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:
May. 10, 1988
Filed:
Mar. 06, 1987
Shigemi Iwata, Inazawa, JP;
Abstract
In an elevator control system employing a variable-voltage and variable-frequency control, a control apparatus having limiter for limiting the maximum value of a slip frequency .omega..sub.s when the frequency .omega..sub.0 of current command values to be delivered to an inverter circuit for operating an induction motor is evaluated in accordance with a condition formula of .omega..sub.0 =.omega..sub.s +.omega..sub.4 (where .omega..sub.r denotes the angular rotational frequency of the induction motor), whereby an actual car speed can be limited to a safe low value even when the detected car speed is erroneous due to a malfunction of the car speed detection device. Also, the time period during which the generated slip frequency command signal exceeds a reference value is measured to determine the current frequency command signal for the induction motor.