Abstract: An inverter for use in a power conversion system of the type used in an aircraft, for example, includes a first subinverter pair that generates a first pair of waveforms and a second subinverter pair that generates a second pair of waveforms. The two subinverter pairs are connected to a summing transformer having two pairs of primary windings and a plurality of secondary windings coupled to the primary windings. A regulator is coupled to the output of the summing transformer and varies the phase angles between the waveforms generated by the two subinverter pairs based upon the voltage and current at the output of the summing transformer in order to regulate the voltage at the output of the summing transformer.

Abstract: An inverter for use in a power conversion system of the type used in an aircraft, for example, includes a first subinverter pair that generates a first pair of waveforms, a second subinverter pair that generates a second pair of waveforms, and a third subinverter pair that generates a third pair of waveforms. The three subinverter pairs are connected to a summing transformer having first, second and third transformers. A regulator is coupled to the output of the summing transformer and varies the phase angles between the three pairs of waveforms generated by the three subinverter pairs based upon the voltage and current at the output of the summing transformer in order to regulate the voltage at the output of the summing transformer.

Abstract: An inverter for use in a variable-speed, constant-frequency power conversion system of the type used in an aircraft, for example, includes a four subinverter pairs, each of which generates a respective set of waveforms. The four subinverter pairs are connected to a summing transformer having eight sets pairs of primary windings and eight sets of secondary windings coupled to the primary windings. A regulator is coupled to the output of the summing transformer and varies the phase angles between the waveforms generated by the four subinverter pairs based upon the voltage and current at the output of the summing transformer in order to regulate the voltage at the output of the summing transformer.

Abstract: A hybrid power system which converts variable-frequency power developed by a brushless generator into DC power which is supplied to a DC load and constant-frequency AC power which is supplied to an AC load includes an AC/DC converter coupled to a main generator portion armature winding of the generator which converts the variable-frequency power produced by the generator into the DC power and a DC/AC converter coupled to the AC/DC converter which converts the DC power into the constant-frequency AC power. A first regulator is coupled to an exciter portion field winding of the generator for supplying current thereto in dependence upon a parameter of the DC power to maintain such parameter substantially at a regulated DC value. A second regulator is coupled to the DC/AC converter for controlling same in accordance with a parameter of the constant-frequency AC power to maintain such parameter substantially at a regulated AC value.

Abstract: A regulator for a stepped-waveform inverter having first and second subinverters which produce waveforms having a variable phase displacement therebetween and a summing transformer which sums the outputs of the subinverters includes circuitry for detecting a deviation of a parameter of the AC output power produced by the inverter from a reference and circuitry coupled to the detecting circuitry for deriving a phase command signal from the detected deviation. A comparator compares the phase command signal with a ramp signal to obtain a comparison signal and circuitry operates the first and second subinverters responsive to the comparison signal to cause the phase displacement to vary in accordance with the phase command signal.

Abstract: A power conversion system utilizes a brushless generator driven by a prime mover when operating in a generating mode and drives the prime mover when operating in a starting mode. The system includes first and second bidirectional converter/inverter units, each of the bidirectional units being operable as either an AC to DC converter or a DC to AC inverter. A DC link couples the first and second bidirectional units. A transformer is connected to the second unit and the first unit is further connected to the armature windings, the transformer further being connected to the external power source. A control unit is connected to the first and second bidirectional units and causes the first bidirectional unit to operate as a converter and the second bidirectional unit to operate as an inverter when operating in the generating mode, and for causing the first bidirectional unit to operate as an inverter and the second bidirectional unit to operate as a converter when operating in the starting mode.

Abstract: A power conversion system utilizes a brushless generator driven by a prime mover when operating in a generating mode and drives the prime mover when operating in a starting mode. The system includes an AC/DC power rectifier and an inverter coupled to the AC/DC power rectifier for developing at least one AC voltage. Contactors are provided for coupling, when in the generating mode, the generator to the rectifier input and the inverter output to an AC load during operation in the generating mode, and for coupling an external power source to the rectifier input and the inverter output to the generator during operation in the starting mode. Transformers are provided for adjusting system voltages so that the generator windings need not be modified to accomplish starting of the prime mover.

Abstract: Prior power conversion system operable in generating and starting modes have utililzed brushless generators which are suitable for only certain applications. In order to overcome this problem, a power conversion system operable in generating and starting modes utilizes a switched reluctance motor/generator which is reliable and inexpensive and which can be used in a variety of environments.

Abstract: Prior power converters utilizing a plurality of switches operated by control circuitry include many components which are subject to failure. When such a failure occurs, it may prove difficult to isolate the problem and repair the power converter. In order to overcome this problem, a power converter is packaged as a plurality of identical line replaceable units each of which may be easily replaced in the event of a malfunction.

Abstract: A variable speed, constant frequency aircraft power system uses current sensing diodes to rectify the power generator output. The current flow through pairs of diodes is compared to generate phase currents to detect feeder faults.

Abstract: A power conversion system is operable in a generating mode to convert motive power developed by a prime mover into electrical power and in a starting mode to convert electrical power developed by a source of AC power into motive power for starting the prime mover. The system includes a stepped waveform inverter having a plurality of subinverters that are operable in the generating mode to produce rectangular waveforms wherein the waveforms are summed by a summing transformer to produce a stepped AC output waveform. During operation in the starting mode, the output of a rectifier bridge and an input of one of the subinverters are connected together by an interphase transformer. DC power is developed at a mid-tap of the interphase transformer and is delivered to the remaining subinverters which in turn develop AC power for operating a brushless generator as a motor.

Abstract: The problem of sensing current through inverter switches is solved by a current transformer which has windings connected with the flyback diodes to demagnetize or reset the current transformer core. Size and weight of the transformer are minimized while avoiding a buildup of flux which would saturate the core.

Abstract: A filter system for removing selected frequencies from AC power provided on at least two phase lines and a neutral line includes a phase-to-phase filter for removing a first selected AC component at a first frequency from the AC power wherein the frequency component has a line-to-phase displacement within first or second ranges. A phase-to-neutral filter is also provided for removing a second selected AC component at a second frequency different from the first frequency from the AC power wherein the second frequency component has a line-to-line phase displacement outside of the first and second ranges.

Abstract: A power conversion system is operable in a generating mode to convert motive power developed by a prime mover into electrical power and in a starting mode to convert electrical power developed by a source of AC power into motive power for starting the prime mover. The system includes a rectifier having an output coupled to a DC link, first and second inverters, each coupled to the DC link and transformer including first and second sets of primary windings and a set of secondary windings wherein the second set of primary winding is coupled to an output of the second inverter. Contactors are provided for coupling the rectifier to the generator armature windings and the first set of primary windings to an output of the first inverter so that AC power produced by the generator is converted into DC power on the DC link and the DC power is converted into fixed frequency AC power which is developed in the set of secondary windings.

Abstract: Prior base drive circuits for Darlington-connected transistors have accomplished a significant increase in the rate at which such transistors can be turned off and on. However, such circuits have utilized relatively numerous circuit elements or components to accomplish this result. In order to overcome this problem, a drive circuit 26 for rapidly switching driver and driven transistors Q3, Q4 connected in a Darlington configuration includes a first controllable switch Q1 coupled to a control electrode of the driver transistor Q3, an inductor L1 coupled to the first controllable switch Q1 and the control electrode of the driver transistor Q3 and a second controllable switch Q2 coupled to the control electrode of at least one of the transistors. A driving stage 32 is coupled to the controllable switches and closes same at the beginning of a turn on sequence to establish current flow through the inductor.

Abstract: An excitation system for a brushless generator includes an exciter portion having a set of polyphase exciter field windings and an additional exciter field winding disposed in a stator of the generator, a source of polyphase, constant-frequency AC power and circuitry coupled to the set of polyphase field winding for connecting the source of polyphase, constant-frequency AC power thereto at a beginning of operation in a starting mode whereby AC power is induced in an exciter portion armature winding by transformer action. AC power is further provided to armature windings of a main generator portion to thereby cause a rotor of the generator to accelerate. An autotransformer is provided to reduce the voltage provided by the source of polyphase AC power prior to application of such power to the polyphase field windings so that the need for an auxiliary inverter is obviated.

Abstract: A load is controlled by a pulse waveform from a source. The source and load are electrically isolated by using two monostable circuits to detect the leading and trailing edge of the pulse waveform, two pulse transformers to isolate the source and the load, and a bistable circuit to reconstruct the original pulse waveform.

Abstract: An electrically compensated constant speed drive which is speed limited so that power flow through the speed compensation link is unidirectional includes a permanent magnet generator which is interconnected with a permanent magnet motor by a power converter. The permanent magnet generator and the permanent magnet motor are controlled by first and second independent control loops. The power converter includes an AC/DC converter coupled to electrical power windings of the permanent magnet generator, a filter coupled to the output of the AC/DC converter and an inverter coupled between the filter and electrical power windings of the permanent magnet motor. The permanent magnet generator, AC/DC converter, filter and the first control loop together develop a voltage on a DC bus.

Abstract: A control operates a permanent magnet brushless DC motor utilizing a phase advance signal to control motor torque. Input signals to the motor comprise a phase advance command signal and rotor position signals. The control provides switching signals to drive an inverter switch circuit to energize the motor. A start circuit is responsive to an analog rotor position signal and develops switching signals according to a preselected pattern stored in a memory. A run circuit compares a periodic sawtooth signal representing motor speed and a maximum desired phase advance, to a phase advance command signal to develop switching signals. The control switches from the start circuit to the run circuit at a preselected speed.

Abstract: Prior circuits for rapidly switching Darlington-connected transistors between on and off states have accomplished relatively fast switching by applying reverse base drive to the transistors to quickly sweep the excess carriers therefrom. However, such circuits have not accomplished the required degree of reduction of turn off time and have induced localized "hot spots" in the base-collector junctions of the transistors.