Abstract: A soft-starting phase-control circuit for controlling both the cold in-rush and normal operating flows of current through a load from an A.C. source. The load may be resistive, may have a non-zero resistance temperature coefficient and may require a load voltage thereacross lower than the voltage provided by the A.C. source connected to the load and the control circuit. The control circuit utilizes at least one power switching device for selectively enabling and disabling the connection between source and load responsive to turn-on and turn-off states of a control signal provided at the output of a gate subcircuit.

Abstract: The present invention provides a device for regulating an ac current circuit using a magnetic relay which is suitable for use in an incandescent lamp circuit or electric motor circuit to eliminate or reduce inrush-current. The present device comprises connecting power switch, diodes, series resistance and relay such that, after closing the power switch, an ac current first flows to a load through the series resistance for a brief time, then to the load through the contacts of the relay after a lapse of the brief time by bypassing the series resistance.

Abstract: A phase control circuit, for energizing lower voltage loads and the like from a higher voltage A.C. source, utilizes power switching means in series with the load across the source. The load voltage and current are sampled and compared to reference values to determine if the load resistance is less than or greater than a desired value and the output voltage of an integrator is adjusted accordingly. The integrator output voltage establishes the time, after each source waveform zero crossing, at which the power switching device enables load current flow. A reset circuit prevents the power switching device from conducting in the event that a line zero crossing is not properly detected, to preclude damage to the switching device and/or load overvoltage. A circuit is also provided for gradually increasing load current at start-up to limit inrush currents to the load.

Abstract: A circuit is provided for regulating the application of power to a load which is relatively insensitive to rapid power fluctuation of the type exemplified by typical AC line sources. In one embodiment, an AC line source is applied at a controlled rate to a tungsten lamp whose operation is controlled by a transistor switching network. The transistor operation, in turn, is controlled by comparing a portion of the rectified signal with a signal proportional to the light output of the lamp.

Abstract: Voltage and current supplied to the primary winding of the transformer-rectifier (T-R) set of an electrostatic precipitator via silicon-controlled rectifiers and a reactor are automatically controlled by sensing spit and spark discharges within the precipitator and the phase shift which occurs between line voltage and line current (usually referred to herein as primary current) when precipitator voltage drops to a low value, as caused by a heavy spark or arc. Signals are developed therefrom which are used to control precipitator voltage through phase control of the SCR's. An arc is extinguished at the end of the current one-half cycle in which it starts. An inhibit circuit is provided for preventing detectable transients caused by SCR turn on from falsely triggering the automatic control system thereby permitting increased sensitivity in the spit sensing circuit.

Abstract: A power control arrangement for controlling the power output of a resistive heating element of the type having a fast thermal response time and a highly variable resistance with temperature. The power control arrangement includes a plurality of operator selectable power settings and an electronic switching system responsive to operator selection of these settings to rapidly couple and decouple a power supply to the element. The switching action is selected to permit rapid heat up of the element without causing an unacceptable current to flow and to prevent excessive cooling of the element after it reaches operating temperatures during steady state operation.