Digital tach and slip signal motor control

Claim 2

A digital control circuit for supplying gating signals to the inverter of a current controlling thyristor circuit for the stator winding of a three phase induction motor, comprising a tachometer coupled to the rotor of said motor and operative to produce two sets of digital tach signals representing the direction of rotation and frequency of said rotor in revolutions per minute, a command signal source producing digital slip signals respresenting the difference between the rotor frequency and the desired frequency of the stator winding of said motor, means for algebraically summing said tach and slip signals, and having a multi-bit binary output register the contents of which is cycled at least one per revolution of said rotor, and decoder mains interposed between said output register and said inverter and operative to convert the binary contents of said register into said gating signals for said inverter.

Claim 3

A digital control circuit for supplying gating signals to the inverter of a current controlling thyristor circuit for the stator winding of a three phase induction motor, comprising a tachometer coupled to the rotor of said motor and operative to produce digital tach signals representing the frequency of said rotor in revolutions per minute, a command signal source producing digital slip signals representing the difference between the rotor frequency and the desired frequency of the stator winding of said motor, means for algebraically summing said tach and slip signals, and having a multi-bit binary output register the contents of which is cycled at least once per revolution of said rotor, and decoder means interposed between said output register and said inverter and operative to convert the binary contents of said register into said gating signals for said inverter, said tachometer being operative to produce over several hundred digital tach signals per revolution of said rotor, said summing means including means for dividing the summed tach and slip signals by a relatively large factor before conversion of the summed signals to said gating signals for said inverter, said summed signals, after division by said dividing means causing the contents of said register to be cycled at least twice per revolution of said rotor, said tachometer being a two channel pulse tachometer producing two sets of signals for each revolution of said rotor, the signals of said two sets being equal in number and being angularly offset from each other, and said summing means comprising at least one up/down counter having its inputs connected to the output of said tachometer and to said command signal source, and operative upon the summing of said tach and slip signals to divide the summed signals by a factor to provide a quotient of two.

Claim 4

A digital control circuit for supplying gating signals to the inverter of a current controlling thyristor circuit for the stator winding of a three phase induction motor, comprising a tachometer coupled to the rotor of said motor and operative to produce digital tach signals representing the frequency of said rotor in revolutions per minute, a command signal source producing digital slip signals representing the difference between the rotor frequency and the desired frequency of the stator winding of said motor, means for algebraically summing said tach and slip signals, and having a multi-bit binary output register the contents of which is cycled at least once per revolution of said rotor, and decoder means interposed between said output register and said inverter and operative to convert the binary contents of said register into said gating signals for said inverter, said tachometer being operative to produce over several hundred digital tach signals per revolution of said rotor, said summing means including means for dividing the summed tach and slip signals by a relatively large factor before conversion of the summed signals to said gating signals for said inverter, said summed signals, after division by said dividing means causing the contents of said register to be cycled at least twice per revolution of said rotor, said tachometer being a two channel pulse tachometer producing two sets of signals for each revolution of said rotor, the signals of said two sets being equal in number and being angularly offset from each other, and said summing means comprising at least one up/down counter having its inputs connected to the output of said tachometer and to said command signal source, and operative upon the summing of said tach and slip signals to divide the summed signals by a factor to provide a quotient of two.

Claim 5

A digital control circuit as defined in claim 2, wherein said tachometer produces on each of said channels 384 digital signals per revolution of said rotor, said tach and slip signals are applied to a divide-by-sixteen up/down counter, and the output of the last-named counter is applied to a divide-by-twelve up/down counter the output of which is connected to said decoder, and is cycled twice per revolution of said rotor.

Claim 6

A digital control circuit as defined in claim 2, including means for detecting which of said two sets of signals from said tachometer leads the other set, thereby to determine the direction of rotation of said rotor.

Claim 7

A digital control circuit for supplying gating signals to the inverter of a current controlling thyristor circuit for the stator winding of a three phase induction motor, comprising a tachometer coupled to the rotor of said motor and operative to produce digital tach signals representing the frequency of said rotor in revolutions per minute, a command signal source producing digital slip signals representing the difference between the rotor frequency and the desired frequency of the stator winding of said motor, means for algebraically summing said tach and slip signals, and having a multi-bit binary output register the contents of which is cycled at least once per revolution of said rotor, and decoder means interposed between said output register and said inverter and operative to convert the binary contents of said register into said gating signals for said inverter, means for regulating current flow to said thyristor circuit, said regulating means including a pair of balanced choke coils connected in two of the lines supplying current to said thyristor circuit, and a Hall generator positioned adjacent said coils to detect current flow therein and operative to develop a feedback signal for said regulating means.

Claim 8

A digital control circuit for supplying gating signals to the inverter of a current controlling thyristor circuit for the stator winding of a three phase induction motor, comprising a tachometer coupled to the rotor of said motor and operative to produce digital tach signals representing the frequency of said rotor in revolutions per minute, a command signal source producing digital slip signals representing the difference between the rotor frequency and the desired frequency of the stator winding of said motor, means for algebraically summing said tach and slip signals, and having a multi-bit binary output register the contents of which is cycled at least once per revolution of said rotor, and decoder means interposed between said output register and said inverter and operative to convert the binary contents of said register into said gating signals for said inverter, means for regulating current flow to said thyristor circuit, said regulating means including a pair of balanced choke coils connected in two of the lines supplying current to said thyristor circuit, and a Hall generator positioned adjacent said coils to detect current flow therein and operative to develop a feedback signal for said regulating means.

Claim 11

A method as defined in claim 6, wherein the contents of said register is cycled twice per revolution of said rotor.

Claim 12

A method as defined in claim 7, wherein said sum of said first and second series of digital signals is divided twice in succession.

Claim 15

For an induction motor control circuit of the type in which the direction of speed of the motor rotor is controlled by selective gating of thyristors in the stator winding leads, and in response to changes in a command signal representing the difference between actual and desired rotor speed and direction, the method of producing digital control of the gating signals for said thyristors, including sensing the speed and direction of rotation of said rotor and producing a first series of digital signals representative of actual speed and direction of rotation of the rotor, producing from said command signal for each rotation of said rotor a second series of digital signals representative of the desired slip between the rotor and the stator field winding, and algebraically summing and dividing said first and second series of signals in a binary up/down counter having a multi-bit output register which is cycled a plurality of times per revolution of said rotor, and decoding the contents of said register to produce the gating signals for said thyristors.

Claim 16

For an induction motor control circuit of the type in which the direction of speed of the motor rotor is controlled by selective gating of thyristors in the stator winding leads, and in response to changes in a command signal representing the difference between actual and desired rotor speed and direction, the method of producing digital control of the gating signals for said thyristors, including sensing the speed and direction of rotation of said rotor and producing a first series of digital signals representative of actual speed and direction of rotation of the rotor, producing from said command signal for each rotation of said rotor a second series of digital signals representative of the desired slip between the rotor and the stator field winding, and algebraically summing and dividing said first and second series of signals in a binary up/down counter having a multi-bit output register which is cycled a plurality of times per revolution of said rotor, and decoding the contents of said register to produce the gating signals for said thyristors.

Claim 17

A method as defined in claim 10 including regulating the current flow to said thyristors to hold it proportional to the absolute value of said command signal.

Claim 18

For an induction motor control circuit of the type in which the direction and speed of the motor rotor is controlled by selective gating of thyristors in the stator winding leads, and in response to changes in a command signal representing the difference between actual and desired rotor speed and direction, the method of producing digital control of the gating signals for said thyristors, including sensing the speed and direction of rotation of said rotor and producing a first series of digital signals representative of actual speed of the rotor, producing from said command signal for each rotation of said rotor a second series of digital signals representative of the desired slip between the rotor and the stator field winding, algebraically summing and dividing said first and second series of signals in a binary up/down counter having a multi-bit output register which is cycled a plurality of times per revolution of said rotor, decoding the contents of said register to produce the gating signals for said thyristors, regulating the current flow to said thyristors to hold it proportional to the absolute value of said command signal, supplying current to said thyristors through a pair of balanced choke coils, and sensing the current flow through said coils and producing a feed back signal for controlling current flow to said choke coils.

Claim 19

For an induction motor control circuit of the type in which the direction and speed of the motor rotor is controlled by selective gating of thyristors in the stator winding leads, and in response to changes in a command signal representing the difference between actual and desired rotor speed and direction, the method of producing digital control of the gating signals for said thyristors, including sensing the speed and direction of rotation of said rotor and producing a first series of digital signals representative of actual speed of the rotor, producing from said command signal for each rotation of said rotor a second series of digital signals representative of the desired slip between the rotor and the stator field winding, algebraically summing and dividing said first and second series of signals in a binary up/down counter having a multi-bit output register which is cycled a plurality of times per revolution of said rotor, decoding the contents of said register to produce the gating signals for said thyristors, regulating the current flow to said thyristors to hold it proportional to the absolute value of said command signal, supplying current to said thyristors through a pair of balanced choke coils, and sensing the current flow through said coils and producing a feed back signal for controlling current flow to said choke coils.