SHORT-CIRCUIT DETECTION DEVICE AND SHORT-CIRCUIT DETECTION METHOD FOR A ROTATING ELECTRICAL MACHINE

Abstract

A short-circuit detection device (100) of a rotating electrical machine (10) comprises a signal acquisition unit (61), a signal decomposition unit (62), and a short-circuit detection unit (63), and detects a short circuit in a stator core (21). The signal decomposition unit (62) decomposes a voltage signal from the signal acquisition unit (61) into a plurality of frequency components of different orders. The short-circuit detection unit (63) compares an amplitude change of a low-order oscillation component of an odd order with the amplitude change of a first-order frequency component from the output result of the signal decomposition unit (62) based on two sets of voltage signals acquired at different times, and determines whether the stator core (21) is short-circuited.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a short circuit detection device and a short circuit detection method for a rotating electrical machine. TECHNICAL BACKGROUND

[0002] In the stator core of a rotating electrical machine with a laminated core, a short circuit may occur between the laminations via an axial fastener. If a high short-circuit current flows between the laminations of the stator core, in addition to increased heat loss, problems such as increased vibration of the rotating electrical machine or an imbalance in the three-phase current output by the rotating electrical machine may occur.

[0003] Especially when the rotating electrical machine is operated under high load, the magnetic flux density in the rotating electrical machine is high, and when a short circuit occurs between the laminations of the stator core, the balance of each frequency component of the magnetic flux density changes significantly.

[0004] In the conventional technique described in Patent Document 1, a rotating electric machine is provided in which a rotor carrying an excitation winding and a stator are separated by an air gap. A device for monitoring the excitation magnetic flux in the air gap and a device for detecting the presence of even harmonics of this magnetic flux wave are provided. A fault in the rotating electric machine is then detected by detecting the even harmonics of the voltage induced in a detection coil arranged in the air gap.

[0005] Furthermore, the conventional technique described in Patent Document 2 states that when the magnetic flux generated by the rotating electric machine is affected by magnetic saturation, odd-numbered harmonic currents flow through the stator windings, and the magnetic field generated by these currents generates harmonic magnetic flux within the rotating electric machine. It is also stated that improvements to the structure of the stator core can suppress the generation of harmonic currents caused by magnetic saturation, thereby reducing the vibration and electromagnetic noise of the rotating electric machine. CITATION LISTPATENT DOCUMENT Patent Document 1: Japanese Laid-Open Patent Publication No. S53-84101 Patent Document 2: Japanese Patent Laid-Open Publication No. 2010-130839 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0006] The conventional technique described in Patent Document 1 can detect short circuits in the excitation winding of the rotor by detecting even harmonics of the voltage induced in the search coil, but does not detect short circuits between laminations of the stator core.

[0007] The conventional technique described in Patent Document 2 also reduces the adverse effects of magnetic saturation, but does not consider the detection of short circuits between laminations of the stator core.

[0008] This results in a problem that even if a short circuit occurs between laminations of the stator core while the rotating electrical machine is operating in a state where the magnetic flux density of the stator core is relatively high, the occurrence of the short circuit cannot be detected with high accuracy.

[0009] The present disclosure was made to solve the above-mentioned problem. An object of the present disclosure is to provide a short-circuit detection device and a short-circuit detection method for a rotating electric machine that can accurately detect short circuits occurring between laminations of the stator core while the rotating electric machine is operating in a state where the magnetic flux density of the stator core is relatively high. MEANS TO SOLVE THE PROBLEM

[0010] A short circuit detection device for a rotating electrical machine according to the present disclosure comprises: a signal detecting unit that detects a voltage signal from a magnetic detector arranged on a stator side and facing a rotor of the rotating electric machine; a signal decomposition unit that decomposes the voltage signal into a plurality of frequency components of different orders; and a short-circuit detection unit that determines a short circuit in a laminated stator core based on a low-order vibration component of odd order and a primary frequency component among the frequency components decomposed by the signal decomposition unit, wherein the signal acquisition unit acquires the voltage signal with one or exactly one electrical angle cycle as one or exactly one unit; the short-circuit detection unit detects an amplitude change of the low-order vibration component and the amplitude change of the primary frequency component based on two units of the voltage signal detected at different times, and determines the short circuit in the stator core based on a comparison between the amplitude change of the low-order vibration component and the amplitude change of the primary frequency component.

[0011] A method for detecting a short circuit in a rotating electrical machine according to the present disclosure comprises: a signal detecting step for detecting a voltage signal from a magnetic detector disposed on a stator side and facing a rotor of the rotating electric machine; a signal decomposition step for decomposing the voltage signal into a plurality of frequency components of different orders; and a short-circuit detection step for determining a short circuit in a laminated stator core based on a low-order vibration component of odd order and a primary frequency component among the frequency components decomposed in the signal decomposition step, wherein the signal acquisition step acquires the voltage signal with one or exactly one electrical angle cycle as one or exactly one unit, and the short-circuit detection step detects an amplitude change of the low-order vibration component and an amplitude change of the primary frequency component based on two units of the voltage signal detected at different times, and determines the short circuit in the stator core based on a comparison between the amplitude change of the low-order vibration component and the amplitude change of the primary frequency component. EFFECTS OF THE INVENTION

[0012] According to the short circuit detection device and the short circuit detection method for a rotating electric machine, a short circuit occurring between laminations in the stator core can be accurately detected while the rotating electric machine is operated in a state where the magnetic flux density of the stator core is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig. 1 is a block diagram showing a rotating electric machine and a short circuit detection device according to Embodiment 1. [ Fig. 2] Fig. 2 is a waveform diagram showing a voltage signal in the non-fault state acquired by a signal acquisition unit according to Embodiment 1. [ Fig. 3] Fig. 3 is a waveform diagram showing a voltage signal at a short circuit detected by a signal detecting unit according to Embodiment 1. [ Fig. 4] Fig. 4 is a diagram showing a magnetic flux density distribution when the stator core is short-circuited according to Embodiment 1. [ Fig. 5] Fig. 5 is a spectrum diagram showing the amplitudes of odd-numbered components in the non-fault state and the stator core short-circuited state among the frequency components decomposed by a signal decomposition unit according to Embodiment 1. [ Fig. 6] Fig. 6 is a diagram showing the amplitude ratios of frequency components calculated by a short-circuit detection unit according to Embodiment 1. [ Fig. 7] Fig. 7 is a diagram showing a flowchart for explaining a short circuit detection method according to Embodiment 1. [ Fig. 8] Fig. 8 is a block diagram showing an example of hardware that realizes each function of a signal processing device according to Embodiment 1. [ Fig. 9] Fig. 9 is a block diagram showing another example of hardware that realizes each function of a signal processing device according to Embodiment 1. [ Fig. 10] Fig. 10 is a diagram showing the change amounts of the amplitudes of each frequency component calculated by the short circuit detection unit according to Embodiment 2. [ Fig. 11] Fig. 11 is a diagram showing the difference signal of two different voltage signals detected by the signal detection unit according to Embodiment 3. [ Fig. 12] Fig. 12 is a spectrum diagram showing the amplitude ratio of each frequency component calculated by the short circuit detection unit according to Embodiment 3. DESCRIPTION OF EMBODIMENTS Embodiment 1

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0014] Fig. 1 is a block diagram showing a rotating electric machine and a short-circuit detection device according to Embodiment 1. In Embodiment 1, a turbine generator 10 is used as the rotating electric machine. In Fig. 1 shows a cross section perpendicular to the axial direction of the turbine generator 10.

[0015] As in Fig. As shown in Figure 1, the turbine generator 10 has a stator 20 as the armature and a rotor 30 as the excitation magnet. The stator 20 is arranged on the outside of the rotor 30.

[0016] The stator 20 has a cylindrical stator core 21 and a multi-phase winding 22 (not shown) and a plurality of stator slots 23 formed on the inner circumference of the stator core 21.

[0017] The axial direction of the stator core 21 runs along the axis of the stator core 21 and perpendicular to the plane of the paper in Fig. 1. The radial direction of the stator core 21 is the radial direction of a circle with the center on the axis of the stator core 21. The circumferential direction of the stator core 21 is the direction along an arc of a circle with the center on the axis of the stator core 21.

[0018] Each stator slot 23 formed on the inner circumference of the stator core 21 is provided along the radial direction of the stator core 21. The plurality of stator slots 23 are arranged at equal pitch in the circumferential direction of the stator core 21. The multi-phase windings 22 are wound in the plurality of stator slots 23.

[0019] The stator core 21 has a lamination structure formed by stacking steel sheets, and fastening members 81 and 82 are provided on the inner and outer peripheries of the stator core 21, the fastening members 81 and 82 each passing through the stator core 21 to hold the laminated stator core 21.

[0020] The rotor 30 includes a rotor core 31, an excitation winding 32 (not shown), and a rotating shaft (not shown). The rotor core 31 and the rotating shaft are arranged coaxially with the stator core 21. The rotor 30 can rotate about the rotating shaft.

[0021] A plurality of rotor slots 33 are formed on the outer circumference of the rotor core 31. Each rotor slot 33 is formed along the radial direction of the rotor core 31. In this case, the rotor slots 33 are divided into two slot groups, and a first magnetic pole 34 and a second magnetic pole 35 are formed between the two slot groups. In each slot group, the rotor slots 33 are arranged at equal pitch in the circumferential direction of the rotor core 31.

[0022] The excitation winding 32 is energized by an external DC power source (not shown). This causes one of the first magnetic poles 34 and 35 to become the north pole, and the other to become the south pole. In other words, the turbine generator 10 is a two-pole generator.

[0023] A gap 40 is formed between the stator core 21 and the rotor core 31. The multiphase windings 22 are excited by an external AC power source (not shown). This generates a rotating magnetic field in the air gap 40.

[0024] The short-circuit detection device 100 detects short circuits between laminations of the stator core 21 of the turbine generator 10 and includes a search coil 50 as a magnetic detector, a signal processing device 60 that processes the signals detected by the search coil 50, and a display device 70. The search coil 50 is arranged in the air gap 40 opposite the rotor 30.

[0025] The search coil 50 can also be arranged within the stator core 21, including the stator slot 23 adjacent to the air gap 40, opposite the rotor 30. That is, the search coil 50 is arranged on the stator side 20, including the air gap 40, so that it faces the rotor 30.

[0026] The main magnetic flux and the stray magnetic flux are linked to the search coil 50. The main magnetic flux is the magnetic flux generated in the air gap 40, and the stray magnetic flux is the magnetic flux exiting each rotor slot 33. The magnetic flux linked to the search coil 50 is called the linking magnetic flux.

[0027] The search coil 50 has a first terminal end 51 and a second terminal end 52. When magnetic flux is coupled to the search coil 50, a voltage signal, which is a detection signal, is induced between the first terminal end 51 and the second terminal end 52. The distribution of the coupled magnetic flux in the search coil 50 varies with the rotation of the rotor 30.

[0028] In this case, the short-circuit detection device 100 is equipped with the search coil 50 as a magnetic detector, but the search coil 50 can also be designed separately from the short-circuit detection device 100.

[0029] The signal processing device 60 has a signal acquisition unit 61, a signal decomposition unit 62 and a short-circuit detection unit 63 as functional blocks.

[0030] The signal acquisition unit 61 acquires the voltage signal induced in the search coil 50. The signal decomposition unit 62 decomposes the acquired voltage signal into a plurality of frequency components of different orders. The voltage signal acquired by the signal acquisition unit 61 is treated as a unit of one electrical angular cycle. The signal decomposition unit 62 decomposes the voltage signal of one electrical angular cycle into the respective frequency components. Furthermore, the signal decomposition unit 62 separates each of the decomposed frequency components into amplitude and phase.

[0031] The short-circuit detection unit 63 analyzes the amplitudes of the odd-numbered frequency components among the decomposed frequency components. The odd-numbered frequency components are composed of a fundamental wave component, a first-order primary component that oscillates once per electrical angular cycle, corresponding to the two poles of the first magnetic pole 34 and the second magnetic pole 35, and third-order and higher-order harmonic components, excluding this first-order component. The short-circuit detection unit 63 determines a short circuit in the laminated stator core 21 based on the odd-numbered low-order oscillation components and the first-order component.

[0032] If the operating state of the turbine generator 10 does not change and no short circuit has occurred in the stator core 21, the amplitude of each odd frequency component resolved by the signal decomposition unit 62 remains unchanged.

[0033] Even if the operating state of the turbine generator 10 does not change, a short circuit has occurred in the stator core 21 and the short circuit state remains constant, the amplitude of each odd frequency component resolved by the signal decomposition unit 62 remains unchanged.

[0034] On the other hand, even if the operating state of the turbine generator 10 does not change, the amplitudes of the odd-numbered frequency components decomposed by the signal decomposition unit 62 are not the same for the voltage signal of one electrical angle cycle acquired before the short circuit of the stator core 21 occurred and the voltage signal of one electrical angle cycle acquired after the short circuit occurred. In other words, if an amplitude change between the two units of voltage signals is observed in the odd-numbered frequency components obtained by frequency decomposition of two units of voltage signals acquired at different times, a short circuit of the stator core 21 can be detected.

[0035] The voltage waveforms of the two sets of voltage signals are uniformly detected by the signal detection unit 61, either continuously or intermittently at intervals. If an amplitude change is observed in the odd-numbered frequency components between the two sets of voltage signals—namely, the voltage signal detected in the past before the short circuit occurred and the newly detected voltage signal—a new short circuit of the stator core 21 can be detected.

[0036] The short-circuit detection unit 63 calculates the amplitude ratio as the amplitude change of each odd-numbered frequency component of the voltage signal from two units in which the turbine generator 10 is in the same operating state. In this embodiment, the short-circuit detection unit 63 detects that a short circuit has occurred in the stator core 21 when the amplitude ratio of the third-order component is greater than the amplitude ratio of the first-order component.

[0037] Furthermore, the short-circuit detection unit 63 outputs information about the presence or absence of a short circuit in the stator core 21 to the display device 70.

[0038] The display device 70 is provided outside the signal processing device 60. The display device 70 indicates the presence or absence of a short circuit in the stator core 21 based on the information from the short-circuit detection unit 63. The display device 70 can also be provided outside the short-circuit detection device 100.

[0039] Fig. Fig. 2 is a waveform diagram showing a voltage signal detected by the signal detecting unit 61 when the device is normally operated. Fig. 3 is a waveform diagram showing a voltage signal detected by the signal detecting unit 61 when a short circuit occurred.

[0040] Fig. 2 and Fig. 3 show examples of voltage signals during normal operation and during a short circuit, where the horizontal axis corresponds to a period of the electrical angle corresponding to the two poles - the first magnetic pole 34 and the second magnetic pole 35.

[0041] Fig. 4 shows the magnetic flux density distribution when the stator core 21 is short-circuited, and shows the magnetic flux density distribution at the time when the voltage signal in Fig. 3 was recorded.

[0042] Fig. 2 to Fig. 4 were created by simulating the no-load operating condition in which the turbine generator 10 generates the rated voltage using an electromagnetic field analysis program.

[0043] The simulation during a short circuit was carried out under the condition that the stator core 21 is short-circuited via a fastening element 83 that penetrates and holds the stator core 21 inside or on the outer circumference of the stator core 21. In this case, the fastening element 81A, which is located at the same circumferential position as the Fig. 1 is arranged inside the stator core 21, and the fastening elements 82A arranged at circumferential positions on both sides of the fastening element 81A on the outer circumference of the stator core 21, the fastening elements 83 which form the short circuit.

[0044] When detecting a short circuit in the stator core 21, it is important to quickly detect when a high short-circuit current flows between the laminations of the stator core 21 as a result of a short circuit. For this reason, the short circuit simulation was performed under conditions where the fasteners 83 forming the short circuit are close to each other and a high short-circuit current is likely to flow.

[0045] In this example, the signal processing device 60 uses the voltage signal detected by the signal detection unit 61 to estimate that a short circuit has occurred in the stator core 21. This will be explained below.

[0046] Each in Fig. 2 and Fig. The voltage waveform curve shown in Figure 3 is a voltage waveform for one period of the electrical angle, where circumferential angles from 0° to 180° correspond to the first magnetic pole 34 and circumferential angles from 180° to 360° correspond to the second magnetic pole 35. Therefore, at a circumferential angle of 90°, the center of the first magnetic pole 34 is closest to the search coil 50, and at a circumferential angle of 270°, the center of the second magnetic pole 35 is closest to the search coil 50.

[0047] The Fig. The voltage curve shown in Figure 2 is a voltage curve in the absence of a short circuit and in the normal state of the rotor, with 32 small voltage fluctuations occurring per rotor slot pitch.

[0048] The Fig. The voltage waveform shown in Figure 3 is a voltage waveform during a short circuit, where the amplitude of the harmonic components increases as described below, but the overall waveform is almost identical to Fig. 2.

[0049] As described above, the signal decomposition unit 62 decomposes the voltage signal detected by the signal detection unit 61 into a plurality of frequency components of different orders and further separates each of the decomposed frequency components into amplitude and phase.

[0050] Fig. Figure 5 is a spectrum diagram showing the amplitudes of odd-numbered components in the normal state of the rotor and in the presence of a short circuit among the frequency components decomposed by the signal decomposition unit 62. That is, in Fig. 5 is the amplitude spectrum of the odd components based on the Fig. 2 and the amplitude spectrum of the odd-numbered components based on the Fig. 3 are placed side by side to easily compare the absolute values. Although orders from 21 onwards are available, Fig. 5 For the sake of simplicity, only orders up to and including 19.

[0051] The primary first-order component is the fundamental wave component corresponding to the main magnetic flux among the magnetic fluxes generated in the air gap 40 and has the largest amplitude. The odd-numbered third-order and higher-order components are harmonic components that do not correspond to the main magnetic flux and are caused by pulsation factors such as the number of slots in the rotor 30 or the stator 20 among the magnetic fluxes generated in the air gap 40. When a short circuit occurs, it can be seen that the amplitude of the first-order component hardly changes, but the amplitudes of the third- and fifth-order components increase.

[0052] As in Fig. 4, in the region A enclosed by the fastening member 81A and the fastening member 82A short-circuited to the stator core 21, the magnetic flux density decreases due to magnetic shielding. In contrast, in the region B, which includes the region B1 on the radially inner side of the region A and the region B2 on the opposite side of the region A relative to the axis, the magnetic flux density increases due to the shielded and redirected magnetic flux. The magnetic flux density in the center of the magnetically saturated region becomes high, and the magnetic flux density in the peripheral region also increases, thereby expanding the magnetically saturated region and increasing the harmonic components.

[0053] The redirected magnetic flux follows a semicircular path as in region B, and a total of two or four spatial fluctuations occur on the back of the core or on the tooth side, respectively. This appears primarily as a third- or fifth-order change in the low-order magnetic flux density, rather than a first-order or higher-order change in the magnetic flux density. The effect of magnetic saturation also manifests as a harmonic component at frequencies that are multiples of 2 or 4, but the voltage value decreases with increasing frequency.

[0054] Essentially, the change in permeance is a second-order change, and the change in magnetomotive force is a first-order change, so the difference between the two—the change in magnetic flux density—is a third-order change. If the change in permeance has a fourth-order harmonic component, the change in magnetic flux density will have a third- or fifth-order component. Similarly, even higher-order harmonics will also be included.

[0055] The short-circuit detection unit 63 calculates the amplitude ratio between the same lower orders of the odd harmonic components decomposed by the signal decomposition unit 62.

[0056] Fig. Fig. 6 is a diagram showing the amplitude ratio of each frequency component calculated by the short circuit detection unit 63, and represents the amplitude ratio obtained from the spectrum diagram in Fig. 5 was calculated.

[0057] In Fig. 5, the fifth, eleventh and seventeenth order components, which have relatively small absolute amplitude values, are excluded from the calculation due to a poor SN (signal-to-noise) ratio of the amplitude ratio.

[0058] For example, if one n-order amplitude value is V1n and the other n-order amplitude value is V2n, the amplitude ratio R is calculated as R = (|V1n - V2n| / V1n) × 100 in percentage. The magnetic saturation range increases during a short circuit. When there is no short circuit, the amplitude ratio is almost 0, but when a short circuit occurs, the amplitude ratio changes. The first-, seventh-, and higher-order frequency components are relatively little affected by magnetic saturation and have small amplitude ratios. In contrast, the third- and fifth-order frequency components, which are lower-order harmonic components, are characterized by being strongly affected by magnetic saturation due to a short circuit and have large amplitude ratios.

[0059] In this case, the fifth-order component is excluded, and it can be seen that the amplitude ratio of the third-order component is large. Generally, the amplitude of the third-order component and the fifth-order component is either large and small, or both are medium and balanced, depending on the phase of the two components.

[0060] As in Fig. As shown in Figure 6, the amplitude ratio of the higher-frequency components ranges between 0.0 and 1.2%, while the amplitude ratio of the third-order component is approximately 5%, significantly greater than 1.2%. The amplitude ratio of the first-order component is a relatively low 0.2%, and the amplitude ratio of the third-order component is significantly larger than the amplitude ratio of the first-order component.

[0061] The short-circuit detection unit 63 detects the occurrence of a short circuit in the stator core 21, for example, when the amplitude ratio of the third-order component is clearly greater than the amplitude ratio of the first-order component, based on a comparison between the amplitude ratio of the first-order component and the amplitude ratio of the third-order component. The determination that the amplitude ratio is clearly greater can be made, for example, when the difference or ratio exceeds a predetermined value or target value.

[0062] By using the third-order component, which has the largest absolute value of the amplitude ratio due to the influence of magnetic saturation in the stator core 21, the signal-to-noise ratio of the amplitude ratio is good, and a short circuit can be detected with higher accuracy. Furthermore, when the stator core 21 is magnetically saturated, the amplitude of the harmonic components is larger than in the non-saturated state, so the amplitude ratio of the harmonic components before and after the occurrence of a short circuit in the stator core 21 can be analyzed with a good signal-to-noise ratio. For this reason, a state in which the turbine generator 10 operates with high magnetic flux density is suitable for detecting a short circuit in the stator core 21.

[0063] Next, the short circuit detection method according to this embodiment will be described with reference to the drawings.

[0064] Fig. Fig. 7 is a diagram showing a flowchart for explaining the short-circuit detection method according to Embodiment 1. When the short-circuit detection device 100 is started, the signal processing device 60 executes the short-circuit detection routine shown in the flowchart in Fig. 7, at specified intervals.

[0065] When the short circuit detection routine is started, first, the signal detection unit 61 detects one unit (one electrical angle cycle) of a voltage signal from the search coil 50 (step S110).

[0066] Subsequently, the signal decomposition unit 62 decomposes the detected voltage signal into a plurality of frequency components of different orders and separates them into amplitude and phase (step S120).

[0067] Next, the short-circuit detection unit 63 calculates the amplitude ratio of each odd-numbered frequency component from the results obtained in step S120 based on two units of voltage signals, namely the voltage signal detected in the previous routine and the voltage signal detected in the current routine (step S130).

[0068] Then, the short circuit detection unit 63 determines whether the amplitude ratio of the third-order component is larger than the amplitude ratio of the first-order component (step S140).

[0069] If the amplitude ratio of the third-order component is larger than the amplitude ratio of the first-order component in step S140, the short-circuit detection unit 63 determines that a short circuit has occurred in the stator core 21, outputs information indicating that “a short circuit has occurred” to the display device 70, and terminates the current routine (step S150).

[0070] If the result in step S140 is NO, the short circuit detection unit 63 outputs information indicating that “no short circuit has occurred” to the display device 70 and ends the current routine (step S160).

[0071] As described above, the short circuit detection method according to this embodiment includes a signal detection step of step S110, a signal decomposition step of step S120, and a short circuit detection step of steps S130 to S160.

[0072] In the signal detection step, a unit voltage signal (corresponding to one electrical angular cycle) is detected by the search coil 50, which is arranged to face the rotor 30. In the signal decomposition step, the voltage signal detected in the signal detection step is decomposed into a plurality of frequency components of different orders.

[0073] In the short-circuit detection step, the amplitude ratio of the odd-order low-order vibration component (in this case, the third-order component) and the amplitude ratio of the first-order component are calculated from the amplitude of each order component obtained in the signal decomposition step, based on the voltage signal of the previous routine and the voltage signal of the current routine, that is, two units of voltage signals acquired at different times. Then, in the short-circuit detection step, it is determined that a short circuit has occurred in the stator core 21 when the amplitude ratio of the third-order component is greater than the amplitude ratio of the first-order component. Furthermore, if the amplitude ratio of the first-order component is less than or equal to the amplitude ratio of the third-order component, it is determined that no short circuit has occurred in the stator core 21.

[0074] As described above, the short-circuit detection device 100 according to this embodiment compares the amplitude ratio of the odd-numbered low-order vibration components with the amplitude ratio of the first-order frequency component based on two sets of voltage signals acquired at different times to determine a short circuit in the stator core 21. Therefore, the occurrence of a short circuit in the stator core 21 can be detected with high accuracy while the turbine generator 10 is operating with a relatively high magnetic flux density in the stator core 21.

[0075] It should be noted that when the turbine generator 10 operates with low magnetic flux density in the stator core 21, it is difficult to detect the amplitude change of the harmonic components before and after the occurrence of a short circuit in the stator core 21, and the accuracy of short-circuit detection deteriorates. In this case, the turbine generator 10 operates at a light load, and even if a short circuit occurs between the laminations of the stator core 21, a large short-circuit current does not flow, and no problematic malfunction occurs.

[0076] The short-circuit detection step in the above embodiment newly detects the occurrence of a short circuit in the stator core 21 based on the voltage signal detected in the current routine. The other of the two sets of voltage signals is not limited to the voltage signal detected in the previous routine.

[0077] Since the stator core 21 and the fastening element 83 are short-circuited by a low contact resistance, the contact point can burn out even with a small short-circuit current, thereby clearing the short circuit. Since the short-circuit detection device 100 detects the occurrence of a short circuit in the stator core 21 by detecting changes in two sets of voltage signals acquired at different times, it is not necessary for the later-detected voltage signal to be the one at the time of the short circuit. A short circuit can also be detected if the earlier-detected voltage signal is the one at the time of the short circuit, and the voltage signal acquired after the short circuit is cleared is used as the second set.

[0078] In the above embodiment, the short-circuit detection unit 63 uses the third-order component as the odd-numbered low-order vibration component, but determines that a short circuit has occurred in the stator core 21 when the amplitude ratio of at least one of the third-order and fifth-order components is larger than the amplitude ratio of the first-order component. In this case, the amplitude ratio of the third-order and fifth-order components with the larger amplitude ratio can be compared with the amplitude ratio of the first-order component. In this embodiment, the third-order component, which has the largest absolute amplitude value due to the influence of magnetic saturation, is used for determination, so the signal-to-noise ratio of the amplitude ratio is good, and a short circuit can be determined with higher accuracy.

[0079] In the above embodiment, the rotor 30 is arranged on the inner side of the circumference of the stator 20, but the rotor 30 may also be arranged on the outer side of the circumference of the stator 20.

[0080] In the above embodiment, the turbine generator 10 is used as the rotating electric machine, but the rotating electric machine may be a generator other than the turbine generator 10 or an electric motor.

[0081] Furthermore, although a search coil 50 is used as a magnetic detector, this is not limited to a magnetic detector.

[0082] The functions of the signal processing device 60 of Embodiment 1 are realized by a processing circuit.

[0083] Fig. 8 is a configuration diagram showing an example of hardware that realizes each function of the signal processing device 60. In this case, the signal processing device 60 is configured with a processing circuit 60A, which is dedicated hardware.

[0084] The processing circuit 60A may be, for example, a single circuit, a compound circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

[0085] Fig. 9 is a configuration diagram showing another example of hardware that realizes each function of the signal processing device 60 according to Embodiment 1. In this case, the processing circuit 60B includes a processor 201 and a memory 202.

[0086] In the processing circuit 60B, the functions of the signal processing device 60 are implemented by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 202. The processor 201 implements each function by reading and executing the programs stored in the memory 202.

[0087] It can also be said that the program stored in memory 202 causes the computer to execute the above-described processes or methods of the respective parts. In other words, this program is a short-circuit detection program and a program that causes the computer to execute signal acquisition processing, signal decomposition processing, and short-circuit detection processing.

[0088] Here, the memory 202 refers to non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable and Programmable Read Only Memory), etc. Also included in the memory 202 are magnetic data storage media, flexible data storage media, optical data storage media, compact discs, mini-discs, DVDs, etc.

[0089] The functions of the signal processing device 60 described above can be implemented partly by dedicated hardware and partly by software or firmware.

[0090] In this way, the processing circuit can implement the above-described functions of the signal processing device 60 through hardware, software, firmware, or a combination thereof. Embodiment 2.

[0091] In the above embodiment 1, the short circuit detection unit 63 uses the amplitude ratio as the amplitude change of each frequency component from two units of voltage signals detected at different times, but the amplitude change amount itself may also be used.

[0092] Fig. 10 is a diagram showing the amplitude change amount of each frequency component calculated by the short circuit detection unit 63.

[0093] If one amplitude value is n-th order V1n and the other amplitude value is n-th order V2n, the amplitude change amount ΔV is calculated as ΔV = |V1n - V2n|.

[0094] As in Fig. As shown in Figure 10, the amplitude change of the odd-numbered low-order vibration components—the third- and fifth-order components—is large and significantly larger than the amplitude change of the first-order component. In particular, the amplitude change of the third-order component is large. Furthermore, the amplitude change of the seventh-order and higher vibration components is small, which shows the same tendency as in Fig. 6 of the above embodiment 1 in which the amplitude ratio is used.

[0095] The short-circuit detection unit 63 then detects the occurrence of a short circuit in the stator core 21 based on a comparison between the amplitude change of the first-order component and the amplitude change of the third-order component, for example, when the amplitude change of the third-order component is clearly larger than the amplitude change of the first-order component.

[0096] As described above, in this embodiment, the amplitude change of the odd-numbered low-order vibration components is compared with the amplitude change of the first-order frequency component based on two units of voltage signals detected at different times to determine whether the stator core 21 is short-circuited.

[0097] Therefore, as in the above-mentioned Embodiment 1, the occurrence of a short circuit in the stator core 21 during the operation of the turbine generator 10 in a state where the magnetic flux density of the stator core 21 is relatively high can be accurately detected.

[0098] Furthermore, since the magnitude of the amplitude change is used to determine the short circuit, the signal-to-noise ratio is not affected by the magnitude of the absolute amplitude value. Therefore, a short circuit can be accurately detected without having to exclude order components with small absolute amplitude values. Embodiment 3.

[0099] In the above-mentioned Embodiments 1 and 2, the signal decomposition unit 62 decomposed the voltage signal detected by the signal detection unit 61 into the respective frequency components, and the short-circuit detection unit 63 performed the short-circuit detection based on the results of decomposition of two units of voltage signals by the signal decomposition unit 62.

[0100] However, in this Embodiment 3, the signal decomposition unit 62 decomposes the difference signal of two units of voltage signals acquired at different times by the signal acquisition unit 61 into the respective frequency components, and the short-circuit detection unit 63 performs the short-circuit detection based on the results of decomposition of the difference signal by the signal decomposition unit 62.

[0101] Fig. Figure 11 is a diagram showing the difference signal between two different voltage signals detected by the signal detection unit 61. This difference signal shows a voltage waveform representing the difference between the Fig. 2 shown voltage signal (voltage curve in normal state) and the one in Fig. 3 shown voltage signal (voltage curve in short circuit condition).

[0102] The signal decomposition unit 62 decomposes the difference signal of the two voltage signal units into several frequency components of different orders and further separates each of the decomposed frequency components into amplitude and phase. The amplitude of each frequency component in the difference signal indicates the amplitude change when the two voltage signal units are frequency-decomposed.

[0103] The short-circuit detection unit 63 compares the amplitude of the odd-order harmonic components decomposed by the signal decomposition unit 62 with the amplitude of the first-order frequency component.

[0104] Fig. Figure 12 is a spectrum diagram showing the amplitude ratio of each frequency component calculated by the short-circuit detection unit 63. The ratio (%) of the amplitude of each odd-numbered frequency component to the amplitude of the first-order frequency component is expressed as an amplitude ratio. In this case, as in the first embodiment, the fifth-, eleventh-, and seventeenth-order components, which have relatively small absolute amplitude values, are excluded from the calculation.

[0105] If the amplitude value of the first-order frequency component is Va1 and the amplitude value of the n-order component is Van, the amplitude ratio Ra is calculated as Ra = |Van / Val| × 100 in percent.

[0106] As in Fig. As shown in Figure 12, the amplitude of the third-order component is significantly larger than that of the first-order component.

[0107] The amplitude of each frequency component of the difference signal indicates the amplitude change of each frequency component of the two-unit voltage signal and has the same tendency as in Fig. 6 and Fig. 10 of Embodiments 1 and 2. That is, the amplitude of the third-order component is particularly large, and the amplitude of the seventh-order and higher harmonic components is small.

[0108] The short-circuit detection unit 63 detects the occurrence of a short circuit in the stator core 21 based on a comparison between the amplitude of the first-order component and the amplitude of the third-order component, for example, when the amplitude of the third-order component is clearly larger than the amplitude of the first-order component.

[0109] As described above, in this embodiment, the signal decomposition unit 62 decomposes the difference signal from two sets of voltage signals acquired at different times into a plurality of frequency components of different orders. The short-circuit detection unit 63 then performs short-circuit detection based on the result of the decomposition of the difference signal by the signal decomposition unit 62. At this time, the amplitude of the first-order frequency component in the difference signal, which represents the amplitude change of the first-order frequency component of the two sets of voltage signals, is compared with the amplitude of the low-order vibration components in the difference signal, which represents the amplitude change of the low-order vibration components, to determine a short circuit in the stator core 21.

[0110] Therefore, as in the first embodiment, it is possible to accurately detect the occurrence of a short circuit in the stator core 21 while the turbine generator 10 is operated with a relatively high magnetic flux density of the stator core 21.

[0111] Furthermore, since the signal decomposition unit 62 uses the difference signal of two units of voltage signals as input and performs frequency decomposition, the number of signals to be processed is halved and the processing load is reduced.

[0112] Although the disclosure has been described above with reference to various exemplary embodiments and implementations, it should be understood that the various features, aspects, and functions described in one or more of the individual embodiments are not limited to the particular embodiment with which they were described, but rather are applicable individually or in various combinations to one or more of the embodiments of the disclosure.

[0113] Therefore, it should be understood that numerous non-exemplary modifications may be made without departing from the scope of the present disclosure. For example, at least one of the constituent units may be modified, added, or omitted. At least one of the constituent units mentioned in at least one of the preferred embodiments may be selected and combined with constituent units mentioned in another preferred embodiment. DESCRIPTION OF REFERENCE SYMBOLS

[0114] 10 Turbine generator (rotating electrical machine), 20 Stator, 21 Stator core, 30 Rotor, 50 Search coil (magnetic detector), 61 Signal detection unit, 62 Signal decomposition unit, 63 Short circuit detection unit, 100 Short circuit detection device. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 53-84101

[0005] JP 2010-130839

[0005]

Claims

[1] Short-circuit detection device for a rotating electrical machine, comprising: a signal detecting unit that detects a voltage signal from a magnetic detector arranged on a stator side and facing a rotor of the rotating electric machine; a signal decomposition unit that decomposes the voltage signal into a plurality of frequency components of different orders; and a short-circuit detection unit that determines a short circuit in a laminated stator core based on a low-order vibration component of odd order and a primary frequency component among the frequency components decomposed by the signal decomposition unit, wherein the signal acquisition unit acquires the voltage signal with an electrical angle cycle as a unit; the short-circuit detection unit detects an amplitude change of the low-order vibration component and the amplitude change of the primary frequency component based on two units of the voltage signal detected at different times, and determines the short circuit in the stator core based on a comparison between the amplitude change of the low-order vibration component and the amplitude change of the primary frequency component. [2] The short-circuit detecting device for the rotating electric machine according to claim 1, wherein the short-circuit detecting unit determines that the stator core is short-circuited when the amplitude change of the low-order vibration component is larger than the amplitude change of the primary frequency component. [3] The short-circuit detection device for the rotating electric machine according to claim 1 or 2, wherein the signal decomposition unit decomposes the voltage signal detected by the signal detection unit into the plurality of frequency components of different orders, and the short-circuit detection unit compares the amplitude change of the primary frequency component with the amplitude change of the low-order vibration component based on the decomposition results of the two units of the voltage signal by the signal decomposition unit. [4] The short-circuit detection device for the rotating electrical machine according to claim 1 or 2, wherein the signal decomposition unit decomposes the difference signal of the two units of the voltage signal into the plurality of frequency components of different orders, and the short-circuit detection unit compares the amplitude of the primary frequency component in the difference signal, the difference signal being the amplitude change of the primary frequency component, with the amplitude of the low-order oscillation component in the difference signal, the difference signal being the amplitude change of the low-order oscillation component, based on the result of decomposition of the difference signal by the signal decomposition unit. [5] The short-circuit detecting device for the rotating electric machine according to any one of claims 1 to 4, wherein the short-circuit detecting unit uses at least one of a third-order frequency component and a fifth-order frequency component as the low-order vibration component. [6] The short-circuit detecting device for the rotating electric machine according to any one of claims 1 to 5, wherein the short-circuit detecting unit calculates and uses an amplitude ratio as the amplitude change. [7] A method for detecting a short circuit in a rotating electrical machine, comprising: a signal detecting step for detecting a voltage signal from a magnetic detector disposed on a stator side and facing a rotor of the rotating electric machine; a signal decomposition step for decomposing the voltage signal into a plurality of frequency components of different orders; and a short-circuit detection step for determining a short circuit in a laminated stator core based on a low-order vibration component of odd order and a primary frequency component among the frequency components decomposed in the signal decomposition step, wherein the signal detecting step detects the voltage signal with an electrical angular cycle as a unit, and the short-circuit detecting step detects an amplitude change of the low-order vibration component and an amplitude change of the primary frequency component based on two units of the voltage signal detected at different times, and determines the short circuit in the stator core based on a comparison between the amplitude change of the low-order vibration component and the amplitude change of the primary frequency component. [8] A method for detecting a short circuit in the rotating electrical machine according to claim 7, wherein the signal acquisition step repeatedly acquires the voltage signal at different times with an electrical angle cycle as a unit, and the short-circuit detection step determines the short circuit in the stator core based on two units of the voltage signal, namely the previously detected unit and the currently detected unit.

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