SERAPHIM technology appears capable of efficiently driving a tip driven fan. If the motor is powered using an inverter and resonant circuit, the size and weight could be considerably below that of a comparable rotary electric motor.
The Segmented Rail Phased Induction Motor (SERAPHIM) has been proposed as a propulsion method for urban maglev transit, advanced monorail, and other forms of high speed ground transportation. In this report we describe the technology, consider different designs, and examine its strengths and weaknesses.
The Sandia coilgun [1,2,3,4,5] is an inductive electromagnetic launcher. It consists of a sequence of powered, multi-turn coils surrounding a flyway of circular cross-section through which a conducting armature passes. When the armature is properly positioned with respect to a coil, a charged capacitor is switched into the coil circuit. The rising coil currents induce a current in the armature, producing a repulsive accelerating force. The basic numerical tool for modeling the coilgun is the SLINGSHOT code, an expanded, user-friendly successor to WARP-10 [6]. SLINGSHOT computes the currents in the coils and armature, finds the forces produced by those currents, and moves the armature through the array of coils. In this approach, the cylindrically symmetric coils and armature are subdivided into concentric hoops with rectangular cross-section, in each of which the current is assumed to be uniform. The ensemble of hoops are treated as coupled circuits. The specific heats and resistivities of the hoops are found as functions of temperature and used to determine the resistive heating. The code calculates the resistances and inductances for all hoops, and the mutual inductances for all hoop pairs. Using these, it computes the hoop currents from their circuit equations, finds the forces from the products of these currents and the mutual inductance gradient, and moves the armature. Treating the problem as a set of coupled circuits is a fast and accurate approach compared to solving the field equations. Its use, however, is restricted to problems in which the symmetry dictates the current paths. This paper is divided into three parts. The first presents a demonstration of the code. The second describes the input and output. The third part describes the physical models and numerical methods used in the code. It is assumed that the reader is familiar with coilguns.
As computers become faster, have more memory, and use multiple parallel processors, large, complex codes that more accurately simulate physical phenomena have emerged to utilize this capability. Most problems can benefit from this approach and many require it. But not all! There are problems for which simpler methods on more modest computers still work. The trick is to identify those problems, write the codes, and make their implementation sufficiently simple that they can be used conveniently by those who could profit from them. A Simple Plasma Code has been written with this philosophy in mind. It retains just enough physics to allow realistic simulations to be formulated and run quickly, even on a personal computer. This paper describes the physical model, its numerical implementation, and presents a sample simulation.
Microelectronic cathode emitter technology being developed at Sandia for supplying continuous low current for flat panel displays appears to be a promising technology for providing high currents when operated in a pulsed, higher voltage mode. If currents in excess of one amp per square centimeter could be produced for tens of microseconds at several kilohertz repetition rate, important applications in such as large volume food or waste sterilization in situ detection, and high power microwave production could be achieved. A testbed was built to perform the experiments. The desired current densities have been demonstrated using small emitter arrays.
SAE Technical Papers
The Segmented Rail Phased Induction Motor (SERAPHIM) is a compact, pulsed linear induction motor (LIM) offering a unique capability for very high speed train propulsion. It uses technology developed for the Sandia coilgun, an electromagnetic launcher designed to accelerate projectiles to several kilometers per second! Both aluminum cylinders and plates were accelerated to a kilometer per second (Mach 3) by passing through a sequence of coils which were energized at the appropriate time. Although this technology was developed for ultra-high velocity, it can be readily adapted to train propulsion for which, at sea level, the power required to overcome air resistance limits the operational speed to a more modest 300 mph. Here, the geometry is reversed. The coils are on the vehicle and the "projectiles" are fixed along the roadbed. In the 1970's, the Federal Railroad Administration tested a 200 mph train riding on passive wheels and powered by a conventional LIM. In a LIM, electrical windings generate a backward moving wave of magnetic flux in a conducting reaction rail, producing a forward force. SERAPHIM operates not by embedding flux in a conductor, but by excluding it. In this propulsion scheme, pairs of closely spaced coils on the vehicle straddle a segmented aluminum reaction rail. A high frequency current is switched on as a coil pair crosses an edge and remains off as they overtake the next segment. This induces surface currents which repel the coil. In essence, the pulsed coils push off segment edges because at the high frequency of operation, the flux has insufficient time to penetrate. In contrast to conventional LIMs, the performance actually improves with velocity, even for a minimal motor consisting of a single coil pair reacting with a single plate. With either distributed onboard power, a passive wheeled train powered by a SERAPHIM is an attractive alternative to one which is levitated using superconducting magnets (MAGLEV) and propelled by switched electrified coils in the roadbed. This paper will present results of proof-of-principle tests, electromagnetic computer simulations, and systems analysis. It is concluded that this new linear induction motor can be implemented using existing technology and is a promising alternative propulsion method for very high speed rail transportation. © Copyright 1995 Society of Automotive Engineers, Inc.
We are attempting to develop and demonstrate a new type of linear synchronous induction motor capable of propelling a vehicle at high speed. The technology, based on a passive guideway containing sequential aluminum plates, was developed in Sandia`s electromagnetic launch program. As such, it was called a ``re-connection gun`` and launched an aluminum plate from between pairs of pancake coils. In the proposed propulsion scheme, the plates are fixed and the coils move. Pairs of closely spaced pancake coils on the vehicle straddle vertically mounted aluminum plates in the roadbed. The current in the coils is turned on when the plate is fully covered, peaks at some optimal time, and decreases to zero before separation. This induces currents in the plate which interact with the coil current to produce repulsive forces. In essence, the pulsed coils push off the edge of the plate because at the high frequency of operation, the current has insufficient time to fully penetrate. Since no embedded flux is required, the efficiency actually increases with speed. This concept has been named SERAPHIM, for SEgmented RAil PHased Induction Motor.
This paper explains how an induction coilgun works and presents the factors which go into its design. Our purpose is to obtain algebraic expressions which, although crude, provide useful predictors of behavior, illustrate the dependence on various parameters, and suggest ways to optimize the design. Detailed prediction of the gun`s behavior can be obtained from simulation codes, such as SLINGSHOT.