JP2005214104A - Main turbine torque limiting device of steam turbine ship - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control main turbine torque varying according to an actual load to prevent it from becoming over torque. <P>SOLUTION: There is provided the control device equipped with a rotation speed detector for detecting an actual rotation speed of a propeller, a torque detector for detecting actual torque of the propeller and an actual rotation speed table 23 set with command rotation speeds providing shaft torque suited for the actual rotation speed detected by the rotation speed detector. A command rotation speed 24 is output from the actual rotation speed table 23 and the command rotation speed 24 and a handle command 15 or 17 are compared by a lower side selection means 25, selected and output. The device is equipped with an actual torque table set with command rotation speeds providing shaft torque suited for the actual torque detected by the torque detector. A command rotation speed corresponding to the actual torque is output from the actual torque table. The command rotation speed and the main command rotation speed are compared, the lower rotation speed is output as a handle command rotation speed and an opening degree of the operation valve is controlled so that torque of the main turbine do not exceed a setting value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for limiting torque so that a main turbine in a steam turbine ship does not enter an overtorque operating state.

  Conventionally, the operation of the main turbine of a steam turbine ship is controlled by the rotation speed control in the maneuvering zone such as when operating in a port, and the opening of the control valve is constant in the navigation mode such as during ocean navigation. Is done by control. The constant control of the opening of the control valve in this navigation mode is an operation control with a constant amount of steam supplied to the main turbine. As shown in the graph of FIG. 6, the control valve opening on the horizontal axis and the main turbine rotation on the vertical axis. From the correspondence with the number, the rotation speed of the main turbine is controlled by opening control (lift amount control) of the control valve, and the main turbine is operated at a constant torque.

  Further, the main turbine operated in this way is usually designed so that the main turbine does not operate at a high torque during operation in a plain water area. For example, the design point is that the shaft rotation speed of the main turbine shown on the horizontal axis and the output shown on the vertical axis are 100% of each other as in the main turbine operation restriction curve shown in the graph of FIG. The shaft speed is 105%, the output is 103%, and the engine is designed to operate within the range enclosed by the diagonal lines with the operating torque limited to 105%.

  However, when sailing on the ocean, there may be stormy weather when high waves and strong winds occur.In such stormy weather, the hull speed is reduced by the external force of waves and wind acting on the hull, and the rotation speed of the main turbine that drives the propeller is reduced. The pressure acting on the turbine blades drops and increases in a high torque operation state, and in some cases, there is a possibility of an overtorque operation state.

  Therefore, during such stormy weather, the engine chief or the like performs an operation for controlling the rotational speed of the main turbine according to the situation so that the main turbine does not operate at a high torque.

As a conventional technology of this kind, the temperature inside and outside the turbine flange is detected, the future temperature with respect to the indicated rotational speed is predicted based on this temperature, and the acceleration / deceleration that makes the temperature difference between the inside and outside of the flange constant. Is set, and the number of revolutions is increased or decreased according to a schedule along that time (see, for example, Patent Document 1).
JP 49-50302 (page 3-9, FIG. 2)

  By the way, normally, since the situation in which overtorque occurs during the above-described rough weather or the like is the operation state of the navigation mode, the operation control of the main turbine is the control of the opening degree of the control valve. For this reason, it is difficult to control the rotation speed of the main turbine according to the situation by controlling the opening of the control valve during stormy weather when the load situation changes greatly, and it is controlled depending on the experience and intuition of the engine manager etc. There are many.

  However, in recent years, the number of skilled engine managers has decreased, and it has become difficult to perform stable operation control according to the situation such as stormy weather. In addition, since the main turbine is controlled by the control valve opening control regardless of the load torque and no control is performed on the over torque, there is a possibility that the main turbine operation control at the time of stormy weather becomes an over torque operation state. There is. Therefore, if the operation is performed in such an overtorque state, the main turbine and the speed reducer may be damaged. In particular, a large load may act on the gear of the speed reducer that drives the propeller to cause damage.

  Furthermore, in the past, the main turbine and other components were designed with a large margin for output, but in recent years, the main turbine and other components have a margin for the hull in order to reduce manufacturing costs and reduce the size. From this point, too, the operation during stormy weather becomes an overtorque operation state, which may cause damage to the main turbine and the speed reducer as described above.

  For this reason, a device that can limit the main turbine so as not to be in an overtorque operation state even in an operation situation with a large load fluctuation such as during stormy weather is desired.

  In addition, the said patent document 1 tries to increase / decrease a rotation speed based on the internal / external temperature of a turbine flange, and cannot restrict | limit so that the main turbine may not be in the operation state of an overtorque.

  Therefore, in order to solve the above-mentioned problem, the present invention relates to steam that performs rotation speed control in a navigation mode of a main turbine that drives a propeller of a steam turbine ship with a main steam amount by adjusting an opening degree of a control valve based on a steering wheel command. A main turbine torque limiting device for a turbine ship, in which a rotation speed detector for detecting the actual rotation speed of the propeller and a command rotation speed to be a shaft torque suitable for the actual rotation speed detected by the rotation speed detector are set. The actual rotational speed table is output, the command rotational speed corresponding to the actual rotational speed is output from the actual rotational speed table, and the command rotational speed is compared with the rotational speed of the handle command, and the low rotational speed is set as the handle command rotational speed. A control device is provided for controlling the opening degree of the control valve so that the torque of the main turbine is output and does not exceed a set value. In this way, it is possible to limit the torque of the main turbine so as not to exceed the set value based on the actual rotational speed.

  Further, a main turbine torque limiting device for a steam turbine ship that performs rotation speed control in a navigation mode of a main turbine that drives a propeller of the steam turbine ship with a main steam amount by adjusting an opening degree of a control valve based on a handle command, A torque detector that detects the actual torque of the propeller, and an actual torque table that sets a command rotational speed that is a shaft torque suitable for the actual torque detected by the torque detector, are provided from the actual torque table to the actual torque. The command rotational speed is output, the command rotational speed is compared with the rotational speed of the steering wheel command, and the low rotational speed is output as the steering wheel command rotational speed so that the torque of the main turbine does not exceed the set value. You may provide the control apparatus which controls an opening degree. In this way, it is possible to limit the torque of the main turbine so as not to exceed the set value based on the actual torque.

  Furthermore, a main turbine torque limiting device for a steam turbine ship that performs rotation speed control in a navigation mode of a main turbine that drives a propeller of the steam turbine ship with a main steam amount by adjusting an opening degree of a control valve based on a handle command, A rotational speed detector for detecting the actual rotational speed of the propeller and a torque detector for detecting the actual torque of the propeller are provided, and a command rotational speed that becomes a shaft torque suitable for the actual rotational speed detected by the rotational speed detector. The actual rotational speed table is set, the command rotational speed corresponding to the actual rotational speed is output from the actual rotational speed table, and the command rotational speed is compared with the rotational speed of the steering wheel command so that the lower rotational speed is the main command rotational speed. Is provided, and an actual torque table is set in which a command rotational speed is set to a shaft torque suitable for the actual torque detected by the torque detector. The command rotation speed for the main turbine is output, the command rotation speed is compared with the main command rotation speed, and a low rotation speed is output as the handle command rotation speed so that the torque of the main turbine does not exceed the set value. If a control device for controlling the opening degree of the valve is provided, it is possible to more stably limit the main turbine torque so as not to exceed the set value based on the actual rotational speed and the actual torque.

  Further, in the main turbine torque limiting device for the steam turbine ship, the command rotational speed with respect to the actual rotational speed is compared with the rotational speed of the steering wheel command, the low rotational speed is set as the main command rotational speed, and the main command rotational speed is set to the time. If the scheduler performs acceleration / deceleration in a predetermined time and compares the increased or decreased main command rotational speed with the command rotational speed for the actual torque, and outputs a lower rotational speed as the steering wheel command rotational speed, the final In addition, the steering command rotation speed output to the control valve can be limited by the actual torque, and the torque increase due to the load increase can be stably limited.

  The present invention can limit the main turbine torque that changes according to the actual load so as not to become an overtorque by the means described above.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a main turbine torque limiting device in a steam turbine ship showing an embodiment of the present invention. In this embodiment, an example will be described in which the actual turbine speed and the actual torque are limited so that the torque of the main turbine does not become overtorque.

  As shown in the figure, the reduction gear 2 that drives the propeller shaft 5 of the propeller 1 is provided with a high-pressure main turbine 3 and a low-pressure turbine 4. In this embodiment, the heat recovery efficiency is increased by the low-pressure turbine 4, but the low-pressure turbine 4 may be omitted.

  A supply pipe 6 for supplying main steam is connected to the main turbine 3, and a control valve 7 for controlling the supply amount of the main steam is provided in the supply pipe 6. The propeller shaft 5 is provided with a rotational speed detector 8 for detecting the actual rotational speed of the propeller shaft 5 and a torque detector 9 for detecting the actual torque acting on the propeller shaft 5. The rotation speed detector 8 and the torque detector 9 are connected to the control device 10 by wirings 11 and 12.

  The control device 10 and the control valve 7 are connected by a wiring 13 and are configured such that the opening degree is adjusted based on a signal from the control device 10. The amount of main steam supplied to the main turbine 3 is controlled by adjusting the opening degree of the control valve 7. When the steam turbine ship is operated in the navigation mode, the rotation speed of the main turbine 3 is determined by the main steam amount by adjusting the opening degree of the control valve 7. Details of the main turbine torque limiting device 50 will be described below.

  FIG. 2 is a block diagram showing the function of limiting the torque of the main turbine based on the actual rotational speed in the main turbine torque limiting device shown in FIG. 1, and FIG. 3 is a commanded rotation for the actual rotational speed shown in FIG. It is a graph which shows a number. 4 is a block diagram showing a function of limiting the torque of the main turbine based on the actual torque in the main turbine torque limiting device shown in FIG. 1, and FIG. 5 shows the command rotational speed for the actual torque shown in FIG. It is a graph to show. In these figures, the expression “handle command” and “command rotational speed” are different, but the “handle command” is a rotational speed signal that commands the rotational speed of the main turbine. The expression is different depending on the position of the signal.

  As shown in FIG. 2, a steering wheel command 15 from the bridge 14 (Wheel House) and a steering wheel command 17 from the engine control room 16 (Engine Control Room) are controlled by the control device 10 (the right side of the vertical line in the figure is inside the control device). And one of these commands is selected by the selection 18. Reference numeral 19 is a conversion table for converting the lever tilt angle output from the bridge 14 and the engine control room 16 into the steering wheel commands 15 and 17 of the control valve opening percentage.

  Then, the handle command 15 or 17 on the side selected by the selection 18 is converted into a handle command rotational speed 21 (handle command) by the handle command table 20 and output. The steering wheel command speed 21 is determined by the steering wheel command table 20 according to the magnitude of the steering wheel command 15 or 17 (horizontal axis) at the forward (AHEAD), backward (ASTERN), or stop (STOP) position. Is output as the main command rotational speed (vertical axis) as a percentage of the maximum rotational speed.

  On the other hand, the actual rotational speed 22 detected from the propeller shaft 5 (FIG. 1) is input to the control device 10. The input actual rotational speed 22 is output as a first command rotational speed 24 by the actual rotational speed table 23 so that the main turbine does not become overtorque.

  As shown in FIG. 3, in the actual rotational speed table 23 in this embodiment, the horizontal axis indicates the ratio of the actual rotational speed to the maximum rotational speed, and the vertical axis indicates the ratio of the command rotational speed to the maximum rotational speed. Further, in this embodiment, both the forward side (AHEAD) shown on the right side of the figure and the reverse side (ASTERN) shown on the left side of the figure have command rotations in the ship maneuvering mode that is in the range of about 50% of the actual rotational speed shown on the horizontal axis. The number 24 is kept constant at 50% so as not to limit the command rotational speed. In the navigation mode in which the actual rotational speed exceeds 50%, the forward speed and the reverse speed are both restricted to increase the command rotational speed 24 so as to be substantially proportional to the actual rotational speed.

  As shown in FIG. 2, the first command speed 24 output from the actual speed table 23 is the handle command speed output from the handle command table 20 by the first low-side selection means 25 (LOW SELECT). Compare with 21. The low side selection means 25 is a means for comparing the steering wheel command rotational speed 21 with the first command rotational speed 24 and selecting and outputting the lower one. For example, when the handle command rotational speed 21 is higher than the first command rotational speed 24, the first command rotational speed 24 is selected and output, and when the handle command rotational speed 21 is lower than the first command rotational speed 24, The steering wheel command rotational speed 21 is selected and output.

  That is, in the navigation mode, the steering wheel command rotational speed 21 corresponding to the steering wheel command 15 or 17 is compared with the upper limit command rotational speed 24 suitable for the operation of the main turbine 3 from the actual rotational speed, and the lower one of them is compared. It is selected by the low-side selection means 25 and output as a main command rotational speed 26 (when there is no rotational speed limitation by actual torque described later, this is the steering wheel command rotational speed).

  Therefore, in the navigation mode, even if a large steering command 15 or 17 is issued regardless of the rotational speed of the propeller shaft 5, if the actual rotational speed of the propeller shaft 5 is low, the actual rotational speed table 23 is suitable for the actual rotational speed. Therefore, even when the steering wheel command 15 or 17 exceeds the command rotational speed 24, the command rotational speed 24 is selected by the low-side selection means 25 and exceeds the rotational speed suitable for the actual rotational speed. Restricted so that the directive is not. As a result, when the rotational speed of the propeller shaft 5 decreases due to an increase in load or the like, the main command rotational speed 26 is limited, so that it is possible to limit the torque of the main turbine 3 from significantly increasing.

  In this embodiment, since the rotational speed is used as the main command rotational speed 26 (handle command rotational speed), the low-side selection means 25 is provided after the handle command table 20, but the steering wheel command is calculated from the actual rotational speed. If configured to output the same signal as 15 or 17, the low-side selection means 25 is provided in front of the handle command table 20.

  On the other hand, the valve opening 27 of the control valve 7 is input to the control device 10. The valve opening is converted into a signal 29 corresponding to the rotational speed by the valve opening conversion table 28. In this figure, it is converted by one valve opening conversion table 28, but a plurality of conversion tables may be provided.

  The signal 29 corresponding to the rotational speed and the main command rotational speed 26 are selected by the selector 30 and output to [A] shown in the figure.

  As shown in FIG. 4, [A] in FIG. 2 and [A] in FIG. 4 are the same, and the main command rotational speed 26 (or signal 29 corresponding to the rotational speed) input from the selection unit 30 is the time. Input to the scheduler 31. The time scheduler 31 is controlled to gradually increase the rotational speed up to the main command rotational speed 26 (handle command rotational speed) indicated on the vertical axis at a predetermined time indicated on the horizontal axis. The time scheduler 31 is set according to the steam turbine ship. The main command rotational speed 26 output from the time scheduler 31 is compared with the rotational speed signal 32 taken in the control device 10 (inside the vertical lines shown on both sides in the figure) by the comparison section 33, and the time scheduler 31 The feedback control is performed so as to maintain the relationship between the time based on the rotation speed and the rotation speed.

  On the other hand, the actual torque 34 detected from the propeller shaft 5 (FIG. 1) is input to the control device 10. The input actual torque 34 is output as a second command rotational speed 36 so that the main turbine does not become overtorque by the actual torque table 35.

  As shown in FIG. 5, in the actual torque table 35 in this embodiment, the horizontal axis indicates the ratio of the actual torque to the maximum torque, and the vertical axis indicates the ratio of the command rotation speed to the maximum rotation speed. In this embodiment, in the ship maneuvering mode in which the actual torque shown on the horizontal axis is in the range of about 30%, the command rotational speed 36 is kept constant at approximately 68% so as not to limit the command rotational speed. In the navigation mode in which the actual torque exceeds approximately 30%, there is a restriction that the rate of increase of the command rotational speed 36 gradually decreases as the actual torque increases.

  The second command rotational speed 36 output from the actual torque table 35 is compared with the main command rotational speed 26 from the time scheduler by the second low side selection means 37 (LOW SELECT). The second low-side selection means 37 is means for comparing the main command rotational speed 26 and the second command rotational speed 36 and selecting the lower one. For example, when the main command rotational speed 26 is higher than the second command rotational speed 36, the second command rotational speed 36 is selected and output, and when the main command rotational speed 26 is subtracted from the second command rotational speed 36, The main command rotational speed 26 is selected and output.

  That is, in the navigation mode, the main command rotational speed 26 is compared with the upper limit command rotational speed 36 suitable for the operation of the main turbine 3 based on the actual torque, and the lower one is selected by the low-side selection means 37. It is output as the steering wheel command rotational speed 38.

  Therefore, in the navigation mode, even if a large main command rotational speed 26 at which the torque acting on the propeller shaft 5 becomes an overtorque is output from the time scheduler 31, the actual torque 34 of the propeller shaft 5 is high when the actual torque 34 is high. Since the command table speed 36 suitable for the actual torque 34 is output by the torque table 35 as the handle command speed 38, when the main command speed 26 exceeds the command speed 36, the low-side selection means 37 performs the command speed. The number 36 is selected and the command is limited so that a command exceeding the rotation speed suitable for the actual torque 34 is not issued.

  The steering wheel command rotation speed 38 output from the low-side selection means 37 is converted into an electric signal for operating the control valve 7 (FIG. 1) by the valve opening conversion table 41 via the selection unit 40 with the automatic operation signal 39. Then, it is output from the control device 10 to the control valve 7 as a signal for operating the opening degree of the control valve 7. In this valve opening conversion table 41, the rotation speed signal is converted into a signal for controlling the valve lift amount of the control valve 7. However, a conversion table corresponding to the device configuration may be provided for conversion. .

  Accordingly, the amount of main steam supplied to the main turbine 3 by the control valve 7, that is, the valve lift amount of the control valve 7 so as to correspond to the steering command rotational speed 38 output as the rotational speed signal of the main turbine 3. Is controlled.

  In addition, in this embodiment, as shown in FIG. 2 described above, the steering wheel command 15 or 17 is limited by the command rotational speed 24 corresponding to the actual rotational speed 22, and the main command rotational speed limited by this command rotational speed 24. 26 is limited by a command rotational speed 36 corresponding to the actual torque 34 as shown in FIG. 4, so that the main turbine torque does not become an overtorque based on the actual rotational speed and the actual torque. It is possible to stably limit the value so as not to exceed the value.

  That is, according to this embodiment, in the navigation mode, even if a large steering command 15 or 17 is issued regardless of the rotation speed of the propeller shaft 5, the actual rotation speed table is used when the actual rotation speed of the propeller shaft 5 is low. 23, a command rotational speed 24 suitable for the actual rotational speed is output, and when the steering wheel commands 15 and 17 exceed the command rotational speed 24, the command rotational speed 24 is selected by the low side selection means 25 and the main command rotational speed is selected. The main command rotational speed 26 is then compared with the command rotational speed 36 output from the actual torque table 35 as the rotational speed suitable for the actual torque of the propeller shaft 5, and the main command rotational speed 26 is obtained. When the command rotational speed 36 is exceeded, the command rotational speed 36 is selected by the low-side selection means 37 so that the command rotational speed is not more than the rotational speed suitable for the actual torque. Since the command rotational speed 38 is limited, the valve opening of the control valve 7 is prevented so that the main steam is not supplied to the main turbine 3 in an amount equal to or higher than the rotational speed limited from both the actual rotational speed and the actual torque. Can be controlled.

  Therefore, the main turbine 3 is not operated in an overtorque state regardless of the operation of the operator or the like, and the main turbine 3 is stably operated within the design range even when an external force is applied during stormy weather. It becomes possible to do.

  In the embodiment described above, the amount of main steam to the main turbine 3 is limited by the first command speed 24 and the second command speed 36 output from the actual speed table 23 and the actual torque table 35. However, the main steam amount to the main turbine 3 can be limited only by either the actual rotational speed or the actual torque. When the main steam amount is limited, an alarm may be issued so that a pilot or the like can check.

  The limit curves for the command rotation speeds 24 and 36 in the actual rotation speed table 23 and the actual torque table 35 in the embodiment described above are merely examples, and are set according to the size of the hull, the characteristics of the main turbine 3, and other use conditions. What is necessary is just to be sufficient and it is not limited to embodiment mentioned above.

  In the above-described embodiment, the actual rotational speed and the actual torque are detected from the propeller shaft 5, but they may be detected from the speed reducer 2 and the main turbine 3.

  Further, the above-described embodiment shows an example of the best embodiment, and various modifications can be made without departing from the gist of the present invention, and the present invention is not limited to the above-described embodiment. .

  The steam turbine ship main turbine torque limiting device according to the present invention is useful for operating the main turbine of the steam turbine ship so as not to be over-torque in various marine conditions.

It is a block diagram of the main turbine torque limiting apparatus in the steam turbine ship which shows one Embodiment of this invention. FIG. 2 is a block diagram showing a function for limiting the torque of the main turbine based on the actual rotational speed in the main turbine torque limiting device shown in FIG. 1. It is a graph which shows the command rotation speed with respect to the actual rotation speed shown in FIG. FIG. 2 is a block diagram showing a function for limiting the torque of the main turbine based on the actual torque in the main turbine torque limiting device shown in FIG. 1. It is a graph which shows the command rotation speed with respect to the actual torque shown in FIG. It is a graph which shows the relationship between the control valve opening degree at the time of the control valve opening constant control in a steam turbine ship, and the main turbine rotation speed. It is a graph which shows the main turbine operation restriction curve in a steam turbine ship.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Propeller 2 ... Reduction gear 3 ... Main turbine 4 ... Low pressure turbine 5 ... Propeller shaft 6 ... Supply pipe 7 ... Steering valve 8 ... Speed detector 9 ... Torque detector 10 ... Controller 11, 12, 13 ... Wiring 14 ... Funabashi 15 ... Handle command 16 ... Engine control room 17 ... Handle command 18 ... Selection 19 ... Conversion table 20 ... Handle command table 21 ... Handle command rotation speed 22 ... Actual rotation speed 23 ... Actual rotation speed table 24 ... First command rotation Number 25 ... 1st low side selection means 26 ... Main command rotation speed (handle command rotation speed)
27 ... Valve opening 28 ... Valve opening conversion table 29 ... Signal corresponding to rotation speed 30 ... Selection unit 31 ... Time scheduler 32 ... Revolution signal 33 ... Comparison unit 34 ... Actual torque 35 ... Actual torque table 36 ... Second command Number of revolutions 37 ... second low side selection means 38 ... steering wheel command speed 39 ... automatic operation signal 40 ... selection unit 41 ... valve opening conversion table 50 ... main turbine torque limiter

Claims (4)

A main turbine torque limiting device for a steam turbine ship that performs rotation speed control in a navigation mode of a main turbine that drives a propeller of a steam turbine ship with a main steam amount by adjusting an opening degree of a control valve based on a handle command,
A rotational speed detector for detecting the actual rotational speed of the propeller, and an actual rotational speed table in which a command rotational speed that is a shaft torque suitable for the actual rotational speed detected by the rotational speed detector is set. Outputs the command rotation speed for the actual rotation speed from the number table, compares the command rotation speed with the rotation speed of the steering wheel command, and outputs a low rotation speed as the steering wheel command rotation speed, and the torque of the main turbine exceeds the set value. A main turbine torque limiting device for a steam turbine ship provided with a control device for controlling the opening degree of the control valve so as not to exist. A main turbine torque limiting device for a steam turbine ship that performs rotation speed control in a navigation mode of a main turbine that drives a propeller of a steam turbine ship with a main steam amount by adjusting an opening degree of a control valve based on a handle command,
A torque detector that detects the actual torque of the propeller, and an actual torque table that sets a command rotational speed that is a shaft torque suitable for the actual torque detected by the torque detector, are provided from the actual torque table to the actual torque. The command rotational speed is output, the command rotational speed is compared with the rotational speed of the steering wheel command, and the low rotational speed is output as the steering wheel command rotational speed so that the torque of the main turbine does not exceed the set value. A main turbine torque limiting device for a steam turbine ship provided with a control device for controlling the opening degree. A main turbine torque limiting device for a steam turbine ship that performs rotation speed control in a navigation mode of a main turbine that drives a propeller of a steam turbine ship with a main steam amount by adjusting an opening degree of a control valve based on a handle command,
A rotational speed detector for detecting the actual rotational speed of the propeller and a torque detector for detecting the actual torque of the propeller are provided, and a command rotational speed that becomes a shaft torque suitable for the actual rotational speed detected by the rotational speed detector. The actual rotational speed table is set, the command rotational speed corresponding to the actual rotational speed is output from the actual rotational speed table, and the command rotational speed is compared with the rotational speed of the steering wheel command so that the lower rotational speed is the main command rotational speed. Is provided with an actual torque table in which a command rotational speed that is suitable for the actual torque detected by the torque detector is set, and the command rotational speed for the actual torque is output from the actual torque table. A control device for controlling the opening degree of the control valve so that the torque of the main turbine does not exceed a set value by comparing the rotational speed with the main command rotational speed and outputting a low rotational speed as the handle command rotational speed. The main turbine torque limiting device of the steam turbine ship provided. The command rotational speed with respect to the actual rotational speed is compared with the rotational speed of the steering wheel command, and the low rotational speed is set as the main command rotational speed. 4. The main turbine torque limiting device for a steam turbine ship according to claim 3, wherein the main command rotational speed and the command rotational speed for the actual torque are compared and a low rotational speed is output as the steering wheel command rotational speed.

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