Electric motor protection switches
US4532488A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 23, 1984 |
| Grant date | Jul 30, 1985 |
| Priority date | — |
| Expiry date | Jan 23, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01H71/164
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An overload protection switch for an electric motor comprises a bimetallic switch-actuating element carrying a moving contact of the switch, a first terminal part having an extension which defines a mounting for the bimetal, and a second terminal part having an extension which mounts a fixed contact of the switch, the first and second terminal parts being received in a moulded plastics switch body portion. In contrast to prior art switches of this type where the terminal parts were manufactured of material having a low electrical resistance, the invention manufactures these parts of high resistance material selected such that under very high overload current levels the resistance heating in the terminal parts does not significantly determine the switching characteristics of the switch on account of the overwhelmingly predominant bimetallic heating, but towards the other end of the overload current scale the self-heating of the terminal parts significantly affects the switch operation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.