Synchronous vs induction mechanisms for linear motors
“What are the benefits and drawbacks between the two different types of linear motors?”
Thanks to the constant ingenuity of humanity, it turns out there is not only one way but actually two ways to design a linear motor! The separate cases are know as the Linear induction motor (in which the changing magnetic field of the primary outpaces the one of the secondary) and a linear synchronous motor (In which the magnetic field field of both the primary and the secondary match-up).
Linear induction motors have numerous advantages. First of all, the construction of such systems have a similar layout to existing electric railway infrastructure, making it easier to integrate into an older system. The track for the LIM is also very simple, making it easier for vehicles of all different shapes and sizes to be integrated. However, induction based technology has a lower efficiency than not only synchronous motors but normal rotary motors as well! In addition, LIM systems have higher weights, which limits their maximum travel speed and carrying capacity!
Luckily, we have more than one option when deciding to use linear motor technology. Linear synchronous motors use lighter-weight technology, which allows for higher speed and cargo levels. The disadvantages of such systems is that exact data is required for monitoring the magnets (to make sure that they are within sync with the LSMs). This results in a much more complicated design for maintaining the guideway. As each train on the platforms must be individually analyzed, a lower train density ensues. Since LSMs are designed to be completely in sync with the magnets, even very small impingements on the systems could result in drastic consequences.
In summation, Engineers have many choices for what type of linear motors they select.