Abstract: A commutation circuit for thyristors alternately turned ON by pulse width modulation (PWM) for the generation of a fundamental sine wave is characterized by two separate primary windings associated with respective positive and negative thyristors with a common secondary winding at the output, and two commutating networks for the respective poles, each including an auxiliary thyristor for fixed-commutation and the resonant combination of a capacitor and an inductor. The thyristors, the commutating networks, the DC source, and the output transformer have a symmetrical disposition as well as symmetrical commutation steps.

Abstract: A lock-out control logic circuit for a feedback inverter system, which senses the load current in each load switching element of the inverter system and utilizes the sensed current through the presently conducting load switching element to inhibit the next firing of the presently non-conducting load switching element. Current transformers are inserted in series with each switching element and coupled to a CMOS logic circuit which inhibits the firing pulse to a non-conducting load switching element in the event a current conduction condition is sensed.

Abstract: An improved, D.C. shut-off control circuit for a thyristor is provided by means of a transformer having a tapped primary which is connected between a D.C. supply and the thyristor and which has two secondary windings: one is used during shut off to generate an opposing magnetic field in the transformer core which cancels the magnetic field generated by the flow of current through the primary winding to the thyristor. When current to the first secondary winding is shut off, this secondary magnetic field collapses and causes a reverse current in the primary which effectively blocks current to the thyristor and simultaneously generates a voltage in the second secondary winding of the transformer which biases a transistor switch to connect the primary tap to the circuit ground, thereby using the magnetically induced voltage in the primary to reverse bias the thyristor and positively shut it off.

Abstract: A DC convertor for converting power at a particular input voltage level to a higher or a lower voltage level and operable despite changes in the direction of power flux between the input and output voltage levels. Main switching thyristors operate in conjunction with turn-off thyristors, a commutation capacitor, magnetically coupled inductor windings and bypass diodes to define the magnitude and direction of the flow of current in the convertor and the voltage conversion ratio of the convertor.

Abstract: A DC-to-DC chopper circuit has a first switch that is selectively actuated to supply load current to a regulated bus and bus voltage to a resonating circuit which increases the applied voltage to approximately twice the value of the bus voltage, and a second switch selectively actuated so that the current on the bus flows through the resonating circuit discharging the increased voltage stored therein to zero whereupon a freewheeling circuit permits the established current to freewheel until the next chopper cycle.

Abstract: A power circuit arrangement for a power conditioning system adapted to supply variable frequency, variable magnitude voltage to an electromagnetic device such as an electric motor having a center-tapped winding includes first and second inverting thyristors connected to the respective winding ends and connected in series with a transistor chopper across a unidirectional source so that the inverting thyristors may be gated on alternately at a relatively low modulation frequency while the chopper is time ratio controlled at a higher carrier frequency to selectively vary the voltage applied to the winding; a capacitor in shunt to the chopper which is overcharged due to winding leakage reactance when the chopper is turned off to reverse bias and "soft" commutate the thyristors when they are not conducting load current; a free-wheeling thyristor connected between the winding center tap and the chopper and poled to form a low-impedance free-wheeling path for winding current in series with the inverting thyristors w

Abstract: A chopper control device is disclosed, comprising: a series circuit having a dc power source, a dc load, and a thyristor; a transistor connected in parallel to the thyristor; a current transformer having a primary winding for detecting the load current; and another transistor for deriving a current from a secondary winding of the current transformer and supplying it to the base of the transistor.

Abstract: Disclosed is a variable DC voltage device wherein one terminal of a DC power supply, a switch, a first coil of a transformer, a second coil mounted on a core of the transformer with the same polarities with those of the first coil, a diode for preventing a shortcircuiting of the DC power supply when the switch is closed and the other terminal of the DC power supply are connected in series in the order named; a load is interconnected between the junction between the first and second coils and the other terminal of the power supply; and a compensation circuit is provided for restoring to an initial state the flux variation caused when the switch is closed, whereby the load is controlled by the alternate opening and closing of the switch.

Abstract: In a constant frequency chopper for low-rate supply for an inductive load, a cut-off capacitor discharge circuit is added which shunts the cut-off capacitor and which, when the motor is required to operate at a low rate, helps to bypass the excess energy stored in the cut-off capacitor.

Abstract: A semi-conductor controlled rectifier (SCR) d.c. interrupter in which any (optional) number m of identical, self-contained and parallel connected phases each form an identical series connection of a semi-conductor controlled retifier (Th.sub.1) . . . (TH.sub.m) and a diodes (D.sub.1 . . . (D.sub.m). An m number of identical, self-contained resonant arms are arranged in star or Y-connection, with any of the arms having an identical series connection of a capacitor (C.sub.1) . . . (C.sub.m) and a reactor (L.sub.1) . . . (L.sub.m) respectively. The star vertices are connected between the cathodes of the semi-conductor controlled rectifiers (Th.sub.1) . . . (Th.sub.m) and the anodes of the diodes (D.sub.1) . . . (D.sub.m). The star neutral is associated with the d.c. power source (BA) positive or negative pole.

Abstract: In force-commutated single phase and polyphase thyristor inverters, a single commutating pulse generator produces commutating impulses for all the commutating thyristors which are individually transformer-coupled to the power circuit to turn off a selected load thyristor. Coasting thyristors to provide zero output voltage levels are also commutated without additional components. The basic commutating pulse generator has one capacitor with provision for recovering trapped energy, and pulse waveshaping and two-level overcurrent capability can be added economically.

Abstract: A rectifier for a medium voltage rectifier system as well as for high voltage-direct current transmission includes a plurality of thyristor switches. The switches have asymmetric voltage breakdown strengths, the asymmetry being at least 10% for the forward blocking direction compared with the reverse blocking direction. The thyristor switches are dimensioned voltage-wise to safely block even long lasting overvoltages in both the forward and reverse blocking directions occurring during operation and to withstand momentary surge and switching voltages limited by an overvoltage suppressor in the reverse blocking direction.

Abstract: There is disclosed an improved switching circuit with overload protection for transforming a source of direct current power into a pulsating voltage of constant frequency and variable pulse duration adapted to be connected through a load to a first controllable rectifier of the switching circuit which in turn is connected through a current sensing resistor to a common circuit ground. The gate electrode of the first controllable rectifier is connected to a source of constant frequency pulses of variable duration. The secondary winding of a current transformer is connected from the common circuit ground in series with a diode, the cathode of which is connected to the anode of a second controllable rectifier, the cathode of the second controllable rectifier being connected to the common circuit ground. The gate of the second controllable rectifier is coupled to a source of pulses which are the exact complement to the pulses applied to the gate of the first controllable rectifier.

Abstract: A static inverter is provided suitable for use as a high frequency power supply utilizing sets of switching thyristors which are switched in pairs in a predetermined sequence, with series-related capacitors, and which includes diodes connected to insure turn-off of the thyristors and to limit the maximum voltage that can occur across the sets of thyristors.

Abstract: A high frequency transistor ballast is utilized to drive flourescent lamps. The electrical system of the ballast consists of a central rectifying and control panel and a high frequency inverter. There is also provided a low energy switch in the high frequency inverter system controlling the operation of the high frequency transistor ballast.