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. 11, 2000
Filed:
Sep. 03, 1997
Applicant:
Inventor:
Friedhelm Heuer, Oldendorf, DE;
Assignee:
K. A. Schmersal GmbH & Co., Wuppertal, DE;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G08B / ;
U.S. Cl.
CPC ...
340648 ; 318671 ; 318768 ; 318780 ;
Abstract
A method and apparatus for monitoring a three-phase electric motor which has been disconnected from the electrical mains and is running down, one phase of the voltage generated by the motor being checked respectively in each of two channels for zero crossings and, if a zero crossing occurs, a signal being produced which, after DC-decoupling, is used to control the operation of a safety device. The safety devices are mutually interlocked and control signals therefor are produced only when the period between zero-crossings detected in both channels indicates that the motor output shaft has ceased rotation.