Induction motor control system with voltage controlled oscillator circuit

Claim 2

A voltage controlled oscillator circuit comprising: integrating means including a single electrical integrator responsive to an input electrical potential applied with respect to a circuit reference potential point for providing an output having a slope of a magnitude in a first polarity direction proportional to said input potential and including switching means responsive to a switching signal for causing said slope of said output to assume a slope of like magnitude but of opposite polarity direction; and comparator means responsive to a fixed reference potential and selected equal-amplitude but opposite-polarity outputs of said integrating means for providing said switching signals to said switching means whereby each said slope is caused to be of equal length and wherein an alternating current output is available from said output of said integrating means which varies in frequency directly with said electrical input potential; whereby an alternating current signal is provided at the output of said single electrical integrator with respect to said circuit reference potential point.

Claim 3

A voltage controlled oscillator circuit as set forth in claim 1 further comprising: second integrating means including a second single electrical integrator responsive to said input electrical potential for providing an output having a slope of a magnitude proportional to said electrical input potential in a first polarity direction and including second switching means responsive to a switching signal for causing said last named slope of said last named output to assume a slope of like magnitude but of opposite polarity direction; and zero crossing detection means responsive to the output of said first named electrical integrator for providing switching signals to said second switching means whereby each said slope of said output of said second single electrical integrator is of equal length and wherein an alternating current output is available from the output of said second integrator which is of like frequency and amplitude to that of the output of said first integrator but is displaced in phase by 90*.

Claim 4

A voltage controlled oscillator circuit as set forth in claim 1 wherEin said comparator means comprises: a differential amplifier; a feedback path from the output to the non-inverting input of said differential amplifier; and a bi-potential voltage regulator connected between the non-inverting input of said differential amplifier and said circuit reference potential point; and means for connecting the output of said single electrical integrator to the inverting input of said differential amplifier and the output of said differential amplifier to said switching means.

Claim 5

A voltage controlled oscillator circuit as set forth in claim 3 wherein said single electrical integrator comprises: a second differential amplifier; a capacitor connected between the output and inverting input of said second differential amplifier; a first resistor connected in series with the inverting input of said differential amplifier; a second resistor connected in series with said first resistor between the inverting input and the non-inverting input of said second differential amplifier and a third resistor of like value to said second resistor being connected between said last named inverting input and said circuit reference potential point; and said switching means comprises a transistor switch and a fourth resistor, said fourth resistor being connected in series with the output circuit of said transistor switch between the inverting input of said second differential amplifier and said circuit reference potential point, and said switching signals are applied to the input of said transistor switch.

Claim 6

In a motor control system in which an induction motor is controlled in speed by a voltage controlled two-phased oscillator, and said system comprising: reference voltage means for providing a selected direct current voltage representative of an optimum slip frequency at a maximum torque for a said motor; rate means connected to the output of said motor for providing a direct current output voltage proportional to the speed of said motor; summing means proportional to the output of said rate means and said reference voltage means for providing an output proportional to the sum of the output of said rate means and said reference voltage means; first integrating means including a first single electrical integrator responsive to the output of said summing means for providing an output having a slope of a magnitude in a first polarity direction proportional to its input and including switching means responsive to a switching signal for causing said slope of said output to assume a slope of like magnitude of opposite polarity direction; and comparator means responsive to a fixed reference potential and and selected equal-amplitude but opposite-polarity outputs of said first integrating means for providing said switching signals to said switching means whereby each said slope is caused to be of equal length and wherein an alternating current output is provided at the output of said first integration means which varies in frequency directly with said output of said summing means; second integrating means including a second single electrical integrator responsive to said output of said summing means for providing an output having a slope and a magnitude proportional to its input in a first polarity direction and including second switching means responsive to a switching signal for causing said last named slope of said last named output to assume a slope of like magnitude but of opposite polarity direction; and zero crossing detection means responsive to the output of said first single electrical integrator for providing switching signals to said second switching means whereby each said slope of said output of said second single electrical integrator is of equal length and wherein an alternating current output is provided from the output of said second integrator which is of like frequency and amplitude to that of the output of said first integrator but is displaced in phase by 90*.

Claim 7

In a motor control system in which an induction motor is controlled in speed by a voltage controlled two-phased oscillator, and said system comprising: reference voltage means for providing a selected direct current voltage representative of an optimum slip frequency at a maximum torque for a said motor; rate means connected to the output of said motor for providing a direct current output voltage proportional to the speed of said motor; summing means proportional to the output of said rate means and said reference voltage means for providing an output proportional to the sum of the output of said rate means and said reference voltage means; first integrating means including a first single electrical integrator responsive to the output of said summing means for providing an output having a slope of a magnitude in a first polarity direction proportional to its input and including switching means responsive to a switching signal for causing said slope of said output to assume a slope of like magnitude of opposite polarity direction; and comparator means responsive to a fixed reference potential and and selected equal-amplitude but opposite-polarity outputs of said first integrating means for providing said switching signals to said switching means whereby each said slope is caused to be of equal length and wherein an alternating current output is provided at the output of said first integration means which varies in frequency directly with said output of said summing means; second integrating means including a second single electrical integrator responsive to said output of said summing means for providing an output having a slope and a magnitude proportional to its input in a first polarity direction and including second switching means responsive to a switching signal for causing said last named slope of said last named output to assume a slope of like magnitude but of opposite polarity direction; and zero crossing detection means responsive to the output of said first single electrical integrator for providing switching signals to said second switching means whereby each said slope of said output of said second single electrical integrator is of equal length and wherein an alternating current output is provided from the output of said second integrator which is of like frequency and amplitude to that of the output of said first integrator but is displaced in phase by 90*.