The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 29, 1981
Filed:
Mar. 12, 1979
Michael R Cesarz, Mequon, WI (US);
Richard E Stobbe, Greenfield, WI (US);
Kearney & Trecker Corporation, West Allis, WI (US);
Abstract
A tachometer is coupled to the rotor of an A.C. motor and generates an output voltage proportional to the rotor's speed. A VELOCITY COMMAND voltage is generated having an amplitude which specifies a desired rotor speed. The tachometer voltage is subtracted from the VELOCITY COMMAND voltage to produce a VELOCITY ERROR voltage. The output of a D.C. power source is chopped at a fixed frequency and variable pulse width, the pulse width being proportional at any time to the amplitude of the VELOCITY ERROR voltage. The chopped D.C. voltage is filtered to provide a variable D.C. voltage having an amplitude which is proportional to the amplitude of the VELOCITY ERROR voltage. The variable D.C. voltage is applied to an inverter which changes it into an A.C. voltage. The A.C. voltage is applied to the stator windings of the motor to drive the rotor thereof. The frequency of the A.C. voltage is variable and is proportional, at rotor speeds above 150 RPM, to the amplitude of the velocity command voltage. At rotor speeds below 150 RPM, the frequency of the A.C. voltage is held fixed at approximately 28 Hz. The amplitude of the A.C. voltage is proportional to the VELOCITY ERROR voltage at all speeds. The frequency of the A.C. voltage is determined by an oscillator which drives a ring counter whose counting direction is controlled by a direction flip-flop. The state of the direction flip-flop is changed whenever the polarity of the VELOCITY ERROR voltage changes so that deceleration of the motor always occurs in a plugging mode.