Variable threshold starting circuit for induction motor
US4047082A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 4, 1975 |
| Grant date | Sep 6, 1977 |
| Priority date | — |
| Expiry date | Sep 4, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P1/42
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A circuit for the automatic starting of an induction motor of the type having a sensing means for producing a signal proportional to the main winding current and control means for allowing current flow through a start winding only when energized by a start winding control signal. The starting circuit includes means for continuously producing a variable threshold level which is proportional to a condition capable of affecting the current level in the main winding and which defines an adjustable threshold switching level. A comparison means continuously compares the adjustable threshold switching level to the signal proportional to the main winding current and, whenever the latter signal exceeds the former, the comparison means generates a start winding control signal which activates the start winding control means thereby establishing current flow through the start winding. When the main winding current decreases to a sufficient extent, the comparison means is characterized by the absence of a start winding control signal whereby the start winding control means will block the flow of current through the start winding.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.