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:
Apr. 16, 1991
Filed:
Dec. 26, 1989
Peter J Unsworth, Lewes, GB;
John C Merrison, Wauwatosa, WI (US);
Timothy M Rowan, Wauwatosa, WI (US);
Allen-Bradley Company, Inc., Milwaukee, WI (US);
Abstract
A three-phase motor is operated by a controller having sets of thyristors which trigger electricity from each phase of a supply to the motor. The controller measures the interval .phi. between the voltage and the current when one phase of the motor makes a zero crossing and measures the interval .gamma. when the thyristors are non-conductive during a half-cycle of the voltage for one phase. A control angle .theta. is calculated according to the equation .theta.=.phi.+K.gamma., where K is a positive number. The control angle .theta. is compared to a reference value to derive an error value. The times at which the thyristors are triggered is controlled in response to the error value. To start the motor, the reference value is gradually decreased to trigger the thyristors progressively earlier during each half cycle of the supply voltage. To stop the motor, the reference value is gradually increased to trigger the thyristors progressively later during each half cycle of the supply voltage.