People movers reward a drive that pulls the same in the wet as in the dry, holds a schedule on a grade, and asks nothing of the wheel-rail contact to do it. A linear induction motor delivers thrust by acting directly on a reaction rail rather than through friction at the wheels — which changes what a transit system can promise its riders in poor conditions and on demanding alignments.
Adhesion-independent thrust
A linear induction motor is a rotary motor unrolled: a straight primary winding creates a magnetic field that travels along the track instead of rotating, and that travelling field drags a conductive reaction plate to produce thrust. Because the force is developed electromagnetically across the air gap rather than through the wheel-rail contact patch, tractive effort does not depend on adhesion. That removes the drive-slip ceiling that limits a friction drive, so acceleration and braking effort can be set by the motor and the duty rather than by how much grip the wheels happen to have.
Wet and icy conditions
Rain, ice and greasy railheads degrade a friction drive by reducing the grip available at the wheel-rail interface, which is precisely the interface a linear motor does not use for propulsion. The travelling field acts on the reaction rail across a controlled air gap, so wet or icy weather does not create the drive-slip limit that forces a friction system to back off acceleration and lengthen braking. In practice this makes performance far more repeatable across the seasons, which is what a headway-sensitive people-mover needs to hold its timetable.
Steep grades
On a gradient a friction drive is limited by the grip that ties the wheels to the rail, and that grip is exactly what the weather erodes. A linear motor develops the same thrust up an incline as it does on the level, within its current, air-gap and thermal limits, because none of that thrust is routed through wheel adhesion. That typically allows steeper alignments than a friction system would sustain reliably in poor conditions — useful where the corridor is constrained and civil works want to follow the terrain rather than cut and fill around it.
Station stops and duty
People-mover duty is repetitive and stop-heavy: accelerate from a station, cruise a short block, brake into the next platform, dwell, repeat. An inverter drive lets us set the travelling-field speed through the drive frequency and the pole spacing, so the same motor can hold a smooth acceleration profile and a controlled approach to each stop across the whole run. We size that duty by running the full route in simulation and checking thermal limits over the busiest expected timetable, so the motors and their reaction rail are matched to the real stop pattern rather than to a single peak point.
Long-guideway cost trade-offs
Over a long guideway the dominant decision is where the powered part lives, and it is genuinely a trade-off rather than a clear winner. The two arrangements load the cost onto different parts of the system, so the right choice depends on route length, station spacing and how many vehicles share the line.
On-board primary
The powered short primary rides on the vehicle and a passive reaction rail runs the whole route. This needs the fewest motors, but you pay for continuous reaction rail along every metre of guideway — which tends to suit shorter routes or fleets where the motor count, not the track length, drives cost.
Wayside primary
The powered long primary is built into the track and the vehicle carries only a short passive plate. The vehicle stays light and simple, but you wind and energise the whole active length of guideway — which tends to favour high-frequency, many-vehicle corridors where a light passive car earns its keep.
We help resolve this with route and duty simulation rather than a rule of thumb, because the balance shifts with fleet size, headway and the length of powered guideway a given service actually needs.
Safety and braking integration
The linear motor itself can brake as well as drive, and a permanent-magnet eddy-current brake adds a smooth, contactless secondary stage: fixed magnets and relative motion induce eddy currents in a conductive plate that oppose motion, with no pads to wear or fade and no external power drawn while the vehicle is moving. Its retarding force rises with speed and can taper over the working range, shaped by the magnet geometry, pole pitch, air gap and reaction-plate material — but it falls to zero at a standstill. Because it is a dynamic brake, it cannot hold a stopped vehicle, so we pair it with a mechanical holding brake wherever zero-speed restraint is required, giving a braking chain that stays effective in the wet without depending on wheel adhesion.
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