Showing papers on "Relay published in 1990"

Automated dual-party-relay telephone system

Abstract: A facility is provided for automating dual party relay service so that the cost of such a service may be reduced. The desired result is achieved by automating particular features of dual party relay service to appreciably decrease the amount of time that a service attendant is involved in a dual party relay call. Such automation is obtained by employing text-to-speech processing, and, on a limited basis, automatic speech recognition.

Voice bridge for a relay center

Abstract: A voice bridge for a telephone relay for the hearing impaired is constructed so as to pass voice data to and/or from a user who is capable of either speaking or hearing voice. The voice bridge is capable of passing voice communication between a pair of telephone lines while excluding data carrier TDD signals from passage. Several methods are possible to achieve TDD signal exclusion. A privacy option is also included to exclude the relay station operator from overhearing parts of conversation when the operator's assistance is not required.

Communication system employing multiple relay satellites operating on common downlink frequency

Abstract: A mobile satellite communication system utilizes spread spectrum techniques to allow messages to be transmitted from a ground-based cenral station (20) to a number of essentially identical receiver terminals (32) through two or more relay satellites (28, 30) operating on the same downlink carrier frequency (f2) and covering the same geographic area. This arrangement allows the capacity of the system to be increased without the use of additional radio frequency spectrum on the downlink, and without reliance on directional tracking antennas at the receiving terminals. The system can also determine the positions of the receiver terminal (32) for navigational and tracking purposes.

Defibrillator with reliability verification

Abstract: A defibrillator is described with dual processors for verifying the performance of the defibrillator and halting the application of a defibrillation pulse to a patient if a failure of system components is detected. In accordance with one aspect of the invention, verification is performed to determine whether a transfer relay switch should be closed to permit the application of a defibrillation pulse through the transfer relay switch to a patient. In addition, in one form of the invention, an electronic switch is provided in a series discharge circuit through the patient. Verification by both processors of proper conditions for application of a defibrillation pulse is required before a determination pulse is applied through the switch. In addition, an impedance circuit is provided with a mechanism for checking the accuracy of the circuit during operation of the defibrillator.

Inter-truncked radio systems bridge protocol

Abstract: A radio signal relay system for use with dispatch communication systems is disclosed. The radio signal relay system includes a linking device constructed with a first and a second full duplex transceivers such that it has the capability of communicating with the communication controller and at least one repeater in each of at least two adjacent communication systems.

A Kalman filter based digital percentage differential and ground fault relay for a 3-phase power transformer

Abstract: The design and real-time implementation of a Kalman-filter-based digital percentage differential and a ground-fault protection scheme for three-phase power transformers are presented. A set of eleven-state Kalman filters is used to estimate the fundamental and up to fifth harmonic components of the transformer current signals. The protective relay is equipped with an even harmonic restraint during magnetizing inrush conditions and a fifth harmonic restraint during overexcitation conditions. The restraint during external faults is provided by means of a percentage differential characteristic. The relay operates in half a cycle during internal faults. In order to achieve sensitive ground-fault protection, separate primary and secondary ground-fault protection are provided. The relay algorithm is implemented on a single TMS320 digital signal processor and tested in real time using a three-phase laboratory power transformer. >

High voltage DC relays

Abstract: A high voltage DC relay with arc suppression in which a MOSFET in parallel with the relay contacts is turned on during contact break mode by the controlled discharge of a capacitor between the MOSFET source and drain through a constant current diode to suppress arcing. A sensing coil positioned near the relay coil generates current used to charge the charging capacitor during the make contact mode to suppress arcing.

Auto electric tester

Abstract: An auto electric tester has been provided that is simpler in construction, easier to manufacture and can expedite the location of several electrical problems more easily than all known prior art. The tester comprises a casing, circuitry mounted within the casing, four electrical conductors extending from the casing and connected to the circuitry. The circuitry comprises a full-wave bridge rectifier connected to a first two of the conductors, a relay connected across the bridge so that current flowing in two conductors in either direction to the bridge can activate the relay, a first circuit tap made between the bridge and relay extends to a third one of the conductors and includes in series a diode and a load resistor, second and third circuit taps extend in parallel from the first circuit between said diode and said load resistor to the fourth conductor, said second circuit including in series a relay switch operated by said relay and audible indicator, said third circuit including in series a resistance and a visual indicator.

Electrostatically switched integrated relay and capacitor

Abstract: An electrostatically energized and integrable relay is disclosed that has dimensions that permit closure and maintenance of a contact between electrodes using electrostatic forces exclusively. The physical dimensions are such that it could be formed using integrated circuit fabrication techniques. Small spacing between the electrodes of the relay permit the device to be usable in an integrated form, perhaps on an integrated circuit substrate.

Lamp lighting circuit with an overload protection capability

Abstract: A lighting circuit for a metallic halide lamp for vehicular headlight applications is disclosed. Included are a pair of input terminals between which a battery is connected for feeding the lamp via a normally open relay switch which is closed upon energization of an associated relay coil. The relay coil is connected in series with an operator actuated lamp switch and a protection switch, so that both lamp switch and protection switch must be closed to energize the relay coil and hence to close the relay switch. The protection switch is automatically opened to deenergize the relay coil when the battery develops overvoltage or when the lamp will not glow upon closure of the lamp switch. In an alternate embodiment, the protection switch is also opened in response to the development of overcurrent or overvoltage by a d.c. voltage booster circuit included in the lighting circuit.

Contact erosion in automotive DC relays

Abstract: Contact degradation of automotive relays was studied to understand the relationships between switching operations (make, break, and make-and-break) and loads (resistor, lamp, and motor). This information is essential in proper relay design, specification, and application in an automotive electrical system. Contact resistance was measured and the eroded surfaces were analyzed to explain the degradation process. Significant dependence of degraded contact resistance on types of load and switching operation was found. Prominent pips and craters that can cause premature relay failures were formed during the make operation by anode-to-cathode transfer. Break arcs transferred material from cathode to anode and formed a porous layer to increase contact resistance. The amount of material transferred decreased with shorter arcing time, which also decreased with load inductance. The degradation process is explained as an interaction among switching mechanics, load current characteristics, and arc phenomena. >

Effect of waveform distortion on protective relays

Abstract: The authors attempt to show, theoretically and by laboratory tests, the influence of harmonics on protective relays. Representative relays using various operating principles were tested using fundamental currents and/or voltages. They were then tested using single-frequency inputs that were multiples of the fundamental frequency. Finally, tests were made using realistic combinations of fundamental and harmonics. From the theoretical concepts and expectations discussed and the series of tests performed, it is evident that the influence of mixed frequency harmonics (with magnitude decreasing with order) on the steady state behavior of the protective relays studied is minor and insignificant. The influence of pure single-frequency inputs, above the fundamental, on various protective relays was also evaluated. Results showed a distinct change in relay operation. >

Solid state overload relay

Abstract: An overload control circuit and method of operation for protecting a three-phase motor from damage due to overload includes monitors reading the load on each phase of the motor and circuitry for combining the three separate phase signals into a single combined load signal which triggers the overload circuit. The gain on the combined load signal and the overload trip delay time may be calibrated and monitored by an external meter to provide for accurate and inexpensive calibration to accommodate specific operating characteristics of the motor being monitored. The circuit provides visual readouts of the mode of operation, including: (1) operating mode; (2) overload onset; (3) shut down initiated; and (4) delay to restart.

Photoelectric switch and relay system with disabling fail-safe monitoring circuitry

Abstract: A hand operated photoelectric switch having a channel providing an interrupt area for an operator's hand to pass into the path of an infrared light beam passing from a light emitting diode to a phototransistor sensor. Said housing further including circuitry for operating a mechanical relay to be activated for the operation of electrical machinery. A monitoring circuit is provided to monitor the light emitting diode and a driver transistor for the mechanical relay whereby to detect the failure of either one and disable the circuit from accidentally providing contant closure of the mechanical relay.

An expert system for protective relay setting of transmission systems

Abstract: An expert system for setting protective relays in a high-voltage transmission system is proposed. Multilevel frames are used to represent relay specifications and system information. Setting rules are stored in the hierarchical rule base. The frame-based inference mechanism is adopted for an efficient integration of framework and rule. An easy system modification environment is achieved through predefined predicates and a frame editor. The use of the system would expedite the relay setting process with increased accuracy and consistency regardless of the power system's complexity. >

Load protection circuit

Abstract: A battery operated standby inverter power supply uses an electromechanical relay switching network to connect and disconnect line power between input and output terminals. An overcurrent relay pulser rapidly opens the switching system relay contacts upon transition to battery mode, and a breakover diode network accelerates field collapse in the relay coil attendant to reversion of the relay to its normally closed condition attendant to each battery to line transition. A fault detector establishes acceptable line voltage thresholds, the exceeding of either of which triggers operation from line to battery mode. These triggering thresholds are automatically pulled closer together during initial system startup. During system startup and attendant to each battery-to-line transition, the fault detector is momentarily latched to indicate acceptable line voltage conditions, thereby removing its susceptibility to transient retriggering. During start-up mode a low-current transformerless power supply connected to the power line input terminals charges a storage capacitor sufficiently to power the fault detector through a single interrogation cycle, to actuate the switching circuitry to line mode operation if proper line voltage conditions are sensed. Collapse of this capacitor voltage during this operation terminates the interrogation cycle, a new cycle begins when the capacitor has been suitably charged. An overload detector senses the load current in line mode and prevents actuation to battery mode if the load connected to the power supply output exceeds the rated current value of the inverter.

Selective power combiner using phase shifters

Abstract: A circuit for selecting and combining power signals of a pair of parallel amplifiers (3,4) using phase shifters (5,6) having fixed phase. Either amplifier (3,4) may be selected to produce a power signal of power P at the circuit output (9), where P is the power at the output (11,12) of each amplifier (3,4). Alternatively, power from the two amplifiers (3,4) may be combined to produce a signal of power 2P at the circuit output (9). By using a passive circuit to achieve the selection and combination, the use of heavier and less reliable relay switches is avoided.

Effect of voltage harmonics on the operation of solid state relays in industrial applications

Abstract: The results of a study on the effects of voltage and current harmonics on the operation of four types of solid-state relays (SSRs) used in control schemes of many industrial applications are presented. This study started after repeated malfunctions of electrophotographic printers in some data processing centers. The misoperation of zero-switching SSRs was suspected as the cause of the malfunction. Tests on the SSRs were performed using a single-phase harmonic generator and a LeCroy digital oscilloscope with signal processing software capabilities. The results reported indicate that voltage harmonic distortion may cause a delay in the turn-on time of more than a cycle. In some cases, complete failure to turn on or off may occur. Recommendations based on academic research, user's experience, and manufacturers viewpoints are given. >

Switched mode power supply controller having a stand-by state using a frequency divided burst mode

Abstract: The present invention relates to a power supply device adapted for various electric or/and electric instruments. The present invention generates lower voltages during a standby mode except for power to a microcomputer, using a frequency-dividing circuit and provides the normal output voltages in operation mode to minimize the power consumption without a relay circuit.

Vehicle battery discharge prevention circuit - uses interlocking relays and external master switch to cut off current supplied to loads when vehicle is locked

Abstract: The battery (2) supplies the loads (V) via a relay (7,10) and toggle switch (3), the rest position of the toggle switch being N. The switch has two ganged contacts (4,12) and an indicator lamp (16). The winding of the relay passes through the normally closed contacts (8) of a second relay (9). When the switch is momentarily switched to I, the winding of relay (7) is activated via switch contact (4), contacts (10) are closed, and power is supplied to the loads (V). The toggle switch returns to the N position, but winding (7) continues to be energised via the lead (14) and switch contact (12). Only when the switch is moved to position O do the contacts (10) open, disconnecting the loads. The external key-operated master switch controls the winding of the second relay. When the key contacts (17) are closed, the winding (9) is activated, contacts (8) open and the relay (7) is rendered completely inactive, thus isolating the loads. This master switch could be located in a car door or boot lid. USE - Switches off car radio etc. when vehicle is locked from outside.

Digital differential relaying scheme for teed circuits based on voltage and current signal comparison

Abstract: The paper describes the basis of an alternative approach to the problem of differential protection of teed feeders that involves deriving signals which are functions of both voltages and currents. It is shown that, unlike conventional current differential protection, this approach obviates the need for bias to compensate for capacitance spill current, thus improving the overall performance of the relay. Methods are outlined for compensating for the variable responses of practical transducers. Other practical considerations include the means developed for signal compression to simplify the digital hardware requirements and reduce the bandwidth requirements for digital communication between the three ends. The protection has been developed using CAD techniques, and the methods proposed are readily implemented using present generation signal processing hardware.

Multiple overcurrent relays using a single microprocessor

Abstract: The implementation of a four-overcurrent-relay system using a single 8085 microprocessor is described. The implementation is based on the concept of multitasking in microprocessors. The relays are considered to be independent of each other. Each relay is realized by a separable counter and a look-up table in the memory. The software development and hardware testing are done using the HP-64000 UX Microprocessor Development System. The system does not depend on the 8085 microprocessor; other microprocessors can be used. The hardware and software are modular, and more relays can be added. >

Mobile radio communication system

Abstract: A mobile radio comprises a base station BS arranged to communicate with a mobile subscriber unit SU by means of a relay station R2. The provision of the relay R2 enabling the subscriber unit to transmit on a lower power than would be required to make direct contact with the base station BS.

Intelligent power controller

Abstract: 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 latching relay controls the current for each phase. Current samples in the three phases are scaled and converted to DC values by scalers and RMS to DC converters. The DC values are converted to digital current values by an analog-to-digital converter which sequentially scans the DC values of the currents in the three phases. A central processing unit monitors the digital current values to detect significant phase imbalances and overcurrents which persist for time periods which exceed allowable limits according to a predetermined time-dependent function, and to initiate opening of the relays in response thereto. The central processing unit also opens and/or resets the relays in response to remote control signals. The relays are opened in a zero-crossover mode when the currents exceed predefined threshold values; and in order to minimize the effects of noise are opened without regard to zero crossover when the currents are below said threshold values. Relay status contacts are employed to reduce power consumption during relay operation by terminating relay coil drive pulses when the relay contacts have achieved the desired state.

Electropneumatic air brake control system for railway vehicles

Abstract: An electromagnetic air brake control system including a module portion and an integral relay valve portion. The module portion includes a brake pipe cut-off valve. A bistable electropneumatic valve device pneumatically connected to the brake pipe cut-off valve. A pole changing relay electrically connected to an electric coil of the bistable electromagnetic device. The pole changing relay having an electric coil connected to a d.c. voltage. A quick release relay having an electric connection to the d.c. voltage and having contacts connectable to contacts of the pole changing relay. A pair of relay driver circuits supplied by a supplemental power supply for causing the electric coils of the pole changing and quick release relays to be energized and deenergized in accordance with output signals received from a command control circuit and a monitor checking circuit.

Relay control apparatus

Abstract: A relay control for a cooking appliance having a heating element includes a sensor for detecting the occurrence of an arc upon a change of state of a relay coupled between the heating element and a power supply. Upon detecting an arc, the sensor provides a timing signal which is coupled to a microprocessor that controls the energization and deenergization of the relay. The microprocessor is responsive to the timing signal from the sensor to determine the time delay between the last energization/deenergization of the relay and the changing of the relay's state. From the time delay, the microprocessor determines a delay constant. Subsequently, the microprocessor energizes the relay at a time after the detection of a zero crossover point of the power supply signal, wherein the time is equal to the determined delay constant to cause the relay to change state at or slightly before a zero crossover point of the power supply signal. The sensor may take the form of an optical sensor mounted inside the housing of the relay or outside of the housing. Alternatively, the sensor may include an electromagnetic or RF pick-up coil for sensing an electromagnetic or RF signal in the radio frequency (RF) range radiated upon the generation of an arc. Alternatively, the sensor may be a vibration sensor, such as a piezoelectric transducer, capable of detecting vibrations associated with the opening or closing of the relay contacts.

Some aspects of the digital implementation of protection time functions

Abstract: A basic model for implementing protective time functions is reviewed and the factors affecting coordination when using relays representing different technologies are analyzed. A simple test based on a mathematical expression is presented as a means of assessing the dynamic performance of a relay with respect to varying input signals. Factors affecting the precision of digitally implemented time functions are analyzed together with sources of errors with respect to time computation. Tests presented indicate that conventional relays match the proposed ideal model. >

Flexible inverse overcurrent relaying using a microprocessor

Abstract: The fundamentals of inverse time overcurrent relaying, recent changes in transformer characteristic curves, and a flexible microprocessor-based relay that has wide application possibilities are described Insight into the process of selecting a particular time-current operating characteristic shape for a given application is provided Guidelines are presented for the selection of a setting for an instantaneous-trip device based upon its transient reach tendencies It is concluded that the availability of a microprocessor-based inverse time overcurrent relay that has selectable characteristics built in will greatly relieve the application difficulties that have been associated historically with their fixed-characteristic electrochemical counterparts >

Development of computer-aided assessment for distribution protection

Abstract: A simulation package for the assessment of overcurrent relay performance on interconnected distribution networks has been developed which gives a new approach to identifying isolated nodes or split networks and fast detection of fault isolation in fault-current calculation. Other types of relay characteristics can be included into the package by simple modification of the program