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:
Jun. 09, 2009
Filed:
Jan. 25, 2007
Koichiro Nagata, Mito, JP;
Toshiaki Okuyama, Tokai-mura, JP;
Kouki Yamamoto, Hitachinaka, JP;
Hiroyuki Tomita, Funabashi, JP;
Koichiro Nagata, Mito, JP;
Toshiaki Okuyama, Tokai-mura, JP;
Kouki Yamamoto, Hitachinaka, JP;
Hiroyuki Tomita, Funabashi, JP;
Hitachi Industrial Equipment Systems Co., Ltd., Tokyo, JP;
Abstract
An object of the present invention is to provide a driver for an induction motor which performs an operation at an acceleration suitable for the magnitude of a load and is excellent in efficiency, without an acceleration failure. The driver for an induction motor includes a slip frequency estimate value arithmetic operation sectionfor arithmetically operating a slip frequency ωs^ of an induction motorand a maximum torque generation slip arithmetic operation sectionfor arithmetically operating a slip frequency ωsmax at which a maximum torque is generated. When the slip frequency ωs^ exceeds a predetermined value ωsmaxTH (=0.9 ωsmax, etc.) corresponding to the slip frequency ωsmax at which the maximum torque is generated, a speed change rate arithmetic operation sectionand a speed change rate correcting sectionreduce a rate of increase in a speed command ωr*. In addition, when the slip frequency approaches the maximum torque generation slip frequency too closely, the load concerned is judged to be overloaded, and an alarm is generated.