Digital sine wave generator and motor controller
AssigneeReliance Electric Company
InventorRobert J. Pond
Life of this patent
Estimating the term…
Abstract
Digital sinusoidal waves are generated using a method based on an error measuring algorithm used to generate a synthesized circle. X and Y waves are generated step-wise to follow the contour of a reference circle in the x-y plane by computing the mean square error at each step and using the error value to calculate the next values of X and Y. The digital sine waves are converted to three-phase, pulse width modulated signals. Direct current power is inverted to three phase power to operate a motor under the control of the PWM signals. The controller permits control of voltage, voltage-frequency ratio, boost voltage, and acceleration-deceleration.
Claims21
A digital sine wave generator for an inverter, comprising, in combination:
- means to define a reference circle having a radius V;
- means to increment a value of one of digital signals X and Y as an independent variable on an x-y coordinate system in combination with the other of signals Y and X as a dependent variable signal to form at least part of a synthesized circle;
- means to determine the algebraic sign of an error signal between a point (X.sub.n, Y.sub.n) on the synthesized circle and the reference circle;
- feedback means to increment the dependent variable responsive to the algebraic sign of the error signal on each previous increment;
- means to obtain the sequential digital values of at least one of the X and Y signals to generate a digitized sine wave;
- and
- means to control an inverter responsive to the sine wave.
A motor and controller, comprising:
- a motor;
- means to generate a digital wave signal comprising a series of values of one of coordinates X.sub.n and Y.sub.n of a synthesized digital circle having coordinates (X.sub.n, Y.sub.n), said synthesized circle being generated by measuring error E.sub.n between a point (X.sub.n, Y.sub.n) of the synthesized circle and a reference circle having a given radius V and using a sign of the error E.sub.n to select a subsequent point (X.sub.n+1, Y.sub.n+1) so as to minimize the error E.sub.n+1 of the subsequent point;
- and
- means to control power to the motor responsive to the digital wave signal.
An inverter control, comprising, in combination;
- means to increment values X and Y on an x-y coordinate system to approximate part of the circumference of a circle and to obtain at each increment the digital values of the x and y components thereof;
- means to compute at each increment an algebraic sign of an error between the point on the x-y coordinate system and a reference circle having radius V;
- feedback means using the sign of the error to minimize said error for a subsequent increment;
- and
- means to obtain at each increment at least one of the values X and Y to control at least one phase of an inverter.
A method of controlling an inverter, comprising the steps of:
- defining a reference circle having a radius V;
- calculating a sign of an error between a point (X, Y) on a synthesized circle and the reference circle;
- incrementing a independent variable chosen from one of X and Y;
- incrementing a dependent variable chosen from the other of X and Y responsive to the sign of the error calculated;
- and
- controlling current in an inverter with a signal comprising at least one of the values X and Y.
Dependencies are inferred from the claim text.