
suspension concept relies on attractive levitation rather than
the repulsive nature of the EDS. With EMS, the hyperloop
capsule could be hanging underneath the track inside the
tube. It is postulated by the companies that a hanging capsule
could improve cornering when it turns inside the tube.
Still, the radius of curvature would need to be much higher
for the hyperloop than classical rail to restrict the centrifugal
g-force experienced by passengers (e.g., a 0.2 g-force
comfort level implies a curvature radius of 39.3 km at
1000 km/h cruising speed). In 2018, Virgin Hyperloop (VH)
switched its strategy from the Inductrack
to the EMS to integrate its suspension
with LSM propulsion.
1,000
1,200
Option 2: Large-Scale Tube
Electrification With a
Lightweight Capsule
The concept of the rail as a propulsor
was popularized by the German
Transrapid maglev system. However,
it has been concluded that the
reason the system failed was that
the guideways were too expensive,
even though the ride itself was perfect.
VH and Hardt are now pursuing
this option for the hyperloop,
even though it is well-known that it
has massive infrastructure needs.
A basic sketch of the system is
presented in Figure 7.
The track propulsor can indeed
be tailored to the propulsion needs
along the track, and therefore,
needs less powerful components in
the cruise zone of the tube. The
LSM can achieve very good efficiency
and power factor, given that the
system only energizes the portion
of the track where the capsule is
situated every time instant. Due to
no slip between the primary and
the secondary,
it can reach the
highest cruising speeds for a given
power supply, contrary to LIMs.
However, the need for synchronism
implies higher complexity in how
the system is operated.
200
400
600
800
1.2
0.2
0.4
0.6
0.8
1
−0.2
10
20
30
40
50
Distance (km)
Figure 6. The speed profile, G-force, and acceleration power of the Hyperloop Alpha passenger
capsule, with a total weight of 15 tons. Maximum and minimum speeds are 1,220 km/h and 480 km,
respectively. The acceleration force is 1 G over the boosting zone. In between the acceleration
spots, aerodynamic forces are acting to deaccelerate the capsule, proportional to the square of
the instantaneous speed. The mean electrical power absorbed during acceleration is 34.74 MW.
The capsule uses approximately 21 s inside the boosting zone and 9 min and 9 s in between.
Note that 202.2 kWh kinetic energy is injected under each spike, while discharged the same
amount of energy in between due to natural air resistance and friction. The boosting interval
repeats periodically through the whole cruising zone of the track.
IEEE Electrification Magazine / DECEMBER 2021
63
Option 3: Electromagnetic Launch System
With Self-Propelled Cruising
As illustrated earlier, a long track-length is needed for
acceleration if the propulsion power level is not sufficiently
high enough. This is where the concept of the tube as a
propulsor (i.e., option 2) finds its benefit with excellent
acceleration performance. For this reason, the Spanish
hyperloop company Zeleros has proposed a similar system
as an electromagnetic launch system during acceleration
(LSM as a track propulsor), even though it is pursuing
a self-propelled capsule in the cruising zone (https://zeleros
.com/hyperloop-technology/). In this way, its capsule is
saving a massive amount of energy needed for acceleration
[e.g., potentially reducing the energy reservoir's mass
with up to 50% (Nøland 2021)], which makes its vehicle
lighter than a fully energy-autonomous solution. It also
reduces the tube length needed for acceleration, but at the
expense of higher complexity compared to a fully selfpropelled
solution. Contrary to all of the other commercial
Acceleration Power (MW)
G-Force
5
Speed (km/h)
118
123
236
241
354

https://zeleros.com/hyperloop-technology/ https://zeleros.com/hyperloop-technology/

IEEE Electrification - December 2021

Table of Contents for the Digital Edition of IEEE Electrification - December 2021