Sigma Instruments, Inc.

John G Gamble

Matthew G Dillon

In a sensor for sensing current in a conductor, a magnetic laminar arrangement adapted to surround the conductor passes through a coil. Inside the coil the laminar arrangement forms a gap with two projections extending transverse to lamina within the arrangement and facing each other. In one embodiment the coil drives a display to form part of a fault indicator.

Faulted current indicators with improved signal to noise ratios

A sensor in a faulted current indicator includes a coil and a magnetic arrangement passing through the coil and around a current-carrying conductor for coupling the coil to the conductor. The magnetic arrangement has given magnetic reluctance and forms a higher reluctance section, such as a gap, within the coil. Preferably the magnetic arrangement includes a U-shaped laminate and two core laminations joined to the U-shaped laminate by two gaps to allow for installation around the conductor. The ferromagnetic plate outside the coil shields the coil. The sensitivity of the sensor is increased by coating the inner surface of the U-shaped laminate and the core lamination surfaces contacting the U-shaped laminate with a high Ni content ferromagnetic material.

In the disclosed device, a pair of magnets supported in the ends of a C-shaped yoke bias an armature into one of the two rotary positions. A short pulse to a coil about the center of the yoke induces a short term magnetic field that supplements the polarity at one end of the yoke so as to either maintain the armature in its biased position or swing the armature to its other biased position. A subsequent pulse, producing a field in the opposite direction, returns the armature to its first position. In each case, the magnets retain the armature in its biased position even after the pulse stops. The armature pivots between portions of the yoke magnetized by the same magnet.

Bistable toggling indicator

The electric motor includes a mover, which may be a rotor or actuator, and a stator having a number of poles projecting toward the mover. The poles have soft-magnetic teeth projecting toward the mover and extending transverse to the direction of mover movement, and the mover has soft-magnetic teeth projecting toward the stator teeth and extending transverse to the direction of mover movement. Windings energize the stator to move the mover. Dividing each pole transverse to the direction of mover movement to define two pole portions per pole, and locating permanent magnetic material between stator teeth in only one portion of each of the poles, enhances the motor torque while achieving a saving of permanent magnetic material. Preferably the magnetic material exists on alternate pole portions in successive poles.

Magnetically enhanced stepping motor

Iron surfaces of stator poles, rotor periphery, or both stator poles and rotor periphery, of stepping motors are manufactured without teeth. The stepping effects of teeth are obtained by bonding, to the toothless surfaces, webs composed of fluted magnetic material having alternate thin and thick sections magnetized in the direction of the thickness of the material and carrying soft magnetic inserts in the flutes. The inserts form virtual teeth. The thick sections are magnetized in the direction opposite to the thin section and the flutes extend in the direction transverse to the direction of relative motion between rotor and stator.

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Hull, MA, United States of America

John G Gamble