Rotor position detection method for multiplexing synchronous motor body as rotary transformer
By reusing the synchronous motor body as a rotary transformer and using independent detection windings and external functional circuits to calculate the rotor position, the detection problem of reluctance synchronous motors in high temperature, strong electromagnetic interference and fully enclosed environments is solved, realizing high-precision and low-cost rotor position detection and expanding application scenarios.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN CHUANXIONG ELECTRONIC TECHNOLOGY CO LTD
- Filing Date
- 2026-02-04
- Publication Date
- 2026-05-19
AI Technical Summary
Existing rotor position detection methods for reluctance synchronous motors rely on physical sensors, which suffer from problems such as space occupation, installation errors, high costs, and poor adaptability to operating conditions. They cannot be effectively applied in high-temperature, strong electromagnetic interference, and fully enclosed environments. Furthermore, permanent magnet rotor motors have problems such as high rare earth costs, the risk of permanent magnet decay, and detection failure at low speeds.
The synchronous motor body is reused as a rotary transformer. By embedding independent detection windings in the stator slots, the excitation current interference is eliminated by matching the number of detection coils and the winding direction design. Combined with external functional circuits, lossless rectification and potential shifting are achieved to calculate the rotor position.
It achieves high-precision rotor position detection in high-temperature, strong electromagnetic interference and fully enclosed environments, eliminates excitation interference, reduces costs, expands application scenarios, and improves the stability of motor starting and low-speed operation.
Smart Images
Figure CN122068801A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of position sensor technology, specifically relating to an indirect detection technology for the rotor position of a synchronous motor. It is particularly suitable for special occasions such as high temperature, strong electromagnetic interference, and fully enclosed environments, such as drive motors for new energy vehicles, linear motors, and fully enclosed compressors for home appliances. It can achieve closed-loop position control within the zero-speed to full-speed range and has the advantages of fast response speed, high control accuracy, and low production cost. Background Technology
[0002] Reluctance synchronous motors have been initially applied in fields such as new energy vehicle drive and industrial drive due to their advantages such as rotors without rare earth elements, low manufacturing cost, and power density comparable to permanent magnet synchronous motors. However, the normal operation of existing reluctance synchronous motors all rely on physical rotor position sensors, which has become the core constraint on the expansion of their application scenarios.
[0003] Currently, the rotor position sensors commonly used in reluctance synchronous motors are mainly divided into three categories: photoelectric rotor position sensors, Hall effect rotor position sensors, and rotary transformers. All three types of sensors require physical assembly installation on the motor body, which has the following inherent drawbacks: 1. Space Occupancy and Installation Errors: The physical sensor assembly needs to occupy the axial or radial space of the motor, which is limited when adapting to miniaturized motors; during installation, mechanical coaxiality, circumferential angle and other installation errors are easy to occur, which directly affect the detection accuracy.
[0004] 2. High cost: All three types of sensors are independent precision components, especially the rotary transformer, which is expensive and significantly increases the overall manufacturing cost of the motor; photoelectric and Hall effect sensors also require auxiliary parts such as mounting brackets and protective housings, which further increases the cost.
[0005] 3. Poor adaptability to operating conditions: Photoelectric sensors are susceptible to dust contamination, and the maximum operating temperature of the core electronic components does not exceed 55℃, making them unsuitable for high-temperature operating conditions; Hall effect sensors are sensitive to iron filings and magnetic dust, and also have an upper limit of 55℃ for operation, and the hysteresis characteristic of the magnetic field response of the Hall element will cause hysteresis in the detection signal, resulting in a large control error; Although rotary transformers are resistant to high temperatures and have high precision, they are expensive, which seriously reduces the cost-effectiveness of the product.
[0006] The aforementioned limitations prevent reluctance synchronous motors from being applied in certain critical scenarios, such as inverter air conditioner compressors and inverter refrigerator compressors in the home appliance industry. In these scenarios, the compressor interior is a fully enclosed environment characterized by high temperature, high pressure, and high corrosion, making it strictly forbidden to install any physical sensor assemblies. However, reluctance synchronous motor rotors do not have permanent magnets, making it impossible to use the back electromotive force indirect position detection technology of permanent magnet rotor motors. Currently, there is no effective indirect rotor position sensing solution for reluctance synchronous motors.
[0007] Current home appliance compressors are all forced to use permanent magnet synchronous motors or DC brushless motors (collectively known as permanent magnet rotor motors). These motors have obvious shortcomings: the rotor permanent magnets contain a large amount of rare earth elements, which are expensive; the permanent magnets are subject to the risk of natural decay of residual magnetism and rapid decay of magnetic properties at high temperatures, which affects the service life of the motor; the back EMF detection method is only effective when the rotor is rotating at medium to high speeds. When the rotor is stationary or rotating at low speeds, the back EMF amplitude is too small, and the detection method is completely ineffective. Only open-loop position control can be used, which leads to compressor start-up vibration and poor stability at low speeds.
[0008] In summary, there is an urgent need for a sensorless, adaptable, high-accuracy, and low-cost method for detecting the rotor position of a reluctance synchronous motor, in order to overcome the application limitations of reluctance synchronous motors and replace the high-cost and high-risk permanent magnet rotor motors. Summary of the Invention
[0009] The purpose of this invention is to address the shortcomings of existing technologies by providing a rotor position detection method that reuses the synchronous motor body as a rotary transformer using a detection winding. The core objective is to eliminate the need for a physical rotor position sensor and reuse the synchronous motor body as a core component of the rotary transformer, thereby achieving sensorless rotor position detection; adapting to special operating conditions such as high temperature, strong electromagnetic interference, and full enclosure; eliminating excitation current interference and improving detection accuracy; achieving effective detection across the zero-speed to full-speed range, while maintaining the advantages of reluctance motors being rare-earth-free and low-cost, thus expanding their application scenarios.
[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a rotor position detection method for reusing a synchronous motor body as a rotary transformer. 1. Embedding and Layout of Independent Detection Windings: Independent detection windings are embedded in the stator slots, with the number of rotor salient poles corresponding to the detection coils in the independent detection windings. The detection coil parameters of all independent detection windings are completely identical, and the independent detection windings of each phase strictly adhere to the predetermined electrical phase difference. This phase difference is calculated as 360° electrical angle divided by the number of phases of the independent detection windings. They are evenly distributed in a circle within the stator slots to ensure consistent electrical characteristics.
[0011] 2. Matching and winding design of detection coils: The number of detection coils in the independent detection winding is even and corresponds to 1 / 2 of the number of rotor salient poles. n Where n is a natural number less than 10: When n is 0, each phase independent detection winding is divided into two detection coils as a coil group. The detection coils in the coil group have the same winding direction, and the detection coils in adjacent coil groups have opposite winding directions. The coils in an independent detection winding are arranged in a centrally symmetrical manner with the center of the stator as the center of symmetry. When n is not 0, each phase independent detection winding is a coil group with one detection coil as a coil group. The two adjacent detection coils are wound in opposite directions. The coils in an independent detection winding are arranged in a centrally symmetrical manner with the center of the stator as the center of symmetry. Both matching methods enable the electromotive force induced by the current in the excitation winding in the independent detection winding to cancel each other out, thus avoiding interference with the detection signal.
[0012] 3. Series Connection and Lead-out of Independent Detection Windings: Detection coils within the same phase are connected in series sequentially, and the independent detection windings of each phase are connected in series end-to-end to form an overall series structure. Contact leads are drawn from the series connection points of each phase's independent detection windings. The remaining start and end leads at both ends of the overall series structure are multiplexed as dual-function leads for carrier input and envelope input. Specifically, the contact leads serve as envelope signal output leads, and the dual-function leads serve as both carrier signal input and envelope signal output leads.
[0013] 4. Composition and Working Process of External Functional Circuit: The external functional circuit includes a carrier generator electrically connected to the circuit, and a precision full-wave rectifier, a potential shifting circuit, and a position conversion module connected in sequence. The specific working process is as follows: The carrier generator inputs equal-amplitude, positive-negative symmetrical carrier signals to the independent detection winding through dual-function leads; The magnetic reluctance between the rotor salient pole and the stator teeth is regularly distributed along the rotor circumference. The conjugate magnetic circuits between the independent detection windings of each phase form a mutual inductance structure. The regular modulation of the magnetic reluctance of the mutual inductance coefficient causes the carrier voltage at both ends of the independent detection windings of each phase to be distributed according to the rotor position, forming an envelope wave loaded with rotor position information. The precision full-wave rectifier performs lossless full-wave rectification on the envelope wave output from the docking point lead and the dual-function lead, converting the AC envelope wave into a unidirectional pulsating waveform; The potential shifting circuit performs DC potential compensation on the unidirectional pulsating waveform and outputs a positive and negative symmetrical AC waveform with symmetrical amplitude and zero-point centering. The position conversion module collects multi-phase interleaved positive and negative symmetrical AC waveform data, and calculates and outputs the real-time angular position data of the rotor based on the waveform characteristics and phase difference.
[0014] 5. Adaptability Design: This method is applicable to synchronous motors with no less than 2 phases and no more than 512 rotor salient poles, which are even numbers. The number of phases of the independent detection winding determines the circumferential distribution angle of the independent detection winding. The number of rotor salient poles and whether permanent magnet blocks are installed on the rotor salient poles do not affect the layout rules of the independent detection winding and the operation logic of the external functional circuit. It can flexibly adapt to different types of synchronous motors (including all reluctance motors, most brushless DC motors, and most permanent magnet synchronous motors). Beneficial effects
[0015] Compared with the prior art, the present invention has the following outstanding advantages: 1. No physical sensors, reusing the motor body: Abandoning the traditional physical sensor assembly, only an independent detection winding is embedded in the stator slot, reusing the synchronous motor body as the core sensing component of the rotary transformer. The independent detection winding occupies almost no space in the motor body and has no mechanical installation error. The independent detection winding is a pure electromagnetic element with no vulnerable electronic components. It is resistant to high temperature, dust, corrosion, and electromagnetic interference, and can work stably in special working conditions such as fully enclosed compressors, breaking through the application limitations of synchronous motors.
[0016] 2. High detection accuracy and no excitation interference: By matching the number of detection coils, designing the winding direction, and following the series connection rules, the induced electromotive force of the excitation current in the independent detection windings is completely canceled, thus eliminating the interference of the excitation system on the detection signal. The mutual inductance coefficient is modulated by the law of stator and rotor magnetic reluctance change, and the envelope wave signal has a strict correspondence with the rotor position. After precision rectification and potential shifting, the position conversion module can accurately calculate the rotor angle, and the detection accuracy is comparable to that of a rotary transformer.
[0017] 3. Effective detection across the entire speed range, with no zero / low-speed blind spots: Based on the carrier mutual inductance modulation principle, this invention provides a fixed magnetic reluctance value when the rotor is stationary, and the independent detection winding can output an envelope wave signal corresponding to a fixed position. When the rotor rotates at low or high speeds, the amplitude of the envelope wave fluctuates continuously and regularly with the position, realizing real-time rotor position detection across the entire speed range from zero to full speed. This overcomes the defect of the back EMF detection of permanent magnet rotor motors failing at zero / low speeds, and improves the stability of motor startup and low-speed operation.
[0018] 4. Low production cost and high cost performance: The independent detection winding and excitation winding can complete winding and other processes simultaneously without the need for additional precision components; the external functional circuits are all conventional analog / digital circuits, and the manufacturing cost is far lower than that of the rotary transformer; at the same time, the reluctance motor rotor is made of only silicon steel sheets and has no rare earth components. Compared with the permanent magnet rotor motor, the overall manufacturing cost is reduced by more than 30%, and there is no risk of permanent magnet decay, resulting in a significantly improved service life.
[0019] 5. Strong adaptability and wide application value: This method is applicable to synchronous motors with no less than 2 phases and no more than 512 salient poles, and the number of poles is even. It can not only replace permanent magnet rotor motors in household appliance compressors, but also be applied to new energy vehicles, industrial closed drives, metallurgical high-temperature equipment and other fields, and has broad industrial application value. Attached Figure Description
[0020] Figure 1 It is a distribution diagram of the independent detection winding and the excitation winding in the stator; Figure 2 This is a diagram showing the unfolded shape of the excitation winding and the independent detection winding; Figure 3 It is a block diagram of the entire system; Figure 4 It is a carrier generator outputting a constant amplitude carrier waveform; Figure 5 It is a single-phase independent detection of the envelope waveform at both ends of the winding after the rotor rotates; Figure 6 It is the waveform after precision full-wave rectification of the winding envelope waveform for single-phase independent detection; Figure 7 It is a waveform whose envelope waveform at both ends of a single independent detection winding is precisely rectified and then shifted to a positive-negative symmetry by potential translation; Figure 8 It is a waveform whose output envelope waveform of the three-phase independent detection winding is precision full-wave rectified and shifted to a positive and negative symmetrical waveform; Figure 9 This is a diagram showing the distribution of independently tested windings in the stator of a synchronous motor with permanent magnet blocks mounted on the rotor salient poles. In the diagram, 1 is the excitation winding, 2 is the independent detection winding, 3 is the stator, 4 is the rotor salient pole, 5 is the carrier generator, 6 is the precision full-wave rectifier, 7 is the potential shifting circuit, 8 is the position conversion module, 9 is the dual-function lead, 10 is the contact lead, 11 is the voltage axis, 12 is the time axis, and 13 is the permanent magnet. Detailed Implementation
[0021] The present invention will be further described in detail below with reference to the accompanying drawings and an embodiment of a three-phase four-pair magnetic reluctance synchronous motor. The scope of protection of the present invention is not limited to this embodiment, and all equivalent transformations based on the technical solution of the present invention fall within the scope of protection of the present invention.
[0022] This invention embeds independent detection windings within the stator slots, with each phase's independent detection winding containing a number of detection coils equal to half the number of rotor salient poles. n , where n is a natural number less than 10, so that the electromotive force induced by the excitation current in the excitation winding in the independent detection winding cancels itself out, thus eliminating the interference of the excitation current on the detection signal.
[0023] The following description uses a three-phase 4-pole reluctance synchronous motor as an example. It is a three-phase star connection with an electrical phase difference of 120° between each phase excitation winding 1. It has 4 rotor salient poles, 4 coils in each phase excitation winding 1, and 2 coils in each phase independent detection winding 2.
[0024] Step 1: Independently test the fabrication of the windings and their placement in the stator slots.
[0025] 1. Fabricate the detection coil for the three-phase independent detection winding 2; the wire diameter, number of turns, and winding process of the detection coil must be completely consistent to ensure that there are no differences in electrical parameters; 2. Divide the stator slots of stator 3 into three-phase regions circumferentially at a 120° electrical angle. Each phase region is equipped with an excitation winding containing 4 excitation coils and an independent detection winding 2 containing 1 detection coil with opposite winding directions. 3. The independent detection winding 2 is arranged in a centrally symmetrical manner with the center of the stator 3 as the center of symmetry. The winding directions of two adjacent detection coils are opposite to ensure that the electromotive force induced by the excitation current cancels each other out.
[0026] Step 2: Independently test the series connection of the windings and the lead wires.
[0027] 1. After the three-phase independent detection winding 2 completes the intra-phase series connection, the ends are connected in series in the manner of A phase tail to B phase head and B phase tail to C phase head to form a three-phase overall series structure. 2. Lead wires are drawn from the start of phase A, the series connection of phases AB, the series connection of phases BC, and the end of phase C. Among them, the series connection leads of phases AB and BC are lead wires 10, with a total of 2 leads; the leads of the start of phase A and the end of phase C are dual-function leads 9, with a total of 2 leads. 3. Contact lead 10 serves as the envelope signal output terminal, and dual-function lead 9 serves as both the carrier signal input terminal and the envelope signal dual-function output terminal, completing the wiring and lead-out of the independent detection winding 2.
[0028] Step 3: Connecting and setting parameters of external functional circuits.
[0029] 1. Carrier generator 5: Outputs a symmetrical square wave carrier with equal amplitude and negative amplitude of 20kHz and ±5V. Its output terminal is electrically connected to the dual-function lead 9 to input the carrier signal to the independent detection winding 2. 2. Precision full-wave rectifier 6: The precision full-wave rectifier circuit is composed of high-precision operational amplifiers. Its input terminal is electrically connected to 2 contact leads 10 and 2 dual-function leads 9. The rectification accuracy is ≤±0.5%. It performs lossless precision full-wave rectification on the envelope waves of each phase output by the independent detection winding 2. 3. Potential shifting circuit 7: A potential compensation circuit composed of a DC voltage source and an operational amplifier is used to shift the unidirectional pulsating waveform after precision full-wave rectification by DC potential, and compensate it into a positive and negative symmetrical sinusoidal waveform with zero center and amplitude ±4V. 4. Position conversion module 8: It adopts an embedded microcontroller MCU, with a built-in inverse trigonometric function calculation program, a sampling frequency of 400kHz, and its input terminal is electrically connected to the potential shift circuit 7 to collect the amplitude of the positive and negative symmetrical sine waveforms with a 120° phase difference of the three phases in real time.
[0030] Step 4: Signal transmission and calculation process for rotor position detection.
[0031] 1. Carrier Input and Envelope Generation: The square wave carrier from carrier generator 5 is input to the independent detection winding 2 of the three-phase integrated series structure via dual-function lead 9. Because the air gap between the rotor salient pole 4 and the stator teeth is sinusoidally distributed circumferentially, and the magnetic reluctance between the stator and rotor matches the air gap, the change in magnetic reluctance modulates the mutual inductance coefficient of each phase's independent detection winding 2 as the rotor salient pole 4 rotates. This causes the carrier voltage across each phase's independent detection winding 2 to be distributed sinusoidally according to the real-time rotor position, forming an envelope wave carrying rotor position information. The single-phase envelope wave waveform is shown below. Figure 5 ; 2. Envelope Wave Rectification: The envelope waves of each phase output from the two contact leads 10 and the two dual-function leads 9 are input to the precision full-wave rectifier 6. After full-wave rectification, they are converted into unidirectional pulsating waveforms for each phase. The uniphase waveforms are shown below. Figure 6 Eliminate the negative half-cycle of the envelope wave and retain the amplitude characteristics of the position information; 3. Potential Shifting: The unidirectional pulsating waveform of each phase is input to the potential shifting circuit 7. After DC potential compensation, the output is a symmetrical positive and negative sinusoidal waveform with zero center. The single-phase waveform is shown below. Figure 7 After processing, the signal from the three-phase independent detection winding 2 outputs a three-phase positive and negative symmetrical sinusoidal waveform with a phase difference of 120°, as shown in the figure. Figure 8 ; 4. Rotor position calculation: The position conversion module 8 collects the amplitude data of the three-phase sinusoidal waveform in real time, calculates the real-time angular position electrical signal of the rotor salient pole 4 through the built-in inverse trigonometric function calculation program, and outputs the signal to the motor driver to realize the closed-loop control of the reluctance synchronous motor.
[0032] The detection method in this embodiment is applied to a three-phase, four-pair magnetic reluctance synchronous motor of a variable frequency air conditioner compressor. Actual measurements show that: 1. Detection accuracy: The angular error of rotor position detection is ≤ ±0.8° electrical angle, which is better than Hall effect sensors and close to the accuracy of rotary transformers; 2. Operating condition adaptability: It can work stably in a temperature range of -30℃ to 120℃, resist refrigerant corrosion, and is free from dust interference. It is suitable for fully enclosed compressor operating conditions. 3. Speed adaptation: It can realize the position detection of the rotor from zero speed to 15000r / min, with no blind spots in start-up / low speed, no vibration when the compressor starts, and a 5dB reduction in noise at low speed. 4. Cost control: Compared with permanent magnet rotor compressor motors of the same power, the overall manufacturing cost is reduced by more than 35%, and there is no risk of permanent magnet decay, and the service life is extended to more than 15 years.
Claims
1. A method for rotor position detection in a synchronous motor body reused as a rotary transformer, characterized in that, The core steps include the following: a. An independent detection winding (2) is embedded in the slot of the stator (3). The number of detection coils contained in each phase independent detection winding (2) is equal to 1 / 2n of the number of rotor salient poles (4), where n is a natural number less than 10. This allows the electromotive force induced in the independent detection winding (2) by the excitation current of the excitation winding (1) to cancel itself out, thus eliminating the interference of the excitation current on the detection signal. b. The detection coil parameters of all independent detection windings (2) are completely consistent, and the electrical phase difference between each phase independent detection winding (2) is equal to 360° electrical angle divided by the number of phases of the independent detection winding, and is evenly distributed in the circumference of the stator (3) slot; c. Each phase independent detection winding (2) is connected in series from beginning to end to the carrier signal generated by the carrier generator. The real-time angle position of the rotor salient pole (4) is calculated through a precision full-wave rectifier, a potential shift circuit and a position conversion module.
2. The rotor position detection method according to claim 1, characterized in that, When n is 0, each phase independent detection winding (2) is divided into two detection coils as a coil group. The detection coils in the coil group have the same winding direction, and the detection coils in adjacent coil groups have opposite winding directions. The coils in an independent detection winding are arranged in a centrally symmetrical manner with the center of the stator (3) as the center of symmetry. Or when n is not 0, each phase independent detection winding (2) takes one detection coil as a coil group, the two adjacent detection coils are wound in opposite directions, and the coils in an independent detection winding are arranged in a centrally symmetrical manner with the center of the stator (3) as the center of symmetry.
3. The rotor position detection method according to claim 1 or 2, characterized in that, The wiring rules for the independent detection winding (2) are as follows: All detection coils within the same phase are connected in series. The independent detection windings (2) of each phase are connected in series from beginning to end to form an overall series structure; In the overall series structure, the series connection of each phase independent detection winding (2) leads out the envelope wave connection lead (10), and the remaining first end lead and tail end lead at both ends of the overall series structure are reused as carrier input end lead and envelope wave output dual function lead (9). The contact lead (10) serves as the envelope signal output lead, and the dual-function lead (9) serves as both the carrier signal input lead and the envelope signal output lead.
4. The rotor position detection method according to claim 3, characterized in that, The external functional circuit includes a connected carrier generator (5) and a precision full-wave rectifier (6), a potential shifting circuit (7), and a position conversion module (8) connected in sequence. The working process of each module is as follows: The carrier generator (5) inputs a carrier signal with equal amplitude and positive and negative symmetry to the series structure of the independent detection windings (2) of each phase through the dual-function lead (9). The carrier signal is a sine wave or a square wave. The independent detection winding (2) modulates the mutual inductance coefficient by changing the magnetic resistance between the stator and rotor teeth, so that the carrier voltage obtained at both ends of each phase independent detection winding (2) is distributed according to the rotor position law, forming an envelope wave loaded with rotor position information. The precision full-wave rectifier (6) performs lossless full-wave rectification on the envelope wave output by the dual-function lead (9) and the contact lead (10), converting the AC envelope wave into a unidirectional pulsating waveform. The potential shifting circuit (7) performs DC potential compensation on the unidirectional pulsating waveform and outputs a positive and negative symmetrical AC waveform with symmetrical amplitude and zero point; The position conversion module (8) collects multi-phase interleaved positive and negative symmetrical AC waveform data, and calculates and outputs the real-time angular position data of the rotor salient pole (4) based on the waveform characteristics and phase difference.
5. The rotor position detection method according to claim 4, characterized in that, The magnetic resistance between the rotor salient pole (4) and the stator teeth is regularly distributed along the rotor circumference. The conjugate magnetic circuits between the independent detection windings (2) of each phase form a mutual inductance structure. The mutual inductance coefficient is modulated according to the law of magnetic resistance change, so that the envelope wave amplitude value output by the independent detection windings (2) of each phase changes with the rotor position in a corresponding law. And at any time, the sum of the envelope wave amplitude values of each phase is equal to the rated amplitude of the carrier output by the carrier generator (5).
6. The rotor position detection method according to any one of claims 1-5, characterized in that, This method is applicable to synchronous motors with a phase number of not less than 2 and a rotor salient pole number of not more than 512 and an even number. The phase number of the independent detection winding determines the circumferential distribution angle of the independent detection winding (2). The number of rotor salient poles, the phase number of the excitation winding, and the number of coils of the excitation winding do not affect the layout rules of the independent detection winding (2) and the operation logic of the external functional circuit.
7. The rotor position detection method according to any one of claims 1-6, characterized in that, This method can achieve closed-loop control of rotor position from zero speed to full speed range of synchronous motor, and is suitable for high temperature, strong electromagnetic interference, fully enclosed and highly corrosive working conditions.