Fail-safe and fault-tolerant alternating current output circuit
US4926281A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 27, 1989 |
| Grant date | May 15, 1990 |
| Priority date | — |
| Expiry date | Feb 27, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H3/044
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A protected digital output circuit coupled to a programmable controller, for controlling a load supplied through alternating-current (ac) power lines, including a fuse and a single controlled output switch connected in series with the load, and a pair of series-connected crowbar switches connected together across the ac power lines. The crowbar switches can be commanded closed together in the event that the output switch is commanded open but fails to open, thereby shorting the ac power lines and disconnecting the load by blowing the fuse. In routine diagnostic testing, the crowbar switches can be commanded closed separately to check their operation without blowing the fuse. A current detection circuit is used to check for current in the closed crowbar switch. A current sensor is also used to detect current through the output switch, when commanded closed for switching the load on, or for diagnostic turn-on testing when the load is disconnected.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.