Seraphim Linear Induction Motor

The monorail is powered by a linear induction motor (LIM). LIMs have been around for some time. LIMs were used to propel test trains at speeds up to 250 mph at the Transportation Technology Center in Colorado in the 1970s. The monorails at Euro Disney are powered by LIMs, as is the Vancouver rapid transit system. The senatorial transit system in Washington DC, and many roller coasters and baggage handling systems, are all powered by linear motors. How a Seraphim LIM Works
	Step #1 Mount a permanent magnet to the underside of a vehicle. Now slide another magnet along the track, and if the second magnet is oriented correctly, the magnets will repel each other, causing the vehicle to move.
	Step #2 Instead of sliding a magnet along the track, put in a whole series of magnets. Replace the magnet on the underside of the vehicle with an electromagnet so that you can turn it on and off. Now when the electromagnet is in the correct position relative to a magnet on the track (just beyond its center), turn it on so that the magnets repel and the vehicle is pushed along. Turn the electromagnet off before it gets too close to the next magnet (or it will brake the vehicle). Let the vehicle run on just past the next magnet, and then pulse the electromagnet again so that the vehicle continues moving forward. Continue this process. To brake the vehicle, pulse the electromagnet just before it reaches a magnet on the track.
	Step #3 Instead of using permanent magnets in the track, use a segmented aluminum rail (a ladder-like structure) which will act as a series of electromagnets, but do not supply any power to the rail. Now when the electromagnet on the vehicle is in the correct position relative to a segment on the track, turn it on. It will induce surface currents in the segment, generating a magnetic field, so that the electromagnet on the vehicle will be repelled and the vehicle will move forward. Keep pulsing the electromagnet on the vehicle every time it is in the correct position relative to a rail segment on the track. The segmented rail along the track is called a "reaction rail".
	Step #4 To go fast, mount a number of electromagnets to the underside of the vehicle so that at any one time 40% of them are in the correct position relative to a rail segment on the track and are pushing forward smoothly. An alternative to using onboard power is to use a power pick-up to connect each electromagnet on the vehicle to the "third rail" which is connected to an external power supply.

The advantages of a LIM over conventional motors and drive systems are several:

• Because there are no moving parts, a LIM is very quiet.

• Propulsion is by electromagnetic forces between the active coils on the vehicle and the reaction rail - not through traction between the wheels and rail. This means a monorail with a LIM can climb steep grades and operate in rain, snow and ice without depending on wheel traction. The monorail's wheels carry the vehicle weight and provide guidance, not traction, minimizing wheel and track wear.

• If the reaction rail is placed on top of the guideway beam, as is the case with our maglift monorail, then there is a vertical component to the electromagnetic forces between the active coils and reaction rail. This uplift force can be as great as 90% of the weight of the vehicle. This magnetic lift improves ride quality, makes the monorail even quieter, reduces tfriction in the suspension system (static and rolling drag), and improves energy efficiency and acceleration.

Comparison of the Seraphim and Conventional LIMs

The Seraphim motor is a new form of LIM that generates thrust by pulsing an alternating current through each active coil mounted on the vehicle when it is properly positioned over the unpowered reaction rail. The reaction rail is not continuous as is the case with conventional LIMs, rather, it is a segmented structure. The magnetic flux from the driving coil induces currents in the segmented reaction structure, creating forces for the propulsion or braking due to the interaction of the magnetic fluxes. This is unlike a conventional LIM where magnetic flux is embedded in the continuous reaction rail in order to create propulsive forces.

Since the Seraphim motor relies on the exclusion of flux from the reaction rail, it has the following advantages over conventional LIMs for use as a high-speed rail propulsion technology:

• It permits a larger gap between the active coils on the vehicle and the reaction rail on the guideway, up to 1", and perhaps larger, which improves ride quality and relaxes guideway tolerances, significantly reducing construction and maintenance costs.

• Very low magnetic drag is induced in the reaction rail (assuming proper motor control), which improves motor efficiency.

• It is smaller, lighter, and more compact than a conventional LIM, and costs significantly less to build and operate.

• The efficiency of the motor increases with speed.

The power of the Seraphim motor is limited only by the power available, the frequency of pulsing relative to the required energy input necessary for a desired speed of operation, and by the maximum acceleration/deceleration forces that can be comfortably accomodated by passengers.

The bottom line is:

• The Seraphim motor may be one of the fastest motors ever developed.

• At the same time, it is not complex, and is therefore ralatively inexpensive to manufacture and maintain.