Direct AC converter for converting a balanced AC polyphase input to an output voltage

A direct AC converter including input phase conductors for a balanced polyphse AC input voltage system;

• a plurality of output phase conductors for an AC input voltage system having at least one characteristic such as frequency, amplitude, phase angle or phase displacement which is different from that of the input voltage system;
• a plurality of bidirectional switch means for individually connecting each input phase conductor to each output phase conductor;
• control means comprising oscillator means for generating equiphase displaced sinusoidal outputs equal in number at least to the number of input phase conductors and for maintaining said equiphase displacement between said sinusoidal outputs, and timing means for receiving said equiphase displaced sinusoidal outputs and producing a repeating sequence of mutually abutting sinusoidally-width-modulated drive pulses;
• and means for utilizing said drive pulses to operate said bidirectional switch means at a frequency substantially higher than the frequencies of both the input and output systems, to connect, in respect of each said output phase conductor, only one input phase conductor at a given time to that output phase conductor and for connecting all of said input phase conductors to each output phase conductor a plurality of times during any cycle of said input system or of said output system.

A direct AC converter including input phase conductors for a balanced N-phase AC input voltage system;

• output phase conductors for a balanced polyphase AC output voltage system having at least one characteristic such as frequency, amplitude, phase angle or phase displacement which is different from that of the input voltage system;
• a plurality of bidirectional electronic switch means for individually connecting each input phase conductor to each output phase conductor;
• control means which includes two groups of N frequency controllable sinusoidal oscillator means, each group of N oscillator means for producing N equally phase-displaced sinusoidal outputs, the frequencies of said two groups of oscillator means being, respectively, (i) the desired frequency of said output system less the frequency of said input system with said phase displaced outputs arranged in one sense, and (ii) the sum of the frequencies of said input and output systems but with the phase displaced outputs arranged in a sense opposite from said one sense;
• means for controlling the amplitudes of the outputs of said groups of oscillator means in response to a common control signal;
• means for controlling the amplitude of the outputs of one of said groups of oscillator means differentially with respect to the outputs of the other said group of oscillator means;
• summing means for summing the outputs of the oscillator means of one said group of oscillator means individually with the outputs of the oscillator means of the other said group of oscillator means to produce N.sub.2 summed outputs;
• means for converting said summed outputs into sequences of abutting sinusoidally-width-modulated drive pulses;
• and means for utilizing said drive pulses to operate said bidirectional switch means to connect, in respect of each said output phase conductor, only one input phase conductor at a given time to that output phase conductor.

A direct AC converter including input phase conductors for a balanced polyphase AC input voltage system;

• at least one output phase conductor for an AC output voltage system having at least one characteristic such as frequency, amplitude, phase angle or phase displacement which is different from that of the input voltage system;
• a plurality of bidirectional switch means for individually connecting each input conductor to said at least one output phase conductor;
• control means comprising oscillator means for generating equiphase displaced sinusoidal outputs equal in number at least to the number of input phase conductors and timing means for receiving said equiphase displaced sinusoidal outputs and producing a repeated sequence of mutually abutting sinusoidally-width-modulated drive pulses;
• and means for utilizing said drive pulses to operate said bidirectional switch means at a frequency substantially higher than the freequencies of both the input and output voltage systems, to connect, in respect of the said at least one output phase conductor, only one input phase conductor at a time to that output phase conductor and for connecting all of said input phase conductors to said at least one output phase conductor a plurality of times during any cycle of said input system or of said output system.

An engine speed control system comprising:

• an engine having a shaft;
• tachometer means coupled to the shaft for generating a signal indicative of the speed of said shaft;
• a direct AC converter including input phase conductors for a balanced polyphase A.C. input voltage system a plurality of output phase conductors for a balanced polyphase A.C. output voltage system having at least one characteristic such as frequency, amplitude, phase angle or phase displacement which is different from that of the input voltage system;
• a plurality of bidirectional switch means for individually connecting each input phase conductor to each output phase conductor;
• means coupling either said input phase conductors or said output phase conductors to said engine;
• timing means for producing a repeated sequence of mutually abutting width-modulated drive pulses;
• means for utilizing said drive pulses to operate said bidirectional switch means at a frequency substantially higher than the frequencies of both the input and output voltage systems, to connect, in respect of each said output phase conductors, only one input phase conductor at a time to that output phase conductor and for connecting all of said input phase conductors to each said output phase conductor a plurality of times during each cycle of said input system or of said output system;
• control means connected to receive an output signal indicative of shaft speed from said tachometer means and utilizing said tachometer output signal to adjust the width modulated drive pulses produced by said timing means and thereby control the engine speed.