Alternating current motor system

Claim 3

The invention as set forth in claim 1 further including a digital to analog converter for converting said digital signal into said level.

Claim 4

The invention as set forth in claim 1 including means responsive to said second signal for inhibiting the provision of said digital signal when said first signal reaches a value corresponding to speeds less than a certain speed below said given speed whereby to provide only said second signal for controlling the speed of said motor.

Claim 5

The invention as set forth in claim 3 further including means for providing said analog value of said digital signal so that the highest value thereof is less than said value of said first signal corresponding to speeds less than said certain speed whereby said second signal which results when said first signal is of said last named value then operates said inhibiting means.

Claim 8

The invention as set forth in claim 5, wherein said first and second tuned circuits are each series resonant tuned circuits, and said circuit means includes rectifier circuits connected to said circuits, and circuit means connected to said rectifiers for obtaining the difference in the voltage across said rectifiers to provide said output signal.

Claim 9

The invention as set forth in claim 5 further comprising a source of voltage, a threshold gate circuit responsive to the voltage produced by the one of said rectifier circuits connected to the one of said tuned circuits which is tuned to the lower frequency for gating to an output of said threshold gate circuit the voltage from said source when said one rectifier circuit voltage drops below a certain threshold value corresponding to speeds of said motor between stop and a certain low motor speed.

Claim 10

The invention as set forth in claim 7 further comprising means for combining said threshold gate output with said output signal to provide said first signal.

Claim 13

The invention as set forth in claim 9 wherein said control signal generator means includes means for providing said first control signal as a digital signal having a plurality of bits, and said first means includes a plurality of parallel circuits each corresponding to a different bit of said digital signal and each including a switch device and a resistor in series, each of said last named resistors having a value related to the value of the bit of the digital signal to which it corresponds, and means for driving the switch device of each of said circuits with the digital signal bit corresponding thereto.

Claim 14

The invention as set forth in claim 10 wherein said motor is a polyphase motor having a plurality of rotor windings, a plurality of groups each containing said plurality of circuits, each group connected to a different one of said rotor windings.

Claim 15

The invention as set forth in claim 10 wherein said second means includes a resistor and phase controlled switching means operated by said second signal for connecting said resistor across said winding for different periods of each cycle of the voltage induced into said rotor winding the duration of which periods is controlled by said second signal.

Claim 16

The invention as set forth in claim 12 wherein said second means resistor and said permanent resistor have substantially the same resistance.

Claim 17

The invention as set forth in claim 10 wherein said second means includes a SCR and a resistor connected across said rotor winding, and means responsive to said second signal and to the voltage at the slip frequency which is induced into said rotor winding for providing said second signal as pulses synchronous with said slip frequency rotor voltage, and means for applying said pulses to trigger said SCR.

Claim 18

The invention as set forth in claim 10 wherein said motor is a polyphase motor having a polyphase rotor winding, and said second means comprises a plurality of SCR's each for a different one of the phases of aid rotor winding, a resistor, a plurality of diodes, a different one of said SCR's and a different one of said diodes being connected in series and polarized in the same direction, said resistor being connected in parallel with each of said series connected SCR's and diodes, said phases being connected each to a junction of a different one of said series connected SCR's and diodes, and means responsive to said second signal for triggering said SCR's.

Claim 19

For use with a wound rotor A.C. motor for controlling the speed thereof and limiting the starting current drawn by said motor, a regulating system which comprises a. means for providing a control signal which is a function of the speed of said motor, b. an error amplifier for amplifying said control signal, c. a vernier error amplifier for further amplifying said control signal and providing a vernier control signal, d. an analog to digital converter responsive to the output of said error amplifier for providing a multi-bit digital signal corresponding to said control signal, e. a digital to analog converter for converting said digital signal into an analog signal which varies in steps each step corresponding to a successive range of the amplitude of said control signal, f. means for applying said analog signal to said vernier error amplifier for conditioning said vernier error amplifier to provide vernier control signals which vary over an amplitude range corresponding to the amplitude range between each successive step of said control signal, g. threshold gate means connected to an output of said vernier error amplifier for inhibiting said digital signals and thereby said analog signals corresponding thereto when said control signals have an amplitude corresponding to motor speed between stop and a certain speed below desired motor speed, g. a plurality of current control resistors each corresponding to a different bit of said digital signal connected to said motor winding, i. at least one vernier current control resistor connected to said motor winding, j. means including a plurality of SCR's connected to said current control resistors and operated by said digital signals for varying the current through said rotor windings in steps, and k. vernier means including at least one SCR connected to said vernier control resistor for continuously varying the current through said rotor winding during the range of said motor speed between start up and said certain speed and between said successive steps.

Claim 20

For use with a wound rotor A.C. motor for controlling the speed thereof and limiting the starting current drawn by said motor, a regulating system which comprises a. means for providing a control signal which is a function of the speed of said motor, b. an error amplifier for amplifying said control signal, c. a vernier error amplifier for further amplifying said control signal and providing a vernier control signal, d. an analog to digital converter responsive to the output of said error amplifier for providing a multi-bit digital signal corresponding to said control signal, e. a digital to analog converter for converting said digital signal into an analog signal which varies in steps each step corresponding to a successive range of the amplitude of said control signal, f. means for applying said analog signal to said vernier error amplifier for conditioning said vernier error amplifier to provide vernier control signals which vary over an amplitude range corresponding to the amplitude range between each successive step of said control signal, g. threshold gate means connected to an output of said vernier error amplifier for inhibiting said digital signals and thereby said analog signals corresponding thereto when said control signals have an amplitude corresponding to motor speed between stop and a certain speed below desired motor speed, g. a plurality of current control resistors each corresponding to a different bit of said digital signal connected to said motor winding, i. at least one vernier current control resistor connected to said motor winding, j. means including a plurality of SCR's connected to said current control resistors and operated by said digital signals for varying the current through said rotor windings in steps, and k. vernier means including at least one SCR connected to said vernier control resistor for continuously varying the current through said rotor winding during the range of said motor speed between start up and said certain speed and between said successive steps.

Claim 21

The invention as set forth in claim 16 wherein there are provided a plurality of flip-flops for storing said bits of said digital signal, said latches being input connected to said analog to digital converter and output connected to said digital to analog converter and means for connecting the output of said threshold means to the reset input of said flip-flops for resetting said fip-flops to zero, thereby inhibiting said digital signal.

Claim 22

The invention as set forth in claim 16 including a limiter circuit connected at the output of said control signal amplifier to limit said control signal to a range of signal amplitude corresponding to a high motor speed at one end of said range and a low motor speed at the opposite end of said range, said control amplitude at the opposite end of said range being sufficiently greater than the analog voltage provided by said analog to digital and digital to analog converter such that said vernier error signal exceeds the threshold of said threshold gate.

Claim 23

The invention as set forth in claim 18 wherein said control signal amplifier and said vernier signal amplifier comprise a plurality of cascade connected amplifier stages, one of said stages in said vernier amplifier being a difference amplifier and having said analog signal from said digital to analog converter applied thereto.

Claim 24

The invention as set forth in claim 19 wherein a feedback circuit is connected from the output to an input of at least one of said cascade connected amplifiers, said feedback path including a R-C circuit, and a gate diode connected between the output of said cascade connected amplifiers and said R-C circuit for blocking said feedback path when said vernier control signal increases in amplitude at greater than a certain rate.

Claim 25

The invention as set forth in claim 18 further comprising a source of voltage, a diode providing a threshold gate connected between said source of voltage and said control signal amplifier, means included in said control signal providing means and connected to said threshold gate diode for providing a control voltage for inhibiting said gate and preventing application of said source voltage to said amplifier unless said motor speed is below a certain value, said source voltage being of equal or exceeding said control signal amplitude at the opposite end of said range whereby to insure exceeding the threshold of said threshold gate which enables the inhibiting of said digital signal.

Claim 26

The invention as set forth in claim 16 including power supply means for said analog to digital converter for delaying the application of operating power thereto for a certain time interval upon turn-on of said system.

Claim 27

The invention as set forth in claim 16 wherein said vernier means for varying the current through said winding comprises a synchronous pulse generator for generating pulses for triggering said SCR of said vernier means, said pulse generator comprising an input filter circuit connected to said rotor windings and tuned to pass slip frequency signals induced in said rotor when said rotor speed differs from the synchronous speed of said motor. a squaring circuit connected to said filter for providing square wave signals corresponding to the signals passed by said filter, a capacitor, means responsive to said vernier control signal for controlling the flow of current from said square wave generator into said capacitor, and means for producing a pulse up said capacitor charging to a certain voltage.

Claim 28

The invention as set forth in claim 23 wherein said pulse producing means includes a uni-junction transistor having its gate electrode connected to said capacitor, and means responsive to the current flow through said uni-junction transistor for providing said pulse.

Claim 29

The invention as set forth in claim 23 wherein said vernier control signal responsive means includes a transistor having its collector to emitter path connected between the output of said squaring circuit and said capacitor, and means for applying said vernier control signal to the base of said transistor.

Claim 30

A speed regulated motor system which comprises a. a wound rotor induction motor having a shaft, b. means responsive to the speed of rotation of said shaft for providing a first signal responsive to deviation thereof from a certain shaft rotation speed, c. means responsive to said first signal for generating second and third signals, said second signal representing relatively large changes in said first signal corresponding to relatively large shaft speed changes within a first speed range encompassing said certain speed, said third signal representing relatively small changes in said first signal corresponding to vernier changes in shaft speed and also representing large changes in said signal corresponding to shaft speeds below said range during the starting cycle of said motor, d. means responsive to said second and third signals connected to the winding of said rotor for controlling the current in said rotor thereby regulating the speed of said motor.

Claim 31

A speed regulated motor system which comprises a. a wound rotor induction motor having a shaft, b. means responsive to the speed of rotation of said shaft for providing a first signal responsive to deviation thereof from a certain shaft rotation speed, c. means responsive to said first signal for generating second and third signals, said second signal representing relatively large changes in said first signal corresponding to relatively large shaft speed changes within a first speed range encompassing said certain speed, said third signal representing relatively small changes in said first signal corresponding to vernier changes in shaft speed and also representing large changes in said signal corresponding to shaft speeds below said range during the starting cycle of said motor, d. means responsive to said second and third signals connected to the winding of said rotor for controlling the current in said rotor thereby regulating the speed of said motor.

Claim 32

The motor system according to claim 26 including an A.C. generator driven by said shaft and wherein said means for providing said first signal, includes frequency detector means responsive to the frequency of the A.C. produced by said generator.

Claim 33

The motor system as set forth in claim 27 further including means responsive to the power produced by said generator for generating a fourth signal corresponding thereto, and means for adding said fourth signal to said first signal and applying the sum of said first and fourth signal to said control signal generator.