Permanent magnet motor turn-to-turn short circuit fault diagnosis method based on annular detection coil

Abstract

The invention discloses a permanent magnet motor turn-to-turn short circuit fault diagnosis method based on an annular detection coil, a stator core is composed of six H-shaped module units, each module comprises a stator yoke, two stator teeth and a short circuit bridge, armature windings are wound on the stator teeth, and the two armature windings of each module belong to the same phase winding; the short-circuit bridge is provided with annular detection coils, the annular detection coils are mutually independent, and positive and negative outgoing lines are led out from the interior of the motor. When the motor operates normally, magnetic fluxes flowing through the short-circuit bridges are the same, and back electromotive force amplitudes generated by the six annular detection coils are the same. When a turn-to-turn short circuit fault occurs in the motor, the amplitude of counter electromotive force generated by the annular detection coil of the module unit where the fault coil is located is larger than that of other phases, and the module unit where the fault is located is rapidly positioned. And accurately positioning the coil where the turn-to-turn short circuit fault is located according to the amplification of the counter electromotive force amplitude of the fault coil. According to the method, the turn-to-turn short circuit fault position can be quickly and accurately positioned, and the fault processing time and cost are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet motors, and more specifically to a method for diagnosing inter-turn short-circuit faults in permanent magnet motors based on a ring detection coil. Background Technology

[0002] Inter-turn short-circuit faults are common winding faults in permanent magnet motors. Their short-circuit currents are dozens of times the rated current, easily leading to winding insulation breakdown, localized high temperatures, and other problems. They are characterized by their significant harm, ease of propagation, and difficulty in diagnosis. Therefore, quickly and accurately diagnosing the location of inter-turn short-circuit faults in permanent magnet motors and rapidly disconnecting the faulty winding are effective means to reduce the impact of inter-turn short-circuit faults on permanent magnet motors.

[0003] Currently, in the diagnosis of inter-turn short circuit faults, the presence of harmonic components in the stator current and the quadrature / direct axis plane current components under inter-turn short circuit conditions can be utilized. By extracting specific harmonics using Fast Fourier Transform (FFT), inter-turn short circuit fault diagnosis can be achieved. However, this method is susceptible to changes in motor operating conditions, making inter-turn short circuit fault diagnosis challenging under multiple operating conditions. Furthermore, inter-turn short circuit faults disrupt the symmetry of the motor's phase voltages, causing distortion of the zero-sequence voltage. Diagnosing inter-turn short circuit faults can be achieved by constructing an additional three-phase impedance balancing network to detect the neutral point voltage. This method is suitable for star-connected motors and requires additional voltage detection circuitry. Winding a detection coil around the motor stator teeth is also a commonly used method for inter-turn short circuit fault diagnosis. During normal motor operation, the detection coil voltage only contains harmonics of multiples of 3. When an inter-turn short circuit fault occurs, a higher content of the first harmonic component appears in the voltage. The difference in harmonic content between the detection coil voltage under normal and short-circuit fault conditions can be used to diagnose inter-turn short circuit faults. However, this method also requires Fourier decomposition to process the fault characteristics, is easily affected by the motor operating conditions, and makes it difficult to determine the fault location. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for diagnosing inter-turn short-circuit faults in permanent magnet motors based on a ring detection coil.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A method for diagnosing inter-turn short-circuit faults in permanent magnet motors based on a ring detection coil:

[0007] The permanent magnet motor has stator slots on its stator, and the stator core is composed of six H-type modular units. Each H-type modular unit includes a stator yoke, two stator teeth, a short-circuit bridge, two split teeth, an armature winding, and a ring detection winding. The H-type modular unit is symmetrical about its central axis and radially arranged. The inner side of the stator yoke has two stator teeth, the ends of which are connecting parts. The two connecting parts are connected by a short-circuit bridge, and the ends of the two connecting parts are split teeth. The armature winding is wound on the stator teeth, and the ring detection winding is wound on the short-circuit bridge.

[0008] Determine the connection method of each phase armature winding. Each phase armature winding includes 4 coils, and all coils have the same polarity.

[0009] By comparing the back electromotive force amplitude of the six-phase ring detection winding, it is determined that the armature winding of a certain H-type module unit has an inter-turn short circuit fault. The coil that has an inter-turn short circuit fault is determined by the magnitude of the increase of the back electromotive force of the faulty armature winding when the two coils have inter-turn short circuit faults. That is, the coil with the larger increase has an inter-turn short circuit fault.

[0010] Furthermore, the six H-type module units are arranged counterclockwise as Module 1, Module 2, Module 3, Module 4, Module 5 and Module 6. The A-phase windings are distributed on Module 1 and Module 4, the B-phase windings are distributed on Module 3 and Module 6, and the C-phase windings are distributed on Module 2 and Module 5.

[0011] Furthermore, the permanent magnet motor also includes a rotor, and there is an air gap between the stator and the rotor.

[0012] Furthermore, the rotor includes a rotor core and permanent magnets, with the permanent magnets attached to the surface of the rotor core, and the rotor adopts any type of rotor structure.

[0013] Furthermore, the annular detection windings wound on the short-circuit bridges of Module 1, Module 2, Module 3, Module 4, Module 5, and Module 6 are W1, W2, W3, W4, W5, and W6, respectively. Among them, W1, W2, and W3 are wound in the same way, with the wire entering from the air gap side and exiting from the stator slot. W4, W5, and W6 are wound in the same way, with the wire entering from the stator slot and exiting from the air gap side.

[0014] Furthermore, the short-circuit bridge is in the shape of an inverted trapezoid, with an upper base width of 10mm, a lower base width of 6mm, a thickness of 2.4mm, and a lower base distance of 3.8mm from the stator inner diameter.

[0015] Furthermore, the central angle of the split tooth is 12°, and the spacing angle between the two split teeth is 28°.

[0016] Furthermore, the armature winding adopts a double-layer, fractional-slot concentrated winding structure with a span of 1.

[0017] The present invention has the following beneficial effects:

[0018] (1) The stator structure composed of H-type module units described in this invention has less short-circuit bridge flux when the armature winding is running normally. When an inter-turn short-circuit fault occurs in the armature winding, the flux flowing through the short-circuit bridge increases. The difference in short-circuit bridge flux under normal and inter-turn short-circuit fault conditions provides a basis for diagnosing the location of inter-turn short-circuit faults.

[0019] (2) The motor inter-turn short circuit fault diagnosis method of the present invention does not require complex topology design. It only requires winding a ring detection winding on the short circuit bridge. By testing the back electromotive force of each phase fault detection winding, the location of the inter-turn short circuit fault can be quickly and accurately determined, which greatly improves the fault diagnosis speed and reduces the fault handling cost.

[0020] (3) The motor inter-turn short circuit fault diagnosis method of the present invention diagnoses the fault location based on the increase in the back electromotive force amplitude of the fault detection winding. It has low requirements for the number of turns of the fault detection winding and does not significantly sacrifice the slot fill factor of the armature winding, thus having good practicality. Moreover, the ring detection winding is applicable to any rotor type, and has good robustness and scalability. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a permanent magnet motor used in an embodiment of the present invention for inter-turn short-circuit fault diagnosis based on short-circuit bridge flux;

[0022] Figure 2 This is a partial dimensional diagram of the H-type permanent magnet motor module unit according to an embodiment of the present invention;

[0023] Figure 3(a) is a graph of the magnetic flux density of the short-circuit bridge when the permanent magnet motor is running normally under no-load in an embodiment of the present invention.

[0024] Figure 3(b) is a graph of the back electromotive force of the annular detection winding when the permanent magnet motor is running normally under no-load in an embodiment of the present invention.

[0025] Figure 4 This is a graph showing the back electromotive force curve of the annular detection winding when the permanent magnet motor load is running normally according to an embodiment of the present invention.

[0026] Figure 5(a) is a diagram of the magnetic field distribution when an inter-turn short circuit fault occurs in the coil of permanent magnet motor A1 according to an embodiment of the present invention;

[0027] Figure 5(b) is a short-circuit bridge flux density curve when an inter-turn short-circuit fault occurs in the coil of permanent magnet motor A1 according to an embodiment of the present invention.

[0028] Figure 6 This is a graph showing the short-circuit bridge flux density when the coils A1 and A2 of the permanent magnet motor in this embodiment of the invention experience inter-turn short-circuit faults.

[0029] Figure 7 This is a graph showing the back electromotive force curve of the annular detection winding when an inter-turn short circuit fault occurs in the coil A1 of the permanent magnet motor according to an embodiment of the present invention.

[0030] Figure 8 This is a graph showing the back electromotive force curve of the annular detection winding when an inter-turn short circuit fault occurs in the A2 coil of the permanent magnet motor according to an embodiment of the present invention.

[0031] Figure 9 This is a graph showing the back electromotive force curves of the ring detection winding when the coils B3 and B4 of the permanent magnet motor in this embodiment of the invention experience inter-turn short circuit faults.

[0032] In the diagram, 1-stator yoke, 2-stator tooth, 3-short-circuit bridge, 4-connector, 5-split tooth, 6-armature winding, 7-ring detection winding, 8-rotor core, 9-permanent magnet. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0034] A method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil includes the following steps:

[0035] Step (1): Determine the stator structure of the permanent magnet motor. The stator has 12 stator slots. The stator core is composed of six H-type module units. Each module unit includes a stator yoke, two stator teeth, one short-circuit bridge, and two split teeth. The module units are named in the counterclockwise direction as: Module 1, Module 2, Module 3, Module 4, Module 5, and Module 6.

[0036] Step (2): Determine the connection method of each phase armature winding. The armature winding is wound on the stator teeth. Each phase winding includes 4 coils, and the polarity of each coil is the same. The armature winding has obvious modular distribution characteristics. Phase A winding is distributed in Module 1 and Module 4. The coils in Module 1 are named A1 and A2, and the coils in Module 4 are named A3 and A4. Phase B winding is distributed in Module 3 and Module 6. The coils in Module 3 are named B1 and B2, and the coils in Module 6 are named B3 and B4. Phase C winding is distributed in Module 2 and Module 5. The coils in Module 2 are named C1 and C2, and the coils in Module 5 are named C3 and C4.

[0037] Step (3) Determine the spatial position and winding method of the fault detection coil (i.e., the ring detection winding). The fault detection coil is wound on the short-circuit bridge. Each fault detection coil is independent of the others, and the positive and negative leads are both led out from inside the motor. When the motor is running normally, the back electromotive force of the fault detection coils is symmetrical. After an inter-turn short-circuit fault occurs, the back electromotive force of the detection coil of the faulty module unit increases compared with other detection coils. Therefore, based on the change of magnetic flux of the short-circuit bridge before and after the fault, the back electromotive force of the fault detection coil can be tested to achieve accurate positioning of the fault coil. The ring detection windings on the short-circuit bridges of Module 1, Module 2, Module 3, Module 4, Module 5 and Module 6 are respectively labeled as W1, W2, W3, W4, W5 and W6. Among them, the winding methods of ring detection windings W1, W2 and W3 are the same, all of which enter from the air gap side and exit from the stator slot; while the winding methods of ring detection windings W4, W5 and W6 are opposite, all of which enter from the stator slot and exit from the air gap side.

[0038] Step (4): Verify the effectiveness of the fault diagnosis method described in this invention using finite element software. When the motor is running normally, the magnetic flux flowing through the six short-circuit bridges is the same, the back electromotive force amplitude of the fault detection coil is the same, and the phase difference is 60°. When an inter-turn short-circuit fault occurs, taking module one as an example, due to the presence of the short-circuit current component, the magnetic flux of the short-circuit bridge in the module unit where the fault detection coil is located will increase, and the back electromotive force of the corresponding fault detection coil will increase compared with the back electromotive force of other detection coils. Moreover, when an inter-turn short-circuit fault occurs in coil A2, the back electromotive force of winding W1 increases more than that of coil A1. Therefore, an inter-turn short-circuit fault occurs in coil A2.

[0039] like Figure 1 This is a cross-sectional view of a permanent magnet motor for inter-turn short-circuit fault diagnosis based on short-circuit bridge flux according to an embodiment of the present invention. The embodiment uses a 12-slot / 16-pole surface-mounted permanent magnet synchronous motor as the research object. This motor includes a stator and a rotor, with an air gap between them. The stator includes a stator core, an armature winding 6, and a ring detection winding 7. The stator has 12 stator slots. The stator core consists of six H-type module units. Each H-type module unit includes a stator yoke 1, two stator teeth 2, a short-circuit bridge 3, and two split teeth 5. The module units are named sequentially in a counter-clockwise direction: Module 1, Module 2, Module 3, Module 4, Module 5, and Module 6. The armature winding 6 is wound on the stator teeth 2, and the ring detection winding 7 is wound on the short-circuit bridge 3. The armature winding 6 adopts a double-layer, fractional-slot concentrated winding structure with a span of 1. The rotor includes a rotor core 8 and a permanent magnet 9, with the permanent magnet 9 attached to the surface of the rotor core 8. The rotor can be any rotor structure type, such as surface-mounted or built-in. For clarity, the dimensions of the H-type module unit are as follows: Figure 2As shown, the short-circuit bridge 3 of the H-type module unit is inverted trapezoidal in shape, with a thickness of 2.4 mm, an upper base width of 10 mm, a lower base width of 6 mm, and a distance of 3.8 mm from the stator inner diameter. The split teeth 5 of the H-type module unit are symmetrically distributed about the center line of the stator slot, with a central angle of 12° and a spacing angle of 28° between two split teeth. A connecting part 4 exists between the short-circuit bridge 3 and the split teeth 5.

[0040] Figure 3(a) shows the magnetic flux density curves of the short-circuit bridges of the permanent magnet motor in this embodiment of the invention during normal no-load operation. P1, P2, P3, P4, P5, and P6 are the center points of the short-circuit bridges in modules one, two, three, four, five, and six, respectively. As can be seen from the figure, the magnetic flux density on the six short-circuit bridges is symmetrical during normal motor operation. Therefore, the back electromotive force curves of the six-phase ring detection windings of the permanent magnet motor in this embodiment of the invention during normal no-load operation are also symmetrical, as shown in Figure 3(b). Furthermore, Figure 4 The curve of the back electromotive force of the ring detection winding of the permanent magnet motor under normal load in the embodiment of the present invention is shown. When the motor is running under normal load, the back electromotive force curves of the six-phase ring detection winding are also symmetrical to each other, that is, the amplitude is the same, and the back electromotive force of each phase has only a phase difference.

[0041] When an inter-turn short-circuit fault occurs in coil A1, the magnetic flux flowing through the short-circuit bridge of module one increases significantly compared to other modules, as shown in Figure 5(a). Figure 5(b) is the magnetic flux density curve of the short-circuit bridge when an inter-turn short-circuit fault occurs in the coil A1 of the permanent magnet motor according to the embodiment of the present invention. The tangential magnetic flux density at point P1 increases significantly, while the magnetic flux densities at points P2, P3, P4, P5, and P6 are basically the same. Figure 6 By comparing the short-circuit bridge flux density curves of the permanent magnet motors A1 and A2 when inter-turn short-circuit faults occur respectively, it can be seen that there is no significant difference in the radial flux density at point P1. However, when the A2 coil experiences an inter-turn short-circuit fault, the amplitude of the tangential flux density at point P1 is significantly greater than that when the A1 coil experiences an inter-turn short-circuit fault.

[0042] Figure 7 This is the back electromotive force (EMF) curve of the ring detection winding when an inter-turn short circuit fault occurs in the coil A1 of the permanent magnet motor according to an embodiment of the present invention. The back EMF amplitudes of phases W2, W3, W4, W5, and W6 are all 5.3 V, while the back EMF amplitude of W1 increases to 8.9 V. Further, Figure 8This is the back electromotive force (EMF) curve of the ring detection winding when an inter-turn short circuit fault occurs in the A2 coil of the permanent magnet motor according to an embodiment of the present invention. The back EMF amplitudes of the five phases W2, W3, W4, W5, and W6 remain at 5.3 V, while the back EMF amplitude of W1 increases to 11.7 V. Taking module one as an example, the inter-turn short circuit fault diagnosis method of the present invention firstly determines that an inter-turn short circuit fault has occurred in the armature winding of module one by comparing the back EMF amplitudes of the six-phase ring detection winding; then, the back EMF of W1 will be greater when an inter-turn short circuit fault occurs in the A2 coil than when an inter-turn short circuit fault occurs in the A1 coil, thereby determining the specific coil that has experienced an inter-turn short circuit fault.

[0043] Similarly, Figure 9 This is the back electromotive force curve of the ring detection winding W3 when the permanent magnet motor B1 and B2 coils respectively experience inter-turn short circuit faults in an embodiment of the present invention. The back electromotive force of W3 is also greater when the B2 coil experiences an inter-turn short circuit fault than when the B1 coil experiences an inter-turn short circuit fault. The other coils also have the same characteristics when experiencing inter-turn short circuit faults, which will not be described in detail.

[0044] In summary, the stator structure composed of H-type modular units described in this invention exhibits low short-circuit bridge flux during normal armature winding operation. However, when an inter-turn short-circuit fault occurs in the armature winding, the flux flowing through the short-circuit bridge increases. The difference in short-circuit bridge flux under normal and inter-turn short-circuit fault conditions provides a basis for diagnosing the location of inter-turn short-circuit faults. The inter-turn short-circuit fault diagnosis method of this invention does not require complex topology design; it only requires winding a ring-shaped detection winding on the short-circuit bridge. By testing the back electromotive force of each phase's fault detection winding, the location of the inter-turn short-circuit fault can be quickly and accurately determined, greatly improving fault diagnosis speed and reducing fault handling costs. Moreover, this invention diagnoses the fault location based on the increase in the back electromotive force amplitude of the fault detection winding, requiring a lower number of turns in the fault detection winding and not significantly sacrificing the slot fill factor of the armature winding, thus possessing good practicality. The ring-shaped detection winding described in this invention is applicable to any rotor type, exhibiting good robustness and scalability.

[0045] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil, characterized in that: The stator of the permanent magnet motor is provided with stator slots, and the stator core is composed of six H-type module units. Each H-type module unit includes a stator yoke (1), two stator teeth (2), a short-circuit bridge (3), two split teeth (5), an armature winding (6), and an annular detection winding (7). The H-type module unit is symmetrical about its central axis. In the radial direction, the inner side of the stator yoke (1) has two stator teeth (2), the ends of the stator teeth (2) are connecting parts (4), the two connecting parts (4) are short-circuit bridges (3), and the ends of the two connecting parts (4) are split teeth (5). The armature winding (6) is wound on the stator teeth (2), and the annular detection winding (7) is wound on the short-circuit bridge (3). Determine the connection method of each phase armature winding. Each phase armature winding includes 4 coils, and all coils have the same polarity. By comparing the back electromotive force amplitude of the six-phase ring detection winding, it is determined that the armature winding of a certain H-type module unit has an inter-turn short circuit fault. The coil that has an inter-turn short circuit fault is determined by the magnitude of the increase of the back electromotive force of the faulty armature winding when the two coils have inter-turn short circuit faults. That is, the coil with the larger increase has an inter-turn short circuit fault.

2. The method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil according to claim 1, characterized in that, The six H-type module units are arranged counterclockwise as Module 1, Module 2, Module 3, Module 4, Module 5 and Module 6. The A-phase windings are distributed on Module 1 and Module 4, the B-phase windings are distributed on Module 3 and Module 6, and the C-phase windings are distributed on Module 2 and Module 5.

3. The method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil according to claim 2, characterized in that, The permanent magnet motor also includes a rotor, and there is an air gap between the stator and the rotor.

4. The method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil according to claim 3, characterized in that, The rotor includes a rotor core (8) and a permanent magnet (9), with the permanent magnet (9) attached to the surface of the rotor core (8). The rotor can adopt any type of rotor structure.

5. The method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil according to claim 3, characterized in that, The annular detection windings wound on the short-circuit bridges of Modules 1, 2, 3, 4, 5, and 6 are W1, W2, W3, W4, W5, and W6, respectively. Among them, W1, W2, and W3 are wound in the same way, with the wire entering from the air gap side and exiting from the stator slot. W4, W5, and W6 are wound in the same way, with the wire entering from the stator slot and exiting from the air gap side.

6. The method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil according to claim 1, characterized in that, The short-circuit bridge (3) is in the shape of an inverted trapezoid, with an upper base width of 10mm, a lower base width of 6mm, a thickness of 2.4mm, and a lower base distance of 3.8mm from the inner diameter of the stator.

7. The method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil according to claim 1, characterized in that, The central angle of the split tooth (5) is 12°, and the distance angle between the two split teeth is 28°.

8. The method for diagnosing inter-turn short-circuit faults in a permanent magnet motor based on a ring detection coil according to claim 1, characterized in that, The armature winding (6) adopts a double-layer, fractional-slot concentrated winding structure with a span of 1.

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