JP2011202557A - Steam compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the abnormal stop of a steam compressor caused by such a state that differential pressure between suction pressure and discharge pressure exceeds the allowable differential pressure of the steam compressor even if pressure of steam supplied to the steam compressor is fluctuated.SOLUTION: This steam compressor includes: a screw rotor 22 arranged in a steam chest in a housing 20; a motor 4 rotatively driving the screw rotor 22; a suction pressure detection section 6 detecting pressure of steam sucked into the steam chest 20a through the suction port 20b of the housing 20; a discharge pressure detection section 10 detecting pressure of steam discharged from the steam chest 20a through the discharge port 20c of the housing 20; and a rotational speed regulation section 14 regulating the rotational speed of the screw rotor 22 by driving of the motor 4. The rotational speed regulation section 14 includes a differential pressure limitation section 28a limiting the rotational speed of the screw rotor 22 so that the differential pressure of the pressure detected by the discharge pressure detection section 10 with respect to the pressure detected by the suction pressure detection section 6 does not exceed the limiting value of the differential pressure allowed by a compressor body 2.

Description

  The present invention relates to a steam compressor for compressing and delivering steam.

  2. Description of the Related Art Conventionally, a compressor that includes a screw rotor and compresses air by rotation thereof is known. For example, Patent Document 1 below includes a compressor main body having a cylinder and a rotor disposed in the cylinder, and the rotor rotates by driving a motor to suck air into the cylinder and compress the air. A compressor that sends out compressed air from a discharge port of a cylinder is disclosed. In this compressor, the pressure of the compressed air discharged from the discharge port of the cylinder is detected, and the rotational speed of the rotor driven by the motor is adjusted so that the detected pressure matches the target pressure.

JP 2006-152848 A

  By the way, in steam utilization facilities such as factories, it is desired to increase the pressure of used steam for reuse and return it to the steam supply line. A compressor is used for boosting the steam after use. It is being considered. However, when the compressor described in Patent Document 1 is applied to the compressor as it is, the pressure of the steam discharged from the compressor (discharge pressure) with respect to the pressure of the steam sucked into the compressor (intake pressure). May exceed the allowable differential pressure of the compressor, and the compressor may stop abnormally.

  Specifically, unlike air, the pressure of steam supplied to the compressor fluctuates, so that the differential pressure between the intake pressure and the discharge pressure may be large even if the discharge pressure of the compressor is low. For this reason, even if the rotational speed of the rotor is controlled so that the discharge pressure matches the target pressure as in the compressor of Patent Document 1, the differential pressure between the intake pressure and the discharge pressure is an allowable difference of the compressor. The pressure may be exceeded.

  The present invention has been made in order to solve the above-described problems. The purpose of the present invention is to achieve a difference in pressure between the intake pressure and the discharge pressure even when the pressure of the steam supplied to the steam compressor fluctuates. It is to prevent the occurrence of abnormal shutdown of the steam compressor due to exceeding the allowable differential pressure of the machine.

  In order to achieve the above object, a steam compressor according to the present invention is a steam compressor for compressing and delivering steam, and is provided with a steam chamber therein and for sucking steam into the steam chamber. A housing provided with an intake port and a discharge port for discharging steam from the steam chamber; and disposed in the steam chamber and driven to rotate to suck and compress the steam into the steam chamber; A screw rotor that discharges the compressed steam from the discharge port, a motor for rotationally driving the screw rotor, an intake-side pressure detection unit that detects the pressure of the steam sucked into the steam chamber through the intake port, A discharge-side pressure detection unit that detects the pressure of steam discharged from the steam chamber through the discharge port; and a rotation speed adjustment unit that adjusts the rotation speed of the screw rotor by driving the motor. The rotation speed adjustment unit limits the rotation speed so that the differential pressure of the detection pressure of the discharge side pressure detection unit with respect to the detection pressure of the intake side pressure detection unit does not exceed the differential pressure allowed by the compressor. Including a differential pressure limiting unit.

  In this steam compressor, the differential pressure limiting unit of the rotation speed adjusting unit prevents the differential pressure of the detection pressure of the discharge side pressure detection unit from the detection pressure of the intake side pressure detection unit from exceeding the differential pressure allowed by the compressor. In order to limit the rotation speed of the screw rotor, even if the intake pressure of the steam compressor fluctuates, the differential pressure between the intake pressure and the discharge pressure of the steam compressor does not exceed the allowable differential pressure of the steam compressor can do. Therefore, in this steam compressor, even when the pressure of the steam supplied to the steam compressor fluctuates, the differential pressure between the intake pressure and the discharge pressure of the steam compressor exceeds the allowable differential pressure of the steam compressor. It is possible to prevent the occurrence of an abnormal stop of the steam compressor due to the above.

  In the steam compressor, the rotation speed adjusting unit is a torque required for the motor to rotate the screw rotor based on a detection pressure of the intake side pressure detection unit and a detection pressure of the discharge side pressure detection unit. The required torque is calculated, the rotational speed of the motor is detected, the allowable torque of the motor corresponding to the rotational speed is calculated, and the calculated allowable torque is equal to or greater than the calculated required torque. It is preferable to further include a torque limiting unit that limits the rotational speed of the motor.

  According to this configuration, since the necessary torque necessary for rotating the screw rotor of the steam compressor is maintained below the allowable torque of the motor, a torque over that the required torque exceeds the allowable torque of the motor occurs and the motor is An abnormal stop can be prevented.

  In the steam compressor, it is preferable that the rotation speed adjusting unit further includes an output limiting unit that limits the rotation speed so that an output of the motor is equal to or lower than a maximum output of the motor.

  According to this configuration, it is possible to prevent the motor from being abnormally stopped due to an output over which the output of the motor exceeds the maximum output of the motor.

  As described above, according to the present invention, even when the pressure of the steam supplied to the steam compressor fluctuates, the difference in pressure between the intake pressure and the discharge pressure of the steam compressor is an allowable difference in the steam compressor. It is possible to prevent the abnormal stop of the steam compressor caused by exceeding the pressure.

1 is a system diagram showing a schematic overall configuration of a vapor compressor according to an embodiment of the present invention. It is a figure which shows the structure of the compressor main body which comprises the steam compressor shown in FIG. It is a figure which shows the range which can operate | move a steam compressor in the relationship between the intake pressure and discharge pressure of a steam compressor when the rotation speed of a motor is 6000 rpm. It is a figure which shows the range which can be drive | operated of a steam compressor in the relationship between the discharge pressure and motor rotation speed when the intake pressure of a steam compressor is -0.05MPaG. It is a figure which shows the range which can operate | move the steam compressor in the relationship between the discharge pressure and motor rotation speed when the intake pressure of a steam compressor is 0 MPaG. It is a figure which shows the range which can be drive | operated of a steam compressor in the relationship between the discharge pressure and motor rotation speed when the intake pressure of a steam compressor is 0.2 MPaG. It is a figure which shows the range which can operate | move the steam compressor in the relationship between the discharge pressure and motor rotation speed when the intake pressure of a steam compressor is 0.5 MPaG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, with reference to FIG.1 and FIG.2, the structure of the steam compressor by one Embodiment of this invention is demonstrated.

  The steam compressor according to the present embodiment boosts the used steam used in a steam utilization facility such as a factory for reuse, and compresses and feeds the steam supplied to the compressor body 2. To do. Specifically, as shown in FIG. 1, the steam compressor includes a compressor body 2, a motor 4, an intake side pressure detection unit 6, an intake side temperature detection unit 8, and a discharge side pressure detection unit 10. A discharge-side temperature detection unit 12, a rotation speed adjustment unit 14, and a pressure control valve 16.

  The compressor body 2 is a part that compresses the supplied steam. As shown in FIG. 2, the compressor body 2 includes a housing 20, a screw rotor 22, and a bearing 24.

  The housing 20 is provided with a steam chamber 20a therein, and is provided with an intake port 20b for sucking steam into the steam chamber 20a and a discharge port 20c for discharging compressed steam from the steam chamber 20a. ing.

  The screw rotor 22 is disposed in the steam chamber 20a. The screw rotor 22 rotates to suck and compress the steam into the steam chamber 20a, and discharge the compressed steam from the discharge port 20c. Specifically, the screw rotor 22 is integrally provided with a rotation shaft 22a so as to extend on both sides in the axial direction, and the rotation shafts 22a extending on both sides thereof are respectively provided by bearings 24 provided in the housing 20. It is supported. Thereby, the screw rotor 22 can rotate around its axis in the steam chamber 20a. Although not shown in FIG. 2, the screw rotor 22 closes the steam sucked into the steam chamber 20 a through the air inlet 20 b into the space formed by the screw of the rotor 22 and rotates the rotor 22. Accordingly, the vapor confined in the space is compressed by reducing the space while moving the space toward the discharge port 20c. Thereby, the compressed vapor | steam is discharged outside from the vapor | steam chamber 20a through the discharge outlet 20c.

  The motor 4 (see FIG. 1) is an electric motor that rotationally drives the screw rotor 22. Specifically, the drive shaft of the motor 4 is connected to the rotary shaft 22a, and the screw rotor 22 rotates when the motor 4 is driven. That is, the rotational speed of the screw rotor 22 is equal to the rotational speed of the motor 4. The rotation speed data of the motor 4 is sent to a control section 28 (described later) of the rotation speed adjustment section 14 via the inverter 26.

  The intake-side pressure detector 6 is connected to a steam supply path connected to the intake port 20b, and detects the pressure of the steam sucked into the steam chamber 20a through the intake port 20b. The data of the detected pressure of the intake side pressure detection unit 6 is sent to a control unit 28 described later of the rotation speed adjustment unit 14.

  The intake side temperature detection unit 8 is connected to a steam supply path connected to the intake port 20b, and detects the temperature of the steam sucked into the steam chamber 20a through the intake port 20b. The detected temperature data of the intake side temperature detection unit 8 is sent to a control unit 28 (to be described later) of the rotation speed adjustment unit 14.

  The discharge-side pressure detection unit 10 is connected to a vapor discharge path connected to the discharge port 20c, and detects the pressure of the vapor discharged from the vapor chamber 20a through the discharge port 20c. Data of the detected pressure of the discharge side pressure detection unit 10 is sent to a control unit 28 described later of the rotation speed adjustment unit 14.

  The discharge side temperature detector 12 is connected to a steam discharge path connected to the discharge port 20c, and detects the temperature of the steam discharged from the steam chamber 20a through the discharge port 20c. Data of the detected temperature of the discharge side temperature detection unit 12 is sent to a control unit 28 described later of the rotation speed adjustment unit 14.

  The pressure control valve 13 is provided in a steam discharge path connected to the discharge port 20c, and controls the pressure of the steam discharged from the discharge port 20c to the steam discharge path to a predetermined pressure.

  The rotation speed adjustment unit 14 adjusts the rotation speed of the screw rotor 22 driven by the motor 4. Specifically, the rotation speed adjustment unit 14 adjusts the rotation speed of the screw rotor 22 by adjusting the rotation speed of the motor 4. The rotation speed adjusting unit 14 can adjust the differential pressure between the intake pressure and the discharge pressure of the compressor body 2 by adjusting the rotation speed of the screw rotor 22, and when the intake pressure is constant, While the discharge pressure can be adjusted by adjusting the differential pressure, the intake pressure can be adjusted by adjusting the differential pressure when the discharge pressure is constant. The rotation speed adjustment unit 14 includes an inverter 26 and a control unit 28.

  The inverter 26 is electrically connected to the motor 4, and electric power is supplied to the motor 4 via the inverter 26. The inverter 26 adjusts the rotational speed of the motor 4 in accordance with a control signal sent from the control unit 28.

  The control unit 28 causes the inverter 26 to adjust the rotation speed of the motor 4. The control unit 28 causes the inverter 26 to control the rotation speed of the motor 4 within a range that does not exceed all the limitations of differential pressure limitation, torque limitation, and output limitation described later. Specifically, the control unit 28 includes a differential pressure limiting unit 28a, a torque limiting unit 28b, and an output limiting unit 28c as functional blocks.

  The differential pressure limiting unit 28a is configured such that the differential pressure of the detection pressure (discharge pressure) of the discharge side pressure detection unit 10 with respect to the detection pressure (intake pressure) of the intake side pressure detection unit 6 is a differential pressure allowed by the compressor, specifically, compression. The rotational speed of the motor 4 is limited so as not to exceed the differential pressure allowed by the machine body 2. Specifically, the differential pressure limiting unit 28a calculates the differential pressure by subtracting the detection pressure of the intake side pressure detection unit 6 from the detection pressure of the discharge side pressure detection unit 10, and the calculated differential pressure is the compressor. The inverter 26 is made to limit the rotation speed of the motor 4 so that it may become below the differential pressure which the main body 2 permits.

  The relationship between the rotation speed of the motor 4 and the differential pressure is as follows. When the rotational speed of the motor 4 increases, the rotational speed of the screw rotor 22 also increases. As a result, the amount of steam sucked into the steam chamber 20a is increased and the compression of the steam in the steam chamber 20a is promoted. A decrease in intake pressure and an increase in discharge pressure occur, and the differential pressure between the discharge pressure and the intake pressure increases. On the other hand, when the rotational speed of the motor 4 is decreased, the rotational speed of the screw rotor 4 is also decreased. As a result, the amount of steam sucked into the steam chamber 20a is reduced and the compression of the steam in the steam chamber 20a is suppressed. Therefore, an increase in intake pressure and a decrease in discharge pressure occur, and the differential pressure between the discharge pressure and the intake pressure decreases.

  Based on such a relationship, the differential pressure limiting unit 28a limits the rotational speed of the motor 4 so that the differential pressure of the discharge pressure with respect to the intake pressure is equal to or less than the differential pressure allowed by the compressor body 2.

  The differential pressure allowed by the compressor body 2, that is, the differential pressure limit value of the compressor body 2 is a constant value defined due to the design of the compressor body 2, and the diameter of the rotary shaft 22a It is defined in consideration of the strength of the bearing 24 and the like. As shown in FIG. 3, this differential pressure limit value is represented by a straight line in which the discharge pressure increases in direct proportion to the increase in the intake pressure when expressed by the relationship between the intake pressure and the discharge pressure. The differential pressure limiting unit 28a limits the rotation speed of the motor 4 so that the detection pressure of the intake side pressure detection unit 6 and the detection pressure of the discharge side pressure detection unit 10 do not exceed this straight line. FIG. 3 shows the relationship between the limit values when the rotation speed of the motor 4 is 6000 rpm.

  The torque limiting unit 28 b limits the rotation speed of the motor 4 so that the allowable torque of the motor 4 is equal to or greater than the necessary torque that is necessary for the motor 4 to rotate the screw rotor 22. Specifically, the torque limiting unit 28 calculates the necessary torque based on the detection pressure of the intake side pressure detection unit 6 and the detection pressure of the discharge side pressure detection unit 10. This required torque is obtained by the following equation.

Required torque = (n−V _i ⁽ⁿ⁻¹⁾ ) / ((1−n) × P _s + P _d / V _i ) × V _th
Here, n is a gas constant and is a physical property value of steam. V _i is an internal volume ratio, and corresponds to a volume change rate generated until the space in which the steam is confined by the screw rotor 22 at the position on the intake port 20b side in the steam chamber 20a reaches the discharge port 20c. P _s is the inlet pressure, _{P d} is the discharge pressure. V _th is the volume of the space in which the screw rotor 22 traps steam per rotation on the intake port 20b side. Note that the density of the steam sucked into the steam chamber 20a and the density of the steam discharged from the steam chamber 20a vary depending on the temperature of the steam. For this reason, the torque limiting unit 28b has a density of steam sucked into the steam chamber 20a based on the detected temperature (intake air temperature) of the intake side temperature detector 8 and the detected pressure (intake pressure) of the intake side pressure detector 6. And the density of the steam discharged from the steam chamber 20a based on the detected temperature (discharge temperature) of the discharge side temperature detector 12 and the detected pressure (discharge pressure) of the discharge side pressure detector 10; A correction coefficient is obtained from the calculated density of the intake steam and the density of the discharge steam, and the necessary torque obtained by correcting the influence of the temperature of the steam is obtained by multiplying the correction coefficient by the necessary torque obtained by the above formula.

  The torque limiter 28 b detects the rotational speed of the motor 4 and calculates the allowable torque of the motor 4 corresponding to the rotational speed based on the torque characteristics of the motor 4. Specifically, the motor 4 has a torque characteristic in which the torque changes with the rotational speed. The allowable torque of the motor 4 corresponds to the actual torque of the motor 4 according to the rotation speed when the motor 4 is driven at a certain rotation speed. The control unit 28 stores the torque characteristics of the motor 4, and the torque limiting unit 28 b is based on the stored torque characteristics and corresponds to the rotation speed data of the motor 4 sent from the motor 4. The allowable torque of the motor 4 at the time is calculated.

  When the required torque exceeds the allowable torque of the motor 4, the motor 4 becomes overtorque and stops abnormally. For this reason, the torque limiting unit 28b causes the inverter 26 to limit the rotational speed of the motor 4 so that the calculated allowable torque is equal to or greater than the calculated necessary torque. According to the limitation of the rotation speed of the motor 4 by the torque limiting section 28b, the intake pressure and the discharge pressure are limited within a range equal to or less than the straight line of the torque limit value shown in FIG.

  The output limiting unit 28 c limits the rotation speed of the motor 4 so that the output of the motor 4 is less than or equal to the maximum output of the motor 4. Specifically, the output limiting unit 28c detects the rotational speed of the motor 4 and calculates the output of the motor 4 that is the product of the rotational speed and the torque of the motor 4 corresponding to the rotational speed. The control unit 28 stores the maximum output of the motor 4, and the output limiting unit 28 c causes the inverter 26 to limit the rotation speed of the motor 4 so that the calculated output is equal to or less than the maximum output of the motor 4. According to the limitation of the rotation speed of the motor 4 by the output limiting section 28c, the intake pressure and the discharge pressure are limited within a range equal to or less than the straight line of the output limit value shown in FIG.

  The control unit 28 stores the maximum number of rotations of the motor 4, and the control unit 28 includes an inverter so that the number of rotations of the motor 4 does not exceed the maximum number of rotations apart from the above-described restrictions. 26 controls the rotational speed of the motor 4.

  Then, the control unit 28 limits the rotational speed of the motor 4 by the differential pressure limiting unit 28a (differential pressure limitation), limits the rotational speed of the motor 4 by the torque limiting unit 28b (torque limitation), and limits the output. The inverter 26 is caused to control the rotational speed of the motor 4 so as to satisfy all of the rotational speed limitation (output limitation) of the motor 4 by the unit 28c. Thereby, at a certain rotational speed of the motor 4, the discharge pressure and the intake pressure are controlled within the hatched range in FIG.

In each case where the intake pressure P _s is −0.05 MPaG, 0.00 MPaG, 0.20 MPaG, and 0.50 MPaG, the differential pressure limit, the torque limit, the output limit, and the maximum rotational speed limit of the motor 4 (8000 rpm or less) ) Is as shown in FIGS. In each of these cases, the rotation speed and discharge pressure of the motor 4 are controlled in the hatched region A in FIGS. 4 to 7 so as to satisfy all the above-described restrictions.

Specifically, when the intake pressure is low and P _s = −0.05 MPaG (see FIG. 4), the discharge pressure limit value due to the differential pressure limit is lower than the discharge pressure limit value due to the torque limit, And it becomes below the limit value of the discharge pressure by output restriction. Therefore, in this case, the rotation speed and discharge pressure of the motor 4 are controlled within a range defined by the differential pressure limit and the maximum rotation speed limit of the motor 4.

In the case the intake pressure _{P s} is 0.00MPaG (see FIG. 5), in the region near the rotational speed of the motor 4 is the maximum rotational speed (8000 rpm), the discharge due to the limit value is a differential pressure limit of the discharge pressure due to the output limit Below the pressure limit. Therefore, in this case, the rotational speed and discharge pressure of the motor 4 are controlled within a range defined by the differential pressure limit, the output limit, and the maximum rotational speed limit of the motor 4. In other words, the rotation speed and discharge pressure of the motor 4 are controlled within a range excluding the B area in FIG. 5 from the range defined by the differential pressure limit and the maximum speed limit.

In the case the intake pressure _{P s} is 0.20MPaG (see FIG. 6) or in the case of 0.50MPaG (see FIG. 7), the limit value of the discharge pressure by the torque limit is below the limit value of the discharge pressure due to the differential pressure limit, Further, the discharge pressure limit value due to output limitation is lower than the discharge pressure limit value due to torque limitation in a region where the rotational speed of the motor 4 is relatively high. Therefore, in these cases, the rotational speed and discharge pressure of the motor 4 are controlled within a range defined by the output restriction, the torque restriction, and the maximum rotational speed limit of the motor 4. In other words, the rotation speed and discharge pressure of the motor 4 are controlled within a range excluding the area C in FIG. 6 or 7 from the range defined by the torque limit and the maximum rotation speed limit.

  As described above, in the steam compressor according to the present embodiment, the differential pressure limiting unit 28a included in the control unit 28 of the rotation speed adjusting unit 14 has the discharge side pressure detection unit 10 for the detected pressure of the intake side pressure detection unit 6. In order to limit the rotational speed of the screw rotor 22 so that the differential pressure of the detected pressure does not exceed the differential pressure allowed by the compressor body 2, even if the intake pressure fluctuates, the differential pressure between the intake pressure and the discharge pressure is It is possible to prevent exceeding the allowable differential pressure of the compressor body 2. Therefore, in this embodiment, even when the pressure of the steam supplied to the steam compressor fluctuates, the steam compression caused by the difference between the intake pressure and the discharge pressure exceeding the allowable pressure difference of the steam compressor. It is possible to prevent the machine from stopping abnormally.

  In the present embodiment, the torque limiting unit 28b included in the control unit 28 of the rotation speed adjusting unit 14 causes the motor 4 so that the allowable torque of the motor 4 is greater than the necessary torque required to rotate the screw rotor 22. In order to limit the number of rotations, the required torque is maintained below the allowable torque of the motor 4. For this reason, it is possible to prevent the motor 4 from abnormally stopping due to a torque over which the required torque exceeds the allowable torque of the motor 4.

  In the present embodiment, the output limiting unit 28c included in the control unit 28 of the rotation speed adjusting unit 14 limits the rotation speed of the motor 4 so that the output of the motor 4 is equal to or lower than the maximum output of the motor 4. Therefore, it is possible to prevent the output of the motor 4 from exceeding the maximum output of the motor 4 and causing the motor 4 to stop abnormally.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  Specifically, in the above embodiment, the control unit 28 of the rotation speed adjusting unit 14 includes the differential pressure limiting unit 28a, the torque limiting unit 28b, and the output limiting unit 28c, but the present invention is not limited to this configuration. For example, the control unit 28 of the rotation speed adjusting unit 14 may include only the differential pressure limiting unit 28a. The control unit 28 includes a differential pressure limiting unit 28a and a torque limiting unit 28b, and may not include the output limiting unit 28c. The control unit 28 includes a differential pressure limiting unit 28a and an output limiting unit 28c, and may not include the torque limiting unit 28b.

  In addition, a pressure holding valve may be provided instead of the pressure control valve 13 provided in the steam discharge path connected to the discharge port 20c.

4 Motor 6 Intake side pressure detection unit 10 Discharge side pressure detection unit 14 Rotational speed adjustment unit 20 Housing 20a Steam chamber 20b Inlet port 20c Discharge port 22 Screw rotor 28a Differential pressure limiting unit 28b Torque limiting unit 28c Output limiting unit

Claims (3)

A steam compressor for compressing and delivering steam,
A housing in which a steam chamber is provided and an intake port for sucking steam into the steam chamber and a discharge port for discharging steam from the steam chamber;
A screw rotor that is disposed in the steam chamber and is rotationally driven to suck and compress the steam into the steam chamber and discharge the compressed steam from the discharge port;
A motor for rotationally driving the screw rotor;
An intake-side pressure detector that detects the pressure of steam sucked into the steam chamber through the intake port;
A discharge-side pressure detector that detects the pressure of steam discharged from the steam chamber through the discharge port;
A rotation speed adjusting unit that adjusts the rotation speed of the screw rotor driven by the motor;
The rotational speed adjustment unit is configured to prevent the screw rotor from detecting a pressure difference detected by the discharge side pressure detection unit with respect to a pressure detected by the intake side pressure detection unit. A steam compressor including a differential pressure limiting unit that limits the rotational speed.   The rotation speed adjustment unit calculates a necessary torque that is a torque necessary for the motor to rotate the screw rotor based on a detection pressure of the intake side pressure detection unit and a detection pressure of the discharge side pressure detection unit. In addition, the rotational speed of the motor is detected, the allowable torque of the motor corresponding to the rotational speed is calculated, and the rotational speed of the motor is limited so that the calculated allowable torque is equal to or greater than the calculated required torque. The steam compressor according to claim 1, further comprising a torque limiter that performs the operation.   3. The steam compressor according to claim 1, wherein the rotation speed adjustment unit further includes an output limiting unit that limits a rotation speed of the motor so that an output of the motor is equal to or lower than a maximum output of the motor.

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