Linear Induction Motors (LIM)


Flight of Fear at Paramount's King's Dominion in Ohio




Mr. Freeze at Six Flags over Texas




Batman and Robin: The Chiller at Six Flags Great Adventure

How does an LIM roller coaster work?

A basic LIM roller coaster works by placing hundreds of tiny motors along the coaster track at key places were acceleration will be needed – at the launching pad and at the base of each element (twists, turns, inversions, etc.). 

            Within an LIM the stator (the fixed part of a rotating machine) is flattened out so that it will produce a linear force along its length.  While LIM can be utilized for many different purposes in several different forms, a low-acceleration LIM is used for roller coasters.  This means that the linear moving electric field produces a force which acts on conductor – in this case the conductor is small metal fins placed on the roller coaster cars.  The electric field produces an induced eddy current in the fins, which produces and opposing electric field.  The two electric fields repel each other, pushing the cars forward on the track.

            At the launch pad there is a very high concentration of these motors, in order to produce a high acceleration to propel the ride through the first element.  Each of the motors are powered in a timed sequence in order to propel the ride forward to reach its maximum velocity.  These LIMs can produce speeds of 60-70 miles per hour in as little as 3-4 seconds!


What are some advantages and disadvantages from using a LIM roller coaster?

            Not only can LIM roller coaster accelerate at speeds of 60-70 mph in as little as 3-4 seconds, but they can also accelerate backwards, as seen in Speed – The Ride in Las Vegas ant the Sahara Hotel and Casino.  This coaster uses LIMs to accelerate the ride through the ride in one direction, and when the end of the track is reached LIMs once again accelerate the ride, this time to ride the track backwards.

One of the main problems of using LIMs in theme parks is that they require large amounts of power to operate.  This becomes a problem with the high frequency of operation in a theme park, and can create voltage sags in the park and nearby areas.  However, if the LIM cannot draw enough current, it will not generate enough power to accelerate the ride to a speed at which the ride can clear the first element, causing the cars to become suck inverted within the first element.  These problems can be solved with the use of a high speed reactive power compensation system which will provide the coaster with the high amount of current needed to operate properly, while eliminating the voltage sags.


What are some rides that utilize LIMs?

     In 1996, Premier Rides, built the first LIM roller coasters as well as the first magnetically launched rollers called the Flight of Fear located at both Paramount’s Kings Island in Ohio and Paramount’s Kings Dominion in Virginia.

            Other famous coasters that utilize these linear induction motors include Mr. Freeze at Six Flags over Texas ,  Batman and Robin: The Chiller at Six Flags Great Adventure, The Joker’s Jinx at Six Flags America.

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