How Do Linear Induction Motors Work?

Linear Induction Motors, LIMs, are a technology that you'll be seeing a lot more from. They are exceedingly reliable, require almost no maintenance, can provide very large accelerations (faster than friction-type drives), and have the huge advantage of allowing a totally passive vehicle (in an automobile replacement system, this means that you don't have to have a portable energy source or prime mover at all in the (thus lightweight!) vehicle... the whole system can operate electrically, without having to resort to carrying lots of heavy batteries in the vehicle). As a bonus, LIMs can work just as well in both directions.

So how do LIMs actually work, anyhow? Here's a simplified explanation.

LIMs, as used on Mr. Freeze, have two sets of coils which create a strong magnetic field between them. In the picture below, you can see the two flat sets of coils within a galvanized-looking outer structure. The gap between them is where the very strong magnetic field is produced.

When a conductor (in the case of Mr. Freeze, the aluminum fins on the side of the trains) is placed within that magnetic field, the changing magnetic field causes (induces, hence the name) an electrical current to flow within the conductor.

The induced electrical current within the conductor creates its own magnetic field.

The interaction between these two adjacent, opposing magnetic fields creates the thrust (in the case of Mr. Freeze, a lot of thrust!) in a linear direction. In the photo above, the conductor being driven by the magnetic field would move through the slot, from the right foreground to the left background, or vice-versa.

If you take a good look at the electric meter outside your home, you'll see that it has a round aluminum plate that goes around and around, but that the aluminum plate doesn't seem to have any coils or brushes or armature or wires or gears or anything else connecting to it that would appear to make it go... only just an electromagnetic structure that it passes between. By now, you should understand that it's a rotary version of the same exact principle that's used to such stunning effect in Mr. Freeze.

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Mr. Freeze and related elements are property of DC Comics, (C) 1997. Photographs of Mr. Freeze LIMs are (C) 1997 Winkle Electric, used by permission. The rest of this page and all linked contents originating with me are Copyright (C) 1997 by Gordon E. Peterson II, all rights reserved worldwide. Last revised June 21, 1997.