An integrated power factor converter utilizes a silicon controlled rectifier (SCR) bridge which limits the inrush current by controlling the conduction angle of the SCR's. The same SCR bridge shuts down the output in case of short circuit and recovers automatically at a predetermined duty cycle rate. In case the input voltage exceeds approximately 275 VAC, the SCR bridge regulates the output voltage to below 400 VDC. The input inrush current is reduced by phasing up the input voltage in a controlled manner. The use of SCR's in the input bridge produces no additional losses, since the rectifier function is required regardless of which topology is used. The integrated power factor converter interfaces universal voltage mains to DC/DC converters while reducing input harmonics.

Pulse width modulated boost converter integrated with power factor correction circuit

A welding power supply having a multiphase alternator and a thyristor rectifier using a control circuit to selectively prevent firing of thyristors when a short circuit occurs. Reliable operation of an alternator welding power supply under short circuit conditions is achieved.

Method and apparatus for providing welding current from a brushless alternator

An engine-driven, multiple-phase, alternator-powered SCR rectified arc welding power supply using a single synchronizing winding within the alternator providing signals to a synchronizing digitizer which masks noise for most of each cycle of the alternator. The synchronizing circuitry prevents spurious synchronizing signals.

Apparatus and method for synchronizing a firing circuit for a brushless alternator rectified d.c. welder

The present invention is directed to a method of utilizing the piezoelectric effect to transport a target substance within an earth formation. An earth formation is identified which bears a target substance. The piezoelectric properties of the earth formation are examined in order to determine the extent of the piezoelectric effect and to determine any optimum frequency of excitation. A voltage is applied to a particular portion of an earth formation in order to develop mechanical stress in the earth formation utilizing the piezoelectric property. The mechanical stress effects the local temperature and permeability of the target substance within the earth formation. A combination of excitation due to the electric field, mechanical stress, the temperature increase, serves to alter the permeability in a desired manner in order to liberate greater amounts of target substance from the earth formation, and to facilitate removal of the target substance utilizing conventional technologies such as pumps. Alternatively, and supplementally, a mechanical vibration and/or sonic energy source may be utilized to develop mechanical and electrical forces on the subsurface earth formation, to alter permeability of a target substance.

Method and apparatus for piezoelectric transport

The production of petroleum from a petroleum bearing formation through an electrically conductive production tubing suspended in a wellbore extending into said formation and lined by an electrically conductive tubular casing is accomplished by a plurality of method steps. A power source of low frequency alternating current is provided. Then, an electrical circuit path is completed, including the production tubing and casing as current paths. The low frequency alternating current is modified by creating transients in it. The modified low frequency alternating current is electrically coupled to the electrical circuit. Mechanical vibration is electrically induced in the casing and production tubing to substantially, continuously, mechanically vibrate the petroleum bearing formation and enhance petroleum production.

Recovery of petroleum by electro-mechanical vibration

A sample of the supply voltage for a power rectifier with phase control is passed through a filter which shifts it through a substantially constant phase angle of approximately n times 90*, where n is an integer, and may change its amplitude over a wide range with variation in supply voltage frequency. The reference signal, which is compared to the phase-shifted sample voltage to derive the rectifier firing signals, is varied in proportion to the amplitude of the filter output voltage. Inasmuch as the phase shift is constant and the ratio of filter output voltage to reference signal is also constant, the firing angles of the rectifier firing pulses are independent of supply voltage frequency and amplitude variations.

A Geiersbach

Papers

Power rectifier having phase control angle of firing signals independent of supply frequency variation