How SENSIL LSM Launchers Work

SENSIL LSM Launchers consist of three parts, a power converter, stators, and magnet arrays.



Usually the stators are located in the track and the magnet arrays are located on the vehicle, but the other way round will also work.


Fig. 1. Typical LSM stator and magnet array

The magnet array has permanent magnets arranged to produce a magnetic field in the gap between them that has a sequence of north and south poles along its length:

The stator has a set of coils that when fed from an AC supply (provided by the power converter) produces a moving sequence of north and south poles along its length:


The interaction between the moving magnetic field from the stator and the magnetic field from the magnets, causes the magnets in the magnet array to be pulled along by the moving field from the stator.


  • Speed

    The thrust force is proportional to the current in the coil and the speed is proportional to the AC frequency of this current.


    There are different types of stator giving a different current to the force ratio. These types are located along the track to control the acceleration profile. 


    Each type of stator has a maximum speed that it can operate at. This is caused by a voltage that is induced in the stators coils by the moving magnets. This voltage is proportional to the speed of the magnets and limits the current that the power converter can apply because of the limited voltage available from the supply. 

  • Compatibility

    Because the magnetic fields interact, it is vital that compatible stators and magnet arrays are used. It is also vital that all the magnets and all the stators are placed on the correct pitch, so they all work together.


    The requirement that all the field maintain alignment also forces the stator coils to be connected in series to guarantee that the fields from all of the stators are in alignment.


  • Automatic Alignment

    The power converter provides the current in the stator coils and arranges the stators field so that the correct force is produced on the magnet array and thus the train. 


    With the SENSIL system this alignment is performed automatically by detecting the relative position of the magnet array from the changes in the current and voltage that are created by the relative movement of the two magnetic fields. 


    This is different to the conventional systems that require additional feedback signals from many sensors.

  • Efficiency

    To improve the efficiency of the whole system, individual stator units are shorted out when they are not required. This means that only the required stators are consuming power.

  • Energy Store

    An energy store can be fitted to a SENSIL system. With an energy store the supply delivers a low current continuously, the energy delivered is stored in the energy store so it can be released suddenly to launch a train. Without an energy store the supply must be large enough to deliver all the launch energy during the short launch time.


    An energy store also aids in the overall safety of the system because sufficient energy is available to complete a launch before the launch is initiated.

  • Stator


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  • Magnet Array


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  • Control Equipment


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