Abstract: This method of making packets for transformer-core manufacture comprises: (i) providing a composite strip comprising many thin layers of amorphous steel strip, (ii) advancing the leading end of the composite strip forward, (iii) cutting the composite strip at a location spaced rearwardly of the leading edge of the strip, thereby detaching a first section of multi-layer strip and creating a new leading end just behind the cutting location, and (iv) then clamping the detached section to a supporting surface. Then the following steps (a) and (b) are carried out. (a) The new leading end of the composite strip is advanced forward, and the strip is cut at a location spaced rearwardly of the new leading edge, thus detaching an additional section of multi-layer strip and creating another new leading end just behind the latter cutting location.

Abstract: This method is practiced by first providing a plurality of spools of amorphous steel strip in each of which the strip is wound in single-layer thickness. Then, in a pre-spooling machine, the single-layer thickness strips are unwound from said plurality of spools and combined to form strip of multiple-layer thickness which is wound to form strip of multiple-layer thickness which is wound onto a plurality of master reels, on each of which the strip is wound in multiple-layer thickness. These master reels are then placed on a plurality of payoffs, and the multiple-layer thickness strip is unwound from these payoffs and combined into a composite strip that has a thickness in strip layers equal to the sum of the strip layers in the combined multiple-layer thickness strips. Then the composite strip is cut into a plurality of sections, or lengths, of composite strip, and with these sections a hollow core form is constructed, which form has a window about which the sections are wrapped.

Abstract: Pursuant to detecting rotor faults in an induction motor by analysis of a frequency spectrum of the current drawn by the motor under test, wherein success of the fault analysis requires an accurate determination of the fundamental frequency of the motor current and the motor slip frequency, method and apparatus are disclosed for determining the fundamental and slip frequency values solely from analysis of the motor current spectra.

Abstract: This extended-foil capacitor comprises a plurality of flattened foil rolls stacked side-by-side. Each foil roll comprises two sheets of foil rolled up in nesting, face-to-face relationship and dielectric film positioned between said foil sheets and electrically insulating the foil sheets from each other. At one end of each foil roll, one of the foil sheets entends beyond both the dielectric film and the other foil sheet in the roll to provide first foil extensions at said one end of the roll. Adjacent foil rolls in the stack have their first foil extensions positioned adjacent each other at one end of the adjacent rolls. At said one end of the adjacent rolls, there is a joint formed by ultrasonic welding and joining together the first foil extensions. This joint includes within it dozens of superposed foil extensions arranged in a substack and joined together by solid-state metallurgical bonds between juxtaposed foil extensions.

Abstract: To detect broken bars in the rotor of induction and synchronous motors, the current drawn by the motor during the transient startup period as the motor runs up to steady state speed is analyzed to identify any dip in the starting motor current amplitude occurring when the motor reaches approximately half-speed. The magnitude of any identified current dip is tested against threshold values to determine if the dip is characteristic of a broken rotor bar condition. Reliable broken rotor bar detection is achieved regardless of whether the motor is loaded or unloaded.

Abstract: This GTO thyristor comprises: (i) a cathode layer that is divided into a large number of cathode-layer fingers, (ii) a gate layer contiguous with the fingers, with a PN junction J1 between each finger and the gate layer, (iii) a cathode electrode on each finger, and (iv) a gate electrode on the gate layer having portions surrounding the fingers disposed in spaced relation to the fingers. Turn-off of the GTO thyristor is effected by forcing a turn-off current to flow between the cathode electrode of each finger and the gate electrode through the associated PN junction J1. This PN junction at each finger has a centrally-located region that is characterized by an avalanche voltage that is substantially lower than the avalanche voltage that characterizes this junction in the region of the junction surrounding the centrally-located region, and this relatively lower avalanche voltage enhances the current turn-off capabilities of the GTO thyristor.

Abstract: A fuse body encloses a fuse element of a current-limiting fuse wherein the fuse body is formed from an inexpensive material and provided with a shield between the inner surface of the fuse body and the fuse element. Thus, when the fuse element melts and arcs during interruption, the fuse body is protected from the hot gaseous arc products by the protective shield thereby preventing burning of the fuse body. The protective shield can be a spray coating such a ceramic spray coating applied to the inner surface of the fuse tube, a glass coating, or ceramic paper. The fuse body can be made from glass filament wound epoxy material.

Abstract: For shear-cutting a stack of thin sheets of amorphous steel along a cutting plane that extends transversely of the stack, we utilize apparatus that comprises two blades that are positioned at the start of a cutting operation on opposite sides of the stack. Each of the blades has a first surface for engaging one side of the stack and a second surface extending transversely of the first surface and generally parallel to said cutting plane and intersecting the first surface at a corner. The first surface of each blade is disposed at a predetermined rake angle with respect to a reference plane extending through a point on the corner of the blade and normal to said cutting plane. By making the sum of these rake angles of a negative value and beween 5 and 35 degrees, we are able to substantially improve the wear resistance of the blades and lengthen their working life.

Abstract: This amorphous steel core transformer comprises: (i) a coil subassembly having a coil window of generally rectangular cross-section bounded by two end faces and two side faces, at least one of the side faces being slightly concave, and (ii) a core having a leg that fits within the coil window and comprises superposed aligned strips of amorphous steel stacked in the direction of the leg thickness and between said side faces. Each strip has two edges and, disposed between the two edges, a width that approximates the distance between the end faces of the coil window. The strips are further characterized by a slightly greater thickness in their central region than in the region of their edges. The core leg has a thickness that is substantially less in both edge regions of the strips than in the central region of the strips, thus rendering the leg capable of fitting more tightly within said coil window.

Abstract: Arc-confining structure for an electric circuit interrupter has an arc-exposed portion constructed of an electrical insulating material that is the thermosetting reaction product of the constituents of a mixture consisting essentially of the following constituents in the following percentages by weight of the mixture:(a) 25 to 55 percent granular high-forsterite olivine,(b) 20 to 50 percent of a second granual constituent consisting essentially of silica sand, and(c) 15 to 28 percent phosphoric acid.The mixture is essentially free of asbestos.

Abstract: A circuit for preventing the generation of an erroneous output signal from a protective relay for detecting faults in a three phase alternating current electrical power distribution system, which relay uses a full wave rectified signal as an operate quantity. The circuit includes a band pass filter having an input adapted to receive the full wave rectified signal; a center frequency which is tuned to the frequency of at least one principal harmonic component of the full wave rectified signal; a gain substantially equal to -1; and an output. A two-input summing amplifier has one input which is adapted to receive the full wave rectified signal and the other input which is connected to the output of the band pass filter.

Abstract: a protective relay for detecting faults in electrical power distribution system generates a signal .DELTA.i(t) which is substantially equal to the magnitude of the power distribution system current i measured at a first time subtracted from the magnitude of the power distribution system current i measured at a second time, the second time occurring later than the first time. The signal .DELTA.i(t) is utilized to generate measurement of the distance of a fault to the relay and is also utilized to generate operate signals if the fault occurs within the zone protected by the relay.

Abstract: This dual voltage transformer comprises a primary winding having a tap at a location intermediate its length, a first termination for connection to line voltage, and a second termination for connection to ground. When the transformer is to be operated at a relatively high voltage, the first termination is connected through a dual voltage switch to line voltage; and when the transformer is to be operated at a relatively low voltage, the tap is connected through said switch to line voltage. First varistor means is connected across the primary winding between said first and second terminations both when the transformer is operated at high voltage and at low voltage; and second varistor means having a lower breakover voltage than the first varistor means is connected between said tap and ground when the transformer is operated at low voltage.

Abstract: A method of constructing a transformer having an amorphous steel core with a coil about a leg of the core wherein the core leg is formed to a cross-section that more closely conforms to the configuration of the coil window of the coil that surrounds the core leg.

Abstract: A protective relay for detecting faults within a predetermined protected zone of a three phase alternating current electrical power distribution system, of the type which utilizes at least one restraint signal in conjunction with at least one operate signal to generate a net operate signal, generates an operate quantity which is related to a zero sequence component of current flowing in the power distribution system and a second operate quantity which is related to a negative sequence component of the current flowing in the power distribution system. The operate quantities are summed to form an operate signal. An adaptive restraint, which is proportional to a negative sequence component and a zero sequence component of a phase voltage of the power distribution system, is generated and utilized to provide increased sensitivity to higher resistance ground faults.

Abstract: An out-of-step blocking unit of a protective relay for detecting faults in a three phase alternating current electrical power distribution system utilizes restraint signals in conjunction with an operating signal to generate a net operate signal as a restraint to the relay in order to prevent operation of circuit breakers associated with the relay as a result of load swings in the power distribution system. The restraint signals include a signal related to a negative sequence component of current flowing in the distribution system; a signal related to a zero sequence component of current flowing in the power distribution system; and a signal related to a .DELTA. (IZ-V) quantity which is the difference between fault and prefault values of the quantity (IZ-V).

Abstract: A protective relay for detecting faults within a predetermined protected zone of a three phase alternating current electrical power distribution system generates a polarizing signal V.sub.POL which includes a signal V.sub.1 related to a positive sequence component of a phase voltage of the three phase power distribution system. A signal I.sub.1 Z.sub.R, which is a signal related to a positive sequence component of a phase current of the three phase power distribution system multiplied by a replica impedance of the protected zone of the three phase power distribution system, is also generated. The coincidence of the V.sub.POL and I.sub.1 Z.sub.R signals are compared and an operate signal is generated as a result of positive coincidence. A first restraint signal is generated as a result of negative coincidence. A second restraint signal related to V.sub.1 is also generated.

Abstract: A transformer core is made by winding a strip of ferromagnetic material, such as amorphous metal or silicon iron, on a winding mandrel to form a first annulus and cutting once through this annulus to create a plurality of individual laminations which are then assembled in packets about a nesting mandrel of a smaller diameter than the winding mandrel to form a second annulus. Each packet consist of a predetermined number of groups of laminations, with the ends of each lamination group lapping each other to form a lap joint. The lap joints of each packet are arranged in staggered positions to create a repeating step-lap joint pattern confined within a predetermined joint region. By decreasing the lap joint dimension and increasing the number of groups in successively assembled packets, the increase in build of the joint region over that of the remainder of the second annulus is minimized. The complete transformer core is uniquely characterized by its variable lap joint dimension and the absence of short sheets.

Abstract: This surge arrester is for protecting against high-energy and very fast surges and comprises first and second electrodes and a metal oxide varistor (MOV) disk between the electrodes. Each electrode has a central region and, at generally diametrically-opposed sides thereof, a source terminal and a load terminal. The terminals of each electrode are connected in the protected circuit in such a manner that load current in each of the conductors of the protected circuit flows through the electrode via a path that extends in series through the source terminal, the central region, and the load terminal. The source terminals of the two electrodes are generally aligned with each other about the periphery of the MOV disk, and the load terminals are also generally aligned with each other about the periphery of the disk.

Abstract: An apparatus for preventing operation of a full range chemically augmented electrical fuse due to induced current surges includes a low inductance device electrically connected in series between an air gap device and a first terminal of a trigger circuit for triggering exothermic material within the fuse. A second air gap device is electrically connected in series with a second low inductance device. This series connection of the second air gap device and the second low inductance device is electrically connected in parallel with a high inductance device, the parallel connected combination being connected in series with a second terminal of the trigger circuit. All of these elements are electrically connected in parallel with the main fuse element which is electrically connected in series with the protected electrical power distribution system.