Abstract: A waveform synthesizer is controlled in response to a stored program control utilizing tabular data stored in memory as the basis for generating timing signals to drive the power switching devices of the synthesizer. A plurality of tables of differing modulation indices define rated current output and a below rated current output. The table defines rated level output timing signals as both pulse width and frequency modulated to reduce harmonics. Various overload conditions result in selection of different modulation indices or a total current shutdown. A high peak current overload results in a halt in a progressive upward selection of modulation indices during start-up. A high average current overload results in a reduction in modulation indices until the overload has cleared.

Abstract: A power failure detector for an off-line switcher provides an indication of power failure to a microprocessor load to permit an orderly shutdown without loss of data. The failure detector includes a voltage storage device shunting a secondary winding of a converter power transformer prior to the isolating diode. When its voltage drops below a preset threshold, the microprocessor load is notified that a shutdown action is to be taken.

Abstract: The start-up trajectory of the operating point of a DC-to-DC converter normally includes a high current locus which must be traversed to reach the steady-state operating point. In the case of a converter powered by a current-limited source, such as a power supply system where one converter powers a plurality of subsequent converters, the subsequent converters may be unable to turn on due to inadequate current drive. By using a control circuit adapted to control the start-up trajectory of a DC-to-DC converter as a continuous function of the input voltage applied to it by the current-limited source, the start-up characteristics are constrained to be compatible to both source and load permitting the converter to proceed to its steady-state operating point.

Abstract: Current limit protection against current overload is obtained in a core-reset, forward-type converter by inserting a properly selected impedance in the flyback current path. The voltage developed across the impedance is impressed against the secondary winding of the power transformer. During current overload, the voltage drop across the impedance maintains a voltage drop across the secondary winding delaying a zero crossing of the voltage and, hence, delaying the initialization of conduction in the converter power switch. The time delay in conduction initiation in the power switch reduces current output and effectively counteracts the overload current.

Abstract: A mounting washer arrangement for a new type power transistor package comprises two interlocking washers. A first mounting washer part of heat sinking material fits under the transistor body; a second mounting washer part of electrically insulating material interlocks with the first mounting washer part and fits under a terminal lug of the transistor. Together the two mounting washer parts provide economical heat sinking and electrical insulation. The interlocking arrangement prevents cracking and twisting of the two mounting washer parts when the transistor is firmly secured by torquing anchoring screws to the chassis.

Abstract: A system of determining optimum start/stop times for HVAC equipment in a building utilizes quantized inside and outside air temperature values as the controlling data input. Lead-times necessary to achieve the desired control temperatures, given input and output temperature levels are stored in a matrix in a central processor storage. System performance is monitored and results are used to modify the lead-times so that the operating system can more closely achieve the desired results.

Abstract: A power train of an uninterruptible power supply selectively transforms its load from a primary source of power to a reserve source of power under control of a stored program control operating in real time. A microprocessor operating in conjunction with a prioritized interrupt controller and a plurality of external counters monitors and responds to signal conditions existing at various points of the power supply. In particular, the amplitude of a primary AC voltage source is sampled at precise angles of the sinusoidal waveform in response to a comb pulse waveform generated to conform to the actual period of the primary AC voltage. The frequencies range is determined by comparing a count interval to the period of the primary AC voltage. Relative power flow from the primary AC voltage source and a reserve AC voltage signal is controlled by relative phasing of the two signals.

Abstract: A DC power plant system has the operation of its individual rectifiers controlled by a stored program control system for the purpose of optimizing power efficiency. Load power requirements are compared with rated capacities of operating rectifiers of the system and individual rectifiers are turned on or off so that the plant efficiency is always maximized. Rectifiers are selected for turn on and off in the basis of their rated power capacity and their accumulated operating times.

Abstract: A power conversion circuit is operated at high frequency in the radio frequency spectrum to utilize adjunct reactive impedances of the active semiconductor devices as part of an impedance transformation circuit. Power is transferred through the converter at substantially a single frequency. Energy storage of the adjunct reactances is positively utilized to limit power dissipation within the converter.

Abstract: A current monitoring scheme operates in an indirect fashion to estimate the current output of a circuit from a measured voltage output. Voltage data is processed in accord with state variable theory to derive a current estimate without direct sensing of the current.

Abstract: An uninterruptible power supply utilizes a controlled ferroresonant regulator to derive a regulated DC voltage from a primary AC source. A reserve source of DC power is coupled to the output through a DC voltage regulator which is activated when the DC output voltage of the power supply drops below a predetermined threshold.

Abstract: A current controlled switching type voltage regulator achieves voltage regulation by controlling an average current flow through the switching device. This current is sensed and transformed into a signal frequency. The signal frequency is counted to determine its average value and this count is compared to a variable current reference count which is continuously adjusted in response to an output voltage monitor which includes circuitry to generate an error count responsive to the deviation of the voltage output from a desired regulated value. In order to counteract instability problems inherent in current controlled switching type voltage regulators the transducer converting current into a signal frequency has a threshold characteristic to insure a definite fixed signal frequency at very low currents.

Abstract: A circuit support enclosure has drop-in receptacles in a base chassis structure for individual circuit components. After circuit components are placed in the drop-in receptacles, a retaining chassis structure is mated with the base chassis structure. The base chassis structure includes two tongs which have pawls which interlock with slots in the retaining chassis structure. The retaining chassis structure includes bifurcated retainers and clamp nodules that clamp the electrical components into their respective drop-in receptacles in the base chassis structure.

Abstract: A bleeder circuit is utilized to insure proper operation of a filter inductor in a pulsed power system. A control arrangement couples a bleeder resistor to the filter inductor in response to actual current discontinuities in the inductor. The control arrangement responds to actual current discontinuities by responding to a voltage collapse in the inductor and activates a switch to couple the bleeder resistor to the inductor.

Abstract: A three-phase transformer structure has a double-window magnetic structure with an independent flux path encircling each window and an outer flux path encircling both windows. A shunt path for the outer flux path bridges both windows and two additional shunt paths bridge each window independently. Hence, each flux path has an independent and isolated shunt permitting operation of the three-phase transformer in a ferroresonant mode.

Abstract: A power supply system having a plurality of individual power supplies utilizes a master control to periodically compensate for errors in individual power supplies. The master control is periodically coupled to individual power supplies by multiplexing means to provide compensation signals to counter drifts and errors due to varying circuit parameters therein.

Abstract: An uninterruptible power supply includes a digital control circuit to control the transfer of power from a primary and a secondary power source to a load circuit to be energized. The digital control circuit controls through digital techniques the relative phase angles of a primary power signal, a secondary power signal, and a load signal to advantageously minimize the power drain on an idling secondary power source when the primary power source is active and to minimize transients in the load signal when converting from one power source to another.

Abstract: An uninterruptible power supply utilizes a switching circuit which under normal operation modulates at a high frequency a signal provided by a commercial AC line to control the energy flow through a transformer between an input accepting the AC line source and a rectified DC output. The switching circuit which performs the modulation is optimally arranged to be coupled to a reserve energy source such as a charge storage capacitor or battery. It operates upon failure of the AC signal input to provide energy from the reserve source to the load by operating as a switching regulator.

Abstract: A power supply load transfer system reduces the transients produced at a moment of transfer by reducing the first and second half-cycle durations of the reserve signal output following the moment of transfer by equal amounts so that a previous phase lag between a primary signal and the reserve signal is eliminated.

Abstract: A control arrangement for a three-phase, uninterruptible power supply generates timing signals to drive the static switches of inverters located in each phase. This control arrangement precisely controls the phase differences of the inverter signals with relation to each other so that while the overall three-phase power supplied by the inverters is nulled, power circulation through the inverters compensates for unbalanced output loads thereby maintaining balanced phase angles between the output voltage and a balanced input impedance at the input of the power supply.