Abstract: An eddy current probe array is disclosed comprising a plurality of spatially correlated eddy current probe elements sufficiently disposed within a flexible interconnecting structure to collect a discrete plurality of spatially correlated eddy current measurements for nondestructive near surface flaw detection. A plurality of precisely fabricated, substantially identical elements being sufficiently distributed can accommodate inspecting an area of conductor covered by the active width of the array in a single uni-directional scan. The array structure can flexibly conform to accommodate inspection of large, irregular, curved conductive surfaces which cannot be inspected by conventional means.

Abstract: A control system for regulating electrical power input to the resistive heating elements of an electric heating apparatus, including domestic cooking appliances, is provided which employs at least one piezoceramic relay device. The electrical power is applied with the piezoceramic relay device responsive to control signals and with the control circuitry being directly and ohmically connected to the power source. In one embodiment, the control system employs individual piezoceramic relay devices for power regulation to the individual heating elements while in different embodiments a single piezoceramic relay device regulates power input to a pair of the heating elements. A method of operating the controlled apparatus in such manner and an apparatus having such control system are also disclosed.

Abstract: An autonomous active clamp circuit clamps voltage across an inductive load. The clamp closes when the voltage across it exceeds some value substantially above peak line voltage, conducts with a low voltage drop, and opens when the current going through it reaches nearly zero.

Abstract: A microprocessor-based relay system is used in combination with relay contactors and a control circuit therefor to protect an electric motor from overload currents in addition to phase faults, ground faults, load losses, and load jams. The microprocessor is provided with a data base comprising thermal characteristics of the motor during heating and cooling. The heating data comprise current versus time curves stored as a look-up table for which each data point represents a thermal limit, i.e., the maximum time the motor is permitted to operate at a particular current level. The cooling data comprise motor cooling rates. Phase currents are sampled at preselected fixed time intervals during a predetermined period thereof, and an average motor current value is calculated therefrom. A thermal sum, which is initialized at zero upon first starting the motor, is adjusted depending on the average motor current value relative to a predetermined overload current value.

Abstract: A current sensor for use with a conductor with known cross-sectional characteristics is an electronic circuit having a monolithic Hall-effect element disposed substantially perpendicular to the conductor first major surface. A conductive loop substantially encircles the element and is oriented such that its flux is substantially orthogonal to the element surface. An amplifier sets current flow in the loop responsive to minimization of the differential Hall voltage across element. The loop current, at null, will be related to the conductor current by the ratio of the conductor flux path length to the loop flux path length.

Abstract: An on-chip DC power supply uses at least one series pass element which conducts responsive to a gating signal obtained by clamping an input potential to a preselected polarity and amplitude. A charge storage element serves to maintain an output voltage which is clamped to a predetermined maximum value. An output regulator provides a substantially constant second output voltage at a magnitude less than the output voltage set by the output clamping means.

Abstract: A static trip overload relay includes a plurality of phase current sensing transformers having two-piece cores. One core piece of each transformer core is positionally mounted by the relay housing, while the other piece is positionally mounted by a carrying case movably mounted within the housing. By varying the case position within the housing, the air gaps between the two core pieces of each transformer core are correspondingly and concurrently varied pursuant to calibrating the relay to operate at any one of a range of circuit current ratings.

Abstract: A circuit is provided for controlling energization of the start winding of an alternating current motor whose shaft is divided into a number of angular segments equal to the number of poles of the motor. A shaft pulse is generated each time one of the angular segments rotates past a predetermined point. A line pulse is generated for each half cycle of line voltage. The shaft pulses are multiplied by the denominator of a selected trip-out ratio while the line pulses are multiplied by the numerator of the trip-out ratio. The multiplied shaft and line pulses are provided to an up/down counter which counts the shaft pulses down and the line pulses up. During the counter overflow condition, the circuit connects the start winding to the line voltage source. During the counter underflow condition, the circuit disconnects the start winding from the line voltage source.

Abstract: By monitoring line current before the lamps of a fluorescent lighting system start, an estimate of full load current is made. The estimate is used to adjust the current feedback gain to avoid any current level overflow in the control. The normalized values used within the control result in consistent relative light levels independent of load size.

Abstract: A wall box dimmer is connected to a conventional fluorescent lighting system for providing a wide range of dimming. Overvoltages generated during chopping of the AC input waveform are dissipated and the lighting level is modified to reduce the overvoltages. DC power for the control electronics is derived from the voltage across the dimmer.

Abstract: A conventional non-dimming ballast for fluorescent lamps is modified to achieve a 100:1 dimming ratio by connecting a switching module to the ballast. The switching module switches current to and from the fluorescent lamps under control of a level control, resulting in the desired light output. The switching module may be connected either in series or in parallel with the lamps.

Abstract: A fluorescent lamp dimming system which can be used in a retrofit manner with existing fluorescent lamp ballasts achieves a greater degree of energy management than has been previously possible. A dimming control having closed-loop feedback uses integrals of current as a measure of light output from the fluorescent lamps. The electronic control circuit implements complex control methods in a minimal space and at a minimal cost.

Abstract: In a retrofit dimming installation for a fluorescent lighting system with a conventional ballast, filament power is maintained, even when the lamps are dimmed, by providing a high frequency component to the ballast voltage. The selected high frequency component allows heating of the filaments without adding to the light output of the lamps, thereby practically eliminating the shortened lamp life usually resulting from operating the lamp in a dimmed condition.

Abstract: A force/flash pressure sensor utilizes a stack of annular rings of a magnetoelastic material. One major stack surface is supported at a plurality of points having substantially equal angular displacement therebetween. A member, moving along the axis of the ring stack responsive to an axial force, or pressure, to be measured, presses a different set of points against the opposite stack surface, to distort the ring stack and alter the magnetic flux density saturation magnitude thereof. The plurality of points in abutment with each of the opposite major stack surfaces is advantageously equal; a number of different configurations for applying force (pressure) along the axis of the ring stack are described.

Abstract: An operating circuit for use with a magnetoelastic force/pressure sensor provides for changing the current flow through at least one sensor coil at a frequency responsive to the magnitude of a force impingent upon the sensor. The sensor operating circuit operates in a manner to prevent the sensor magnetoelastic core from being driven deeply into saturation, thus providing an operating circuit with a reduced current drain. A number of embodiments, including clock-driven and self-clocking (toggling) circuit providing digital and/or analog outputs are described.

Abstract: Methods and circuits for providing auxiliary or remote temperature set or set-back capability in comparator-based thermostatic temperature control systems. In particular, the invention is applicable to thermostatic control systems of the general type including a temperature-responsive source for producing a temperature-dependent voltage as a function of sensed temperature, a reference voltage source for establishing a temperature set point, a voltage comparator having a comparison input and a reference input for producing a control output signal for energizing a thermal conditioning element when voltages applied respectively to the comparison and reference inputs have at least a predetermined relationship with respect to each other, an electrical connection between said temperature-responsive voltage source and the comparison input, and an electrical connection between the reference voltage source and the reference input.

Abstract: A two-stage circuit for controlling all operational functions of a reversible air cycle heat pump unit, including room thermostat functions and defrosting functions. All user controllable functions are controlled via a remotely locatable thermostat-like control unit mounted on an inside wall of the room separate from the heat pump unit, and connected to the heat pump unit with only five conductors. A number of desirable functions and features are provided. For example, for optimum energy usage the control provides two stages in both heating and cooling modes of operation, with almost constant temperature differential between the two stages regardless of temperature setting, and almost constant hysteresis for each stage. To facilitate compliance with Government-imposed regulations where applicable, heating and cooling limits are independently adjustable without any modification whatsoever for use in those public buildings where heating and cooling must be limited.

Abstract: A lamp ballast has a pair of adjacent gapped "O" magnetic cores made of nested, almost complete loops of amorphous metal strip with the gaps in the loops shaped and arranged under the secondary coil to simulate any type of restricted cross section for shaping the lamp current. A long slender reactor has a similar configuration in which the gaps are staggered; a different embodiment has a long central core of compressed amorphous metal flake and a helical overwrap of ribbon. An alloy of iron, boron, and silicon with a high B.sub.r /B.sub.s ratio is preferred for these inductive devices.

Abstract: A lamp ballast has a pair of adjacent gapped "O" magnetic cores made of nested, almost complete loops of amorphous metal strip with the gaps in the loops shaped and arranged under the secondary coil to simulate any type of restricted cross section for shaping the lamp current. A long slender reactor has a similar configuration in which the gaps are staggered; a different embodiment has a long central core of compressed amorphous metal flake and a helical overwrap of ribbon. An alloy of iron, boron, and silicon with a high B.sub.r /B.sub.s ratio is preferred for these inductive devices.

Abstract: A speed control system for an electrically commutated motor which is readily adaptable to digital velocity control input and which provides highly efficient and accurate control in a relatively inexpensive manner. Desired motor rotational velocity is commanded by an input clock rate, which may be variable, rather than by a voltage or current signal. A sensor is provided for determining actual rotor position, and actual rotor position is periodically compared with instantaneous desired motor position as indicated by the time of occurance of one of the input clock signals or pulses. Depending upon the results of this periodic comparison, a dynamically established active current limit is modified. Specifically, if motor rotor actual position leads desired position, the current limit is reduced. If, on the other hand, actual motor position is lagging, the current limit is increased. If the rotor is at the correct position, or within a predetermined deadband, the current limit is unchanged.