Did You Know...
...that the Slinky toy was the result of a failed attempt by engineer Richard James to produce an antivibration device for ship instruments? His goal was to develop a spring that would instantaneously counterbalance the wave motion that rocks a ship at sea. Instead, he developed the Slinky.
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| Number | Title | Issue Date |
| 7319576 | Apparatus and method for providing differential protection for a phase angle regulating transformer in a power system Provided is an apparatus and method for providing differential protection for a phase angle regulating transformer having a load side and a source side in a three-phase power system. The method includes calculating a first positive sequence component and a first neg... | 01/15/2008 |
| 7280938 | Method for determining a negative sequence component The invention relates to a method for determining properties of a negative sequence component of a space vector quantity in an electrical network. The method according to the invention includes the steps of determining on the basis of the properties of an ellipse fo... | 10/09/2007 |
| 7279905 | Method and an apparatus for supervising the operation of current transformers A method of supervising the operation of a plurality of current transformers arranged in respective groups and connected to a protection relay forming part of a three-phase electrical power system includes determining a current ratio at an output of each group of cu... | 10/09/2007 |
| 7221140 | Circuit, method and system for providing one or more phase voltages from input voltages The present invention provides a phase voltage circuit. In one embodiment, the phase voltage circuit includes a line voltage stage coupled to at least three input voltage lines and configured to provide at least two corresponding line voltages. Additionally, the pha... | 05/22/2007 |
| 7209333 | Apparatus and method for over-voltage, under-voltage and over-current stress protection for transceiver input and output circuitry A circuit for protection of a transceiver input includes an input transistor and a first resistor connected between the drain of the input transistor and an input node. A plurality of reverse-biased diodes connected between a supply voltage and the input node. An ou... | 04/24/2007 |
| 7205737 | Systems and methods of monitoring a motor load Systems and methods of detecting an overload condition. In one embodiment, a method of monitoring a load of a DC motor includes intermittently de-energizing the motor; monitoring a first voltage; and measuring a first interval of time between a starting time and an ... | 04/17/2007 |
| 7196886 | Reverse wiring detect in circuit interrupting devices A resettable circuit interrupting device having a switch and timer circuit connected to the line side of the interrupting device to cause a leakage current to flow for a defined interval of time when power is applied. The timer and switch circuit comprises a timer p... | 03/27/2007 |
| 7168974 | Three phase lighted plugs and connectors for indicating the absence of at least one phase Indicator means located in a plug or connector indicates when at least one phase of an AC multi-phase voltage is absent. The indicator means can be any one of a variety of light sources and/or an audible generator. The light source can be, for example, an LED, an il... | 01/30/2007 |
| 7158869 | Method,device and bus manager for operating a device that is connected to a motor vehicle communications network A method of operating a device which is connected to a vehicle communications network is described, a switched-off device being reactivated by the bus manager via a frequency pulse transmitted over a power supply line. The device may be switched off by the bus manag... | 01/02/2007 |
| 7149067 | Automatic voltage device and network protector incorporating same A voltage sensing device automatically scales the source and network phase voltages of a power distribution system having one of two operating voltages for input to a network protector relay and also automatically scales a voltage for operating the trip and close ci... | 12/12/2006 |
| 7106565 | Directional ground relay system A directional ground relay (50) for receiving electric values relating to voltage and current from a power transmission line (1) to be protected. The directional ground relay may decide a direction of a fault in the power transmission line based upon t... | 09/12/2006 |
| 7023196 | High level arc fault detector Apparatus and methods for detecting high level arc faults in aircraft power systems are disclosed. One embodiment of the invention with reduced susceptibility to nuisance trips includes three low pass filters each having an output connected to a threshold detector. ... | 04/04/2006 |
| 6975490 | Apparatus and method for detecting phase state In an apparatus and a method for detecting a phase state capable of improving reliability of an air conditioner by preventing an abnormal operation of the air conditioner by detecting a phase state (antiphase and open-phase) of three phase AC power supplied to the a... | 12/13/2005 |
| 6956733 | Device and method for providing electric service An exemplary device and method for providing electric service are disclosed. The exemplary device may provide construction power during the construction of a facility and permanent power at the facility thereafter. The electric service device, when energized at a co... | 10/18/2005 |
| 6922318 | Ground relay system in a multiplex direct grounding system A ground relay system is provided which includes: first current transformers located in the respective phases of a sending end of a high-voltage distribution provided from a distribution substation; over-current relays connected to the first transformers; distributi... | 07/26/2005 |
| 6905961 | Land grid array stiffener for use with flexible chip carriers A flexible chip carrier with contact pads on its upper surface matching those of the chip with said pads conductively connected to land grid array (LGA) pads on its lower surface matching the those of a card or PCB. The chip carrier is provided with a stiffening lay... | 06/14/2005 |
| 6833711 | Protective relay for powers systems having dependable out-of-step blocking capability The apparatus detects an out-of-step condition following the clearing of an external multi-phase fault in a protective relay. The apparatus includes a circuit which detects the presence of an external multi-phase fault on the power line and a timing circuit for read... | 12/21/2004 |
| 6785105 | Ground fault detection system for ungrounded power systems The fault detection system includes at least one valid zero sequence voltage source, either from a local relay or a remote relay on a protected line. Zero sequence current is selected between total (vector sum from both ends of the protected line) measured zero sequ... | 08/31/2004 |
| 6720749 | Three-phase motor protector apparatus A three-phase motor protector uses two toroids to monitor all three phases of a three-phase motor. Current and phase loss are monitored directly in phases A and B while the phase C current level is determined by analysis of the phase A and B relationship. Current is... | 04/13/2004 |
| 6671151 | Network protector relay and method of controlling a circuit breaker employing two trip characteristics A network protector relay controls a circuit breaker connected between polyphase feeder and network busses. A circuit samples polyphase circuit breaker current and network voltage to generate digital polyphase current and voltage samples. A microcontrolle... | 12/30/2003 |
| 6573726 | Sensitive ground fault detection system for use in compensated electric power distribution networks A system for detecting ground faults in a compensated electric power distribution network includes the determination of zero sequence voltage (V0) and zero sequence current (I0) on a power line and calculating the zero sequence condu... | 06/03/2003 |
| 6504693 | Network protector relay providing a close function A network protector relay for a circuit breaker includes a microcontroller routine which provides a positive sequence network voltage from polyphase network voltages on a network bus. Another microcontroller routine provides a positive sequence phasing vo... | 01/07/2003 |
| 6493203 | Phase control switch apparatus A phase control switch apparatus incorporating a phase-based break/make controller (80A, 80B, 80C) for protecting a reactive load such as a transformer (10) from transient surge phenomena taking place upon power-supply breaking/making operation. The phase... | 12/10/2002 |
| 6392858 | Electronic trip device with phase reconstitution and a circuit breaker comprising such a trip device The trip device with phase reconstitution comprises a processing unit comprising means for phase reconstitution receiving signals representive of the current signals supplied by sensors. The means for phase reconstitution comprise means for determining si... | 05/21/2002 |
| 6175810 | Method of generating a signal identifying a three-pole short-circuit occuring in a three-phase power transmission line A method for generating a signal identifying a three-pole short-circuit occurring in a three-phase power transmission line in which the phase currents and phase voltages are sampled forming phase current and phase voltage sampling values and the signal is... | 01/16/2001 |
| 6154687 | Modified cosine filters A high sample rate cosine filter eliminates DC components by summing them such that they sum to zero. A non-orthogonal cosine filter is also provided. When the cosine filter is applied for N=4 samples per cycle, the samples are separated by 90 degrees. Ho... | 11/28/2000 |
| 6147616 | Automatic power interruption and re-supply relay for an electric power line The present invention provides a digital automatic power interruption and re-supply relay for performing detection and comparing operation to inform a state of an accident with voice and numerals and automatically operating a connected relay to interrupt ... | 11/14/2000 |
| 6114859 | Harmonic characteristic measuring method and harmonic characteristic measuring apparatus Single-phase currents at two frequencies f and fଲ (f | 09/05/2000 |
| 6104106 | Solid state circuit breaker A switching circuit that is particularly applicable to high voltage 3 phase solid state circuit breakers (SSCB). The circuit comprises a solid state switch; an energy absorbing device connected in parallel with said switch to form a parallel combination; ... | 08/15/2000 |
| 6064001 | High current electrical switching apparatus with poles interleaved and modules joined by interference fit of joining block in undercut grooves in molded casings Two molded case electrical switches such as circuit breakers, network protectors, disconnect switches and transfer switches, are secured together side-by-side by joining blocks having tongues extending along their sidewalls which engage undercutting groov... | 05/16/2000 |
| 5883578 | Loss of potential determination for use in protective relays for electric power systems The positive sequence voltage on the power line is measured at a given time, i.e. the present time, and also for one cycle earlier, and the ratio thereof is then compared against a threshold value of 0.9. There are four other supervisory tests which also ... | 03/16/1999 |
| 5883796 | Dynamic series voltage restoration for sensitive loads in unbalanced power systems A method and apparatus is provided for restoring a sagging voltage signal on a power transmission line, caused by a remote fault in the utility power system, to a balanced three-phase condition at the pre-fault voltage level. Voltage restoration is provid... | 03/16/1999 |
| 5859530 | Process for determining the phase sequence in a three-phase network (rotary current network) In a first measurement step, the two test probes of a measurement apparatus are contacted with two of the three phase lines. The measurement apparatus determines the frequency of the three-phase voltage. In a subsequent second measurement step, one of the... | 01/12/1999 |
| 5822165 | Sequence based network protector relay with forward overcurrent protection and antipumping feature A digital network protector relay samples the polyphase current, network voltage and phasing voltage at 16, and preferably 32, times per cycle so that up to the seventh and fifteenth harmonics, respectively, are eliminated from the sequence calculation us... | 10/13/1998 |
| 5784240 | Method and apparatus for limiting current surge upon transfer of a load between A.C. power sources A method of and apparatus for actuating an automatic transfer switch for disconnecting a motor load from a normal source of voltage and reconnecting the load to an alternate source of voltage at a time when phase differences between the output voltage of ... | 07/21/1998 |
| 5777835 | Third phase reconstruction from a two current transformer sensor with three-phase true RMS and phase loss determination capabilities A method and apparatus are disclosed to reconstruct a third phase for a three phase sensing system in which only two current transformers sense all three phases. Two phases of the three phase system are used as a single primary winding for each current tr... | 07/07/1998 |
| 5768079 | Adaptive ground and phase fault detection for a power distribution system An adaptive method and apparatus for detecting fault conditions in a power distribution system that services both single phase loads and three phase loads. The present invention accomplishes this by providing an adaptive ground fault detection method and ... | 06/16/1998 |
| 5751132 | Electric motor monitoring circuit An electric motor monitoring circuit apparatus for an electric motor has a three phase electric motor having an electric motor starter circuit. An insulation monitoring circuit is coupled to the electric motor and monitors insulation leakage of the electr... | 05/12/1998 |
| 5710542 | Method of measuring the A.C. current in a conductor in an A.C. power transmission network A method for measuring the current in an AC power transmission network, where a measurement quantity is obtained by means of a current transformer and digital samples are converted. To prevent faulty detection of the current due to a decaying DC component... | 01/20/1998 |
| 5659453 | Arc burst pattern analysis fault detection system A method and apparatus are provided for detecting an arcing fault on a power line carrying a load current. Parameters indicative of power flow and possible fault events on the line, such as voltage and load current, are monitored and analyzed for an arc b... | 08/19/1997 |
