Abstract: A thick layer of epoxy resin is used to bond together the piezoelectric member and a stainless steel cap to form an acoustic transducer having a broad frequency response, and specific assembling steps are taken to manufacture the transducer with good reproducibility of the characteristics.

Abstract: A regulating system for direct current motor control having an inner and an outside loop is prevented from winding up in the outside loop, when the inner loop saturates, by a clamping circuit storing the value of the controlling voltage of the outside loop reached at the moment of saturation and generating an overriding error signal by reference to said stored value for providing effective control after saturation has ended.

Abstract: A digital firing pulse generator for thyristor rectifiers in a power converter system uses a time dependent waveform to trigger a one-shot multivibrator for generating a hard pulse of minimum duration and includes a free running oscillator generating a train of picket fence pulses applied to the thyristor rectifier after the hard pulse in order to insure extended conduction. A pulse suppressor actuated upon an emergency prevents the initiation of a hard pulse but does not shorten the duration of any initiated hard pulse, and suppresses the picket fence pulses. Provision for end stops on the picket fence pulses exist and the generation of a separate hard pulse is digitally controlled when a hard pulse is missing after the selection of a rectifier next to be fired.

Abstract: A compact and portable arc welding apparatus of the transformer reactor type having a main compartment cooled by forced ventilation and a side compartment sealed from hostile environment, the two compartments being part of a common housing which can be stacked on another similar equipped housing of an arc welding apparatus.

Abstract: In a single-stand, or multi-stand rolling mill, when the automatic gauge control circuit controlling the roll speed of one stand saturates, the gauge delivery of such stand is altered by changing the roll gap of the stand in such a way as to restore normal operation of the automatic gauge control out of saturation.

Abstract: A digital pulse generator for firing thyristors in a polyphase converter system is described in an hybrid analog-digital and in an all digital form. A phase locked oscillator associated with a digital counter generates timing waveforms synchronized with the phase lines to establish firing angles in relation to a reference signal. Each firing pulse triggers the logic circuit of a distributor and a multiplexer is coupled with such logic circuitry in order to insure that the proper timing waveform is selected so as to match the selection of the next thyristor to be fired.

Abstract: In an analog data acquisition system, used for digital treatment, analog signals of different levels received from remote locations are amplified with a selected gain before being converted by a common A/D converter. A discretely variable gain amplifier is used in which a series of programmed predetermined ranges are sequentially tested against the capability of the A/D converter in relation to the particular input analog signal. The first acceptable gain is selected and a code can be used to identify the selected gain for digital treatment of the derived corresponding digital signal.

Abstract: A naturally commutated cycloconverter having at the input a source of higher frequency than at its output is used as a static reactive power generator to correct displacement angle in an alternating current power system when coupled thereto at the output. Reactive power correction is obtained with such "high frequency link" by automatically controlling the output voltage of the cycloconverter so as to deviate by a required amount from the AC power system voltage. At the same time, a circulating current is established between the positive and negative banks of thyristors of the cycloconverter of such a magnitude as to compensate for the variations of the lagging quadrature component of the input current of the cycloconverter caused by output current variations, thereby permitting optimization of the high frequency link.

Abstract: An AC/AC frequency changer operating under a one to one frequency ratio has its input coupled to a power system of same frequency and voltage, with an inductor connected between its output and input terminals. The output voltage is controlled so as to deviate by a predetermined amount from the input voltage so that reactive power flows from the output to the input which, owing to the inherent phase inversion in the frequency changer, causes reactive input current and reactive output current to be summed up directly at the input terminals. As a result, the frequency changer requires only a power rating which is half the reactive power which it can supply to the power system.

Abstract: Two movable members driven by individual motors are positioned accurately at any given time and are tracking each other for all displacements. Individual positioning is used with differential positioning to force a follow-up of one member relative to the other. One feedback position loop provides a master reference for a second position loop of the slave motor drive, and the differential position signal makes the second loop operate as a vernier of the master loop. A limiter prevents the master drive from running ahead of the slave drive.

Abstract: The interphase reactors of an unrestricted static frequency changer are mounted on a common multilegged magnetic core without affecting the individual quality of each reactor in the operation of the frequency changer.

Abstract: A field-controlled direct current motor is provided with a circuit responsive to armature current which is adjustable as to the amount of armature current representative signal, and the adjusted current representative signal is used to provide a selected amount of droop in the speed-load characteristic of the motor. A plurality of individually field-controlled direct current motors operating in parallel on a common load are individually adjusted as to the amount of sensed armature current to provide through field control individual selected amounts of droop in the respective speed-load characteristics.

Abstract: An improved force commutated cycloconverter is provided by alternatively switching a capacitor to different groups of main thyristors including a thyristor to be commutated in the controlled sequence of thyristor conductions. The capacitor swing back to an opposite polarity before each successive commutation. Commutation is made possible at low load current by the adjunction of a resonant reset circuit. The force commutating circuit is applied to various configurations of cycloconverters.

Abstract: A tachometerless motor drive of the induction motor type is obtained by synthesizing the motor slip frequency from analog signals sensed at the input of the motor. The slip frequency signal so derived is used as one of the parameters for control, beside voltage and/or frequency or current and frequency at the input of the motor.Analog circuitry is used involving the derivation of a numerator N characteristic of E.sub.1 I.sub.1 Cos .theta., where E.sub.1, I.sub.1 and .theta..sub.1 are given by the vectorial representation of the input current and voltage, and of a denominator D = E.sub.1.sup.2 /.omega..sub.1where .omega..sub.1 is the frequency of the motor supply.

Abstract: A thick layer of epoxy resin is used to bond together the piezoelectric member and a stainless steel cap to form an acoustic transducer having a broad frequency response, and specific assembling steps are taken to manufacture the transducer with good reproducibility of the characteristics.

Abstract: A programmable sequence controller for controlling a machine or process operation including a main low-security programmed sequencer and a high-security programmed sequencer through which selected outputs from the main sequencer must pass before being allowed to control the machine or process operation. This high-security sequencer generates a sequence of steps which relate to machine or process commands under conditions critical to the operation of the machine or process and is controlled in a predetermined order. Any critical output requested by the main sequencer is caused to initiate sequencing by the high-security sequencer and is tested by the high-security sequencer as to the propriety of the generation of a permitted output to the machine or process. The high-security sequencer in this manner effects an improved interlocking between the various critical output commands and actual operative conditions.

Abstract: An improvement in systems for measuring the rate of fluid flow in a pipe or an open unrestricted channel as a current at sea or ocean wherein the time delay between acoustic pulses transmitted upstream and downstream in a fluid passing along a path of travel is multiplied by repeated transmissions over predetermined time intervals. The correction for the speed of sound in the medium is founded on the realization that in a multiple time difference ultrasonic flowmeter, there is a pulse (N.sub.c .DELTA.t) in the generated N.DELTA.t train which is directly proportional to the velocity of the fluid. Accordingly, the time interval during which the train N.DELTA.t last is automatically adjusted so that the time difference, or multiple of .DELTA.t, be in fact N.sub.c .DELTA.t.

Abstract: The invention relates to process control in general and to numerical control machining in particular. A programmable digital controller is associated with a digital motion control unit in which are stored numerical data for point-to-point operation of a machine tool, for instance a grinder. The motion control unit is of the incremental type and generates command pulses which are applied to a stepping motor. Numerical data are stored defining desired displacement, velocity and sign of travel, and dress compensation. A feedback loop with the machine tool provides corrective pulses when the command pulses sent are not in exact relation with the increments of displacement effectively imparted on the tool. The programmable controller can be coupled to a plurality of motion control unit controlling one or more machine tools, or axes, and it is performing sequence control in relation to industrial process as well.

Abstract: Low level analog signals from remote locations are amplified after being converted into two consecutive analog signals of opposite polarities and a digital system causes A/D conversion to occur in two successive readings corresponding to said polarities and an algebraic combination of the two successive readings in binary form provides a true reading which is made available for digital processing by a special control circuit.

Abstract: This invention relates generally to power inverting devices and more particularly, to static inverting devices which produce an output wave shape which closely approximates a sine wave.