Efficiency control system for an induction motor

Claim 2

An efficiency control system for an induction motor system having an induction motor, a power transducer connected to said induction motor, and a detector adapted for separate real-time detection of a voltage signal, a current signal, and a frequency signal of electric power supplied from said power transducer to said induction motor so that an output of said induction motor during operation may be controlled by these signals in response to a load torque, said efficiency control system comprising: an actual slip signal processor for calculating an actual slip of said induction motor during operation on the basis of the voltage signal, current signal, and frequency signal of the electric power supplied from said power transducer to said induction motor and a motor constant; an optimum slip signal processor for calculating an optimum slip desired to obtain the maximum efficiency of said induction motor; and a voltage command signal transmitter for generating and transmitting a voltage command signal to said power transducer, wherein said voltage command signal includes a scalar value calculated by said voltage command signal transmitter, wherein said power transducer adjusts the electrical power supplied to said induction motor in response to said scalar value of said voltage command signal such that the slip of said induction motor is maintained at the optimum value in order to operate said induction motor at the maximum efficiency for a given load torque.

Claim 3

The efficiency control system as defined in claim 1, wherein said actual slip signal processor calculates the actual slip S(n) at a particular point in time n, of said induction motor using the equation: ##EQU18## where V 1 (n) represents the voltage level of the detected voltage signal at time n, I 1 (n) represents the current level of the detected current signal at time n, R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, X 1 (n) represents a primary leakage reactance of said stator at time n, and X m (n) represents a mutual reactance of said stator and rotor at time n, wherein said optimum slip signal processor calculates the optimum slip S*(n+1) at a particular point in time n+1 occurring after time n, using the equation: ##EQU19## where X m (n+1) represents a mutual reactance of said stator and rotor at time n+1, and wherein said voltage command signal transmitter calculates the scalar value |V 1 |(n+1) for a particular point in time n+1 occurring after a present time n, using the equation: ##EQU20## where S(n) represents the actual slip calculated by said actual slip signal processor at time n, S*(n+1) represents the optimum slip calculated by said optimum slip signal processor for time n+1, X m * (n) represents the optimum mutual reactance of said stator and rotor at time n, |V 1 |(n) represents a scalar value of the voltage level of the detected voltage signal at time n, X 1 * (n) represents the optimum primary leakage reactance of said stator at time n, f(n) represents the frequency of the detected frequency signal at time n, and f* (n+1) represents an optimum frequency associated with the optimum slip S* (n+1) for the time n+1.

Claim 4

The efficiency control system as defined in claim 1, wherein said actual slip signal processor calculates the actual slip S(n) at a particular point in time n, of said induction motor using the equation: ##EQU21## where V 1 (n) represents the voltage level of the detected voltage signal at time n, I 1 (n) represents the current level of the detected current signal at time n, R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, X 1 (n) represents a primary leakage reactance of said stator at time n, and X m (n) represents a mutual reactance of said stator and rotor at time n.

Claim 5

The efficiency control system as defined in claim 1, wherein said optimum slip signal processor calculates the optimum slip S* (n+1) at a particular point in time n+1 occurring after time n, using the equation: ##EQU22## where R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, and X m (n+1) represents a mutual reactance of said stator and rotor at time n+1.

Claim 6

The efficiency control system as defined in claim 1, wherein said voltage command signal transmitter calculates the scalar value |V 1 |(n+1) for a particular point in time n+1 occurring after a present time n, using the equation: ##EQU23## where R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, S(n) represents the actual slip calculated by said actual slip signal processor at time n, S* (n+1) represents the optimum slip calculated by said optimum slip signal processor for time n+1, X m (n) represents a mutual reactance of said stator and rotor at time n, X m * (n) represents the optimum mutual reactance of said stator and rotor at time n, |V 1 |(n) represents a scalar value of the voltage level of the detected voltage signal at time n, X 1 (n) represents a primary leakage reactance of said stator at time n, X 1 * (n) represents the optimum primary leakage reactance of said stator at time n, f(n) represents the frequency of the detected frequency signal at time n, and f* (n+1) represents an optimum frequency associated with the optimum slip S* (n+1) for the time n+1.

Claim 9

The method as defined in claim 6, wherein the actual slip S(n) at a particular point in time n, of said induction motor is calculated using the equation: ##EQU24## where V 1 (n) represents the voltage level of the detected voltage signal at time n, I 1 (n) represents the current level of the detected current signal at time n, R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, X 1 (n) represents a primary leakage reactance of said stator at time n, and X m (n) represents a mutual reactance of said stator and rotor at time n, wherein the optimum slip S* (n+1) at a particular point in time n+1 occurring after time n, is calculated using the equation: ##EQU25## where X m (n+1) represents a mutual reactance of said stator and rotor at time n+1, and wherein the scalar value |V 1 |(n+1) for a particular point in time n+1 occurring after a present time n, is calculated using the equation: ##EQU26## where S(n) represents the actual slip at time n, S* (n+1) represents the optimum slip for time n+1, X m * (n) represents the optimum mutual reactance of said stator and rotor at time n, |V 1 |(n) represents a scalar value of the voltage level of the detected voltage signal at time n, X 1 * (n) represents the optimum primary leakage reactance of said stator at time n, f(n) represents the frequency of the detected frequency signal at time n, and f*(n+1) represents an optimum frequency associated with the optimum slip S*(n+1) for the time n+1.

Claim 10

The method as defined in claim 6, wherein the actual slip S(n) at a particular point in time n, of said induction motor is calculated using the equation: ##EQU27## where V 1 (n) represents the voltage level of the detected voltage signal at time n, I 1 (n) represents the current level of the detected current signal at time n, R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, X 1 (n) represents a primary leakage reactance of said stator at time n, and X m (n) represents a mutual reactance of said stator and rotor at time n.

Claim 11

The method as defined in claim 6, wherein the optimum slip S*(n+1) at a particular point in time n+1 occurring after time n, is calculated using the equation: ##EQU28## where R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, and X m (n+1) represents a mutual reactance of said stator and rotor at time n+1.

Claim 12

The method as defined in claim 6, wherein the scalar value |V 1 |(n+1) for a particular point in time n+1 occurring after a present time n, is calculated using the equation: ##EQU29## where R 1 represents a motor constant, which is the resistance of the stator of said induction motor, R 21 represents a motor constant, which is the resistance of the rotor of said induction motor, S(n) represents the actual slip at time n, S*(n+1) represents the optimum slip for time n+1, X m (n) represents a mutual reactance of said stator and rotor at time n, X m *(n) represents the optimum mutual reactance of said stator and rotor at time n, |V 1 |(n) represents a scalar value of the voltage level of the detected voltage signal at time n, X 1 (n) represents a primary leakage reactance of said stator at time n, X 1 *(n) represents the optimum primary leakage reactance of said stator at time n, f(n) represents the frequency of the detected frequency signal at time n, and f*(n+1) represents an optimum frequency associated with the optimum slip S*(n+1) for the time n+1.