Abstract: A switching AC voltage regulator including a transformer, two solid state AC switches, and sensing means controlling the switches to produce the desired output voltage. The two switches conduct alternately and are switched at a rate much higher than the frequency of the regulated AC voltage. When the first switch is activated, the transformer is shorted out, causing the output of the transformer to equal the input. When the second switch is activated, normal transformer action occurs, creating an output voltage either higher or lower than the input, depending on the transformer arrangement. The duty cycle of the switches is varied to provide precise control of the output voltage.

Abstract: An apparatus for AC line voltage regulation has an input port for connection to an AC source, an output port for connection to a load, and a transformer assembly connected between the input and output ports. The transformer assembly comprises a buck/boost winding and a primary winding wound about a common transformer core, and a switch arrangement for controlling the connection of the primary winding in circuit with the buck/boost winding. The switch arrangement is controlled by switch actuators responsive to a voltage sensor assembly to connect the primary winding in either of two possible conditions when the voltage is outside predetermined limits. The transformer assembly comprises either a step down transformer for reducing or bucking the output voltage or a step up transformer for boosting the output voltage according to the condition of the switch arrangement. The primary may comprise separate windings controlled by the switching assembly for connection in different configurations.

Abstract: An AC voltage regulator maintains a predetermined, desired output voltage despite changes in the input voltage, the load, or other operating conditions. The regulator generates an AC reference voltage signal of the same frequency and in phase with the input voltage, and having an amplitude proportional to the predetermined, desired output voltage. The AC reference voltage signal is compared instantaneously to a portion of the actual output voltage to determine an error between the actual output voltage and the predetermined, desired output voltage. The error is instantaneously corrected by altering the actual output voltage to conform to the predetermined, desired output voltage.

Abstract: The voltage stabilization of the secondary outputs of switched mode power supplies is effected with high efficiency by means of a regulation circuit where the current feeding the storage capacitor (26) is flowing through the primary coil (32) of a transformer (72). One end of the secondary coil (33) of this said transformer (72) is connected to one end of the primary coil (32) via a diode (34), whereas the other end of the secondary coil (33) is connected to the other end of the primary coil (32) via another diode (35) and a switching element (36). The switching element (36) is controlled by a comparator circuit (38) comparing the voltage between the output connectors (40,41) with a reference voltage. In case the output voltage goes below the preset value the switching element (36) is shorted and the storage capacitor (26) is charged at the highest possible voltage.

Abstract: A voltage regulating transformer utilizing a microprocessor and a versatile multipurpose set of hardware modules and software modules it is described. A standard tap changing mechanism is driven in response to an analog control signal to change the output voltage of the transformer in response to digitally sampled values of voltage and current which have been transformed from the time domain to the frequency domain through a software program using Fourier transform techniques. The output current is also transformed and digitally processed to determine the power factor and the direction of power flow through the transformer. By inserting the digital values of the line characteristics to the load, line drop compensation is provided for. The difference in voltage across the input and output transformers is transformed to a digital signal and internally processed to provide an indication of the position of the tap changing mechanism without relying upon mechanical devices.

Abstract: An AC variable voltage source utilizing pulse width modulation is provided that converts an input of two AC voltage waveforms of the same frequency but opposite phase into a single AC voltage output of the same frequency but with a variable amplitude. The variable voltage source includes a control voltage input that determines the amplitude of the AC voltage output. The two AC input voltage waveform are provided by buck and boost windings of an AC input transformer having a primary winding connected to an AC source. The variable voltage source utilizes phase switch stages each connected to a respective one of the buck or boost windings and including back to back power MOSFETS. Each of the phase switch stages is controlled at a switching frequence much higher than the AC input frequency with the duty cycle of operation of each of the phase switch stages determining the amplitude of the controlled output.

Abstract: This invention relates to the distribution of electrical power to subsea petroleum recovery installations, and more particularly to methods and apparatus for sensing and limiting the electrical current drawn through power cables disposed on the sea floor. A transformer having primary winding and a secondary winding is located at a subsea power distribution module and has its primary winding connected in series with the power cable. A variable impedance device is connected to the secondary winding and is actuated, in response to a control signal indicative of the current drawn through the power cable, to substantially open-circuit the secondary winding when the current exceeds a predetermined value. Additionally, the variable impedance device substantially short-circuits the secondary winding when the load current falls to a level less than a preselected minimum value.

Abstract: An injection transformer has a primary winding series connected with a pair of inverse parallel-connected thyristors between a pair of input terminals. A control circuit is connected across a pair of output terminals for firing the thyristors. The injection transformer has a secondary winding connected between one of the input terminals and one of the output terminals for producing an injection voltage. A filter has components presenting a high impedance to the harmonic frequencies of the injection voltage and a low impedance to the fundamental frequency of the injection voltage, and has components presenting a high impedance to the fundamental frequency of the injection voltage and a low impedance to the harmonic frequencies of the injection voltage.

Abstract: A regulator for providing two different steps of bucking and two different steps of boosting correcting voltages to maintain the value of its output voltage within a selectable range with the regulator effecting each step correction for the next half-cycle based on the peak output voltage of the last half-cycle.