Over-load and light-load protection for electric machinery
US4541029A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 3, 1983 |
| Grant date | Sep 10, 1985 |
| Priority date | — |
| Expiry date | Oct 3, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H7/093
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An apparatus for protecting machinery driven by electric motors from operating during over-load and light-load conditions, comprising: a current transformer operatively associated with an electrical supply line for the induction motor; a current-voltage transforming circuit for generating a control signal having a magnitude proportional to current flowing in the supply line; an upper limitation magnitude comparator for generating an over-load signal output whenever the magnitude of the control signal exceeds a predetermined upper safety value; a lower limitation magnitude comparator for generating a light-load signal output whenever the magnitude of the control signal is less than a predetermined lower safety level; an inhibitable protection timer for producing a fault persistence output signal whenever one of the over-load and light-load signal outputs is generated for a period of time longer than a predetermined protection time; a steady state timer for inhibiting an enable output signal for a predetermined period of time after start-up and during shut-down of the electric motor; a start-up/shut-down comparator for producing an output signal for enabling operation of the protecti…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.