Energizing a coil of a solenoid of a directional control valve

1. A method of energizing a coil of a solenoid of a directional control valve, wherein an armature of the solenoid moves between a first position in which the solenoid is operating and a second position in which the solenoid is not operating, the method comprising:

energizing the coil with a voltage;

controlling the voltage to operate the solenoid with a first current;

detecting a second current in the coil, at which the armature of the solenoid moves between the first position in which the solenoid is operated, and the second position in which the solenoid is not operated; and

using, as an operating current for energizing the coil of the solenoid, an operating current that is less than the first current but greater by a margin than the second current.

2. The method according to claim 1 , wherein controlling the voltage comprises:

increasing the voltage;

detecting the movement of the armature from the second position to the first position;

decreasing the voltage when the armature has moved from the second position to the first position, and detecting the movement of the armature from the first position to the second position;

increasing the voltage when the armature has moved from the first position to the second position, and detecting the movement of the armature from the second position to the first position; and

decreasing the voltage to a level at which the current in the coil is the operating current when the armature has moved from the second position to the first position.

3. The method according to claim 2 , wherein the voltage is increased to a maximum voltage after detecting the armature has moved from the second position to the first position and before decreasing the voltage.

4. The method according to claim 1 , wherein detecting the current in the coil at which the armature of the solenoid moves between the first position and the second position comprises detecting a perturbation in the current through the coil due to a change in the inductance of the coil due to the movement of the armature of the solenoid.

5. The method according to claim 1 , wherein controlling the voltage comprises pulse width modulation of voltage applied by drive circuitry for the solenoid.

6. The method according to claim 1 , wherein the directional control valve is a directional control valve of a subsea hydrocarbon production control system.

7. The method according to claim 6 , wherein the voltage is controlled by a processor in a subsea electronics module of a subsea control module.

8. The method according to claim 2 , wherein detecting the current in the coil at which the armature of the solenoid moves between the first position and the second position comprises detecting a perturbation in the current through the coil due to a change in the inductance of the coil due to the movement of the armature of the solenoid.

9. The method according to claim 2 , wherein controlling the voltage comprises pulse width modulation of voltage applied by drive circuitry for the solenoid.

10. A method of energizing a coil of a solenoid of a directional control valve, wherein an armature of the solenoid moves between a first position in which the solenoid is operating and a second position in which the solenoid is not operating, the method comprising:

energizing the coil with a voltage;

controlling the voltage to operate the solenoid with a first current;

detecting a second current in the coil at which the armature of the solenoid moves between the first position in which the solenoid is operated, and the second position; and

using as an operating current for energizing the coil of the solenoid, an operating current that is less than the first current but greater by a margin than the second current;

wherein controlling the voltage comprises:

increasing the voltage;

detecting the movement of the armature from the second position to the first position;

decreasing the voltage when the armature has moved from the second position to the first position, and detecting the movement of the armature from the first position to the second position;

increasing the voltage when the armature has moved from the first position to the second position, and detecting the movement of the armature from the second position to the first position; and

decreasing the voltage to a level at which the current in the coil is the operating current when the armature has moved from the second position to the first position,

wherein detecting the current in the coil at which the armature of the solenoid moves between the first position and the second position comprises detecting a perturbation in the current through the coil due to a change in the inductance of the coil due to the movement of the armature of the solenoid, and

wherein controlling the voltage comprises pulse width modulation of voltage applied by drive circuitry for the solenoid.

11. A system for energizing a coil of a solenoid of a directional control valve, the system comprising:

a DC power supply configured to energize the coil with a voltage; and

a processor configured to: control the voltage to operate the solenoid with a first current; detect a second current in the coil, at which an armature of the solenoid moves between a first position in which the solenoid is operating and a second position in which the solenoid is not operating; and use, as an operating current for energizing the coil of the solenoid, an operating current that is less than the first current but greater by a margin than the second current.

12. The system according to claim 11 , wherein the processor is further configured to:

increase the voltage;

detect the movement of the armature from the second position to the first position;

decrease the voltage when the armature has moved from the second position to the first position, and detect the movement of the armature from the first position to the second position;

increase the voltage when the armature has moved from the first position to the second position, and detect the movement of the armature from the second position to the first position; and

decrease the voltage to a level at which the current in the coil is the operating current when the armature has moved from the second position to the first position.

13. The system according to claim 12 , wherein the processor is configured to increase the voltage to a maximum voltage after detecting the armature has moved from the second position to the first position before the voltage is decreased.

14. The system according to claim 11 , wherein the processor is configured to detect the current in the coil at which the armature of the solenoid moves between the first position and the second position by detecting a perturbation in the current through the coil due to a change in the inductance of the coil due to the movement of the armature of the solenoid.

15. The system according to claim 11 , wherein the processor is configured to control the voltage by pulse width modulation of voltage applied by drive circuitry for the solenoid.

16. The system according to claim 11 , wherein the directional control valve is a directional control valve of a subsea hydrocarbon production control system.

17. The system according to claim 16 , wherein the processor is a processor in a subsea electronics module of a subsea control.

18. The system according to claim 12 , wherein the processor is configured to detect the current in the coil at which the armature of the solenoid moves between the first position and the second position by detecting a perturbation in the current through the coil due to a change in the inductance of the coil due to the movement of the armature of the solenoid.

19. The arrangement according to claim 14 , wherein the processor is configured to control the voltage by pulse width modulation of voltage applied by drive circuitry for the solenoid.

20. The system according to claim 18 , wherein the processor is configured to control the voltage by pulse width modulation of voltage applied by drive circuitry for the solenoid.