Rensselaer researchers have designed a convenient and inexpensive linear permanent magnet machine solution for transportation, conveyance, and other applications. When designed for short-strokes, the machine is very robust and rugged, and exhibits excellent performance characteristics such as very high thrust density, low ripples, and normal forces. Traditionally, linear PM machines had the armature windings in the translator and the PMs in the stator or vice-versa. This novel design allows both the field and armature excitations in the same part of the machine. It improves on the performance of traditional PM machines given the same amount of active machine volume and excitation sources. When the excitation sources are mounted on the translator, the machine could be an inexpensive solution for applications requiring long linear strokes such as transportation, conveyance, and others. Apart from being a cost-effective solution, the machine has several other advantages over traditional direct drive linear actuators: because the windings and the PMs are mounted on the same part of the machine, thermal management is easier; when the excitation sources are mounted on the stationary part of the machine, the translator is made of silicon steel only, which makes the machine mechanically very rugged; magnetic pollution is very low--even for long stroke applications because all the sources are confined to a smaller space. Applications of this technology include: power generation (tidal or wave); transportation-maglevs; electromagnetic aircraft launching systems; remote operated valves; rope-less elevators, conveyors, sliding doors, compressors, plungers. Advantages of the technology include: high thrust density excellent for high-precision applications; modular structure allows various operational phases; modifiable for sinusoidal or trapezoidal back-emf; very low detent force; very low thrust ripples; easy to construct-modular structure with external magnetization; and continued operation under fault conditions due to multiple phase design.

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Natasha Sanford