Comparison of levitation and propulsion methods for hyperloop
Alexander Bilibin
H yperloop is a revolutionary mean of transportation, often referred to as ‘the fifth mode of transport’, proposed first in 2012 by Elon Musk. Since then numerous companies and teams entered the competition to produce the first functioning hyperloop system. The main goal of this competition is to create a train travelling at nearly Mach 1 in a sealed vacuum tube, relying on magnetic levitation and contactless propulsion in order to eliminate friction and air resistance. Maglevs (magnetic levitation trains) have already existed for a substantial amount of time, but their maximum speeds have been limited by air resistance, due to which engineers had to come up with ridiculously impractical shapes for their vehicles. However, no one has yet introduced a fully functioning system, and the speed record of all hyperloop prototypes is still lower than that of Maglevs. Therefore, I decided to research different propulsion and levitation methods in order to come up with the best solution.
1. Propulsion
Linear motors are the best means of propulsion for Maglevs, since they have no moving parts and are pretty much like rotary engines, just ‘unrolled’ on a flat surface (fig. 1). This also means that they can be operated using an identical control system. Linear motors can be divided into two groups: synchronous and induction motors. They are both subdivided in Long Primary (the active part is in the track, LP in short) and Short Primary (the active part is in the vehicle, SP in short). SP system requires batteries to be carried in the train, thus decreasing energy-efficiency drastically. Therefore, only LP configurations of each type are going to be reviewed.
Secondary
Rotor
Primary
Stator
Figure 1
1.1
Linear Induction Motor (LIM)
This type of motor has proven reliable and simple to use, since it is self-starting and can withstand high loads. The working principle of LIMs is identical to that of rotary induction motors and involves the application of AC (alternating current), Biot-Savart ’s Law, Lenz’s Law, Faraday’s Law and Fleming’s Left-hand Rule (LHR). In order to understand it, a simplified version of an induction motor is going to be considered:
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