Maglev takes the wheel out of the equation, and the linear motor is what moves the vehicle once it is off the rail. This page looks at propulsion - the thrust that gets the vehicle moving and holds it at speed - a separate job from the levitation and guidance that carry and steer it.
The contactless thrust path
A linear motor is a rotary motor unrolled flat: rather than spinning, it sends a magnetic field travelling along its length, and that field pulls a reaction plate along with it. The force crosses a small air gap instead of passing through a wheel, so the drive does not depend on grip between vehicle and track - a natural fit for a levitated vehicle with no wheel contact, and free of the wheel slip that holds an ordinary drive back on steep grades or in the wet. A variable-speed drive speeds the travelling field up to match the vehicle, so the motor holds useful thrust from a standing start to line speed rather than at one fixed speed, sized so it stays within its electrical, air-gap and temperature limits right across that range.
Where the primary sits
The active part of the motor is the primary; the passive part it works against is a plain reaction plate or rail. There are two main ways to arrange them, and the choice comes down to route length, service pattern and how the vehicles are maintained.
Primary on the vehicle
The primary travels on the vehicle and works against a plain reaction rail that runs the length of the route. This uses the fewest motors, but needs continuous rail along the whole track.
Primary in the track
The primary is built into the track and the vehicle carries only a short reaction plate. The vehicle stays light and simple, but the track has to be powered and controlled section by section as the vehicle passes.
The reaction rail and the air gap
The plain reaction rail the motor works against has a big say in how much thrust you get. On a levitated vehicle the air gap is held by the suspension rather than by a wheel, so propulsion and suspension have to be designed together: the gap the motor is sized for has to be the gap the vehicle actually runs at, right across its speed range and loads, or the thrust figures will not hold up in service.
Proven over the whole journey
A propulsion system has to work over a real journey, not just at a single design point. We size the motor, model it in detail and simulate the full route - the gradients, station stops and speed profile - and check the temperatures the motor and reaction rail will really see before anything is built. That is where the layout, air-gap budget and drive strategy are proven together, so the figures we quote are ones the system can actually hold in service.
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Planning a levitated vehicle and need the propulsion sized to it?
Tell us the route, speed profile and gap budget, and we will model the thrust path end to end.
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