Abstract: Power sources of a parallel AC electrical power system are synchronized by producing a voltage difference signal representative of the difference in output voltages of the power sources and demodulating that signal to produce a frequency control signal and a voltage magnitude control signal. The output frequency and voltage magnitude of at least one of the power sources is varied in response to the frequency control signal and voltage magnitude control signals, respectively, to minimize the difference in output voltages between the power sources.

Abstract: A control circuit for controlling the operation of a parallel source electrical power system produces a pair of load current signals representative of the load current delivered by corresponding phases of individual channels of the power system. At least one of the load current signals is scaled by a scaling factor to obtain a scaled load current signal that is combined with the load current signal for the other channel to obtain a feedback signal. The feedback signal is used to control the output of one of the paralleled power sources such that the ratio of load currents delivered by the power sources is proportional to the scaling factor.

Abstract: A dispension for whipped beverages made from a concentrate and diluent. The dispenser includes a head structure forming a whipping cavity. A funnel is removably inserted into the cavity bottom. Two conduits communicating with the cavity are formed in the head to introduce concentrate and diluent into the cavity. An air passageway is formed in the head and intersects the diluent conduit downstream from the solenoid valve. A tube is inserted into the air passageway and partially extends into the diluent conduit to introduce air into the diluent conduit via a venturi effect. A whipping motor has an output shaft disposed through a bore in the head and partially residing in the cavity below the conduits. A paddle is connected to the motor shaft within the cavity. A resilient slinger washer is disposed in a circumferential groove about the shaft.

Abstract: A frequency control circuit for controlling the output frequency of an inverter power pole switching arrangement produces a modified clock signal by inhibiting clock pulses of a stable clock signal in response to output pulses of a voltage controlled oscillator. The average frequency of the modified clock signal is then equal to the difference between the original clock signal and the output frequency of the voltage controlled oscillator. A control voltage which represents the difference between a normal inverter output frequency and the frequency of an external power source is used to control the output frequency of the voltage controlled oscillator.

Abstract: A switching time correction circuit for electronic inverters controls the operation of power pole switches by delaying the application of each transition point in a reference pattern signal to the output switches. The length of the delay is reduced for transition points in the reference signal which correspond to negative power transitions in the power pole switch and the amount of delay time reduction is proportional to the output current of the respective power pole switch. By inserting a variable delay between the reference signal and the power switch, transition points in the output voltage are each delayed by a fixed time with respect to transition points in the reference waveform pattern.

Abstract: A current limiting circuit for a DC to AC inverter is provided with means for sensing the current in the inverter output phases and means for switching all of the power poles to the polarity of the minority power pole when an overcurrent condition occurs. This reduces the switching current levels of the inverter power pole switches to reduce switching stresses and improve reliability. A current sensing scheme is illustrated in which self-excited transductors are used to sense the current in two of the three inverter output phases and the current in the remaining output phase is derived from these two sensed currents.

Abstract: A photographic image was produced by storing a geranium leaf in darkness and then projecting a light image on the leaf for a sufficient time to produce a suitable latent starch image, the leaf then being treated to extract the chlorophyll and then flooded with an iodine solution to stain the starch and develop the photographed image. Alternatively, instead of the leaf, a photographic medium may be employed including a film of a starch free, water, carbon dioxide and light permeable matrix, such as gelatin, having dispersed therein chloroplast containing algae or photosynthetic bacteria.

Abstract: A toroidal transformer is provided with an inner winding electrostatic shield formed by bringing together two conductive annular cups having a generally U-shaped radial cross section. The widths and radii of the sidewalls of these cups are dimensioned such that one of the sidewalls of the first cup forms a conductive interference fit with the corresponding sidewall of the second cup, while the other sidewall of the first cup is separated from the corresponding sidewall of the second cup by a gap, which prevents the shield from becoming a shorted turn. The shield formed by these two cups is placed around a wound core and a second winding is wound over the shield to form a transformer.

Abstract: A voltage regulator for aircraft generators controls generator output voltage by controlling exciter field current. Exciter field current sensors and generator output voltage sensors produce control signals which are proportional to exciter field current and generator voltage. These signals are combined and compared with a reference voltage signal by a comparator. A current controller regulates exciter field current in response to the comparator output.

Abstract: A solid state relay is provided with a control logic circuit which receives a low level input control signal and controls a power field effect transistor (FET) switching element by means of an optical isolator. Connecting an external power source to a function selecting input terminal causes the relay to operate as a normally open, normally closed, or latching relay. A voltage spike suppression network protects the FET from voltage spikes appearing across it.

Abstract: A solid state relay is provided with a control logic circuit which receives a low level input control signal and controls at least two power field effect transistor (FET) switching elements by means of optical isolators. Break-before-make operation is accomplished by a logic circuit which momentarily turns off all FET's each time the relay is switched. Connecting an external power source to a function selecting input terminal causes the relay to operate as a normally open, normally closed, or latching relay. A voltage spike suppression network protects the FET from voltage spikes appearing across it. FET turn off time is reduced by using a Zener diode to limit maximum gate voltage.

Abstract: A direct current power controller for use in electrical control systems such as aircraft control circuits. The controller utilizes a field effect transistor (FET) as the switching element. A bias voltage supply circuit powers a gate driving circuit, current limiting circuit, and trip indicating circuit. Gate driving circuitry is not directly connected to the system ground, thus minimizing load interference with controller performance and eliminating the need for level shifting circuitry. Remote control circuitry is provided.

Abstract: For providing an interface between a low level input control signal and a power switch, a control logic circuit is presented for permitting operation of a solid state relay in any one of a plurality of modes of operation including operation as either a normally open relay, a normally closed relay, or a latching relay, and also to make possible combinations of such relays for operation in parallel with a second relay operating in or out of phase with a first relay. The control logic circuit includes logic gates with means for selective interconnection of external terminals to set the operation in the desired mode as well as to permit one relay to be responsive to the condition of another.

Abstract: A control circuit for turning on an optical isolation unit only when an input signal is at least of a given magnitude or threshold level. The circuit exhibits a resistive input below the threshold level and a constant current characteristic above the threshold. An arrangement of transistors is provided to bypass the opto-isolator below the threshold and to drive the opto-isolator with substantially constant current above the threshold.

Abstract: A ramping circuit including a comparator and an integrator connected together in a source follower configuration. First and second operational amplifiers in the comparator and integrator sections, respectively, are used with the first having its negative input terminal supplied the input to the ramping circuit and its output terminal connected to the negative input terminal of the second, a feedback loop is provided from the output of the integrator stage to the positive input terminal of the comparator stage.