Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1994-02-14
1995-09-05
Shoop, Jr., William M.
Electricity: motive power systems
Induction motor systems
Primary circuit control
318804, 318808, H02P 5408
Patent
active
054481503
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vector control unit for an induction motor connected with an inverter, the motor being not only electrically driven but also working in a regenerative condition.
2. Description of the Related Art
A slip frequency control method characterized by both excellent responsiveness and accuracy in control has been known as a variable speed control method for an induction motor. Particularly, a vector control method which can provide responsiveness equivalent to that of a D.C. motor, by controlling a primary current of the induction motor, dividing it into an excitation current and a torque current, and controlling a secondary magnetic flux and the torque current in such a way that their directions are constantly kept in a perpendicular relationship to each other, has been put into force. Recently, a speed sensor has been removed from the method (hereinafter referred to as a PG-less method) and the method has been improved through simplification and improving resistance against adverse environmental conditions.
A PG-less induction motor control unit usually comprises, as shown in FIG. 1, a converter unit which consists of a diode and a capacitor and which converts an electric current from an A.C. source to D.C., a voltage type PWM inverter 1 consisting of an inverter unit for generating A.C. voltage by modulating voltage commands of U-, V-, and W-phase output from a current controller to PWM signals by means of a switching element such as a thyristor or IGBT; electric current detectors 10.sub.1, 10.sub.2, 10.sub.3 for detecting electric currents which flow in U-, V-, and W-phases, respectively, of an induction motor 2; a voltage detector 11 for detecting voltages between two of the U-, V-, and W-phases; a vector control unit 3 for performing vector control; and a command generator 19.
FIG. 2 is a block diagram showing the vector control unit 3 shown in FIG. 1.
The vector control unit 3 is composed of a coefficient meter 4; integrator 5; a function generator 6 which inputs phase .theta..psi.* and generates exp (j.theta..psi.*), i.e., cos .theta..psi.*+jsin .theta..psi.*; a two-phase/three-phase converter 7 which converts a vector having components in the direction of a magnetic flux (hereinafter referred to as a "d axis") and in the direction perpendicular thereto (hereinafter referred to as a "q axis") into a vector having components in the directions of the U-, V-, and W-phases which have phase differences of 120.degree. from one another; a vector operation unit 8 for performing the operation of a vector of r=.alpha.+j.beta. which represents a d-axis component .alpha. and a q-axis component .beta., that is, an amplitude .vertline.r.vertline.=(.alpha..sup.2 +.beta..sup.2).sup.1/2 and a phase tan.sup.-1 (.beta./.alpha.); a vector rotator 9 which inputs vector r and exp (j.theta..psi.*) and arranges its phase to .theta..psi.*+tan.sup.-1 (.beta./.alpha.); a magnetic flux operation unit 12 for detecting a magnetic flux and a torque current by using a primary voltage vector v.sub.l obtained from a voltage detector 11 and a primary current vector i.sub.1 obtained from the current detectors 10.sub.1, 10.sub.2, 10.sub.3 ; a velocity presuming unit 13 for presuming an electrical angular velocity of a rotor by using a torque current detection value I.tau. obtained by the magnetic flux operation unit 12 and a torque current command I.tau.*; a magnetic flux command generator 14 which performs field-weakening control based on the magnitude of the electrical angular velocity of the rotor; subtracters 15.sub.1, 15.sub.2 ; a velocity controller 16 for eliminating the error between an angular velocity command .omega.r* from a command generator 19 and a presumed angular velocity .omega.r to perform PI control; a magnetic flux controller 17 for eliminating the magnetic flux error .DELTA..psi..sub.2 between a magnetic flux command .psi..sub.2 * and a detected magnetic flux .psi..sub.2 to perform PI control; electric current controllers 18.sub.1,
REFERENCES:
patent: 4418308 (1983-11-01), Bose
patent: 4600874 (1986-07-01), Tupper et al.
patent: 5168204 (1992-12-01), Schauder
patent: 5231339 (1993-07-01), Kishimoto et al.
Otani Tsugutoshi
Yamamoto Yo-ichi
Cabeca John W.
Kabushiki Kaisha Yaskawa Denki
Shoop Jr. William M.
LandOfFree
Vector control unit for an induction motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vector control unit for an induction motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vector control unit for an induction motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-474512