Control system for controlling revolution speed of electric motor

Claim 2

A motor speed control system comprising: first means for generating a torque current for driving an electric motor at a revolution speed corresponding to the magnitude of said torque current; second means for producing a motor speed indicative signal representative of a revolution speed of said electric motor; third means, provided equivalent characteristics to that of said electric motor and connected to said first means for receiving said torque current, for generating a first reference speed indicative signal representative of a revolution speed of said electric motor corresponding to the input torque current; fourth means, receiving said first reference signal, for deriving a difference between said first reference signal value and a desired motor speed representative value for controlling said first means for reducing the difference between said first reference signal value and said desired motor speed representative value to zero; and fifth means interposed between said first means and one of said electric motor and said third means, for limiting said torque current to be supplied to at least one of said electric motor and said third means within a predetermined range.

Claim 3

A motor speed control system as set forth in claim 1, wherein said fifth means comprises a first limiter interposed between said first means and said third means for limiting said torque current to be supplied to said third means within a first given range and a second limiter interposed between said first means and said electric motor for limiting torque current to be supplied to said electric motor within a second given range.

Claim 4

A motor speed control system as set forth in claim 2, wherein said second limiter is provided between said first limiter and said electric motor.

Claim 5

A motor speed control system as set forth in claim 1, which further comprises: a sixth means receiving said motor speed indicative signal and said first reference speed indicative signal for deriving a difference between said motor speed indicative signal value and said first reference speed indicative signal value to produce a speed error signal; and seventh means, responsive to said speed error signal, for deriving a compensation signal based on said speed error signal for modifying said torque current for compensating said speed error between said motor speed indicative signal value and said sum value.

Claim 6

A motor speed control system as set forth in claim 4, which further comprises: eighth means for generating a known frequency of a frequency signal which is to be added to said torque current for driving said electric motor with a modified torque current; ninth means, provided equivalent characteristics to that of said electric motor and connected to said eighth means for receiving said frequency signal, for generating a second reference speed indicative signal representative of a revolution speed of said electric motor corresponding to the input frequency signal; said sixth means receiving said motor speed indicative signal, said first reference speed indicative signal and said second reference speed indicative signal, for deriving a difference between said motor speed indicative signal value and a sum value of said first and second reference speed indicative signal values to produce a speed error signal; tenth means, receiving said speed error signal and said frequency signal, for deriving an inertia representative data representative of an assumed inertia moment on said electric motor, and correcting a transfer characteristics of at least one of circuit components in such a manner that the inertia dependent factor in said fourth means becomes coincidence with that of said electric motor.

Claim 7

A motor speed control system comprising: first means for generating a basic torque current for driving an electric motor at a revolution speed corresponding to the magnitude of said torque current; second means for producing a motor speed indicative signal representative of a revolution speed of said electric motor; third means for generating a known frequency of a frequency signal which is to be added to said basic torque current for driving said electric motor with a modified torque current; fourth means, provided equivalent characteristics to that of said electric motor and connected to said first means for receiving said torque current, for generating a first reference speed indicative signal representative of a revolution speed of said electric motor corresponding to the input torque current; fifth means, provided equivalent characteristics to that of said electric motor and connected to said third means for receiving said frequency signal, for generating a second reference speed indicative signal representative of a revolution speed of said electric motor corresponding to the input frequency signal; sixth means, receiving said first reference signal, for deriving a difference between said first reference signal value and a desired motor speed representative value for controlling said first means for reducing the difference between said first reference signal value and said desired motor speed representative value to zero; seventh means receiving said motor speed indicative signal, said first reference speed indicative signal and said second reference speed indicative signal, for deriving a difference between said motor speed indicative signal value and a sum value of said first and second reference speed indicative signal values to produce a speed error signal; eighth means, responsive to said speed error signal, for deriving a compensation signal based on said speed error signal value for modifying said torque current for compensating said speed error between said motor speed indicative signal value and said sum value; and ninth means, receiving said speed error signal and said frequency signal, for deriving an inertia representative data representative of an assumed inertia moment on said electric motor, and correcting a transfer characteristics of at least one of circuit components in such a manner that an inertia dependent factor in said fourth means becomes coincident with that of said electric motor.

Claim 8

A motor speed control system comprising: first means for generating a basic torque current for driving an electric motor at a revolution speed corresponding to the magnitude of said torque current; second means for producing a motor speed indicative signal representative of a revolution speed of said electric motor; third means for generating a known frequency of a frequency signal which is to be added to said basic torque current for driving said electric motor with a modified torque current; fourth means, provided equivalent characteristics to that of said electric motor and connected to said first means for receiving said torque current, for generating a first reference speed indicative signal representative of a revolution speed of said electric motor corresponding to the input torque current; fifth means, provided equivalent characteristics to that of said electric motor and connected to said third means for receiving said frequency signal, for generating a second reference speed indicative signal representative of a revolution speed of said electric motor corresponding to the input frequency signal; sixth means, receiving said first reference signal, for deriving a difference between said first reference signal value and a desired motor speed representative value for controlling said first means for reducing the difference between said first reference signal value and said desired motor speed representative value to zero; seventh means receiving said motor speed indicative signal, said first reference speed indicative signal and said second reference speed indicative signal, for deriving a difference between said motor speed indicative signal value and a sum value of said first and second reference speed indicative signal values to produce a speed error signal; eighth means, responsive to said speed error signal, for deriving a compensation signal based on said speed error signal value for modifying said torque current for compensating said speed error between said motor speed indicative signal value and said sum value; and ninth means, receiving said speed error signal and said frequency signal, for deriving an inertia representative data representative of an assumed inertia moment on said electric motor, and correcting a transfer characteristics of at least one of circuit components in such a manner that an inertia dependent factor in said fourth means becomes coincident with that of said electric motor.

Claim 9

A motor speed control system as set forth in claim 6, wherein said ninth means further modifies transfer characteristics of at least one of said circuit components for maintaining a transfer function of an overall motor speed controlling loop constant.

Claim 10

A motor speed control system as set forth in claim 6, wherein said third means is so designed as to produce said frequency signal which has a signal value variation characteristics to have an average value zero.

Claim 11

A motor speed control system as set forth in claim 6, wherein said third means is so designed as to produce said frequency signal which has a signal value variation characteristics, in which an integrated value becomes zero.

Claim 12

A motor speed control system as set forth in claim 6, wherein said fourth and fifth means have first and second transfer elements having variable transfer characteristics, said first and second transfer elements of said fourth and fifth means being adjusted so that the transfer characteristics reduce said speed error signal value to zero on the basis of said inertia representative data of said ninth means.

Claim 13

A motor speed control system as set forth in claim 10, wherein said sixth means includes a third transfer element which can vary transfer characteristics depending on said inertia representative data, said transfer characteristics of said third transfer element being adjusted so as to maintain a transfer function of an overall speed control loop constant.

Claim 14

A motor speed control system as set forth in claim 6, which further comprises a transfer element which can vary transfer characteristics depending upon said inertia representative data for adjusting the modified torque current to be supplied to said electric motor so as to compensate the difference of inertia factors in said electric motor and said fourth means.

Claim 15

A motor speed control system for an induction motor, comprising: said induction motor; a motor driving circuit for applying power to drive the motor, a sensor means associated with said induction motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.q =Io (constant); I1.sub.d =-(I.sub.T +I.sub.o '); and ωs=(R.sub.2 +Srm)/L.sub.2 ×I.sub.T /I.sub.o -Srm/M×{(I.sub.T +I.sub.o ')/I.sub.o } where I o is a set excitation current value; I T is a set torque current value; I o ' is a core loss current value; R 2 is a secondary resistance; S is a slip; rm is a core loss resistance; L 2 is a secondary inductance; and M is a relative inductance.

Claim 16

A motor speed control system for an induction motor, comprising: said induction motor; a motor driving circuit for applying power to drive the motor, a sensor means associated with said induction motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.q =Io (constant); I1.sub.d =-(I.sub.T +I.sub.o '); and ωs=(R.sub.2 +Srm)/L.sub.2 ×I.sub.T /I.sub.o -Srm/M×{(I.sub.T +I.sub.o ')/I.sub.o } where I o is a set excitation current value; I T is a set torque current value; I o ' is a core loss current value; R 2 is a secondary resistance; S is a slip; rm is a core loss resistance; L 2 is a secondary inductance; and M is a relative inductance.

Claim 17

A motor speed control system as set forth in claim 13, wherein said vector controlling means corrects said set torque current value I T based on a torque command T to establish the following equation: ##EQU15## where A=rmM 2 /ωL 2 ×(1/M-1/L 2 ), B=(1+rm 2 /ω 2 M 2 )×M 2 /L 2 ×I o

Claim 18

A motor speed control system for an induction motor, comprising: said induction motor; a motor driving circuit for applying power to drive the motor, a sensor means associated with said indication motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.d =-{(Rm.sup.2 +ω.sup.2 ML.sub.2)/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.T *-{ωMRm/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o * I1.sub.q ={ω.sup.2 M.sup.2 /(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o *+{(Rmω(M-L.sub.2)/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.T * ωs=(R.sub.2 /M)×(I.sub.T */I.sub.o *) where M is a relative inductance; L 2 is a secondary inductance; R 2 is a secondary resistance; ω is a power source angular frequency; I T * is torque current command; I o * is excitation current command; and Rm is core loss resistance.

Claim 19

A motor speed control system for an induction motor, comprising: said induction motor; a motor driving circuit for applying power to drive the motor, a sensor means associated with said indication motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.d =-{(Rm.sup.2 +ω.sup.2 ML.sub.2)/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.T *-{ωMRm/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o * I1.sub.q ={ω.sup.2 M.sup.2 /(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o *+{(Rmω(M-L.sub.2)/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.T * ωs=(R.sub.2 /M)×(I.sub.T */I.sub.o *) where M is a relative inductance; L 2 is a secondary inductance; R 2 is a secondary resistance; ω is a power source angular frequency; I T * is torque current command; I o * is excitation current command; and Rm is core loss resistance.

Claim 20

A motor speed control system for an induction motor, comprising: said induction motor; a motor driving circuit for applying power to drive the motor, a sensor means associated with said indication motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.d =-(L.sub.2 /M)×I.sub.T *-{ωMRm/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o * I1.sub.q =-{ω.sup.2 M.sup.2 /(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o * ωs=(R.sub.2 /M)×(I.sub.T */I.sub.o *) where M is a relative inductance; L 2 is a secondary inductance; R 2 is a secondary resistance; ω is a power source angular frequency; I T * is torque current command; I o * is excitation current command; and Rm is core loss resistance.

Claim 21

A motor speed control system for an induction motor, comprising: said induction motor; a motor driving circuit for applying power to drive the motor, a sensor means associated with said indication motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.d =-(L.sub.2 /M)×I.sub.T *-{ωMRm/(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o * I1.sub.q =-{ω.sup.2 M.sup.2 /(Rm.sup.2 +ω.sup.2 M.sup.2)}×I.sub.o * ωs=(R.sub.2 /M)×(I.sub.T */I.sub.o *) where M is a relative inductance; L 2 is a secondary inductance; R 2 is a secondary resistance; ω is a power source angular frequency; I T * is torque current command; I o * is excitation current command; and Rm is core loss resistance.

Claim 22

A motor speed control system for an induction motor, comprising: said induction motor; a motor driven circuit for applying power to drive the motor, a sensor means associated with said indication motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.d =-(L.sub.2 /M)×I.sub.T *-(ωMRm/(Rm.sup.2 +ω.sup.2 M.sup.2)×I.sub.o * I1.sub.q =I.sub.o *ωs=(R.sub.2 /M)×(I.sub.T */I.sub.o *) where M is a relative inductance; L 2 is a secondary inductance; R 2 is a secondary resistance; ω is a power source angular frequency; I T * is torque current command; I o * is excitation current command; and Rm is core loss resistance.

Claim 23

A motor speed control system for an induction motor, comprising: said induction motor; a motor driven circuit for applying power to drive the motor, a sensor means associated with said indication motor, for monitoring a revolution speed thereof and producing a motor speed indicative signal; and a vector controlling means for controlling a flux-axis primary current I1 q , a torque-axis primary current I1 d and slip frequency ωs to establish the following condition: I1.sub.d =-(L.sub.2 /M)×I.sub.T *-(ωMRm/(Rm.sup.2 +ω.sup.2 M.sup.2)×I.sub.o * I1.sub.q =I.sub.o *ωs=(R.sub.2 /M)×(I.sub.T */I.sub.o *) where M is a relative inductance; L 2 is a secondary inductance; R 2 is a secondary resistance; ω is a power source angular frequency; I T * is torque current command; I o * is excitation current command; and Rm is core loss resistance.