WO2005033647A1

WO2005033647A1 - Method and device for measuring driving power

Info

Publication number: WO2005033647A1
Application number: PCT/EP2004/052174
Authority: WO
Inventors: Wolfgang Lang; Hanspeter Zinn
Original assignee: Alstom Technology Ltd
Priority date: 2003-09-29
Filing date: 2004-09-15
Publication date: 2005-04-14
Also published as: DE10345180A1

Abstract

The invention relates to a device (3) for measuring power of a drive (1) which rotationally drives a shaft (2). The measuring device (3) comprises a torque sensor (4) which operates in a contact-free manner and is formed such that it can detect a signal (M). Said signal (M) is correlated with the torque which is transmitted by the shaft (2). Said measuring device (3) also comprises an evaluating unit (6) which determines a power signal (P) from the signal (M) of the torque sensor (4) and a rotational speed signal (n). The rotational speed signal (n) is correlated with the rotational speed of the shaft (2) and the power signal (P) is correlated with the power of the drive (1).

Description

Method and device for measuring drive power

Technical field

The present invention relates to a device and a method for measuring a power of a drive rotating a shaft. The invention also relates to the use of a non-contact torque sensor.

State of the art

Drives that drive a shaft are known from a variety of applications. For example, a piston engine drives a crankshaft and a drive train coupled to it. An electric motor drives its rotor shaft and possibly a drive train coupled to it. A turbo machine also drives its rotor. For the operation of such drives or for the operation of systems equipped with such drives, it may be necessary to know the power transmitted from the respective drive to the respective shaft as precisely as possible. If the shaft power is known, operating parameters of the system or the respective drive can be regulated in a power-controlled manner, for example. A direct measurement of the power transmitted from the respective drive to the respective shaft is generally only comparatively difficult to achieve during the intended use of the respective drive. For example, in the case of piston engines, the current engine power is determined from characteristic maps in which the engine power is stored as a function of a throttle valve position and an engine speed. Such maps are recorded in special test benches and have limited accuracy due to the manufacturing tolerances of the piston engines. In the case of electric motors, the power transferred to the rotor can be determined relatively easily from the electric power consumed by the electric motor, empirically determined loss coefficients being taken into account. In the case of a turbo group that drives a generator in a power plant, the power transmitted from the turbo group to the shaft can also be determined on the basis of the electrical power generated by the generator, empirical losses being taken into account here as well.

In addition, the electrical power of the generator can be used to determine the power transmitted from the turbo group to the shaft relatively precisely only in a stationary operating state. During transient conditions, especially when starting up or starting up such a gas turbine system, an exact determination of the active power in modern, clocked drives requires a high measurement effort; or the determination of the drive power is fraught with high uncertainties due to the high-frequency variation of the reactive power. Recording the power when starting or starting a turbo group is therefore very difficult and time-consuming.

In a drive system in which several drives drive a common shaft, it may be necessary that the individual drives Record the output power individually, for example to be able to control the individual drives individually. Here the performance measurement is complex and difficult. With a turbo group, the rotor of which is driven by a gas turbine and a steam turbine, a thermodynamic balancing is used, for example, in order to distribute the power transferred from the entire turbo group to the rotor among the individual drives (gas turbine and steam turbine). Such accounting is, however, fraught with errors. In the case of more extensive systems, which also include, for example, a low-pressure turbine and a medium-pressure turbine, the calculation of the individual power of the individual drives is very complex, with the accuracy simultaneously decreasing.

Presentation of the invention

The invention seeks to remedy this. The invention, as characterized in the claims, deals with the problem of providing an improved way for a drive which drives a shaft to rotate, to measure the power transmitted from the drive to the shaft. In particular, a way is to be shown which enables a direct and continuous measurement of the shaft power. Furthermore, a way is to be shown which simplifies the measurement of the shaft power when starting a turbo group. In addition, a way is to be shown which enables a separate measurement of the individual drive powers of the individual drives in the case of a drive train with several drives.

According to the invention, this problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject of the dependent claims. The present invention is based on the general idea of using a torque sensor to detect a signal that correlates with a torque that is transmitted at the respective measuring point within the shaft. The torque can then be used in conjunction with the current shaft speed to calculate the current shaft power at said measuring point. If the torque sensor detects the respective signal on the shaft without contact, there are no repercussions on the drive. Furthermore, the installation effort is very low.

With the aid of the procedure according to the invention for measuring the shaft power, the power transmitted by the shaft is recorded directly and continuously. In particular, the wave power can thus also be measured in discontinuous processes or in transient processes.

It is particularly advantageous in the procedure according to the invention that in the case of a drive train in which a plurality of drives drive a common shaft, the power transmitted from the individual drives to the shaft can be determined individually without having to resort to complex and error-prone calculation models.

The torque sensor used here works on the basis of an anisotropic magnetostrictive effect that occurs with ferromagnetic waves. The torque transmitted by the shaft creates a torsion in the shaft, which leads to torsional stresses in the shaft material. These torsional stresses change the magnetic permeability in the direction of the expansion stresses and compressive stresses. With the help of the sensor, the permeability or the change in permeability can now be measured at the respective measuring point on the shaft. How the torque sensor works is now based on the knowledge that the permeability in a sufficiently large measuring range is proportional to the torsional stress on the shaft surface. Furthermore, the torsional stress is proportional to the torsion of the shaft, so that when knowledge of the shaft parameters, such as. B. area moment of inertia and material that can be calculated effective torque in the shaft. Accordingly, the present invention makes use of the knowledge that the permeability which can easily be measured with the aid of the torque sensor correlates without contact with the torsional stress and correlates this with the transmitted torque, so that ultimately the permeability which can be detected with the aid of the sensor correlates with the torque transmitted in the measuring point , In this way, a signal correlating with the torque can be easily generated with the aid of the torque sensor.

As explained, in addition to the torque, the speed of the shaft is also required to determine the shaft power. With certain drives, corresponding control devices can readily provide a speed signal that correlates with the speed, so that an already existing speed signal can be used to determine the shaft power. If the speed of the shaft has to be determined separately, a conventional speed sensor can be used. A contactless speed sensor is preferred which can detect the current speed of the shaft inductively or optically, for example. In this way, disadvantageous interaction with the drive can again be avoided.

The invention is particularly suitable for use in a drive train of a turbo group in which several drives, for. B. a gas turbine and a steam turbine, a common shaft, usually a rotor of the turbo group, drive. By an appropriate selection of the The respective measuring point along the shaft can be individually determined with the aid of the invention, the power introduced into the common shaft by the individual drives. This applies both to steady-state operating states and when the turbo group is started up and in other transient states.

Further important features and advantages of the present invention result from the subclaims, from the drawing and from the associated description of the figures with reference to the drawing.

Brief description of the drawings

Preferred embodiments of the invention are shown in the drawing and are explained in more detail in the following description.

The only Fig. 1 shows a circuit diagram-like schematic representation of a device according to the invention.

Ways of Carrying Out the Invention

1, a drive 1 is drive-coupled to a shaft 2, so that the drive 1 drives the shaft 2 in rotation during operation. The drive 1 can in principle be any drive machine suitable for rotating the shaft 2, such as, for. B. a piston engine, an electric motor or a turbomachine. In the example shown here, the drive 1 is a turbine, for. B. a gas turbine or a steam turbine. The turbine 1 can form part of a turbo group which comprises one or more turbomachines. In particular, the turbo group can have several driving fluid machines, such as. B. include one or more gas turbines and / or one or more steam turbines, each of which drives the shaft 2.

The shaft 2 is therefore a basically any output shaft of the drive 1, in particular a crankshaft of a piston engine or a rotor of an electric motor or a drive train coupled to the crankshaft or to the rotor. In the exemplary embodiment shown here, the shaft 2 is a rotor of the turbine

1 or the turbo group, of which the turbine 1 is a component.

Via the shaft 2, the drive 1 generally drives a machine, not shown here, which can be a pump, for example. If the drive 1 is a turbine 1 or a turbo group, the shaft 2 expediently drives at least one generator.

A measuring device 3 according to the invention is provided for measuring the line transmitted from the drive 1 to the shaft 2. The measuring device 3 comprises at least one torque sensor 4, which is arranged at a suitable measuring point 5 along the shaft 2, symbolized by a brace. The torque sensor 2 generates a signal M in a manner which will be explained in more detail below, which signal from the shaft within the measuring point 5

2 transmitted torque correlated.

The measuring device 3 also includes an evaluation unit 6, to which the signal M of the torque sensor 4 is fed. If the torque sensor 4 generates an analog signal M, an analog / digital converter 7 is arranged between the torque sensor 4 and the evaluation unit 6, which converts the incoming analog signal into an outgoing digital signal transformed. Furthermore, the evaluation unit 6 has access to a speed of the shaft 2. For example, the shaft speed is already determined and / or provided for another purpose within another system of the drive 1, so that the evaluation unit 6 only has to be connected to said system. In the embodiment shown here, the shaft speed is determined with the aid of a speed sensor 8, which generates the speed signal n correlating with the shaft speed and feeds it to the evaluation unit 6. The evaluation unit 6 can now determine a power signal P correlating with the power of the drive 1 from the incoming signal M of the torque sensor 4 and the speed signal n; Usually P = M x 2 x π x n.

The speed sensor 8 preferably works without contact and can the speed of the shaft 2 z. B. optically or inductively. According to the invention, the torque sensor 4 also works without contact. On the one hand, this does not result in any adverse interactions between the sensors 4, 8 and the shaft 2 or the drive 1. On the other hand, the installation outlay for the measuring device 3 is considerably reduced, since the torque sensor 4 is virtually at any suitable, appropriately accessible Point along the shaft 2 can be positioned.

The shaft 2 consists of a ferromagnetic material, e.g. B. made of steel. It has been shown that the magnetic permeability of such a shaft 2 changes as a function of the torsional stresses formed therein. This is used in the present invention in that the torque sensor 4 is designed such that it can detect a signal at the measuring point 5 that correlates with the magnetic permeability. Since the permeability is proportional to the torsional stress on the surface of the shaft 2 in a measuring range which is sufficiently large for the measuring purposes at hand is, the signal generated by the torque sensor 4 also correlates with the torsion voltage on the shaft surface at the measuring point 5. Since the torsional stress also results from the torsion of the shaft 2 at the respective measuring point 5 and thus from the torque transmitted by the shaft 2 at the measuring point 5 the torsional stress in turn with the torque. Ultimately, the permeability of shaft 2 thus correlates with the torque transmitted by shaft 2. Accordingly, the signal M determined by the torque sensor 4 correlates with the torque transmitted by the shaft 2 in the area of the measuring point 2.

In a further development of the measuring device 3, the torque measurement with the aid of the torque sensor 4 can also be used to monitor the time course of the torque at the measuring point 5. In particular, torsional vibrations of shaft 2 can be analyzed. This monitoring and evaluation of torsional vibrations can take place in the evaluation unit 6 shown here or alternatively in another, additional evaluation unit which has access to the signal M generated by the torque sensor 4 or is supplied in parallel with this signal M by the torque sensor 4.

The measuring device 3 according to the invention can for example be integrated in a test bench system, with the aid of which a separate shaft power measurement can be carried out. Furthermore, the measuring device 3 can expediently also be integrated into a measuring system which is suitable for measuring separate drive powers of a plurality of drives 1, these drives 1 driving the same shaft 2. For example, a generator, a gas turbine, a compressor and a steam turbine are connected to one another via the shaft 2. By suitably arranging the measuring points 5 between the individual drive and / or drive components, the power consumed by the generator, the power consumed by the compressor, the power introduced by the gas turbine and the power introduced by the steam turbine can be determined individually and with great accuracy by addition or summation. Empirical estimates using thermodynamic calculation methods are not required.

The measuring device 3 can be integrated particularly easily into a power control system for the drive 1. In this way, a power-controlled regulation of the respective drive 1 can be easily represented. For example, the measuring device 3 can be integrated into a closed loop control. This also applies in a corresponding manner to a control system which can individually adjust or regulate the power of a plurality of drives 1 which drive a common shaft 2 with the aid of a corresponding number of measuring devices 3 according to the invention.

In addition, the measuring device 3 can be integrated into another power measurement system that is used to determine the power of a generator. The power values determined by the measuring device 3 according to the invention can be used as redundant values to those of the other power measurement system. In this respect, the measuring device 3 enables inexpensive monitoring of other, usually more complex, power measurement systems.

With the help of drive protection systems, the proper operation of drive 1, for example a turbo group, can be monitored. By integrating the measuring device 3 according to the invention into such a drive protection system, an additional parameter is provided which is advantageous for monitoring the proper operation of the drive 1 can be used. Furthermore, diagnostic and / or monitoring systems are possible, with the aid of which the time course of the drive power can be monitored, evaluated and / or visualized. Here, too, the measuring device 3 according to the invention can deliver the required power signals P in a particularly inexpensive manner.

As already mentioned above, the measuring device 3 according to the invention can also be integrated into a torsional vibration analysis system, with the aid of which the vibration behavior of the shaft 2 can be monitored. The vibration behavior of shaft 2 in turn provides information about the current operating state of drive 1.

LIST OF REFERENCE NUMBERS

1 drive / turbine / turbo group 2 shaft / rotor 3 measuring device 4 torque sensor 5 measuring point 6 evaluation unit 7 analog / digital converter 8 speed sensor

M signal of 4 n signal of 8

P signal from 6

Claims

claims

1. Device for measuring a power of a drive (1) which rotates a shaft (2),

with a non-contact torque sensor (4) for detecting a signal (M) at a measuring position (5), which correlates with a torque transmitted by the shaft (2) at the measuring position (5),

- With an evaluation unit (6) which from the signal (M) of the torque sensor (4) and a speed signal (n) correlating with a speed of the shaft (2) determines a power signal (P) correlating with the power of the drive (1) ,

2. Measuring device according to claim 1, so that the torque sensor (4) is designed such that the signal (M) thus detected has a torsional stress on a surface of the shaft (2) on the Measuring position (5) correlated.

3. Measuring device according to claim 1 or 2, characterized in that the torque sensor (4) is designed such that the signal (M) thus detected correlates with a magnetic permeability of the shaft (2) at the measuring position (5).

4. Measuring device according to one of claims 1 to 3, characterized in that the shaft (2) consists of a ferromagnetic material.

5. Measuring device according to one of claims 1 to 4, characterized in that a speed sensor (8) for detecting the speed signal (s) is provided.

6. Measuring device according to claim 5, characterized in that the speed sensor (8) works without contact.

7. Measuring device according to one of claims 1 to 6, characterized in that the drive (1) is a drive component of a turbo group.

8. Measuring device according to claim 7, characterized in that the shaft (2) is a rotor of the turbo group.

9. Measuring device according to one of claims 1 to 8, characterized in that the same or a different evaluation unit (6) uses the signal (M) of the torque sensor (4) for the analysis of torsional vibrations of the shaft (2).

10. Measuring device according to one of claims 1 to 9, characterized in that that the measuring device (3) is integrated in at least one of the following systems:

- test bench system for separate shaft power measurement,

- Measuring system for measuring separate drive powers of several drives (1) which drive the same shaft (2),

- power control system of the drive (1),

- Power control system for an arrangement of several drives (1) which drive the same shaft (2),

- Power measurement system for the electrical measurement of the power of a generator driven by the shaft (2), the measurement device (3) delivering redundant measured values and / or being used to monitor the electrical power measurement,

- Drive protection system that monitors the proper operation of the drive (1) depending on the drive power,

- Diagnostic system that monitors and evaluates the operation of the drive (1) depending on the drive power,

Monitoring system which records and displays the course of the drive power of the drive (1),

- Torsional vibration analysis system for monitoring the vibration behavior of the shaft (2).

11. Use of a non-contact torque sensor (4) when measuring a power of a drive (1) rotating a shaft (2).

12. Use according to claim 11, so that the torque sensor (4) detects a signal (M) that correlates with the torque that is transmitted by the shaft (2).

13. Use according to claim 12, dad u rc h ge ken nze that from the signal (M) of the torque sensor (4) and a speed signal (n) correlating with the speed of the shaft (2), a power signal correlated with the power (P) is determined.

14. Method for measuring a power of a drive (1) driving a shaft (2),

a signal (M) is detected on the shaft (2) at a measuring position (5) by means of a non-contact torque sensor (4), which signal correlates with a torque transmitted by the shaft (2) at the measuring position (5),

- In which from the signal (M) of the torque sensor (4) and a speed signal (n) correlating with a speed of the shaft (2) a power signal (P) correlated with the power of the drive (1) is determined.

15. The method according to claim 14, so that the signal (M) detected with the torque sensor (4) correlates with a torsional stress on a surface of the shaft (2) at the measuring position (5).

16. The method according to claim 14 or 15, so that the signal M detected by the torque sensor (4) correlates with a magnetic permeability of the shaft (2) at the measuring position (5).