Abstract: Electric power uses or loads in a premises are controlled or managed depending upon whether the use is for heating, hot water, heat pump, air conditioning, lights, appliances, pumps, etc., according to programs that are controlled by the electric Power Company, for the purposes of spreading power uses at the premises over a day or other time interval, to avoid peak load periods encountered by the Power Company, while still providing the normal comfort levels required by the subscriber from the various power uses. Power levels of several uses at the subscriber's premises are sensed and the power for each use is controlled according to a program that includes a schedule of power level and/or the time of day that is inserted in the program or controlled in the program by the Power Company to accomplish the spreading. In a particular embodiment, a programmed computer unit is provided at the premises that is monitored by the Power Company via the subscribers telephone line.

Abstract: A method of removing sludge deposits from the tube plate of a steam generator of the type typically found in a nuclear electric generating plant involves inserting a jet lance into a handhole in the shell of the steam generator just above the tube sheet and along the tube lane, and inserting a flexible suction hose in that or another handhole. A jet nozzle on the lance is directed along one passageway defined by adjacent rows of tubes. The suction hose is adjusted until a suction opening at its end is aligned at the peripheral end of the one tube passageway. Then the sludge is jet blasted with a jet of cleaning fluid from the nozzle, and sufficient suction is applied to the hose so that all of the fluid and entrained sludge is sucked up as it issues from the peripheral end of the tube passageway.

Abstract: An arc suppression device (40) for protecting the load carrying contacts (30, 31, 32) of a power contactor (20) includes gate controlled semiconductor devices (TR1, TR2, TR3) connected in parallel with the contacts. A signal from a control circuit (45) causes gating current to be applied to the semiconductor devices nearly simultaneously with the application of current to and removal of current from the solenoid (25) of the power contactor. Circuit means (90) responds to the control signals to provide gating current for a limited period of time prior to, during and following the closing of the contacts. Gating current is not continued after the contacts have closed to protect the semiconductors from possible damage. Additional circuit means (110) responds to the removal of the control signal to provide gating current for a limited period of time prior to, during and following the opening of the contacts.

Abstract: An arc suppression device for protecting the load carrying contacts (25) of a power contactor (15) includes semiconductor devices (TR1, SCR1,SCR2) connectable in parallel with such contacts through an isolation relay (37,61). Gating current to the semiconductor device is applied after the isolation relay is energized and prior to, during and after the power contacts either close or open; but gating current is not continued after the power contacts have closed to protect the semiconductor against damage. Current to the semiconductor is applied before current is applied to or removed from the coil or solenoid (20) of the power contactor. In one embodiment, relays (39,41,43) within the arc suppression circuit (30) control the isolation relay (37), gating current to the semiconductor (TR1) and the coil of the power contactor in the proper sequence. In another embodiment, time delay means (C4-C7,R1) associated with the relays (61,63,65,67) control their sequence of operation.

Abstract: The power contactor for controlling the application of power to and the character of the current to a load includes a power relay having contacts connected between a source of power and the load, such as a motor or heater, with each of the contacts being provided with arc suppression means. A steering relay is provided to control the direction of current to a motor and thus its direction of rotation or the voltage applied to a heater. A control circuit insures that the steering relay contacts remain either open or closed while power is being applied to the load. The steering relay is provided with bracer bars to prevent short circuiting between relay contacts should any welding occur therebetween. The arc suppression means for each of the power relay contacts includes a solid state device, such as a triac, in parallel therewith, and auxiliary contacts for controlling the gating current to the triac.

Abstract: A power contactor device includes at least one power relay contained within an electrically insulating plastic housing. Electrical busses carrying current to the relay contacts also serve as a means for removing the heat generated by those contacts and other electrical components within the housing. On the exterior of the housing, the busses have a large surface area and transfer heat through electrically insulating but thermal conducting material, such as alumina or beryllium filled epoxy, to a heat sink. The core of the relay is in metal-to-metal contact with the heat sink.

Abstract: An electrical contactor device includes a solid state arc suppression circuit connected in parallel with main relay contacts. Auxiliary contacts provide gating signals to the arc suppression circuit prior to, during and shortly after the main contacts open. Protection contacts connected in series with the arc suppression circuit are part of a relay which is actuated by additional auxiliary contacts of the main relay. The protection contacts prevent the arc suppression circuit from operating during initial closure of the main contacts thereby allowing the contactor device to be used in those applications where a high in-rush current is expected. A delay circuit holds the protection circuit relay contacts closed after the main relay contacts open to permit operation of the arc suppression circuit; the relay contacts thereafter open to isolate the arc suppression circuit and thereby to prevent any leakage current from flowing therethrough and to prevent any false triggering thereof.

Abstract: A method and apparatus for detecting an underfrequency condition of an alternating current power line is disclosed wherein the frequency of the power line is sensed, an underfrequency signal is developed whenever the power line frequency decreases below a predetermined frequency, a known frequency source is thereafter substituted for the alternating current power line, and the frequency of this source is checked by the same circuitry to produce a second output signal, and an underfrequency signal is generated in response to both first and second output signals.

Abstract: An arc suppressor circuit for a relay includes a semiconductor means connected in parallel with the current carrying primary contact points. Auxiliary contact point means supply a gate signal to the semiconductor means to cause it to short the primary contact points during the closing or opening of the primary contact points. The circuit further provides for opening the auxiliary contact point means after the primary contact points are closed to prevent the semiconductor means from carrying load current for any substantial period of time. The semiconductor means may include a triac or a pair of silicon controlled rectifiers arranged to conduct on alternate half cycles.