KN Trakcji i Torów is a registered organization in the department of electrical engineering at the Warsaw University of Technology in Poland. We are an ANSYS Academic Student Team conducting research and running electromagnetic simulation for better understanding of electric traction. During 2017 and 2018, we focused on two main projects:
- Designing electromagnetic passive brakes for a prototype hyperloop vehicle.
- Designing a permanent magnet, linear synchronous motor for personal rapid transit and Maglev technology.
In 2017, our student group was a part of the Hyper Poland University Team, which designed a prototype for the Hyperloop Pod II Competition organized by SpaceX. In August 2017, our design made it to the finals of the competition. This achievement was made possible by student engineers who designed passive electromagnetic brakes to slow down the Hyperloop pod from 100 m/s and bring it to a stop.
The electromagnetic brakes were based on NdFeB N52 permanent magnets. The vehicle used four Halbach arrays of permanent magnets as a primary braking system. A Halbach array works by strengthening the magnetic field on one side of a magnet pack while reducing the other side to near zero magnetic field using a spatially rotating magnetization pattern. Magnet packs were positioned symmetrically on both sides of the central aluminum rail, so that the strengthened magnetic field faced the aluminum rail. Permanent magnets were arranged radially, with the magnetization direction of every magnet cube rotated 45 degrees in relation to its neighbors (see magnetization arrows in individual magnets in Figure 1).
Figure 1. Braking magnets package with magnetization direction above aluminum rail (dimensions in mm)
While moving along the rail, permanent magnets cause eddy currents in the aluminum. The eddy currents create their own magnetic field, which counteracts the magnetic field of the permanent magnets. As a result, a perpendicular force repels the permanent magnets from the aluminum rail. Parallel forces also counteract the movement of the magnets, causing the Hyperloop pod to slow down.
To design the electromagnetic brakes, we conducted hundreds of 3D simulations using ANSYS Maxwell. In these simulations, two sets of permanent magnets moved along the aluminum plate in transient mode to reveal all the eddy currents and magnetic fields in the model (Figures 2 and 3).
Figure 2. Screenshot from transient simulation
Figure 3. Cross section of the model showing predicted magnetic field in the air gap
After a series of simulations, we were able to estimate the final dimensions of the brakes and required number of magnetic cubes. We obtained the following results for one braking Halbach array (Figures 4 and 5):
Figure 4. Characteristic stabilizing force generated by one braking Halbach array versus vehicle speed
Figure 5. Characteristic braking force generated by one Halbach array versus vehicle speed
Permanent Magnet Linear Synchronous Motor
At the end of 2017, our team became interested in personal rapid transit (PRT) and Maglev technology. We decided to design a single-sided, permanent magnet linear synchronous motor (PMLSM) for contactless propulsion and levitation of a PRT or Maglev train to transport people.
Figure 6. Screenshot from simulation of PMLSM propulsion for Maglev
We are still performing the simulations using the transient mode of ANSYS Maxwell 2D; the optimal dimensions have not been obtained yet. When we have determined the dimensions, we will conduct 3D simulations. In the next two years, we are planning to build a small-scale model of a Maglev train and begin investigating the requirements of a full-scale vehicle. To learn more about our team, please follow us on Facebook at https://www.facebook.com/KNTitT/.