Matches 51 - 100 out of 209 < 1 2 3 4 5 >
Match Document Document Title
5502611 Circuit for providing phase loss and phase imbalance protection  
A circuit for detecting phase imbalance in a three phase electrical system. The circuit includes a three phase current transformer or three separate current transformers for monitoring the current...
5434738 Apparatus and method for protecting induction motors from momentary power loss  
An apparatus and method for protecting an induction motor from momentary power loss in a three-phase, alternating current, power supply. The apparatus includes a circuit for detecting when the...
5428495 Electrical switching apparatus with digital trip unit and automatic frequency selection  
A microprocessor based switch such as a circuit breaker generates digital rms representations of analog load currents from n samples of the analog currents per cycle synchronized to the line...
5402071 Ground fault monitoring device for an electrical power distribution system  
The monitoring device comprises a measuring channel of the ground fault voltage, a measuring channel of the ground fault current, and a digital processing circuit whose role is to search for and...
5390067 Phase selection for ground fault  
A method and a device for phase selection for single-pole tripping of high-impedance ground faults in direct grounded power networks. Starting from the ratio of the negative-sequence voltage to the...
5369541 Three-phase unbalance and voltage monitor circuit  
There is disclosed a monitoring apparatus for a multiphase electrical system of very simple and reliable circuit design capable of monitoring such a system and producing fault signals to operate...
5361184 Adaptive sequential controller  
An adaptive sequential controller (50/50') for controlling a circuit breaker (52) or other switching device to substantially eliminate transients on a distribution line caused by closing and...
5337206 Three phase power monitor  
A three-phase power monitor operates a contactor between a supply of three phase electrical power and a three phase load. A phase integrity detector has three inputs connected respectively to the...
5319514 Digital voltage and phase monitor for AC power line  
A digital voltage protection circuit (138) and a phase monitor circuit (154, 160, 162, 168) disconnect AC-powered user equipment (22,182) from the AC power supply (141) whenever the AC power line...
5267117 Electrical phase and amplitude fault detection and response system  
The present invention provides a simple, reliable, comprehensive electrical phase and amplitude fault detection and response system. The system includes means for detecting any of various...
5243489 Protection circuit for multiple phase power system  
A protection circuit for three-phase power systems incorporates overcurrent protection along with phase loss and phase imbalance by means of common current sensing transformers. The phase loss and...
5229908 Multiple circuit overload protection device  
A sensor connected to two different phases of an electrical wiring system provides positive protection against overloading of any single phase by preventing operation of one circuit load when there...
5200737 System and method for detecting partial discharge of gas-insulated switchgear  
A system and method for detecting partial discharge of gas-insulated switchgear wherein a high-frequency component and the fundamental wave component of the voltage applied to the conductor of the...
5184063 Three phase reversal detection system  
A polyphase reversal detection and correction system which operates over a wide range of line frequencies and produces an automatic phase correction for maintaining proper phase sequence to a...
5172291 Intelligent power controller  
A remotely controllable circuit breaker and switch for controlling the flow of current from a three phase AC power source to a three phase load, and usable in either wye or delta configurations. A...
5170309 Four-pole circuit breaker  
In a four-pole circuit breaker having U, V, W and N poles for protection of corresponding phases, only an N phase signal, which is reproduced by a current signal reproducing circuit in response to...
5126678 A.C. Generator fault detector  
Faults in the operation of a multi-phase A.C. generator are detected by monitoring the phase difference between two line-to-line voltage of the generator and comparing this phase difference with a...
RE33874 Electric motor load sensing system  
An underload protection system for an electric motor connected to first and second power supply lines, the lines being connectable to an AC power supply. The system comprises a line voltage sensing...
5079666 Power supply shutdown through loss of sync  
A power supply for a video display device includes a protection circuitry which shutdown the power supply to prevent damage to the power supply or the display device. The protection circuitry...
5077626 Phase-failure detectors responsive to unequal bending of bi-metal members  
Circuit breakers can be used to replace fuses in plant comprising centrifuge machines driven by small three-phase electric motors. The circuit breakers incorporate three bi-metal strips which bend...
5062278 Air-conditioning apparatus including an indoor unit and an outdoor unit having its compressor driven by a three-phase AC power supply  
An air-conditioning apparatus includes a control circuit adapted to detect, from among first to third line voltages of a three-phase AC power supply, the second or third line voltage not...
5057963 Opposite phase detecting device for alternating current electrical equipment  
An opposite phase detecting device for alternating current electrical equipments includes a zero cross circuit synchronizing positive half waves of first and second line voltages of a three-phase...
5047889 Electromagnetic switch with undervoltage and phase failure protection  
A protective device prevents electrical load, such as three-phase induction motor, from overheat fault caused by undervoltage and phase failure condition in a three-phase power supply system. The...
4956739 Device for locating internal faults in a high-voltage capacitor battery  
A device to locate internal faults in a high-voltage capacitor battery that has a plurality of symmetrically parallel and series-coupled capacitor banks arranged in parallel branches coupled by...
4933803 Three phase loss protection circuit  
A three phase loss protection circuit for a three phase rectifier. The rectifier includes a circuit which inhibits its operation when either of two of the three phases are lost. In response to the...
4928219 Adaptable current regulating system  
An adaptable current regulating system provides a regulated current in accordance with both the actual characteristics of a system under control and the actual measured period of an AC supply. The...
4912588 High-tension voltage generator and method of protecting same against electrical arcs  
In an electrostatic paint spraying installation or the like, a high-tension voltage generator comprises a voltage rectifier-multiplier in a mobile subsystem and a grounding connection in a fixed...
4903163 Directional harmonic overcurrent relay device  
A single or multiple phase directional harmonic overcurrent relay device suitable for simultaneously monitoring overcurrents at either of two harmonic frequencies in an electric power system is...
4878208 Voltage-phase responsive, inverter disable circuit for system interconnection  
In a system interconnecting inverter apparatus, an inverter for controlling power of an AC power system is coupled, via a coupling reactor, to the AC power system having a system voltage. A system...
4855859 Detection device for detecting transitions to the normal state in a superconducting winding, in particular for generating electricity, and a protection device for protecting such a winding  
A detection device for detecting transitions to the normal state in a superconducting winding, in particular in an electricity generator, and a protection device for protecting such a winding. A...
4841404 Pump and electric motor protector  
An electrical circuit for providing electrical energy to an electric motor which operates a liquid pump. The motor and the pump are adapted to be submerged in the liquid which is pumped by the...
4833460 Phasing indicator  
An apparatus for visually indicating abnormal phase relationships between incoming or outgoing phases for a plural phase device, comprised of a plurality of light emitting means interconnected...
4833628 Up to speed detector for an electric motor using measured values of the current lag; and voltage ramp controller using the up to speed indication  
An indication that a motor has reached full speed operation is produced by generating an up to speed signal based upon measurement of the phase angle between the voltage applied to the motor and...
4825323 Out-of-step blocking unit  
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...
4823226 Phase loss detection circuit including transient protection  
A phase loss detection circuit for a three phase electrical system providing three phase power as to a motor, the three phase electrical being subject to a phase loss condition and a transient...
4819121 Security apparatus for power converter  
A security apparatus adapted to a power converter, including a power converting circuit connected between a DC power source and an AC system; a phase detector circuit for detecting the voltage...
4802053 Control circuitry including phase failure relay  
A system for sensing the phase of a three-phase AC system and detecting phase reversal and undervoltage and phase unbalance and for providing a switching function when the system is not functioning...
4757416 Protective apparatus, methods of operating same and phase window adjusting apparatus for use therein  
A protective apparatus for use in an A.C. electrical power system with a circuit breaker for connecting and disconnecting first and second electrical conductors that are electrically energizable,...
4757415 Power active filter employing positive sequence filtering  
A power active filter circuit for an electric power system includes a reference generator for producing a plurality of balanced, constant amplitude, positive sequence, AC reference voltages, each...
4745512 Remote protection of three phase distribution transformers  
It is desirable to provide remote digital protection of distribution transformers. This specification discloses a protection system able to measure and compare increases in both negative and...
4731690 Real load unbalance protection system for parallel variable speed constant frequency electrical power systems  
A method for sensing real load unbalance in an electrical power system having at least two clock based power sources which are connected for parallel operation combines a real load difference...
4710843 Selectable integrating characteristic timer  
A characteristic timer, for a protective relay which provides protection for a portion of an AC transmission line, exhibits a phase characteristic which is always integrating and a ground...
4703387 Electric motor underload protection system  
An underload protection system for an electric motor connected to first and second power supply lines, the lines being connectable to an AC power supply. The system comprises a line voltage sensing...
4689709 Digital distance relay  
In a digital distance relay, the distance measuring operation is performed only regarding the phase on duty in the third step if there is no fault, and it is performed regarding either the third...
4675774 Direct transfer trip apparatus for use with an active pilot wire communications channel  
Direct transfer trip apparatus for sharing a common active communication channel utilized for signal transfer between at least two electromechanical units which form a current differential...
4675775 Active pilot wire apparatus for electromechanical current differential relays  
Active pilot wire apparatus for replacing a passive continuous metallic wire pair coupling between the electromechanical units of a conventional electromechanical pilot wire protective relay is...
4669024 Multiphase frequency selective phase locked loop with multiphase sinusoidal and digital outputs  
A circuit for providing a multiphase digitally synthesized sinusoidal output signal representative of a predetermined symmetrical component set of a multiphase source signal and having a...
4658323 RMS calculation circuit for digital circuit interrupters  
The root mean square value of sensed current within a protected circuit is used to determine the occurrence of an overcurrent condition. A frequency multiplying circuit produces a pulse stream...
4600962 Apparatus for monitoring and protecting a device against a plurality of fault conditions  
A control system for protecting a computer system against external fault conditions, including, in combination, circuits for monitoring and reacting to a plurality of power supply fault conditions,...
4562507 Protective relay  
A protective relay which hardly makes maloperation in itself regardless of mixing of low-order higher harmonics in its at least two sinusoidal input signals comprises a first and a second phase...
Matches 51 - 100 out of 209 < 1 2 3 4 5 >