Electric machine having monitoring device and method for monitoring

Abstract

The invention relates to an electric machine comprising a stator (2), a rotor (3) having an axis of rotation, and a monitoring unit, the monitoring unit comprising a radar system (1), and the radar system (1) being designed as an FMCW radar system and being arranged such that the radar system can detect a part of the stator (2) and a part of the rotor (3), the stator (2) having an opening, the rotor (3) has an opening such that a beam starting from the radar system (1) can strike the rotor (3) through the opening, and wherein the beam passes through an air gap between a radially outer edge of the rotor (3) and a radially inner edge of the stator (2) in a radial direction.

Description

Technical Field

[0001] The invention relates to a large electric machine with a monitoring device for monitoring the air gap of the electric machine and the vibration behavior of the electric machine and a corresponding method for monitoring the electric machine. For example, the electric machine can be a generator or a motor generator of a hydroelectric power station. Background Art

[0002] Electric machines with monitoring devices are known in the prior art. For example, WO 2017 / 157679 A1 discloses an electric machine with a monitoring device, which includes a microwave radar system for monitoring the air gap width. Here, the antenna of the microwave radar system is arranged in such a way that the mouth of the antenna ends on one side of the radial air gap to be monitored. For this purpose, the antenna can be arranged in a ventilation slot of the stator of the electric machine. Summary of the invention

[0003] The object of the present invention is to provide an electric machine having a monitoring device which is of simpler construction than the monitoring devices known from the prior art and which can be used, in addition to monitoring the air gap, to monitor the vibration behavior of the electric machine.

[0004] This object is achieved according to the invention by the embodiments corresponding to the independent claims. Further advantageous embodiments of the invention are given in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The present invention will be explained below with reference to the accompanying drawings. In the accompanying drawings:

[0006] FIG1 shows a FMCW radar system;

[0007] Figure 2 An electric machine according to the present invention is shown;

[0008] Figure 3 An electric machine according to the invention is shown. DETAILED DESCRIPTION

[0009] Figure 1 A highly schematic diagram of an FMCW (Frequency Modulated Continuous Wave) radar system, denoted by 1, is shown. An FMCW radar system generally comprises a transceiver with a transmitting antenna and a receiving antenna, and a control device. The transmitting antenna and the receiving antenna can be implemented independently as two separate antennas, or integrated as one antenna which can perform both the transmitting and receiving functions. The control device generally comprises a microprocessor which controls the transceiver, processes the received signals and ensures the connection to a computer which is also part of the FMCW radar system. A feature of an FMCW radar system is that the absolute distance to an object and the change in distance over time, i.e. the velocity of the object, can be measured with high precision.

[0010] Figure 1 The rectangle shown may contain all components of the FMCW radar system or only a portion of them. Generally, at least the computer is a separate unit. Figure 1 The dotted line in the figure represents the beam cone of the radar system, that is, the radiation characteristic of the transmitting antenna.

[0011] Figure 2 The electric machine according to the invention is shown in a highly schematic diagram in the direction of the rotation axis of the electric machine, which is indicated by a small cross. The electric machine comprises a stator, which is indicated by 2, and a rotor, which is indicated by 3. The electric machine also comprises an FMCW radar system 1 for monitoring the electric machine, which is arranged to detect a part of the stator 2 and a part of the rotor 3, wherein the beam emitted by the radar system 1 and the beam reflected by the rotor 3 pass through the air gap between the radial outer edge of the rotor 3 and the radial inner edge of the stator 2 in the radial direction. Here, the dashed line again represents the beam cone of the radar system 1. It can be seen that a part of the stator 2 and a part of the rotor 3 are located inside the beam cone. Since the stator 2 surrounds the rotor 3 in the radial direction, the stator 2 must have suitable openings for this purpose, so that the beam emitted by the radar system 1 can pass through the opening and hit the rotor 3. The reflected beam returns to the receiving antenna of the radar system 1 along the same path. The part of the stator 2 detected by the radar system 1 is a part of the radial outer edge of the stator 2, and the part of the rotor 3 detected by the radar system 1 is a part of the radial outer edge of the rotor 3. The openings can be ventilation slots, for example. In many large electric machines, such ventilation slots usually pass through the stator 2 in the radial direction.

[0012] In this context, the term "stator" refers to all non-rotating parts of an electric machine, ie, for example, a housing that may surround a laminated core of a rotating electric machine. Here, the radar system may also be located inside the stator housing and detect the innermost parts of the stator.

[0013] The inventors realized that by Figure 1 The arrangement shown enables monitoring of the width of the air gap of the motor. Figure 1The FMCW radar system arranged as shown can measure the distance to the detected part of the stator 2 and the distance to the radial outer edge of the rotor 3. At least a part of the stator 2 and the air gap (i.e. the radial intermediate space between the radial inner edge of the stator 2 and the radial outer edge of the rotor 3) extend between these parts. Since the size of the stator 2 is very unlikely to change over time, it is possible to infer a change in the width of the air gap with high confidence from the change in the difference between the above distances. The change in the width of the air gap can have many reasons. For example, the axis of rotation of the rotor 3 may be laterally displaced or even tilted. This will manifest itself in a greater or smaller value in the time change of the distance difference depending on the direction in which the axis of rotation is displaced or tilted. Advantageously, more than one FMCW radar system can be used to detect the change in the width of the air gap caused in this way. For example, another radar system can be arranged opposite to the FMCW radar system shown. Alternatively, another radar system arranged 90° around the axis of rotation of the rotor 3 can also be provided.

[0014] Another reason is that parts of the rotor are displaced radially outwards due to the centrifugal forces to which they are subjected. In any case, this leads to a reduction in the distance difference. Figure 2 As shown, a single radar system is sufficient to detect changes in the air gap width caused in this way.

[0015] The method for monitoring the air gap width according to the present invention comprises the following steps:

[0016] - measuring the distance to the detected part of the stator 2;

[0017] - measure the distance to the outer edge of the rotor 3;

[0018] - The difference between the measured distances is compared with a predetermined limit value.

[0019] The predetermined limit values ​​form the tolerance range. As long as the difference lies within the tolerance range, the air gap width has not changed significantly. If the monitoring device described in the invention detects a change in the air gap width that no longer ensures safe operation of the machine, the monitoring device can generate an alarm and / or shut down the motor.

[0020] The inventors have realized that the arrangement of the invention also enables vibration monitoring of electric machines. This is because the FMCW radar system can also measure speed. Here, the measurable speed band is in a range that is advantageous for detecting the expected vibrations of large electric machines. Vibration monitoring is performed by means of Figure 3 Elaborating on this, an embodiment is shown which is particularly advantageously suitable for vibration monitoring.

[0021] Figure 3A highly schematic illustration shows another embodiment of an electric machine according to the invention from a perspective perpendicular to the rotation axis of the electric machine, which is indicated by a vertical dashed line. For the sake of simplicity, the bearing device of the rotor 3 is not shown here. The reference numerals correspond to Figure 2 The stator 2 is connected to the base marked with 4. Usually, Figure 3 The supporting device of the rotor 3 (not shown) is also at least indirectly connected to the base 4. The FMCW radar system 1 is also connected to the base 4. Here, a vibration decoupling device 5 is arranged between the FMCW radar system 1 and the base 4. Through this arrangement, it is possible to detect the vibrations of the rotor 3 and the stator 2 without distortion by means of the monitoring device, because the vibration decoupling device 5 can prevent the vibrations of the motor from being transmitted to the radar system 1 through the base 4.

[0022] exist Figure 3 In FIG. 5 , the vibration decoupling device 5 is arranged between the radar system 1 and the platform shown as a rectangle. The vibration decoupling device can also be arranged between the platform and the base 4 just as well.

[0023] Therefore, the method for monitoring vibration according to the present invention comprises the following steps:

[0024] - measuring vibrations of the rotor 3 and / or the stator 2 by means of the radar system 1;

[0025] - Compare the measured vibration values ​​with predefined limit values.

[0026] If the monitoring device described in the present invention detects in this way that the vibration behavior of the motor exceeds a predetermined amount, the monitoring device can generate an alarm and / or stop the motor. The predetermined limit value can be, for example, an amplitude value within a certain frequency range. Obviously, the predetermined limit values ​​of the rotor 3 and the stator 2 can be different.

[0027] The motor with the monitoring device according to the invention is simpler to construct than those known from the prior art, since the monitoring device is arranged spatially completely separated from the motor and intervention in the motor is therefore minimal. It is only necessary to provide suitable openings in the stator of the motor for each radar system used, if no openings are present in the first place.

[0028] Obviously, in order to implement the described method, a computer system and a computer program for implementing the method steps are required. In this case, the computer program according to the invention can be stored on a data carrier.

[0029] Reference numerals list

[0030] 1 FMCW radar system

[0031] 2 Stator

[0032] 3 Rotor

[0033] 4 Base

[0034] 5. Vibration decoupling device

Claims

1. An electric motor comprising a stator (2), a rotor (3) having a rotation axis and a monitoring unit, wherein: The monitoring unit comprises a radar system (1), characterized in that the radar system (1) is designed as an FMCW radar system and is arranged so that the radar system can detect a part of the stator (2) and a part of the rotor (3), wherein the stator (2) has an opening so that a beam emanating from the radar system (1) can strike the rotor (3) through the opening, and wherein the beam passes through an air gap between a radial outer edge of the rotor (3) and a radial inner edge of the stator (2) in a radial direction.

2. The motor according to claim 1, wherein: The electric motor comprises a base (4), and the stator (2) and the radar system (1) are connected to the base (4), wherein a vibration decoupling device (5) is arranged between the radar system (1) and the base (4).

3. A method for monitoring an electric machine according to claim 1 or 2, wherein: The method comprises the following steps: - measuring the distance to the part of the stator (2) detected by the radar system (1); - Measure the distance to the outer edge of the rotor (3); - comparing the difference between the measured distances with a predetermined limit value; In this case, the distance is measured by means of the radar system (1).

4. The method according to claim 3, wherein: The method comprises the following steps: - When the difference exceeds a predefined limit value, an alarm is sounded and / or the motor is stopped.

5. A method for monitoring an electric machine according to claim 1 or 2, wherein: The method comprises the following steps: - measuring vibrations of the rotor (3) and / or the stator (2) by means of a radar system (1); - Compare the measured vibration values ​​with predefined limit values.

6. The method according to claim 5, wherein: The method comprises the following steps: - When the measured vibration value exceeds the predefined limit value, an alarm is issued and / or the motor is stopped.

Images