IEEE Electrification - December 2021 - 61

capsule, making the tube less
infrastructure-intensive, the
track fully passive, and thus,
achieve the most affordable and
scalable solution.
Option 1: Partially Electrified Tube
with Booster Zones (Hyperloop
Alpha-2013)
The 2013 white paper proposed air
bearings for suspension based on the
principle of aerodynamic lift. Even
though this levitation principle is
mature, it is not as simple as playing
air hockey inside a tube. In the hyperloop
application, the manufacturing
tolerances are much tighter, considering
that airlift implies a low levitation height at very high
speeds. Moreover, the propulsion power was intended to
be external with 4-km sections of active stator coils along
the track, estimated to be long enough to increase the speed
from 480 to 1,220 km/h at 1 g-force. However, rough calculations
based on the acceleration equation (Newtons's
law of motion) show that a 5-km section would be a more
realistic figure at 1 g-force. The propulsion concept was
using long primary linear induction motors (LP-LIMs). It
was proposed as a lightweight and less bulky solution for
the capsule, which already had compressors on board. On
average, a periodic reboost of the LP-LIM would be needed
roughly for every 110 km (or 70 mi). As a result, less than
4% of the tube's overall length would need active electrification
infrastructure. The kinetic energy injected during
each spike is equivalent to the energy that one ton of batteries
could hold (200 kWh). Table 1 presents the key metrics
of the Hyperloop Alpha system (2013), and Figure 5
depicts the booster station schematically.
To relieve the burden on the power grid, battery reservoirs
could be installed for each
accelerator to be used for peakshaving.
This is because the stator
segments of the LIM, including the
converter and the power stations,
experience huge power spikes for
just a few seconds (i.e., 21 s). It
affects the power grid with very
sharp spikes in their highly pulsating
load profiles and, in the worst
case, they are likely to induce voltage
disturbances and fluctuations
(Tbaileh et al. 2021). They are also
likely to reduce a significant
amount of the frequency stability
reserves of the grid in high-stress
situations. However, it strongly
depends on the point-of-connection
to the local power grid and the
It affects the power
grid with very sharp
spikes in their highly
pulsating load
profiles and, in the
worst case, they are
likely to induce
voltage disturbances
and fluctuations.
voltage level of the transmission line,
where costly substations of higher
voltage levels might be required.
System optimization is an option
for the power fluctuation problem,
where the regenerative braking of
capsules can be coordinated with the
acceleration of others, but the inherent
complexity of such a solution is
inevitable. One would also need to
have some grid-side compensation
equipment (e.g., static VAR compensators,
static synchronous compensators,
dynamic var devices, and so on)
to handle the pulsating loads in active
and reactive power. Alternatively, an
energy storage system in between can
be used to mitigate the highly stressful load profile, which
might be one of the most cost-effective mitigation strategies.
It is also worth noting that the acceleration zones
along the track require coils distributed for 4 to 5 km,
where switches can be used to energize fractions of the
coils close to the capsule's position. This approach will
improve the power factor experienced by the inverters, as
depicted in Figure 5. The fluctuations in speed, g-forces,
and propulsive power experienced by the capsule are plotted
in Figure 6.
The mean velocity for the cruising profile shown in Figure
6 is only 798 km/h, even though the maximum speed
is 1,220 km/h, yielding poor utilization of the track performance.
Moreover, the repetitive spikes of 1 G also make
the travel a less comfortable experience.
The Hyperloop Technical Transition from Option 1
In the transition period between 2013 and 2018, the hyperloop
evolved toward a more traditional maglev approach,
where classical maglev systems are placed inside a
TABLE 1. The Hyperloop Alpha preliminary design (2013).
Cruising speed
Acceleration
Tube pressure
0.0987% of atmospheric sea level
Capsule's frontal area 1.4 m2 w/ dimensions 1.35 m × 1.10 m
Capsule's blockage
Capsule's capacity
35.8% capsule-to-tube area ratio
28 passengers (PAX)-2,000 kg-13.33% of total
capsule mass
Capsule's weight
15,000 kg including PAX
Energy storage on board 4,000 kg-26.67% of total capsule mass
Propulsion system
Suspension system
Based on https://www.tesla.com/sites/default/files/blog_images/hyperloop-alpha.pdf.
Long primary double-sided linear induction motor (LP-DB-LIM)
28 air bearings-2,800 kg-18.67% of total capsule mass
1,220 km/h (max.)-798 km/h (mean)-480 km/h (min)
1 g-force (i.e., 9.81 m/s2)
IEEE Electrification Magazine / DECEMBER 2021
61
https://www.tesla.com/sites/default/files/blog_images/hyperloop-alpha.pdf
IEEE Electrification - December 2021

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