JP6577314B2 - Steam turbine valve drive device and steam turbine valve - Google Patents

Description

  Embodiments described herein relate generally to a steam turbine valve driving device and a steam turbine valve.

  In general, in a steam turbine power generation facility, the rotation speed and output of the steam turbine are adjusted by controlling the position of various valves with various steam turbine valve driving devices for the flow rate of driving steam flowing into the steam turbine. When a steam turbine power generation facility falls into a phenomenon such as an abnormal phenomenon or failure, in order to prevent accidents in advance or minimize damages caused by accidents, various steam turbine valve drive devices can be closed quickly. All valves are fully closed to shut off the driving steam.

  A steam turbine valve drive device that controls the opening degree of a valve such as a steam control valve and a steam stop valve that controls the steam turbine is a drive device that is composed of a hydraulic system, and pistons and cylinders that open and close various valves, and position control signals. It is composed of an electromagnetic valve that introduces and drains hydraulic oil into the cylinder, and an electromagnetic valve that rapidly drains hydraulic oil in the cylinder by an emergency signal. The introduction and drainage of the hydraulic oil of the various valve driving devices are performed through piping from one oil collecting device having a high-pressure fluid pump to the various valve driving devices.

  On the other hand, although not yet common, each steam turbine valve driving device has an independent fluid pump and reservoir, and controls the position of the steam valve by controlling a motor that drives the fluid pump. It has been known. Further, there is known a steam turbine valve driving device in which the position of a steam valve is controlled by rotating the ball screw through a gear connected to a motor and the oil collecting device is unnecessary.

JP-A-8-170503

  The steam turbine valve needs to be held fully open and fully closed. At high temperatures, the steam turbine valve has a differential elongation between the valve shaft and the valve box. Therefore, in order to hold the valve position in the fully open and fully closed positions, as the valve position command signal, a signal of full open or higher (push-up command signal) or full-close or lower (push-down command signal) is given. It is done to hold.

  For example, in a steam turbine valve driving device using a bidirectional pump and a servo motor as driving sources, feedback control is performed based on a deviation between a steam turbine valve position command signal and a valve position detection signal. In this case, if a further push-up command signal is given to the valve position detection signal in the vicinity of the fully open position of the valve, an attempt is made to apply the necessary torque until there is no deviation from the valve position signal, but the deviation disappears. Since this is not the case, overtorque is always applied. For this reason, there is a problem that a large-capacity servo motor that increases the oil temperature excessively has to be selected. There is a similar problem at the time of the push-down command.

  The present invention has been made to solve the above-described problems, and a steam turbine valve drive device and a steam turbine valve that can perform full-open holding and full-close holding of a steam turbine valve without constantly applying excessive torque. The purpose is to provide.

One aspect of the steam turbine valve drive device includes a piston connected to a valve shaft of a steam turbine valve disposed in a steam flow path for supplying steam to the steam turbine, the piston accommodated therein, and partitioned by the piston inside. A cylinder having the first and second oil chambers, and a pump for moving the piston between the first and second oil chambers to open and close the steam turbine valve. A motor that drives the pump, an opening detector that detects the opening of the steam turbine valve, an opening command signal that indicates a required opening of the steam turbine valve, and an opening from the opening detector Based on the detection signal, the driving of the motor is controlled so that the opening degree of the steam turbine valve becomes the required opening degree, and the pressure on the hydraulic oil delivery side by the pump is a predetermined value or more , and the opening degree instruction signal Or said Degree detection signal, in the case of the following first predetermined value or more or the second predetermined value, characterized by comprising a control unit for limiting the torque value of the motor.

The figure which shows the structure of the steam turbine valve drive device in 1st Embodiment. The block diagram for demonstrating the control in 1st Embodiment. The block diagram for demonstrating the control in 1st Embodiment. The flowchart which shows operation | movement of 1st Embodiment. The operation characteristic figure in a 1st embodiment. The flowchart which shows operation | movement of 1st Embodiment. The block diagram for demonstrating the control in 2nd, 3rd embodiment. The flowchart which shows operation | movement of 2nd Embodiment. The flowchart which shows operation | movement of 2nd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically illustrating a schematic configuration of a steam turbine valve driving device and a steam turbine valve according to an embodiment.

(First embodiment)
A steam turbine valve 1 shown in FIG. 1 shows a steam stop valve, for example, and has a built-in sub-valve for performing steam flow control at the time of start-up and the like, and is a mechanism capable of controlling the valve position using a pump 7. ing. Further, the steam turbine valve 1 is a mechanism in which the position where the valve rod 2 comes into contact with the back seat 1c and is restrained is a fully open position, and the position where the valve disc 1a comes into contact with the valve seat 1b is restrained is a fully closed position. ing.

  On the other hand, the hydraulic circuit 110 of the steam turbine valve driving device 100 is a closed circuit filled with hydraulic oil. The piston 5c directly connected to the valve stem 2 is accommodated in the cylinder 5 and moves in the steam turbine valve drive range from the fully open position to the fully closed position. The inside of the cylinder 5 is divided into an upper oil chamber 5b at the upper part and a lower oil chamber 5a at the lower part by a piston 5c. The cylinder volume determined by the piston rod 5d, the piston 5c, and the cylinder 5 is the same in the upper oil chamber 5b and the lower oil chamber 5a in the steam turbine valve drive range from the fully open position to the fully closed position. In addition, if it is outside a steam turbine valve drive range, even if the cylinder volume of the upper oil chamber 5b and the lower oil chamber 5a differs, there is no functional problem.

  One of the oil passages from the pump 7 in the hydraulic circuit 110 is connected to the upper oil chamber 5b, and the other is connected to the lower oil chamber 5a. The upper oil chamber 5b and the lower oil chamber 5a are always filled with hydraulic oil, and the steam turbine valve 1 is opened and closed by the displacement of the upper oil chamber 5b and the lower oil chamber 5a according to the rotation direction of the pump 7. The outflow pressure of the pump 7 can be maintained at a stable pressure by controlling the input shaft torque by the motor 7a.

  The steam turbine valve 1 is provided with a spring mechanism 4 that urges in the closing direction, and overcomes the spring force and steam pressure of the spring mechanism 4 to move from the upper oil chamber 5b of the cylinder 5 to the lower oil chamber 5a. It operates to introduce the hydraulic oil and open the steam turbine valve 1. Further, the hydraulic oil is introduced from the lower oil chamber 5a of the cylinder 5 to the upper oil chamber 5b, and the steam turbine valve 1 is closed. On the other hand, when the steam turbine is abnormal, the operating oil in the lower oil chamber 5a is rapidly introduced into the upper oil chamber 5b so that the steam turbine valve 1 is closed.

  The above-described pump 7 is a reversible rotary volume pump capable of reversing the flow direction by changing the rotation direction of the drive shaft. For example, a gear pump or an axial piston pump can be used. The drive shaft of the pump 7 provided in each steam turbine valve 1 and the drive shaft of the motor 7a are directly connected by a coupling. Since the motor 7a is used for controlling the valve position, for example, an inverter motor or a servo motor is preferably used. In the present embodiment, a case where a servo motor is used as the motor 7a will be described. Pump discharge pressure can be variably controlled by torque control by a servo motor.

  The motor 7 a that drives the pump 7 is controlled by the control unit 120. The control unit 120 includes a motor control device 9 and a servo driver 8. As shown in the block diagram of FIG. 2, the motor control device 9 includes an opening command signal indicating a required opening input from a host control device (not shown) and an actual opening output from the opening detector 6. Is input. The motor control device 9 outputs a rotation speed command to the servo driver 8 so that these deviations are eliminated. The servo driver 8 controls the torque and current value of the motor 7a so that there is no deviation between the actual rotational speed signal from the rotational speed detector 7b provided in the motor 7a and the rotational speed command. Control the opening.

  As described above, when the steam turbine valve 1 is fully opened and fully closed, a signal that is not less than fully open (push-up command signal) or not fully closed (push-down command signal) is given. For this reason, a deviation occurs between the valve opening signal and the opening command signal by the opening detector 6, but the valve rod 2 is already in contact with the back seat 1c and restrained, or the valve seat 1b is in contact with the valve disk 1a. However, when restrained, the valve cannot move even if torque is applied. At this time, since the motor 7a is pushed in with the maximum torque, the pump 7 discharges the hydraulic oil with the maximum pressure. In order to release this maximum pressure, relief valves (safety valves) 12 and 13 are disposed in the respective oil passages on the lower oil chamber 5a side and the upper oil chamber 5b side. A reservoir 11 is provided to connect the return of the relief valves 12 and 13.

  The opening detector 6 is required to accurately detect the valve opening of the steam turbine valve 1. For this reason, in this embodiment, as shown in FIG. 1, the piston rod 5d is penetrated from the cylinder 5, and the opening degree detector 6 is disposed on the piston rod 5d. The installation method of the opening detector 6 is not limited to this. For example, a plate is disposed on the coupling 3 that directly connects the valve rod 2 and the piston rod 5d, and a detection rod is provided on the plate. There are a method of installing an opening detector on the rod, a method of arranging a detection rod on a spring receiver in the spring housing 4a, and providing an opening detector on the detection rod.

  The steam turbine valve 1 needs to quickly shut off the steam flow path when the plant falls into an abnormal state. Further, when the abnormal state of the plant is released, the steam turbine valve driving device 100 is reset by a valve opening permission command from a control device (not shown), and the steam turbine valve 1 enters a standby state. The steam turbine valve drive device 100 can be reset by applying a quick-acting solenoid valve (not shown) to an excited state.

  Next, the control in this embodiment will be described with reference to the block diagram of FIG. 3 and the flowchart of FIG. As shown in FIG. 3, in the present embodiment, an opening command signal from a control device (not shown) and a valve opening signal indicating an actual opening output from the opening detector 6 are input to the motor control device 9. In addition, a signal indicating the hydraulic pressure of the lower oil chamber 5a is input from the pressure transmitter 14, and a signal indicating the hydraulic pressure of the upper oil chamber 5b is input from the pressure transmitter 15. As shown in the flowchart of FIG. 4, when an opening command signal such as a push-up command (opening command signal 100% or more) is input to the motor control device 9 from a control device (not shown) (301), In accordance with the deviation between the command signal and the valve opening signal of the opening detector 6 input to the motor control device 9, the rotational speed and direction of the motor 7a are controlled via the servo driver 8 (302). In this case, the torque value of the motor 7 a is controlled so that the pump 7 mainly discharges a pressure higher than the closing force of the spring mechanism 4.

  When a push-up command (valve opening command signal 100% or more) is output, in the steam turbine valve 1, the valve rod 2 rises to a position where the valve rod 2 comes into contact with the back seat 1 c and is restrained. Here, conventionally, after the valve rod 2 comes into contact with the back seat 1c and is restrained, the torque of the motor 7a increases. When the discharge pressure of the relief valve 12 is reached, the relief valve 12 operates to reduce the pressure of the hydraulic oil. I was missing.

  On the other hand, as shown in the flowchart of FIG. 4, in this embodiment, the pressure is determined to be equal to or higher than a predetermined pressure such as the blowing pressure of the relief valve 12 (or a pressure slightly lower than or slightly higher than the blowing pressure). When detected by the transmitter 14 (304), a torque command for limiting the motor torque is sent from the motor control device 9 to the servo driver 8 so that the pump discharge pressure corresponding to the minimum driving force necessary for maintaining the steam turbine valve fully open. (305).

  As a result, the torque value of the motor 7a decreases, the discharge pressure of the pump 7 decreases, and the relief valve 12 is not operated and the maximum torque of the motor 7a is not applied while maintaining the valve fully open state. This state is maintained until the next command to change the opening is received (306). The control characteristics at this time are shown in FIG. In FIG. 5, the square plot indicates the opening signal, the diamond plot indicates the opening command signal, the circular plot indicates the hydraulic pressure in the lower oil chamber 5a, and the triangular plot indicates the hydraulic pressure in the upper oil chamber 5b.

  At this time, in this embodiment, in addition to the pressure value detected by the pressure transmitter 14, the valve position restriction that makes the torque value restriction of the motor 7 a effective is applied. That is, for example, the valve opening signal (or opening command signal) is not less than a predetermined opening (303) such as 90% or more, and the pressure detected by the pressure transmitter 14 is not less than a predetermined value (304). When this happens, the motor torque value is limited (305), and the pump discharge pressure is limited. At this time, since an opening degree deviation always remains in the motor 7a, a rotational speed limit may be provided so that the motor 7a is not continuously operated at a high rotational speed. FIG. 4 shows the case where the valve position restriction that enables the torque value restriction is applied. However, when the valve position restriction is not applied, the valve opening degree of FIG. Step 303 for determining whether or not there is omitted. The same applies to the flowcharts of FIGS.

  On the other hand, when a push-down command (opening command signal 0% or less) is sent from the control device (not shown) to the motor control device 9, the valve disk 1a is lowered to a position where it contacts and is restrained by the valve seat 1b. Conventionally, after the valve disc 1a comes into contact with the valve seat 1b, the torque of the motor 7a increases, and the relief valve 13 is operated when the pressure of the relief valve 13 reaches the blowing pressure.

  In the present embodiment, as shown in the flowchart of FIG. 6, when an opening command signal such as a push-down command (opening command signal 0% or less) is input to the motor control device 9 from a control device (not shown) (401) ), The number of rotations and the direction of rotation of the motor 7a are controlled via the servo driver 8 in accordance with the deviation between the opening command signal and the valve opening signal of the opening detector 6 input to the motor control device 9. (402). When the valve opening signal (or opening command signal) is not more than a predetermined opening such as 10% or less (403) and the pressure detected by the pressure transmitter 15 is not less than a predetermined value (404). The motor torque value is limited to 405 so that the pump discharge pressure is equivalent to the minimum driving force necessary for the fully closed holding. At this time, since an opening degree deviation always remains in the motor 7a, a rotation speed limit may be provided so as not to continue the operation at a high rotation speed.

  As a result, the torque value of the motor 7a decreases, the discharge pressure of the pump 7 decreases, the valve 7 is kept fully closed, the relief valve 13 is not operated, and the maximum torque of the motor 7a is not applied. This state is continuously controlled, and this state is maintained until a command to change the opening is next issued (406).

(Second Embodiment)
In the first embodiment, when the steam turbine valve 1 is held fully open or fully closed, when the pressure value detected by the pressure transmitter 14 and the pressure transmitter 15 exceeds a predetermined value, the torque value of the motor 7a. It was set as the structure which restrict | limits. However, as shown in the block diagram of FIG. 7, not the pressure value but the current value of the motor 7a is measured and detected by the servo driver 8, and the current value is limited, thereby limiting the torque value of the motor 7a. It can be set as the structure to do. As shown in the block diagram of FIG. 7, the torque value of the motor 7a can be measured and detected by the servo driver 8 to limit the torque value. This point will be described later.

  In the second embodiment, as shown in the flowchart of FIG. 8, when an opening command signal such as a push-up command (valve opening command signal 100% or more) is input to the motor control device 9 from a control device (not shown) ( 501), the motor 7a is driven according to the deviation between the opening command signal and the valve opening signal (502). In the case of the push-up command, in the steam turbine valve 1, the valve stem 2 is raised to a position where the valve stem 2 comes into contact with and restrains the back seat 1c. After the valve stem 2 comes into contact with the back seat 1c, the torque of the motor 7a increases and the current value of the motor 7a also increases. When the current value of the motor 7a reaches a specified value (504), the current value of the motor 7a is limited by the servo driver 8 so that the pump discharge pressure corresponding to the minimum driving force necessary for full opening is maintained (505). . Thereby, it is possible to hold the valve fully open with low power without operating the relief valve 12.

  Similar to the first embodiment described above, in this case, a valve position restriction that enables the current value restriction of the motor 7a may be provided. For example, the current value of the motor 7a is limited (505) when the valve opening signal is not less than a predetermined opening degree such as 90% or more (503) and the current value of the motor 7a is not less than a specified value (504).

  As shown in the flowchart of FIG. 9, when a push-down command (opening command signal 0% or less) is sent from the control device (not shown) to the motor control device 9 (601), the opening command signal and the valve opening The motor 7a is driven in accordance with the deviation from the signal (602), and the valve disc 1a is lowered to a position where it contacts and is restrained by the valve seat 1b. After the valve disk 1a contacts the valve seat 1b, the torque of the motor 7a increases and the current value of the motor 7a also increases. When the current value of the motor 7a reaches a specified value (604), the current value of the motor 7a is limited by the servo driver 8 so as to be equal to or lower than the pump discharge pressure corresponding to the minimum driving force necessary for the fully closed holding (see FIG. 605). Thereby, it is possible to hold the valve fully closed with low power without operating the relief valve 13.

  Similar to the first embodiment described above, in this case, a valve position restriction that enables the current value restriction of the motor 7a may be provided. For example, when the valve opening signal is equal to or less than a predetermined opening (603) such as 10% or less, and the current value of the motor 7a is equal to or greater than a specified value (604), the current value of the motor 7a is limited (605). . Here, the current value of the motor 7a may be limited by sampling a specified number and using an average value or an effective value. Further, the time when the current value of the motor 7a becomes equal to or more than a predetermined value may be limited when it is continuously detected for a predetermined time (for example, seconds).

(Third embodiment)
Next, a case where the torque value of the motor 7a described above is measured and detected by the servo driver 8 and this torque value is limited will be described. As described above, the torque value of the motor 7a can be measured and detected from the servo driver 8. In addition, a torque meter (not shown) may be installed on the motor or pump shaft to measure and detect torque.

  When a push-up command (valve opening command signal 100% or more) is input to the motor control device 9 from a control device (not shown), the steam turbine valve 1 causes the valve rod 2 to come into contact with the back seat 1c and be restrained. Rod 2 rises. After the valve stem 2 comes into contact with the back seat 1c, the torque value of the motor 7a increases. When the torque value of the motor 7a reaches a specified value, the torque value of the motor 7a is limited by the servo driver 8 so that the pump discharge pressure corresponding to the minimum driving force required for full opening is maintained. Thereby, it is possible to hold the valve fully open with low power without operating the relief valve 12.

  Also in this case, it is possible to provide a valve position restriction that makes the torque value restriction of the motor 7a effective. For example, the torque value of the motor 7a is limited when the valve opening signal is not less than a predetermined opening such as 90% or more and the torque value of the motor 7a is not less than a specified value.

  On the other hand, when a push-down command (opening command signal 0% or less) is sent from the control device (not shown) to the motor control device 9, the valve disk 1a is lowered to a position where it contacts and is restrained by the valve seat 1b. After the valve disc 1a contacts the valve seat 1b, the torque value of the motor 7a increases. When the torque value of the motor 7a reaches a specified value, the torque value of the motor 7a is limited by the servo driver 8 so as to be equal to or lower than the pump discharge pressure corresponding to the minimum driving force necessary for the fully closed holding. Thereby, it is possible to hold the valve fully closed with low power without operating the relief valve 13.

  At this time, it is possible to provide a valve position restriction that makes the torque value restriction of the motor 7a effective. For example, the torque value of the motor 7a is limited when the valve position detection signal is equal to or less than a predetermined opening such as 10% or less and the torque value of the motor 7a is equal to or greater than a specified value. Here, the torque value of the motor 7a may be limited by sampling a specified number and using an average value or an effective value. Further, the time when the torque value of the motor 7a becomes equal to or more than a predetermined value may be limited when it is continuously detected for a predetermined time (for example, for a number of seconds).

(Fourth embodiment)
In the first embodiment described above, when the steam turbine valve 1 is held fully open or fully closed, when the pressure value detected by the pressure transmitter 14 and the pressure transmitter 15 exceeds a predetermined value, the torque of the motor 7a. It was set as the structure which restrict | limits a value. However, instead of limiting the torque value of the motor 7a, it may be switched to pressure control.

  In the pressure control, the torque of the motor 7a is controlled from the motor control device 9 via the servo driver 8 so that the pressure detected by the pressure transmitter 14 becomes the specified pressure during the steam turbine valve opening operation and during the valve full opening maintenance. Is the method. Further, during the steam turbine valve closing operation and during the fully closed holding, the torque of the motor 7a is controlled from the motor control device 9 via the servo driver 8 so that the pressure of the pressure transmitter 15 becomes a specified pressure.

  At this time, since the feedback control of the valve position control is disabled, it is necessary to determine the valve position for enabling the pressure control. The valve position in which the pressure control is effective needs to be determined by the difference in elongation between the valve stem 2 and the valve box.

(Other embodiments)
Note that the configurations of the first to fourth embodiments may be used in combination in order to hold the steam turbine valve fully open or fully closed with low power and stability. For example, the torque value limit and the current value limit of the motor 7a may be used in combination. An opening command signal may be used instead of the valve opening signal.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  1 ... Steam turbine valve, 1a ... Valve disc, 1b ... Valve seat, 1c ... Back seat, 2 ... Valve rod, 3 ... Coupling, 4 ... Spring mechanism, 4a ... Spring housing, 5 ... Cylinder, 5a ... Lower oil chamber, 5b ... Upper oil chamber, 5c ... Piston, 6 ... Opening detector, 7 ... Pump, 7a ... Motor, 8 ... Servo driver, 9 ... Motor control device, 11 ... reservoir, 12, 13 ... relief valve, 14,15 ... pressure transmitter, 100 ... steam turbine valve drive device, 110 ... hydraulic circuit, 120 ... control unit.

Claims (5)

A piston connected to a valve stem of a steam turbine valve disposed in a steam flow path for supplying steam to the steam turbine;
A cylinder that houses the piston and has first and second oil chambers partitioned by the piston;
A pump that opens and closes the steam turbine valve by moving the piston by moving hydraulic oil between the first and second oil chambers;
A motor for driving the pump;
An opening detector for detecting the opening of the steam turbine valve;
Based on the opening command signal indicating the required opening of the steam turbine valve and the opening detection signal from the opening detector, the motor is driven so that the opening of the steam turbine valve becomes the required opening. Control, when the pressure on the hydraulic oil delivery side by the pump is a predetermined value or more , and the opening command signal or the opening detection signal is not less than a first specified value or not more than a second specified value, A control unit for limiting the torque value of the motor;
A steam turbine valve drive device comprising: A piston connected to a valve stem of a steam turbine valve disposed in a steam flow path for supplying steam to the steam turbine;
A cylinder that houses the piston and has first and second oil chambers partitioned by the piston;
A pump that opens and closes the steam turbine valve by moving the piston by moving hydraulic oil between the first and second oil chambers;
A motor for driving the pump;
An opening detector for detecting the opening of the steam turbine valve;
Based on the opening command signal indicating the required opening of the steam turbine valve and the opening detection signal from the opening detector, the motor is driven so that the opening of the steam turbine valve becomes the required opening. And when the current value of the motor is not less than a predetermined value and the opening command signal or the opening detection signal is not less than a first specified value or not more than a second specified value, the current of the motor A control unit that limits the value;
A steam turbine valve drive device comprising: A piston connected to a valve stem of a steam turbine valve disposed in a steam flow path for supplying steam to the steam turbine;
A cylinder that houses the piston and has first and second oil chambers partitioned by the piston;
A pump that opens and closes the steam turbine valve by moving the piston by moving hydraulic oil between the first and second oil chambers;
A motor for driving the pump;
An opening detector for detecting the opening of the steam turbine valve;
Based on the opening command signal indicating the required opening of the steam turbine valve and the opening detection signal from the opening detector, the motor is driven so that the opening of the steam turbine valve becomes the required opening. And when the torque value of the motor is greater than or equal to a predetermined value and the opening degree command signal or the opening degree detection signal is greater than or equal to a first prescribed value or less than or equal to a second prescribed value, A control unit that limits the value;
A steam turbine valve drive device comprising: A piston connected to a valve stem of a steam turbine valve disposed in a steam flow path for supplying steam to the steam turbine;
A cylinder that houses the piston and has first and second oil chambers partitioned by the piston;
A pump that opens and closes the steam turbine valve by moving the piston by moving hydraulic oil between the first and second oil chambers;
A motor for driving the pump;
An opening detector for detecting the opening of the steam turbine valve;
Based on the opening command signal indicating the required opening of the steam turbine valve and the opening detection signal from the opening detector, the motor is driven so that the opening of the steam turbine valve becomes the required opening. And when the opening degree detection signal from the opening degree detector is not less than a first specified value or not more than a second specified value, the pressure on the hydraulic oil delivery side by the pump becomes a predetermined value. A control unit for controlling the drive of
A steam turbine valve drive device comprising: A steam turbine valve comprising the steam turbine valve drive device according to any one of claims 1 to 4 .

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