Abstract: A method and apparatus in a control system for an electromagnetic contactor for reducing multiple re-ignitions incorporates a regulated source of electrical power coupled to a contactor actuating coil through a controllable switch. The switch is used to regulate coil current to a desired value whereby opening time of the contactor can be determined within a defined range. Alternating current through tips of the contactor is monitored and each zero crossing of the current wave form is determined. The control system responds to a command to open the contactor tips by coordinating such opening with the zero crossings of the current wave form whereby the contact tips separate within a predetermined phase angle prior to a zero crossing. The system also includes apparatus for detecting a fault current of the alternating current in the contact tips and for inhibiting operation of the contact tips for a predetermined time interval in order to allow fuses to clear the fault prior to opening the contactor.

Abstract: A monolithic integrated circuit device comprises first and second output terminals, a power switching circuit which is connected across the first and second output terminals and through which electric current is supplied to an external load from an external power source, a driving a circuit for generating a first drive signal to be supplied to the power switching circuit, and a third output terminal in electrical connection with the driving circuit for derivation of electric energy from the driving circuit as a second drive signal to be spplied to an external circuit via the third output terminal. The monolithic integrated circuit device is capable of not only controlling power supply to an external load but also driving an external circuit which may be another power switching cirtcuit cooperative with the power switching circuit in the present monolithic integrated circuit device for the purpose of controlled power supply to the external load or which may be other types of electronic circuits.

Abstract: A system is disclosed for sequentially disconnecting multiple phases of a first power source (12) from an electrical load (14) requiring a minimum of interruption and connecting a second power source (28) to the electrical load. A first embodiment of the invention disconnects immediately the phase in which a trip condition requiring disconnection of the first source power is detected and disconnects phases of a first power source (12) in which a trip condition is not detected upon the detection of zero current flow in those phases. In a second embodiment of the invention, each of the phases of the first power source (12) is disconnected immediately from the electrical load (14) upon the detection of a trip condition in any one of the phases requiring disconnection of the first power source. In both embodiments of the invention, the phases of the second backup power source (28) are connected upon the detection of the occurrence of zero voltage points in the respective phases.

Abstract: A solid-state trip device including an instantaneous trip device formed by arc detectors 46R, 44S, 46T located in proximity to the main contacts 17R, 17S, 17T of the circuit breaker 10. The light signals emitted by the arc detectors 46R, 46S, 46T are transmitted by optical fibers 48 to a light-sensitive electronic component which emits an arcing signal. This arcing signal causes tripping of the circuit breaker 10 only if a fault signal is present.

Abstract: A reduced arcing contact switching circuit. It is desirable to control the switching of electrical contacts so that opening and closing occur at the time when zero power is being transferred to the load so as to substantially reduce arcing at the contacts and thus extend contact life. In a purely resistive circuit, for example, the supply voltage and current will be in-phase and contact switching should occur when the current and voltage signals pass through zero degree phase angle. Control of contact switching is accomplished with this invention by producing a count value that represents the phase angle at which contact movement should be initiated, so that the actual closing or opening will occur at the desired phase angle. When the count value and a preselected count are approximately equal, a flip-flop is enabled to pass the control information (open or close contacts) to a relay driver. The relay driver energizes or deenergizes (as the case may be) the relay to open or close the contacts.

Abstract: The contacts of an electrical switch, such as a magnetic contact reed switch or a magnetic contact reed relay used in a burglar alarm system, are protected from being fused together by transient current surges. This protection is accomplished by providing a normally nonconductive shunting path in parallel with the switch. The shunting path includes a voltage responsive device which is biased to conduction in response to a current surge to thereby complete the shunting path and allow the current surge to bypass the switch.

Abstract: A circuit for protecting the power contacts (18, 20) of automatic bus transfer equipment, including high speed solid state switches (30, 32) connected across the respective contacts. A timing and steering circuit (36) is responsive to the electrical energization of a solenoid (22) for firing the solid state switch (32) connected across the closed contact (18). A timer (48) is responsive to the opening of the contacts (18). At the elapse of a time period, the firing circuit (34) is caused to operate the solid state switch (30) before the closing of the contacts (20). The solid state switch (30) is maintained operated for a predetermined period of time by a timer (90).

Abstract: Re-strike in the circuit breaker of a capacitive load applied across an AC voltage power supply is reduced or avoided by connecting across the capacitor bank a tuned discharge circuit. The tuned discharge circuit includes a transformer with a primary connected in parallel with the capacitor bank and a secondary which can be shorted through a switch. The leakage reactance of the transformer is equated to the capacitive reactance of the capacitor bank so that the tuned circuit discharges the capacitor voltage in phase with the supply voltage. The discharge takes place through a number of cycles thus gradually increasing the voltage across the breaker gap. The switch in the secondary preferably comprises an anti-parallel pair of thyristors fired by a circuit responsive to current zero in the capacitive circuit detected over a delay period to avoid firing at normal zero crossing current.

Abstract: The circuit breaker displays a commutation device (4) and a semiconductor valve arrangement (6) which is connected in parallel with the commutation device (4), an isolating switching point (5) connected in series with the semiconductor valve arrangement (6) and a control circuit (11). The control circuit detects the polarity of the current to be disconnected and, together with a switching-off command (24), emits a response command to the commutation device (4) when the detected current flows in the direction of conduction of the semiconductor valve arrangement (6). When the current to be disconnected is interrupted in the semiconductor valve arrangement (6) after the commutation device (4) has responded, the control circuit (11) emits a release command to the isolating switching point (5) forming an isolating gap. As a result, the semiconductor valve arrangement (6) is isolated and the switching-off process is terminated.

Abstract: Load current is diverted from a circuit breaker, when it is opened, through a commutation circuit. The latter has a capacitor, inductance and solid state switch serially connected with the output of a bridge rectifier. The input of the bridge is connected across the breaker. The switch is turned on to discharge the precharged capacitor to form a current pulse, presenting an extremely low resistance across the bridge input and causing load current diversion.

Abstract: The contacts of an isolation relay are positioned between a line interface circuit and the associated feed resistors, the relay being controlled to open the contacts in response to an excessive common mode alternating current through the feed resistors. The common mode a.c. is detected by a sensing amplifier, and is integrated and compared with a threshold level in a dectector unit. If the common mode a.c. is excessive, a zero crossing predictor enables the detector unit to control the isolation relay and open its contacts at a zero crossing of the a.c. A phase shifter in the zero crossing predictor compensates for the response delay of the isolation relay. As the excessive current is now interrupted, the sensing amplifier responds to the line voltage. When this falls below a predetermined peak level, a delayed resetting of the protection arrangement is automatically effected.

Abstract: A low level fault condition in a mine trolley system is distinguished from a normal system load by detection circuitry connected to the trolley system between a main circuit breaker and the trolley wire. The detection circuitry monitors the current through the trolley wire and samples the current at preselected intervals of time to detect a rise in current through the trolley wire. The rate of current rise is compared to an adjustable reference signal. If the current rise exceeds a preselected rate, then activation circuitry of the main circuit breaker is latched to determine if the net current change is above a preset limit. If other available protective devices, such as fuses, in the trolley system fail to isolate the faulted circuitry within a preselected period of time after an excessive current rise is detected, then the activation circuitry is tripped to open the normally closed contacts of the main circuit breaker. In this manner the entire flow of current through the trolley wire is interrupted.

Abstract: A hybrid electrical power controller is provided with a relay having a coil and a pair of mechanical contacts. A solid state switching device is electrically connected in parallel with the mechanical contacts and the parallel combination of that switching device and the contacts is connected between an input and an output terminal. A relay coil energizing circuit is included and means is provided for producing a signal representative of current flowing in the relay coil following deenergization of the relay coil. A solid state switching device control circuit responds to this signal and turns off the switching device when the signals fall below a predetermined magnitude.

Abstract: A zero-current a.c. switching system is provided for controlling actuation of relay contacts between a power supply and a load. A primary switch selectively energizes the relay to maintain the relay contacts in the closed state. The load current flowing through the relay contacts to the load is sensed. A secondary switch responds to the sensed load current for normally conducting to energize the relay in parallel with the primary switch. The secondary switch ceases conducting each time the load current drops below a predetermined level to cease energizing the relay and open the relay contacts the next time the load current drops below the predetermined level following the opening of the primary switch.

Abstract: Synchronous circuit interruption is provided by operation of a diversion circuit for diverting most of the circuit current away from a pair of series-connected electrical contacts over to a solid state current interrupter prior to energizing a contact operator to separate the contacts to interrupt the remaining circuit current. To ensure arcless contact separation, the contact operator is arranged electrically in series with the solid state current interrupter which ultimately dissipates the system energy within a voltage dependent element. The arrangement of the contact operator circuit in series with the solid state current interrupter synchronizes the operation of the contact operator to ensure that the contacts are separated immediately after the circuit current has become diverted.

Abstract: A method for interrupting an inductive load in a three-phase, high voltage network by means of a switch having a quick dielectric recovery, in particular a vacuum switch, in which two of the three vacuum switches, having a quick dielectric recovery, open at least 1/3 of a cycle of the network frequency later than the first vacuum switch, augmented with the minimum arcing time in the first vacuum switch, in order to prevent high over-voltages, caused by virtual chopping.

Abstract: A line voltage charging type DC circuit breaker for use in DC transmission, having a series circuit connected in parallel with a commutation breaker, the series circuit being constituted by a capacitor to be charged by a line voltage, a reactor, and a circuit-closing means connected in series with each other, the DC circuit breaker comprising a circuit for charging the capacitor, the charging circuit including a current direction restricting circuit for restricting a current flowing through the restricting circuit only in one direction and a reverse control circuit for controlling the current direction restricting circuit to reverse the direction of a current for charging the capacitor in accordance with the power flow reversal control of the DC transmission.

Abstract: A hybrid solid state/mechanical switch is provided with a pair of mechanical contacts connected in parallel with a solid state switching device. These components are operated by a control circuit to achieve arcless current interruption under normal conditions. A circuit breaking device, which can be operated by a crowbar circuit, provides failure protection for the hybrid switch if excessive leakage current is detected in the solid state switching device or current continues to flow through the switch at a preselected time following the occurrence of a turn-off command signal.

Abstract: An apparatus for the interruption of DC transmission lines without substantial arcing utilizing in combination a DC circuit breaker, a DC-to-AC current converter, converter control and an AC power sink. Upon command from the converter control, DC current is converted to AC current in the current converter and is then magnetically coupled via a transformer into the AC power sink; thus, drawing power out of the DC transmission line and reducing the DC current toward a zero value at which point the DC breaker can be opened without substantial arcing. Various single and multi-phase converter circuits utilizing thyristors are employed. A bypass switch in parallel with the converter can be provided to pass the DC current around the converter during normal operation of the DC transmission line to minimize electrical losses.

Abstract: The contacts of a power relay are shunted by a gateable semiconductor device to assist in the commutation of contact-destroying arcs upon making and breaking of the power relay contacts; current-detection apparatus, such as a current-sensing transformer and the like, are utilized in the conductors connecting the relay contacts and the gateable switching device to an input from an A.C. source. Control electronics receive the outputs of both current-sensing apparatus to gate the shunting device into conduction during relay contact closure and separation, in a manner to minimize the current passing through the shunting device and therefore to minimize the energy dissipated therein.

Abstract: An apparatus for protecting a vacuum interrupter type on-line tap changer in which a cross current flows between taps through a current limiting resistor for a predetermined time by shorting selected taps therebetween at the time of tap changing operations. Vacuum interrupters are employed as current switching elements. A dial switch selects the position of the tap of the tap changer. A limit switch closes only at a predetermined position of the dial switch during tap changing operations. Thus, a cross current between the taps or a load current flowing for a long time due to a drop in the degree of vacuum of the vacuum interrupters is detected, thereby preventing burn-out of the current limiting resistor and damage to contacts of a disconnecting switch due to interruption of the current.

Abstract: A motor is energized by a source through first and second transfer switches. Each transfer switch is operated by a switching transistor. The switching transistor for the first transfer switch is driven by a drive signal while the switching transistor for the second transfer switch is driven by the output of a delay circuit responsive to an excessively large current flowing through the motor. A self-holding switch is provided to connect the motor to the source through the second transfer switch.

Abstract: A high power a-c circuit breaker having substantially no arcing during interruption consists of two identical switching circuits in series which each include a main high speed switch connected in parallel with a series-connected diode and high speed isolating switch. The diodes of each of the switching circuits oppose one another in polarity. Current flow through the circuit breaker is normally through the closed main high speed switches. A polarity-sensitive operating circuit is provided to open the appropriate high speed switch just before a current zero and to transfer forward current through its related diode. This diode blocks a current reversal, and the associated series-connected isolating switch is opened just after current is commutated into the diode, and at or before the current zero time is reached and while the diode is blocking.

Abstract: Current interruption capability for short-line or terminal faults is achieved by connecting a fluid blast interrupter in series with a high current vacuum interrupter capable of withstanding the initial recovery voltage during such fault. The fluid blast breaker ultimately becomes able to carry the total recovery voltage by delaying opening of the vacuum interrupter for a fixed interval after opening of the fluid blast breaker has been triggered.

Abstract: Apparatus for preventing the occurrence of possible transient phenomena in the circuit including a power source and its load connected thereto when the supply of electric power from the power source to the load, which has been interrupted, is restarted. The apparatus includes means for detecting the occurrence of the interruption of the power supply and means for memorizing the phase angle of the voltage or current of the power source at the time of the occurrence of the interruption of the power supply to maintain the circuit in off-condition. The apparatus further includes means for detecting the coincidence of the phase angle memorized in the memorizing means with a changing phase angle of voltage or current of the power source after the resupply of the electric power from the source to the load becomes possible whereby, upon detecting the coincidence, resupply of the electric power from the power source to load will be restarted.

Abstract: A tap-changing transformer system, utilized for voltage regulation of the line potential applied to a load from a source of energy, has a non-arcing switch to protect tap contacts during a tap change. A fail-safe circuit is utilized to determine that the non-arcing switch and its associated circuitry are operating properly before a movable tap contact is transferred from one stationary tap to another. In the event that the fail-safe circuit detects an improper operation of the non-arcing switch, the source is connected directly to the load to preclude the passage of any load current through the tap-changing transformer. A particular form of transfer switch useful in effecting the connection of the source directly to the load employs a current-limiting impedance arrangement.