Electric actuator for a control valve
US4794309A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Nov 20, 1987 |
| Grant date | Dec 27, 1988 |
| Priority date | — |
| Expiry date | Nov 20, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05D17/02
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
An electric actuator for a control valve for fluids utilizes an induction motor to control the degree of opening of the valve and is provided with a control system which determines the deviation of the actual opening degree from the demand opening degree, generates a valve opening or closing speed command in accordance with the opening deviation, determines the deviation of the actual opening or closing speed from the command speed, generates a torque command in accordance with the speed deviation, and computes by means of the vector computing method the primary current to be supplied to the induction motor to enable the induction motor to output the required torque. When the valve is in the fully closed position, the control system stops the supply current to the induction motor and activates a braking device which locks the motor shaft to prevent reverse rotation of the motor shaft due to load reaction. The actuator has a means for re-starting the induction motor to optimize the thrust load should any change occur in the level of thrust acting on the valve rod. The actuator is furthermore provided with a means for diagnosing whether any abnormal performance is due to wear and/or …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.