Synchronous motor electric field type excitation coupler, system and rotor position identification method

Abstract

The present invention discloses a synchronous motor electric field excitation coupler, system and rotor position identification method. The synchronous motor electric field excitation coupler includes a transmitting electrode plate and a receiving electrode plate; the height of the concentric circular deep grooves in the fan-shaped area of the transmitting electrode plate is lower than the height of the concentric circular deep grooves in other areas of the transmitting electrode plate; the height of the concentric circular deep grooves on the receiving electrode plate is distributed in a staggered pattern of high-low-high-low regularly with the fan-shaped area as a period, and p is the number of pole pairs of the synchronous motor. By establishing the mapping relationship between the coupling capacitance between the transmitting electrode plate and the receiving electrode plate and the rotor electrical angle, the rotor electrical angle is determined according to the identified coupling capacitance. Based on the improvement of the structure of the synchronous motor electric field excitation coupler, the present invention eliminates the expensive and high-failure- rate rotor position sensor without increasing additional hardware costs, has the advantages of economy and reliability, and can accurately identify the rotor position within the full speed range.

Description

Technical Field

[0001] The present invention belongs to the field of electric machines, and more specifically, relates to an electric-field excitation coupler for a synchronous motor, a system, and a rotor position identification method. Background Art

[0002] Synchronous motors have the characteristics of high power density and low torque ripple, and thus are widely used in many fields such as new energy vehicles and ship electric propulsion. According to the establishment method of the rotor magnetic field, synchronous motors can be divided into permanent magnet synchronous motors and electrically excited synchronous motors. Compared with permanent magnet synchronous motors, electrically excited synchronous motors do not have the risks of high temperature and vibration demagnetization of permanent magnets, and the excitation magnetic field is flexibly adjustable, and they have more advantages than permanent magnet synchronous motors in terms of high-temperature reliability, impact resistance, and speed-up operation efficiency. Especially after the wireless excitation technology overcomes the power supply problem of the excitation winding, the electrically excited synchronous motor has an increasingly broad application prospect.

[0003] At the same time, the continuously expanding application scope and increasingly complex working conditions have put forward higher and higher requirements for the control of electrically excited synchronous motors. High-performance control algorithms such as vector control and direct torque control overcome the inherent problems of nonlinearity and strong coupling in synchronous motor control, and achieve high-performance control of synchronous motors through coordinate transformation. However, the implementation process of these control algorithms requires real-time rotor position information.

[0004] Installing sensors such as photoelectric encoders or resolvers on the motor rotor shaft is a traditional way to obtain the rotor position. However, the embedded rotor position sensors not only increase the volume of the motor, but are also easily damaged, resulting in a significant increase in the maintenance cost of the motor and a decrease in reliability. Therefore, those skilled in the art have carried out a large number of related researches on sensorless rotor position identification, and two technical solutions of high-frequency injection method and back electromotive force method are respectively applicable according to the motor speed range.

[0005] (1) Back electromotive force method

[0006] The basic principle of the back electromotive force method is to estimate the rotor flux vector by using the fundamental frequency voltage and current components of the motor, and then extract the rotor position information. Since the higher the motor speed, the greater the back electromotive force and the greater the signal-to-noise ratio during position extraction, and the result is more accurate, the back electromotive force method is more suitable for the medium and high speed ranges of the motor. At medium speeds, the signal-to-noise ratio of the fundamental frequency information is sometimes not sufficient to obtain accurate rotor position information, and methods such as model reference adaptive, extended Kalman filter, and sliding mode observer are also required to process the fundamental frequency information. However, the back electromotive force method is difficult to avoid the problem of flux trajectory deviation and is also easily affected by noise.

[0007] (2) High-frequency injection method

[0008] When the motor is in a stationary state or operating in a low-speed region, the back electromotive force is too small, making it difficult to identify the rotor position by detecting the fundamental frequency information. At this time, the high-frequency injection method needs to be adopted, that is, an additional high-frequency signal is injected into the motor winding, and the rotor position is estimated by extracting the high-frequency feedback signal. According to the types of injected signals, the high-frequency injection method can be divided into forms such as high-frequency rotating signal injection, pulsating high-frequency voltage injection, and square-wave voltage injection. Among them, the high-frequency square-wave voltage injection is widely used because it does not require filtering and the system structure is relatively simple. However, the high-frequency injection method has problems such as difficult signal extraction and filtering, and cannot be used in control systems with rapid current changes.

[0009] In summary, there is currently no rotor position identification technology suitable for the full speed range of synchronous motors, and the implementation of identification methods in the corresponding speed ranges is difficult, and the usability needs to be improved urgently. Summary of the Invention

[0010] In view of the above defects or improvement requirements of the prior art, the present invention provides a synchronous motor electric field excitation coupler, system, and rotor position identification method. Based on the improvement of the structure of the synchronous motor electric field excitation coupler, while eliminating the rotor position sensor with high cost and high failure rate, it does not require additional hardware costs, has the advantages of economy and reliability, and can accurately identify the rotor position within the full speed range.

[0011] To achieve the above object, according to the first aspect of the present invention, a synchronous motor electric field excitation coupler is provided, including:

[0012] At least one pair of transmitting plates and at least one pair of receiving plates, the transmitting plates and the receiving plates are coupled and arranged;

[0013] The transmitting plates are fixedly connected to the stator of the synchronous motor, and the receiving plates are fixedly connected to the rotating shaft of the synchronous motor rotor. The rotation of the rotating shaft drives the rotation of the receiving plates;

[0014] Both the transmitting plates and the receiving plates are disc-shaped, and circular holes are provided in the middle of the transmitting plates and the receiving plates. The transmitting plates are sleeved on the rotating shaft through the circular holes and do not contact the rotating shaft, and the receiving plates are sleeved on the rotating shaft through the circular holes and contact and are fixedly connected to the rotating shaft;

[0015] Concentric circular deep grooves are provided on the opposite surfaces of the transmitting plates and the receiving plates. The concentric circular deep grooves of the receiving plates are embedded in the concentric circular deep grooves of the transmitting plates and do not contact each other;

[0016] The The height of the concentric circular deep grooves in the sector area is lower than that of the concentric circular deep grooves in other areas of the emitting electrode plate; the height of the concentric circular deep grooves on the receiving electrode plate is the sector area as a period shows a staggered distribution of high and low in a regular pattern, where p is the number of pole pairs of the synchronous motor.

[0017] Furthermore, when p = 4, the height of the concentric circular deep grooves in the sector area of the emitting electrode plate is lower than that of the concentric circular deep grooves in other areas of the emitting electrode plate; the height of the concentric circular deep grooves on the receiving electrode plate is staggered in a high-low-high-low pattern with the sector area as a period.

[0018] Furthermore, both the emitting electrode plate and the receiving electrode plate are integrally formed monolithic metal plates.

[0019] Furthermore, the synchronous motor electric field excitation coupler includes multiple pairs of emitting electrode plates and multiple pairs of receiving electrode plates.

[0020] Furthermore, the centers of the emitting electrode plate and the receiving electrode plate are directly opposite to each other.

[0021] According to the second aspect of the present invention, there is provided a synchronous motor electric field excitation system, including a synchronous motor electric field excitation coupler, and the synchronous motor electric field excitation coupler includes:

[0022] At least one pair of emitting electrode plates and at least one pair of receiving electrode plates, and the emitting electrode plates and the receiving electrode plates are coupled and arranged;

[0023] The emitting electrode plate is fixedly connected to the stator of the synchronous motor, and the receiving electrode plate is fixedly connected to the rotating shaft of the rotor of the synchronous motor. The rotation of the rotating shaft drives the receiving electrode plate to rotate;

[0024] Both the emitting electrode plate and the receiving electrode plate are disk-shaped. Circular holes are provided in the middle of the emitting electrode plate and the receiving electrode plate. The emitting electrode plate is sleeved on the rotating shaft through the circular hole and does not contact the rotating shaft. The receiving electrode plate is sleeved on the rotating shaft through the circular hole and contacts and is fixedly connected to the rotating shaft;

[0025] Concentric circular deep grooves are provided on the opposite surfaces of the emitting electrode plate and the receiving electrode plate. The concentric circular deep grooves of the receiving electrode plate are embedded in the concentric circular deep grooves of the emitting electrode plate and do not contact each other;

[0026] The height of the concentric circular deep grooves in the sector area of the emitting electrode plate is lower than that of the concentric circular deep grooves in other areas of the emitting electrode plate; the height of the concentric circular deep grooves on the receiving electrode plate is The sector regions are distributed in a staggered pattern with a high-low-high-low cycle, and p is the number of pole pairs of the synchronous motor.

[0027] Further, p = 4, and the height of the concentric circular deep grooves on the sector region of the emitting plate is lower than that of the concentric circular deep grooves in other regions of the emitting plate; the height of the concentric circular deep grooves on the receiving plate is distributed in a staggered pattern with a high-low-high-low cycle taking the sector region as the period. height of the concentric circular deep grooves on the sector region of the emitting plate is lower than that of the concentric circular deep grooves in other regions of the emitting plate; the height of the concentric circular deep grooves on the receiving plate is distributed in a staggered pattern with a high-low-high-low cycle taking the sector region as the period.

[0028] Further, the electric field excitation system of the synchronous motor further includes a transmitting side circuit and a receiving side circuit;

[0029] the emitting plate is electrically connected to the transmitting side circuit, and the receiving plate is electrically connected to the receiving side circuit;

[0030] the emitting plate, the transmitting side circuit are fixedly connected to the stator of the electric excitation motor, and the receiving plate, the receiving side circuit are fixedly connected to the rotating shaft of the rotor of the electric excitation motor.

[0031] According to the third aspect of the present invention, a method for identifying the rotor position of an electric field excitation system of a synchronous motor is provided. A mapping relationship between the coupling capacitance between the emitting plate and the receiving plate and the rotor electrical angle is established, and the rotor electrical angle is determined according to the identified coupling capacitance.

[0032] Further, the transmitting side voltage or the transmitting side current is selected as a test parameter, a mapping relationship between the test parameter and the coupling capacitance is established, and the coupling capacitance is calculated according to the measured value of the test parameter.

[0033] Generally speaking, by improving the structure of the electric field excitation coupler of the synchronous motor, the present invention can achieve a one-to-one correspondence between the coupling capacitance and the rotor electrical angle within the same electrical cycle, overcoming the limitations of the existing methods for identifying the rotor position of the motor. Compared with the rotor position sensor, the present invention is completely based on the improvement and enhancement of the structure of the electric field excitation coupler of the synchronous motor. While eliminating the costly and high-failure-rate rotor position sensor, it does not require additional hardware costs, and has the advantages of economy and reliability. Compared with the existing sensorless position identification methods, the present invention does not invade the motor body winding, and the identification accuracy is decoupled from the rotational speed, and can accurately identify the rotor position within the full speed range. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is an overall schematic diagram of the electric field coupling type wireless excitation system of the synchronous motor according to an embodiment of the present invention;

[0035] Figure 2 is an overall schematic diagram of the electric field excitation coupler of the synchronous motor according to an embodiment of the present invention;

[0036] Figure 3 Structural schematic diagram of the electric field excitation coupler of the synchronous motor according to the embodiment of the present invention;

[0037] Figure 4 Variation diagram of the coupling capacitance with the rotor angle according to the embodiment of the present invention;

[0038] Figure 5 Flow chart of the rotor position identification method according to the embodiment of the present invention. Detailed implementation manners

[0039] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] In the description of the embodiments of the present application, the meaning of "multiple pairs" is two pairs or more.

[0041] In the embodiments of the present invention, the naming or numbering of steps does not mean that the steps in the method flow must be executed in the time / logical sequence indicated by the naming or numbering. The named or numbered process steps can be changed in the execution order according to the technical objectives to be achieved, as long as the same or similar technical effects can be achieved.

[0042] Referring to "embodiment" herein means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present invention. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0043] The embodiments of the present invention provide a synchronous motor electric field excitation coupler, a system and a rotor position identification method, which will be described separately below.

[0044] The embodiments of the present invention provide a synchronous motor electric field excitation coupler, including:

[0045] At least one pair of transmitting plates and at least one pair of receiving plates, and the transmitting plates and the receiving plates are coupled and arranged;

[0046] The transmitting plates are fixedly connected to the stator of the synchronous motor, and the receiving plates are fixedly connected to the rotating shaft of the rotor of the synchronous motor. The rotation of the rotating shaft drives the receiving plates to rotate;

[0047] The emitter plate and the receiving plate are both disc-shaped, and a circular hole is opened in the middle of the emitter plate and the receiving plate. The emitter plate is sleeved on the rotating shaft through the circular hole and does not contact the rotating shaft, and the receiving plate is sleeved on the rotating shaft through the circular hole and contacts and is fixedly connected with the rotating shaft;

[0048] Concentric circular deep grooves are provided on the surfaces opposite to the emitter plate and the receiver plate, and the concentric circular deep grooves of the receiver plate are embedded in the concentric circular deep grooves of the emitter plate without contacting each other, so that a coupling capacitor is formed between the emitter plate and the receiver plate to realize energy transmission;

[0049] Emitter Plate The height of the concentric circular deep grooves on the fan-shaped area is lower than the height of the concentric circular deep grooves in other areas of the emitter plate; the height of the concentric circular deep grooves on the receiving plate is The fan-shaped area is distributed in a staggered manner with a periodic high-low pattern, and p is the number of motor pole pairs of the synchronous motor.

[0050] Due to the change in the height of the slots on the plates, the effective facing area and equivalent capacitance of the transmitting and receiving plates can be changed in the process of rotor rotation. The circumference changes approximately linearly in the manner of "increase-decrease-increase-decrease...", thereby achieving a one-to-one correspondence between the rotor electrical angle and the coupling capacitance within the same electrical cycle. Combined with parameter identification technology, the rotor electrical angle can be obtained online and in real time.

[0051] Furthermore, the emitter plate and the receiver plate are both integrally formed metal plates. For example, the emitter plate and the receiver plate are both made of a whole piece of metal with good conductivity, such as copper or aluminum, and the whole plate can be regarded as an equipotential body when current is passed.

[0052] Furthermore, the electric field excitation coupler of the synchronous motor includes multiple pairs of emitter plates and multiple pairs of receiving plates, that is, adopts a multi-channel parallel connection method, which can increase the excitation power and improve fault tolerance.

[0053] Furthermore, the centers of the emitter plate and the receiver plate face each other. When the centers of the emitter plate and the receiver plate face each other, the slots thereon are staggered and distributed, so that the two can be nested and arranged on the motor shaft without contact, which can increase the effective facing area and increase the coupling capacitance.

[0054] Let's take p=4 as an example.

[0055] Figure 1This is the overall schematic diagram of the electric field excitation system of the synchronous motor according to the embodiment of the present invention. The system includes: a DC power supply 4, an inverter 5, a resonant network 6, a transmitter 1, a receiver 2, and a rectifier 7. 8 is the excitation winding of the synchronous motor. Among them, the transmitter 1 and the receiver 2 together form an electric field excitation coupler of the synchronous motor, and its function is to transmit the energy from the stator emission side to the rotor reception side in a non-contact manner through electric field coupling, supply the excitation winding 8, and generate the main magnetic field of the motor.

[0056] Figure 2 This is the overall schematic diagram of the electric field excitation coupler of the synchronous motor according to the embodiment of the present invention. This embodiment corresponds to a 4-pole motor ( ). This embodiment includes a transmitter 1 and a receiver 2. The transmitter 1 includes two transmitting plates 11 and 12; the receiver 2 includes two receiving plates 21 and 22.

[0057] The transmitting plates are fixed to the stator of the motor and remain stationary throughout the operation of the motor; the receiving plates are fixed on the rotating shaft 3 and rotate coaxially with the rotor winding of the motor. Further, both the transmitter 1 and the receiver 2 are made of a whole aluminum plate. When current is applied, the whole plate can be regarded as an equipotential body. There is electric field coupling between the transmitter 1 and the receiver 2, which can be regarded as a capacitor, and alternating current can flow through normally, so as to realize the supply of excitation energy from the exciter to the rotor winding.

[0058] Figure 3 This is the structural diagram of the electric field excitation coupler of the synchronous motor according to the embodiment of the present invention. The goal of rotor position identification is the rotor electrical angle . According to the basic electromagnetic relationship of the synchronous motor, the rotor electrical angle , the mechanical angle and the number of pole pairs of the motor have the following relationship:

[0059] ;

[0060] That is to say, A complete electrical cycle of a 4-pole motor corresponds to mechanical cycles.

[0061] The receiving side of the electric field excitation coupler of the synchronous motor is mechanically fixed coaxially with the rotor, and the mechanical cycles of their rotation are the same when the motor is working. On this basis, if the coupling capacitance can be designed to change monotonically within mechanical cycles through the structural design of the electric field excitation coupler of the synchronous motor, a one-to-one mapping between the rotor electrical angle and the coupling capacitance can be realized.

[0062] Such as Figure 3As shown, in this embodiment, the emitting electrode plate 11 is generally disk-shaped, and circular deep grooves are concentrically distributed on the surface opposite to the receiving electrode plate 21. At the same time, the grooving height in the 1 / 4 sector area of the emitting electrode plate is lower than that of other parts. The receiving electrode plate 21 is also generally disk-shaped, and circular deep grooves are concentrically distributed on the surface opposite to the emitting electrode plate 11. At the same time, the grooving height on the receiving electrode plate is distributed in a staggered pattern of "high - low - high - low" with a 1 / 4 sector area as a cycle.

[0063] It should be noted that when the diameter of the electrode plate of the synchronous motor electric field type excitation coupler and the number of grooves remain unchanged, the larger the grooving depth, the larger the peak coupling capacitance of the synchronous motor electric field type excitation coupler, and the higher the excitation power transmission capacity of the system. The greater the difference between the "high" and "low" of the grooving height, the greater the change range of the coupling capacitance of the synchronous motor electric field type excitation coupler within one electrical cycle, which is beneficial to improving the accuracy of rotor position identification, but poses higher requirements for the control performance of the excitation control system. It can be designed according to specific requirements during use.

[0064] Figure 4 It is a graph of the coupling capacitance varying with the rotor angle in the embodiment of the present invention. As Figure 4 shown, during the process of the rotor mechanical angle rotating , the rotor electrical angle will turn through a complete cycle, and the coupling capacitance of the synchronous motor electric field type excitation coupler shows a monotonic change in each electrical cycle. This means that the present invention realizes the one-to-one correspondence between the coupling capacitance and the rotor angle within the same electrical cycle through the structural design of the synchronous motor electric field type excitation coupler.

[0065] When the wireless excitation system is working, the coupler rotates with the rotating shaft, and its coupling capacitance cannot be directly measured. Therefore, the corresponding rotor electrical angle is also difficult to directly obtain and needs to be indirectly measured through parameter identification. Therefore, the embodiment of the present invention proposes a rotor position identification method for the synchronous motor electric field type excitation system, establishing a mapping relationship between the coupling capacitance between the emitting electrode plate and the receiving electrode plate and the rotor electrical angle, and determining the rotor electrical angle according to the identified coupling capacitance.

[0066] Furthermore, select the transmitting side voltage or the transmitting side current as the test parameter, establish a mapping relationship between the test parameter and the coupling capacitance, and calculate the coupling capacitance according to the measured value of the test parameter.

[0067] Figure 5 It is a flow chart for realizing rotor position identification by using the synchronous motor electric field type excitation coupler. This method is based on the parameter identification technology that has been mature in the field of wireless power transmission and is divided into two steps: modeling and identification.

[0068] Step 1: Modeling. First, it is necessary to establish an equivalent circuit model based on the actual circuit of the wireless excitation system and analyze it to obtain the mapping relationship between the parameters to be identified and the easily measurable parameters. In the electric field type wireless excitation system, when the parameter to be identified is the coupling capacitor, the voltage and current on the transmitting side, which are easy to measure, can be selected as the easily measurable parameters to establish the mapping relationship between the voltage and current on the transmitting side and the coupling capacitor.

[0069] Step 2: Identification. When the system is working, the voltage and current on the transmitting side are measured in real time, and the coupling capacitor at this time is calculated according to the established mapping relationship; according to Figure 4 , the electric field excitation coupler of the synchronous motor realizes the one-to-one correspondence between the coupling capacitor and the rotor electrical angle within the same electrical cycle. According to the calculated coupling capacitor, the real-time electrical angle of the synchronous motor rotor can be obtained by using the look-up table method.

[0070] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A synchronous motor electric field type excitation coupler, characterized in that, Comprising: At least a pair of transmitting plates and at least a pair of receiving plates, wherein the transmitting plates and the receiving plates are arranged in a coupled manner; The transmitting plates are fixedly connected to the stator of the synchronous motor, and the receiving plates are fixedly connected to the rotating shaft of the rotor of the synchronous motor. The rotation of the rotating shaft drives the rotation of the receiving plates; Both the transmitting plates and the receiving plates are disc-shaped, and circular holes are provided in the middle of the transmitting plates and the receiving plates. The transmitting plates are sleeved on the rotating shaft through the circular holes and do not contact the rotating shaft, and the receiving plates are sleeved on the rotating shaft through the circular holes and contact and are fixedly connected to the rotating shaft; Concentric circular deep grooves are provided on the opposite surfaces of the transmitting plates and the receiving plates. The concentric circular deep grooves of the receiving plates are embedded in the concentric circular deep grooves of the transmitting plates and do not contact each other; The height of the concentric circular deep grooves in the fan-shaped area of the emission electrode plate is lower than that of the concentric circular deep grooves in other areas of the emission electrode plate; The height of the concentric circular deep grooves on the receiving plate is distributed in a staggered pattern of high-low-high-low at a period of the fan-shaped area, where p is the number of pole pairs of the synchronous motor.

2. The synchronous motor electric field type excitation coupler according to claim 1, wherein, p = 4, the concentric circular deep grooves on the sector region of the emission electrode plate have a height lower than that of the concentric circular deep grooves in other regions of the emission electrode plate; The height of the concentric circular deep grooves on the receiving plate electrode is distributed in a staggered pattern of high-low-high-low with the fan-shaped area as the period.

3. The synchronous motor electric field type excitation coupler according to claim 1, wherein Both the transmitting plates and the receiving plates are integrally formed monolithic metal plates.

4. The synchronous motor electric field type excitation coupler according to claim 1, wherein Comprising multiple pairs of transmitting plates and multiple pairs of receiving plates.

5. The synchronous motor electric field type excitation coupler according to claim 1, characterized in that, The centers of the transmitting plates and the receiving plates are aligned.

6. A synchronous motor electric field excitation system, characterized in that, Comprising a synchronous motor electric field type excitation coupler, the synchronous motor electric field type excitation coupler comprising: At least a pair of transmitting plates and at least a pair of receiving plates, wherein the transmitting plates and the receiving plates are arranged in a coupled manner; The transmitting plates are fixedly connected to the stator of the synchronous motor, and the receiving plates are fixedly connected to the rotating shaft of the rotor of the synchronous motor. The rotation of the rotating shaft drives the rotation of the receiving plates; Both the transmitting plates and the receiving plates are disc-shaped, and circular holes are provided in the middle of the transmitting plates and the receiving plates. The transmitting plates are sleeved on the rotating shaft through the circular holes and do not contact the rotating shaft, and the receiving plates are sleeved on the rotating shaft through the circular holes and contact and are fixedly connected to the rotating shaft; Concentric circular deep grooves are provided on the opposite surfaces of the transmitting plates and the receiving plates. The concentric circular deep grooves of the receiving plates are embedded in the concentric circular deep grooves of the transmitting plates and do not contact each other; The height of the concentric circular deep grooves in the fan-shaped area of the emission electrode plate is lower than that of the concentric circular deep grooves in other areas of the emission electrode plate; the height of the concentric circular deep grooves on the receiving electrode plate is staggeredly distributed in a high-low-high-low pattern with the fan-shaped area as the period, where p is the number of pole pairs of the synchronous motor.

7. The field excitation system of the synchronous motor according to claim 6, wherein, p = 4, the height of the concentric circular deep grooves in the fan-shaped area is lower than that of the concentric circular deep grooves in other areas of the emission electrode plate; The height of the concentric circular deep grooves on the receiving electrode plate is distributed in a staggered pattern of high-low-high-low with the fan-shaped area as the period.

8. The field excitation system of a synchronous motor according to claim 6, characterized in that, Further comprising a transmitting side circuit and a receiving side circuit; The transmitting plates are electrically connected to the transmitting side circuit, and the receiving plates are electrically connected to the receiving side circuit; The transmitting plates, the transmitting side circuit are fixedly connected to the stator of the electric excitation motor, and the receiving plates, the receiving side circuit are fixedly connected to the rotating shaft of the rotor of the electric excitation motor.

9. The rotor position identification method of the synchronous motor electric field type excitation system according to any one of claims 6 to 8, characterized in that, Establish a mapping relationship between the coupling capacitance between the transmitting plates and the receiving plates and the rotor electrical angle, and determine the rotor electrical angle according to the identified coupling capacitance.

10. The rotor position identification method of the synchronous motor electric field type excitation system according to claim 9, wherein, Select the transmitting side voltage or the transmitting side current as the test parameter, establish a mapping relationship between the test parameter and the coupling capacitance, and calculate the coupling capacitance according to the measured value of the test parameter.

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