Abstract: An apparatus having a rectifier topology for use on a three-phase electrical system is disclosed. The apparatus includes an input filter at each phase, a rectifier set at each phase in power communication with and downstream of each respective input filter, and a separate and independent booster section at each phase in power communication with and downstream of each respective rectifier set. Each booster section comprises two switches, thereby providing a six-switch three-level discontinuous conduction mode (DCM) boost rectifier.

Abstract: The systems and methods described herein provide for a universal controller capable of controlling multiple types of three phase, two and three level power converters. The universal controller is capable of controlling the power converter in any quadrant of the PQ domain. The universal controller can include a region selection unit, an input selection unit, a reference signal source unit and a control core. The control core can be implemented using one-cycle control, average current mode control, current mode control or sliding mode control and the like. The controller can be configured to control different types of power converters by adjusting the reference signal source. Also provided are multiple modulation methods for controlling the power converter.

Abstract: A power conversion equipment capable of dealing with an imbalance fault by changing characteristics of a filter for extracting negative-phase-sequence voltage in a steady state and at the time of a system fault, and a control device for the conversion equipment. The control device for power conversion equipments includes a negative-phase-sequence component extractor including first and second negative-phase-sequence component extraction filters having different extracting capabilities, and for extracting a negative-phase-sequence component from the two phase voltage using the first negative-phase-sequence component extraction filter in a steady state and extracting a negative-phase-sequence component from the two phase voltage using the second negative-phase-sequence component extraction filter in a transient state.

Abstract: In a current transformer arrangement for three-wire three-phase systems, use is made of a single busing transformer (4) arranged on the three-phase side. Two of the total of three phase conductors are pushed through the bushing transformer, specifically either with the same number of turns per unit length and in mutually opposite defined directions or with the same direction and with the ratio of different numbers of turns per unit length of 2:1 or with the same direction and a current flow halved in a phase conductor by a shunt (15). These arrangements prevent the occurrence of a zero resultant magnetic flux. The double secondary voltage produced by a double AW value occurring twice during each period is halved by an electronic correcting circuit. The control commands are derived from suitable control pulses for the thyristors (21-26) of the three-phase bridge circuit (16). Two correcting circuits are specified.

Abstract: A three-phase transformer is supplied by a three-phase AC line voltage. Two phases are connected via switches comprising head-to-tail connected thyristors. The third phase is connected directly to the transformer. The switches are of the zero voltage switching type. Under steady state conditions, the start of each series of cycles is obtained by closing in a fixed order a first switch at a time near the zero-crossing of the voltage across it (alternating between series of cycles the sign of the derivative of the voltage across it immediately before it is closed) and then the second switch approximately 90.degree. after the first switch. The duration of a series of cycles if 570.degree. plus a null or integer number of periods of the AC line voltage. This is achieved by counting thyristor firing command signals from pulse transformers driven by monostables.

Abstract: An improved control system for static volt ampere reactance compensator provides for a transformation of the three phases into a two-variable system which thus isolates any common mode in the associated delta. Improved control is provided by utilizing the flux change as an advance indication of a disturbance. Lastly, the two-variable system, as it is inverse transformed into a three variable system, has its phasors rotated to prevent oscillation.

Abstract: A control system for a three-phase motor has two triac switches connected in respective supply lines to the motor. Both switches are initially closed so that power is supplied to the motor on all three lines. After a predetermined time, when the motor has reached its operating speed, one switch is opened by a logic unit so that single phase power is supplied to the motor on two lines. One of the switches is subsequently periodically closed for short intervals, and the other switch is periodically opened for short intervals under control of a monostable unit, so as to produce hunting of the motor. Hunting of the motor is detected by a speed monitor responsive to the counter EMF of the motor. The system has a phase detector responsive to the phase relationship between signals on the supply lines which prevents the switches being closed if there is not the desired phase relationship between the signals.

Abstract: A control circuit is connected between a three-phase power supply and a motor and ensures the correct application of phase signals to the motor, regardless of the way in which the control circuit is connected to the power supply. A first output signal of the supply is connected directly to an input of the motor via the circuit. Supply of power to the other two inputs is controlled by four switches, two of which receive signals from the second supply output and have their outputs connected to respective motor inputs, and the other two of which receive signals from the third supply output and have their outputs connected to respective motor inputs. The switches are controlled such that two switches are on, and the other two switches are off if the third output signal is positive with respect to the first output signal when the second signal passes through zero with respect to the first signal in a positive sense.

Abstract: In an apparatus for controlling the power factor of a power distribution system connected to inductive loads, banks of delta connected capacitors are added to or removed from the power lines of the power distribution system by a plurality of solid state switching devices which are under the control of a microprocessor. The solid state switching devices include optically isolated SCR devices that do not generate electrical interference and provide transient free operation. The microprocessor is also capable of calculating the power factor and displaying it on a digital readout.

Abstract: A multiple phase electricity switching apparatus having electrical components arranged and mounted on a heat sink structure which having the same external dimensions as a conventional electromagnetic relay. The switching apparatus controls the amount of electrical energy passing therethrough and into electrical resistance heating elements thereby controlling the temperature of the molten plastic raw materials. The switching apparatus includes a pair of inverse parallel connected SCR's (silicon control rectifier), a photo coupling, and a zero cross switching circuit. The SCRs are separately mounted on and separated by a structure having two parallel members. The electronic circuit components permit the electrical power supplied to the load to be switched more frequently thereby realizing improved temperature regulation.

Abstract: A power controlling circuit for automatic temperature regulator or the like using a zero voltage switching control. Clocks are dispersed and selected, in accordance with control factor, from among the clocks synchronized with the load power supply when zero voltage is detected from the load side to perform the zero cross control of the energization to the load through the detection of the zero voltage from the load side thereby to drive the zero cross control by the selection clock. The current limit close to the phase control can be achieved without any production of the noises. Also, the power control can be achieved without any production of the noises and does not damage the resolution and response property.

Abstract: First and second input currents to a three-phase AC induction motor of either delta or wye winding configuration are directly regulated by a pair of phase-triggered, gate-controlled, semiconductor switches series-inserted between the motor and two phases of its three-phase AC power source, the third input current being the Kirchoff resultant of the two regulated input currents. The half-cycle firing points or firing angles of the gate-controlled switches are varied together to apply more or less power to the motor as a function of mechanical load to optimize the power factor of the motor. Voltage imbalances in the motor windings caused by directly regulating only two of three input currents are tolerable due to the current limiting effect of the gate-controlled switches when the induction motor is at less than full mechanical load, such current limiting minimizing heat losses (I.sup.2 R) caused by the voltage imbalance condition.

Abstract: A circuit arrangement contains an oscillator for producing high frequency pulses, a gate circuit, a pulse transformer and a triac. The high frequency pulses can be connected to the primary winding of the transformer by way of the gate circuit. The secondary winding of the transformer is connected in the control circuit of the triac. The line voltage load is connected in the output circuit of the triac. A switch is arranged at the output of the gate circuit and is connected to the primary winding of the transformer. The switch is closed only during the presence of one polarity of the pulses so that a current can only flow through the primary winding of the transformer during a corresponding interval.