The pulsed linear induction motor concept for high-speed trains

Abstract

The SERAPHIM (SEgmented RAil PHased Induction Motor) concept is a linear induction motor concept which uses rapidly-pulsed magnetic fields and a segmented reaction rail, as opposed to low-frequency fields and continuous reaction rails found in conventional linear induction motors. These improvements give a high-traction, compact, and efficient linear motor that has potential for advanced high speed rail propulsion. In the SERAPHIM concept, coils on the vehicle push against a segmented aluminum rail, which is mounted on the road bed. Current is pulsed as the coils cross an edge of the segmented rail, inducing surface currents which repel the coil. The coils must be pulsed in synchronization with the movement by reaction rail segments. This is provided by a sense-and-fire circuit that controls the pulsing of the power modulators. Experiments were conducted to demonstrate the feasibility of the pulsed induction motor and to collect data that could be used for scaling calculations. A 14.4 kg aluminum plate was accelerated down a 4 m track to speeds of over 15 d s e c (33 mph) with peak thrust up to 18 kN (4040 pounds force) per coilset. For a trainset capable of 200 mph speed, the SERAPHIM concept design is based on coils which are each capable of producing up to 3.5 kN thrust, and 30 coil pairs are mounted on each power car. Two power cars, one at each end of the train, provide 6 MW (8,000 hp) ftom two gas turbine prime power units. The thrust is about 210,000 N (47,100 pounds force) and is essentially constant up to 200 km/hr (120 mph), since wheel slippage does not limit thrust as with conventional wheeled propulsion. A key component of the SERAPHIM concept is the use of passive wheel-on-rail support for the high speed vehicle. Standard steel wheels are capable of handling over 200 mph. The SERAPHIM cost is comparable to that for steelwheel high-speed rail, and about 10% to 25% of the projected costs for a comparable Maglev (Magnetically levitated) system. A brief cost and revenue analysis suggests that full cost recovery is possible on intercity routes where the potential ridership is more than 20,000 passengers per mile per year. Such regional routes as the NE Corridor, San Francisco-San Diego, and Los Angeles-Las Vegas appear to be good possibilities.

The Physics of SERAPHIM

“…The plate position would again be sensed and the coils energized in such a manner as to expel them, providing thrust for the vehicle. Needing a catchy acronym, the concept was dubbed SERAPHIM, for Segmented Rail Phased Induction Motor [6]. A proof-of-principle demonstration was built and successfully tested with Department of Energy (DOE) funding, arising from dual-use national defense issues.…”