Abstract: A two coil system is described which produces a linear gradient field inside and an arbitrarily low field outside the two coil set. By eliminating the field outside the gradient coils, interaction between the gradient coils and external structure can be eliminated. A reduction in eddy current effects of greater than a factor 100 are readily obtained. Two coils are required for each gradient axis instead of one so that some increase in power supply capability may be required.

Abstract: A high DC current switch includes a pair of annular, conductive rails with a pair of brushes mounted for rotary movement therebetween. DC current is conducted by the rails to and from the brushes in directions to electromotively accelerate the brushes into a switching cycle. The rails incorporate a switching gap through which the brushes move. Beyond this switching gap, the rails are split into inner and outer arcuate sections into which current is commutated by the brushes. The directions of commutated current flow to and from the brushes is now such as to decelerate the brushes to a stop.

Abstract: A permanent magnet assembly for use in magnetic resonance imagers requires a minimum of permanent magnet material. The magnets are arranged with a radial direction of magnetization and an iron return path is used. The specific configurations of the permanent magnets provide highly uniform magnetic fields in the bore of the assembly.

Abstract: An inductively compensated trigger conductor for use in a chemically augmented fuse, of the type in which current flow through the fuse generates a magnetic field, employs at least one loop of electrically conductive material to inductively couple the trigger conductor to the magnetic field of the fuse. This inductive coupling increases the electrical inductance of the trigger circuit, and allows the fuse to be constructed so that the current division between the fuse conductor and the trigger conductor is constantly proportional, or at least more nearly so. When employed in a fuse which also includes a non-magnetic fuse support structure, a trigger device, and a means for chemically augmenting the separation of the fuse conductor into more than one segment during current interruption, the trigger circuit of this invention provides triggering action which is responsive only to the level of current flowing through the fuse, and not to a high rate of rise of current.

Abstract: A method of assembling a dc permanent magnet machine using a high permeability epoxy iron mixture to join magnets and flux guides. The epoxy iron mixture serves as an adjustable spacer. The epoxy iron mixture which can be half iron powder and half epoxy by volume, is situated between the magnets and the flux guides and the rotor inductance is measured while compressing the machine in a fixture until a predetermined value of rotor inductance is achieved.

Abstract: The coil structure for a discoidal winding for use in an axial gap dynamoelectric machine includes a continuously wound substantially flat annular disc portion containing the active coil sides and toroidal-shaped inner and outer ring portions formed by the inner and outer head turn portions respectively for the coil structure. The inner and outer toroidal-shaped ring portions are divided into a plurality of complementary, annular helically-shaped segments that are fitted together to form the complete coil structure having toroidal-shaped inner and outer circumferential ring portions, which define the inner and outer circumferential edges, respectively, of the discoidal winding, separated by the annular disc portion containing the active coil sides.

Abstract: In a high-speed homopolar inductor alternator rotor, formed laminations are employed to reduce eddy current losses in the pole faces. The lamination configuration keeps magnetic path reluctance to a minimum, while also reducing leakage flux, since each lamination, in extending from a pole face where flux enters the rotor to a pole face where it exits, passes through a region radially-inward of the salient poles, while presenting a minimum of magnetic material in a position to contribute to unwanted leakage flux.

Abstract: A porous aluminum body comprised of aluminum pellets bonded together with a substantial portion of said space therebetween remaining open and a method for making such body wherein said aluminum pellets are (1) coated with a powdered solder mixed with a paste-like flux, (2) placed in a mold, and (3) heated in a substantially inert environment to a temperature sufficient to bond adjacent aluminum pellets together.