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. 12, 1995
Filed:
Mar. 21, 1994
Donald R Janke, Milwaukee, WI (US);
James A Rodrian, Grafton, WI (US);
Square D Company, Palatine, IL (US);
Abstract
A line isolation monitor (LIM) indicates the maximum hazard current of an ungrounded polyphase power distribution system. The LIM is microcontroller based and continuously monitors a fault impedance for the distribution system. The fault impedance is determined by the LIM by injecting a continuous sine wave measurement current into a ground terminal to generate a measurement voltage across the fault impedance. Using the measurement voltage and current, the LIM calculates the fault impedance and, using this impedance, calculates the hazard current based on the maximum line to ground voltage of the ungrounded system. The LIM has means for self-calibration and self-testing while on-line and during a power-up sequence to verify that components in the measurement circuitry are within specified tolerances.