Load current monitoring device for detecting predetermined degree of change in load impedance
US4539562A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 30, 1982 |
| Grant date | Sep 3, 1985 |
| Priority date | — |
| Expiry date | Dec 30, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H7/226
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Current provided to a generally constant impedance load is monitored to detect a predetermined load current decrease not resulting from normal load voltage fluctuations, such decrease indicating an abnormal increase in load impedance. A latching alarm is actuated when the predetermined load current decrease is detected. The degree of load current decrease tolerable without activating the alarm is determined by a user-adjustable percentage-of-change sensitivity control. A logic gate blocks alarm functions when the load current decreases to an abnormally low level. The disclosed device can be used to monitor the status of a line voltage energized heat trace cable constituted by a plurality of parallel-connected resistance wire heating elements. Multiple monitoring devices can be used in conjunction with a master alarm which can be reset without resetting the particular monitoring device alarm that triggered the master alarm.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.