Abstract: An electrically-compensated constant speed drive according to the present invention includes a speed summer having first and second input shafts and an output shaft at which constant speed motive power is developed wherein the first input shaft is coupled to a prime mover output shaft. A speed-compensating permanent magnet machine includes a motive power shaft coupled to the second input shaft of the speed summer and electrical power windings. A control permanent magnet machine includes a motive power shaft coupled to either of the first or output shafts of the speed summer and also includes electrical power windings.

Abstract: Prior DC-DC converters of the resonant type often require the use of parallel-connected power switches to provide adequate current levels and further require large input and output filters. However, parallel operation of switching devices encounters the problem of current sharing and large filters are disadvantageous from a size and weight standpoint. Such problems are overcome by the DC-DC converter of the present invention which includes a plurality of subconverters having outputs which are combined to produce the output power. Each subconverter includes an inverter and a rectifier for developing a full wave rectified output having a ripple component therein. The subconverters are operated so that a phase displacement of 2.pi./N electrical degrees exists in the output current from one subconverter relative to the output current from other subconverters.

Abstract: A controller for a resonant DC/DC converter having at least one power switch which is controlled to develop intermediate AC power in a resonant circuit includes means for developing a signal representing the current in the resonant circuit, an integrator having an input coupled to the developing means for integrating the signal developed thereby and a multiplier having a first input coupled to an output of the integrator and further having a second input and an output at which is developed a multiplied signal. A comparator is coupled to the output of the multiplier for comparing the multiplied signal at such output against a reference signal and a frequency-to-voltage converter is coupled between the output of the comparator and a second input of the multiplier for developing a feedback signal which is multiplied by the multiplier with the output of the integrator to derive the multiplied signal.

Abstract: An electrically-compensated constant speed drive according to the present invention includes a speed summer having first and second input shafts and an output shaft at which constant speed motive power is developed wherein the first input shaft is coupled to a prime mover output shaft. A speed-compensating permanent magnet machine includes a motive power shaft coupled to the second input shaft of the speed summer and electrical power windings. A control permanent magnet machine includes a motive power shaft coupled to the output shaft of the speed summer and also includes electrical power windings.

Abstract: Bi-directional switches for use with neutral point clamped PWM inverters have utilized clamping switches which are operated alternately with main power switches in the inverter to periodically connect an output terminal of the inverter to a neutral voltage. However, a delay period is typically interposed between turn-off of a main power switch and turn-on of the clamping switch to minimize the possibility of a potentially destructive shoot-through condition. This delay adversely affects the quality of the power developed by the inverter and leads to an undesired increase in the size of snubber circuits coupled across the power switches. In order to overcome these problems, a bi-directional switch according to the present invention includes circuitry for providing a high impedance path in series circuits including the main power switches and the clamping switch so that shoot-through currents are blocked even when one of the main power switches and the clamping switch are simultaneously on.

Abstract: A proportional base drive circuit which overcomes the problems of the prior art relative to relatively long turn-off time of power switches in an inverter and the absence of protection circuitry therefor includes a current transformer having a primary winding coupled to a main current electrode of a pair of power switches and first and second secondary windings each of which develops regenerative currents proportional to load current. First and second auxiliary switches are coupled between the secondary windings and the control electrodes of the power switches. Means are included for operating the auxiliary switches in synchronism with the power switches so that the power switches operate in rapid fashion. Means are also included for disabling the power switches when an overcurrent condition is sensed.

Abstract: Prior types of neutral point clamped PWM inverters have included memories for storing a plurality of PWM waveforms, one of which is utilized to control switches in the inverter to maintain an output parameter within prescribed limits. Such types of inverter controls, however, cannot provide the necessary degree of regulation in some applications. To overcome this problem, an inverter control according to the present invention permits on-line generation of PWM patterns for a neutral point clamped PWM inverter. The control includes circuitry for generating a depth of modulation signal representing the deviation of the output of the inverter from a desired level. A microprocessor and memory are coupled to the generating circuitry for calculating switching points for the inverter switches during operation of the inverter based upon the depth of modulation signal for a given number of pulses to be produced during each half cycle of the output.

Abstract: A push-pull converter has transistor power switches which conduct alternately to connect a DC source with the primary windings of an output transformer. A turn-off snubber circuit is connected with each power switch. When a power switch is turned on, snubber current pulses flow in the circuits connected with both switches. A switch current sensor circuit has a current transformer with an output winding inductively coupled with each of the conductors connected between the power switches and the primary windings of the output transformer. The snubber current pulses through the conductors are 180.degree. out of phase and are suppressed in the current transformer output. The switch current signal from the secondary of the current transformer is free of snubber current pulses and is used in a flux balance circuit and in a pulse-by-pulse current limiter.