Patent Application
20250052337
This invention relates to methods and systems for operating actuators such as those used to operate valves, dampers, or the like.
Actuator operated valves are found in many industries. A complex installation, such as found in oil and gas facilities, may include many such actuators. These are often controlled remotely from a limited number of locations in the installation to open or close on command. In some known systems, control of actuators has been achieved by modifying the three-phase electric power supply used to power the motors operating the actuators. For example, the A Range actuators of Rotork plc (https://www.rotork.com/uploads/documents-versions/2875/1/pub003-001-00_0401.pdf) are operated by changing the phase sequence (also known as “phase rotation”) of the three-phase supply. The operator will direct a three-phase supply to a given actuator with a given phase sequence. The actuator will have been manually configured when installed or set up so that this will result in the motor driving in a given direction. The operator can reverse this direction by reversing two of the three phases which immediately leads to the motor operating in the reverse direction.
A more advanced type of actuator can have an electronic control system included in the actuator. However, these systems typically require the presence of a separate control circuit in addition to the three-phase power supply. An example of this is the AWT SynchroPAK range of Rotork plc (https://www.rotork.com/uploads/documents-versions/21705/1/pub005-002-00_0715.pdf). This product provides a control system between the three-phase supply and the motor. The control system has a separate control circuit input that is used to provide inputs to the control system to control operation of the actuator. The control system is configured so that the motor drive direction is determined for opening or closing the valve, and the control system ensures that the phase sequence applied to the motor is correct for that direction, irrespective of the phase sequence delivered to the actuator. Therefore, even if the phase sequence supplied to the actuator changes during an open or close operation, or remains constant over all operations, the control system will ensure that the motor will operate in the desired direction. Actuators such as these are not compatible with control via the three-phase supply.
This invention aims to provide an actuator with an electronic control system that can be operated in a manner that is reverse compatible with three-phase control systems and, more broadly, allows the power supply for the motor to be used to control the direction of the motor.
One aspect of this invention comprises a method for operating an actuator for a flow control valve or the like, wherein the actuator comprises:
Another aspect of the invention comprises an actuator for a flow control valve or the like, comprising:
Signals to start the electric motor and provide the direction of drive can be provided over the electric power supply without the need for a separate control circuit with its associated cabling. Therefore, controlling the characteristic feature of the power supply can be the sole way to control the direction of operation of the motor.
The electric power supply can be a three-phase supply. The electric motor can be a three-phase motor. In this case, the characteristic feature is the sequence of phases in the three-phase supply. The connector can be configured such that changing the phase sequence of the three-phase supply reverses the direction of drive of the electric motor. Other electric power supplies and electric motors can be used, for example, single-phase supply or DC. In these cases, the characteristic feature can be a signal applied to the electric power supply, such as a modulation or other change in the electric power supply that can be detected at the actuator. The characteristic can be related to the voltage, current, or phase depending on the specific nature of the electric power supply used.
The term “connector” includes mechanical (electromechanical) or electronic connections, or electrical/electronic motor controllers, depending on the nature of the particular electric motor, electric power supply, and control system used.
The predetermined set of operating conditions can include conditions linked to the intended direction of operation. For example, the actuator can further comprise a position sensor arranged to output a signal indicative of the position of the output shaft. In this case, the control system can be configured to determine if the position of the output shaft is at or below a predetermined limit for movement in a predetermined direction and inhibit operation of the connector if the intended direction of drive of the electric motor would move the output shaft in the predetermined direction past the predetermined limit position. After the connector has been operated to connect the electric power supply to the motor to cause the electric motor to move in a predetermined direction, the control system can be configured to operate the connector to disconnect the electric power supply from the electric motor when the position sensor outputs a signal indicating that the output shaft has reached the predetermined limit for movement in the predetermined direction. This can help prevent damage to the actuator or valve from continuing to operate the electric motor when the valve has reached a fully open or fully closed position, for example, and may be against a physical stop or limit.
The actuator can further comprise a toque sensor arranged to measure torque at an output of the actuator, e.g. an output shaft. In this case, the control system can be configured to determine if the torque is at a predetermined limit for movement in a predetermined direction and inhibit operation of the connector if the intended direction of drive of the electric motor is the predetermined direction and would result in a torque exceeding the predetermined limit. After the connector has been operated to connect the electric power supply to the electric motor to cause the motor to move in a predetermined direction, the control system can be configured to operate the connector to disconnect the electric power supply from the electric motor when the torque sensor outputs a signal indicating that the torque has reached a predetermined limit for movement in the predetermined direction. This can help prevent damage to the actuator or valve from continuing to operate the electric motor when the valve has reached a fully open or fully closed position, for example, and is against a physical stop or limit or is otherwise stopped from moving further due to jamming or the like.
The predetermined set of operating conditions for the electric motor can also include conditions that are independent of the intended direction of operation. These include: the temperature of the motor must not exceed a predetermined level; the detection of a change in the electric power supply beyond a predetermined level; the detection of an error in a sensor; and the detection of a failure in the control system.
The control system can be configured to generate a position indication signal indicative of the position of a valve attached to the output shaft and generate a display of the position to the outside of the actuator using the position indication signal.
Another aspect of the invention comprises a system, comprising a series of actuators and a control station, wherein each of the actuators is connected to the control station by means of the electric power supply, and the control station includes a central control system for separately selecting the characteristic feature in the electric power supply of each actuator. The electric power supply is the only contact between the control station and the control system in each actuator.
Other aspects of the invention will be apparent from the description.
In the actuators of
An actuator according to the invention has the same basic structure as that shown in
The switching section 134 includes two configurable switches C1, C2. In a first configuration, switch C1 is open and switch C2 is closed and the phases of the three-phase supply are connected to the motor 112 in the same sequence as in the supply. In a second configuration, switch C2 is open and switch C1 is closed and the order of two of the phases of the three-phase supply are reversed. When not operating, both switches C1 and C2 are open, i.e. there is no power to the motor 112. Only one of the switches C1, C2 can be closed at any one time. In an alternative embodiment, the switching section is electronic and can form part of an electronic motor drive.
The particular drive direction at the motor 112 for a given phase sequence, and whether this translates to opening or closing of a valve attached to the actuator will be established when the actuator is originally set up. The control system 130 detects when power is provided to the three-phase supply 128 and that there are no conditions detected that would prevent operation of the actuator in the intended direction before configuring the switching section 134.
The consequence of this arrangement is that when the switching section 134 is in the first configuration, as long as power is applied via the three-phase supply 128, the motor will operate in a given direction dependent on the phase sequence of the supply. A change in the phase sequence during operation will cause the motor 112 to reverse from its original direction.
The control system 130 includes a number of sensor inputs that will prevent operation or cease operation if certain conditions exist. The system 130 includes a monitor relay 138 which provides a motor inhibit signal that prevents the switching section 134 from providing power to the motor. This allows operation of the motor 112 to be inhibited to avoid damage to the actuator, in particular to the motor.
Some of the conditions inhibiting operation of the motor can apply independently of the intended direction of operation of the motor 112. The motor 112 includes a thermostat 136. If the temperature in the motor windings is above a predetermined level, the thermostat will trip and cause the monitor relay 138 inhibit power to the motor. Other inhibit signals causing the monitor relay 138 to inhibit the motor include signals from the phase detection system indicating the loss of a phase on the three-phase supply; the detection of an error in a position sensor (e.g. an encoder) 140 connected to the actuator shaft; and detection of a failure in the control system 130.
There are other conditions that may inhibit operation of the motor dependent on its direction of drive. For example, if the valve is fully open or fully closed, further operation in the open or close direction could cause damage to the actuator or valve. However, operation in the reverse direction (i.e. from open to closed, or closed to open) can be permitted.
The actuator includes a position sensor 140, for example at an output shaft of the actuator. Where this indicates that the valve is at a limit position, the control system 130 can inhibit operation of the motor if the phase detector 132 indicates that the intended direction of operation of the motor 112 would drive the valve further towards the limit position. If the intended direction drives the valve away from the limit opposition, there is no inhibition. The position sensor 140 can also be used to indicate when to stop operation of the motor because the valve has reached a limit position.
The actuator also includes a torque sensor 142 for detecting the torque, for example at an output of the actuator. The torque will be affected by resistance to movement of the valve (or any other factor internal to the valve or actuator that acts against the effect of the motor to turn the valve, e.g. internal jamming). Therefore, the torque will rise when the valve reaches a limit position and is prevented from moving further in the same direction. In such a case, the control system will inhibit operation of the motor 112 in the given direction but will allow operation in the reverse direction. As well as limit positions, the torque may rise due to something blocking further movement of the valve in a given direction even though the valve is not at a limit position. The output of the torque sensor 142 can also be used to stop operation of the motor 112 in this situation.
The use of the position sensor 140 and torque sensor 142 both provide a direction-dependent inhibition that prevents the control system from operating the switching section 134 to connect the power supply 128 to the motor 112 if the incoming power supply shows an intended direction of operation towards the limit or obstruction, but has no effect if operation is way from this position.
The control system 130 also includes a number of intermediate position switches S1-S4 that can be configured to open or close relays at any predetermined mid-travel position of the actuator (i.e. other than fully open or fully closed).
The control system phase detection system 132 detects the phase sequence of the incoming power supply and from this the control system 130 determines the direction of operation of the motor. This determined direction can be used, together with an output of the position encoder 140 to generate a signal indicating the direction of operation of the valve attached to the actuator.
The actuator can also include local control selectors 126 and a position indicator 124 that is visible from the outside of the housing. The valve position and direction output from the control system can be shown on the indicator 124. A battery 144 is also provided to maintain electronics functions when the three-phase power is not provided.
Various changes can be made within the scope of the invention. While a three-phase motor and power supply are described above, the same concept can be applied for other motor topologies and power supplies, such as a DC supply, using a characteristic feature of the power supply to configure the motor drive to operate in a given direction. This feature can be a signal superposed on the current supply, for example.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2118289.4 | Dec 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2022/053142 | 12/8/2022 | WO |
