Dual-unit permanent magnet synchronous motor with on-site adjustable misalignment angle and adjusting method thereof

Abstract

The application provides a double-unit permanent magnet synchronous motor with an adjustable dislocation angle and an adjusting method thereof, and relates to the technical field of synchronous motors.The scheme is as follows: a casing or a base, a rotating shaft or a fixed hollow shaft, and a first unit motor and a second unit motor arranged in the casing or the base along an axial direction are provided; a relative circumferential dislocation angle θ of the first unit motor and the second unit motor can be adjusted on a site after the motor is completely assembled n The dislocation angle θ n is used to offset target order harmonic waves caused by a tooth slot torque; the motor is also provided with an expansion coupling assembly having a locking state and a loosening state; when the expansion coupling assembly is in the loosening state, the dislocation angle θ n can be adjusted on the site; and after the dislocation angle θ is adjusted to a target value, the expansion coupling assembly is switched to the locking state.In addition, an adjusting method of the synchronous motor is also provided.The application has the effect that the tooth slot torque suppression effect is determined as needed after the motor is shipped, and the maintenance time is greatly shortened.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor technology, specifically to a dual-unit permanent magnet synchronous motor with an adjustable misalignment angle and its adjustment method. Background Technology

[0002] In low-speed, high-torque direct-drive scenarios, permanent magnet synchronous motors are widely used due to their high efficiency and high torque density. Torque pulsation caused by cogging torque directly leads to output torque fluctuations, causing equipment vibration, bearing fatigue damage, and even transmission system resonance, seriously threatening equipment safety and service life.

[0003] To reduce cogging torque and torque ripple, existing technologies have proposed several solutions, mainly including: (i) the misaligned installation scheme, which reduces cogging torque and torque fluctuation by misaligning the inner and outer permanent magnets of the rotor by a certain angle. However, this misalignment angle is fixed once manufactured, which is a typical "open-loop" suppression scheme with the following inherent defects: it cannot cope with manufacturing errors and cumulative tolerances introduced by the processing and assembly process, it cannot compensate for individual differences caused by the dispersion of permanent magnet material performance, and it cannot correct dynamic performance drift caused by bearing wear and mechanical loosening after long-term operation; (ii) the skewed slot / skewed pole scheme, which reduces cogging torque by setting skewed slots to generate a skewed pole effect, and uses stator skewed slot method or rotor skewed pole method to weaken cogging torque. However, the skewed slot / skewed pole technology also has the limitations of fixed angle and inability to be adjusted on-site, and it is mainly effective for high-frequency harmonics, with limited ability to suppress the fundamental and low-order harmonics that contribute the most to torque ripple.

[0004] In summary, regardless of whether it's misaligned installation or skewed slot / pole technology, the suppression angle is determined once during the manufacturing or assembly stage, lacking a systematic, closed-loop correction method for on-site adjustments, from "vibration diagnosis" to "targeted adjustment." Once the motor leaves the factory and is put into operation, the misalignment angle is permanently fixed, making it unable to cope with performance degradation and environmental changes after long-term operation.

[0005] Another issue is the contradiction between fault tolerance and ripple suppression. Although multiphase motors currently possess a certain degree of fault tolerance, torque ripple deteriorates drastically under fault conditions, making it difficult to guarantee stable operation.

[0006] In summary, there is an urgent need for a technical solution that can adjust the tooth cogging torque on-site, achieve closed-loop correction on-site, and maintain stable operation under fault conditions. Summary of the Invention

[0007] The invention aims to provide a dual-unit permanent magnet synchronous motor with an adjustable misalignment angle and its adjustment method, which solves the "open-loop" defect in existing cogging torque suppression schemes (including misaligned installation, skewed slots / skewed poles, etc.) where the misalignment angle is fixed after manufacturing and cannot be adjusted on-site after final assembly and throughout the entire service life. The invention allows for on-site adjustment of the misalignment angle without disassembling the end cover or removing the rotor, thus achieving a cogging torque suppression effect that is fixed at the factory and adjustable as needed throughout the entire service life.

[0008] The specific technical solution adopted is as follows: a dual-unit permanent magnet synchronous motor with an adjustable misalignment angle, comprising a housing or base, a rotating shaft or a fixed hollow shaft, and a first unit motor and a second unit motor axially disposed within the housing or base; the first unit motor and the second unit motor each independently include a stator and a permanent magnet rotor, and are coaxially disposed on the same rotating shaft or fixed hollow shaft; a relative circumferential misalignment angle θ is provided between the first unit motor and the second unit motor, which can be adjusted on-site after the motor assembly is completed. n Misalignment angle θ n Used to cancel target order harmonics caused by cogging torque; the motor is also equipped with a tightening coupling sleeve assembly, which has a locked state and a loosened state. When in the loosened state, it can adjust the misalignment angle θ. n Perform on-site adjustments until the target value is reached, then switch to the locking state. An operation window is provided on the end cover corresponding to the position of the expansion coupling sleeve assembly, and a detachable sealing cover is provided. The expansion coupling sleeve assembly can be loosened or locked through the operation window, so that the misalignment angle can be adjusted on site without disassembling the end cover and rotor.

[0009] Furthermore, the misalignment angle θ n From formula θ n =180° / (n · LCM(Z, 2p)) is determined, where Z is the number of slots in the stator of each unit motor, 2p is the number of poles in the rotor of each unit motor, LCM means taking the least common multiple, and n is the harmonic order to be canceled, where n is a positive integer; The formula applies to both integer slot mating and fraction slot mating.

[0010] Furthermore, the first unit motor and / or the second unit motor are provided with skewed slots or skewed pole structures inside, serving as the first-stage suppression unit; Furthermore, the equivalent angle β of the skewed slot or skewed pole is related to the misalignment angle θ. n Each is determined independently, and the two constitute a hierarchical collaborative architecture of "coarse suppression within the unit + fine cancellation between units": Level 1 (within the unit): skewed slots / skewed poles mainly target high-frequency harmonics to achieve initial suppression of cogging torque; Level 2 (between units): misalignment angles target and cancel the fundamental wave and low-order harmonics (the main contributing components of torque pulsation) to achieve precise cancellation.

[0011] When the motor uses an internal rotor topology: Two stators are fixed to the inner wall of the housing. The first permanent magnet rotor is fixedly connected to the shaft, and the second permanent magnet rotor is fitted onto the shaft through an expansion coupling assembly. An operation window is provided on the end cover at the position corresponding to the locking bolt of the expansion coupling, and a removable sealing cover is provided. An angle indicator assembly is provided at the extended end of the shaft or outside the housing for reading and setting the misalignment angle. An axial thermal compensation mechanism is provided on the shaft to absorb the thermal expansion of the shaft caused by the temperature rise during operation and maintain a constant misalignment angle.

[0012] When the motor uses an external rotor topology: It includes a split base and a fixed hollow shaft. The two permanent magnet rotors are bell-shaped rotating shells and are coaxially arranged around the fixed hollow shaft. The first stator is fixedly mounted on the fixed hollow shaft, and the second stator is adjustablely mounted on the fixed hollow shaft through the expansion coupling assembly. The end cover has an operation window corresponding to the fastening bolt position. An annular magnetic shielding plate is mounted on the fixed hollow shaft between the adjacent end faces of the first stator and the second stator.

[0013] To address the problem of misalignment of the operating window due to the random stopping position of the external rotor motor, this invention provides a precise stopping positioning system: The system includes a cam fixed to the bell-shaped rotating housing, a proximity switch fixed to the stationary component, a controller, and a DC power module; The preset angle position line of the cam-triggered proximity switch, the angle position line of the operation window and the fastening bolt in space, and the angle position line of the rotor permanent magnet when the second stator winding is energized with DC and generates the maximum magnetic attraction force, all three coincide at the same spatial angle position. When a shutdown adjustment is required, the controller reduces the motor to a crawling speed after receiving a shutdown command. In response to the trigger signal of the proximity switch, it injects DC current into the second stator winding and uses magnetic attraction to position the outer rotor assembly to the preset angle, so that the operating window is automatically aligned with the fastening bolt.

[0014] The present invention also provides a method for on-site adjustment of the misalignment angle of the above-mentioned motor, the method being performed at the installation site after the motor is assembled, and including the following steps: S1. On-site vibration diagnosis: At the actual installation site of the motor, the dynamic signals of the motor during operation are collected by vibration sensors and / or torque sensors installed on the shaft or housing; S2. Harmonic Source Analysis: By performing fast Fourier transform spectrum analysis on the collected dynamic signal, the main harmonic order n causing the vibration is identified. S3. Target Angle Calculation: Based on formula θ n=180° / (n · LCM(Z, 2p)) Calculate the target misalignment angle θ n ; S4. On-site adjustment: Using the expansion coupling assembly and the operation window, adjust the misalignment angle between the first unit motor and the second unit motor to the target value θ. n The entire process does not require disassembling the end caps or removing the rotor; The method transforms the misalignment angle from a "one-time fixed" setting during the manufacturing stage to an "adjustable on demand" setting throughout the entire operating lifecycle, thereby achieving continuous optimal suppression of tooth groove torque.

[0015] Furthermore, the two stator windings are provided with a second lead-out group, which is used for series connection under generator operating conditions: the two stator windings are connected to the same rectifier / grid unit after being connected in series through the second lead-out group, and the total output voltage of the series connection is the vector superposition of the electromotive forces of the two units.

[0016] Furthermore, it includes a fault-tolerant operation mechanism, where both units work together under normal operating conditions. When either unit fails, the control system immediately cuts off the power supply to the faulty unit, and only the healthy unit drives it. At this time, although the faulty unit is de-energized, its permanent magnet rotor still rotates with the rotor assembly. Since the two rotor segments are pre-staggered by an angle θ0, the cogging torque waveform generated by the permanent magnet of the de-energized unit is out of phase with the cogging torque waveform of the energized unit, thus passively canceling out the latter.

[0017] Description of signal acquisition and spectrum analysis equipment: The dynamic signal acquisition described in step S1 of this invention can be achieved by using a piezoelectric accelerometer, MEMS accelerometer, or magnetoelectric velocity sensor, which is adsorbed or threadedly connected to the motor housing, end cover, or shaft extension. The Fast Fourier Transform (FFT) spectrum analysis described in step S2 can be implemented using various digital processing devices. As a preferred embodiment, a portable vibration analyzer with a built-in digital signal processor (DSP) can be used. This instrument acquires vibration signals in real time via an external or built-in accelerometer, and converts the time-domain waveform into a frequency-domain spectrum using its internal FFT analysis module, automatically identifying and displaying the main vibration frequencies and their corresponding harmonic orders n. Alternatively, a laptop connected to a data acquisition card can be used with analysis software such as MATLAB or LabVIEW, or an embedded FFT analysis module integrated into a motor online monitoring system can be used. All of the above implementation methods are well-known technologies in the art, and those skilled in the art can flexibly choose according to site conditions and cost requirements; none of these constitutes a limitation on the present invention.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. By using the expansion coupling sleeve assembly in conjunction with the end cover operating window design, the misalignment angle can be adjusted at any time after the motor is assembled and even after many years of on-site operation, without disassembling the end cover or removing the heavy rotor. Maintenance time is reduced from several days (return to factory for major overhaul) in the traditional solution to hours (on-site operation), realizing the transformation of the cogging torque suppression effect from "fixed at the factory and useless when it decays" to "adjustable as needed throughout the entire life cycle and continuously optimal".

[0019] 2. Through a hierarchical collaborative architecture of “skewed slot / skewed pole (coarse suppression within the unit, mainly targeting high-frequency harmonics) + misaligned angle (fine cancellation between units, targeting fundamental and low-order harmonics)”, the two are decoupled and coordinated, which can reduce the total torque ripple to less than 1 / 5 of that of a single suppression scheme, fundamentally solving the vibration and noise problems caused by tooth cogging torque.

[0020] 3. A unified harmonic cancellation formula θ is designed to cover both integer and fractional slots. n =180° / (n · LCM(Z, 2p)), and is equipped with a systematic four-step closed-loop correction method of "vibration diagnosis → harmonic source tracing → targeted calculation → on-site adjustment", which makes the calculation of tooth cogging torque suppression more accurate.

[0021] 4. By using a cam + proximity switch + electromagnetic positioning mechanism, the industry problem of random stopping position and inability to align the operation window of the external rotor motor is completely solved, making the high torque direct drive motor of the external rotor topology available for field maintainability for the first time.

[0022] 5. A axial thermal expansion is compensated by a disc spring assembly, maintaining the stability of the misalignment angle across the entire temperature range; axial magnetic leakage is blocked by an annular magnetic shield, reducing end heating and improving efficiency; the worm gear mechanism has a self-locking function to prevent accidental rotation after adjustment; and the lead wires are protected by a helical flexible buffer section and wear-resistant bushings to avoid insulation wear during frequent adjustments. The system performance is more reliable.

[0023] 6. This invention can adopt either an internal rotor topology or an external rotor topology; it supports both integer slot configuration and fractional slot configuration; it can operate as both a motor and a generator, making it more versatile.

[0024] 7. Fault-Tolerance and Vibration Suppression Coordination Mechanism. When a single unit fails, the permanent magnet rotor of the power-off unit still acts as a "passive filter" to cancel cogging torque, making the torque pulsation after the fault much lower than that of traditional redundancy schemes. Attached Figure Description

[0025] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the overall axial half-section of the internal rotor dual-unit motor of the present invention.

[0027] Figure 2 This is a schematic diagram of the right end cover structure for adjusting the angle of the internal rotor dual-unit motor of the present invention.

[0028] Figure 3 This is a schematic diagram of the worm gear mechanism for adjusting the angle of the internal rotor dual-unit motor of the present invention.

[0029] Figure 4 This is a schematic diagram of the sealing cover plate structure for adjusting the angle of the internal rotor dual-unit motor of the present invention.

[0030] Figure 5 This is a half-sectional schematic diagram of the external rotor dual-unit motor of the present invention.

[0031] Figure 6 for Figure 5 Schematic diagram of cross-section at point AA.

[0032] Figure 7 This is a top view of the frame of the external rotor dual-unit motor of the present invention.

[0033] Figure 8 This is a schematic diagram of the slider limiting plate in the external rotor dual-unit motor of the present invention.

[0034] Figure 9 This is a four-step closed-loop flowchart of the on-site adjustment method of the present invention.

[0035] Figure 10 This is a schematic diagram of the motor operating condition topology of the electrical system of the present invention.

[0036] Figure 11 This is a schematic diagram of the generator operating topology of the electrical system of the present invention.

[0037] In the diagram: 1-Housing, 2-Shaft, 3-Tightening connecting sleeve assembly, 4-Disc spring assembly, 5-Left end cover, 8-Fixed hollow shaft, 10-First unit motor, 11-Left side support bearing, 12-First permanent magnet rotor, 13-Right end cover, 14-Magnetic shielding plate, 15-Safety clearance, 20-Second unit motor, 21-Right side support bearing, 22-Second permanent magnet rotor, 23-First stator, 24-Second stator, 25-End cover sealing plate screw hole, 26-Sealing plate screw hole, 31-Inner ring of tightening sleeve, 32-Outer ring of tightening sleeve, 33-Tightening sleeve locking bolt, 34-Operating window, 35-Sealing cover, 36-Positioning pin groove, 37-End cover positioning pin hole, 38-Anti-movement top pin screw hole, 40- Worm gear mechanism, 41-Manual crank, 42-Digital dial, 43-Pointer, 44-Worm gear mechanism bracket, 51-Outer rotor base, 511-Upper half seat, 512-Lower half seat, 513-Closing bolt, 514-Bearing bush, 515-Rectangular guide groove, 516-Upper slider, 517-Lower slider, 518-Slider fastening bolt, 519-Slider return spring, 520-Limit plate, 521-Slider limit plate bolt, 522-Slider limit plate screw hole, 60-Controller, 61-First inverter, 62-Second inverter, 71-Rectifier grid-connected unit, 81-Cam, 82-Proximity switch, 90-First bell housing, 91-Second bell housing, 93-Bell housing closing bolt. Detailed Implementation

[0038] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this patent without inventive effort are within the scope of protection of this patent.

[0039] like Figure 1-11 As shown, this invention provides a dual-unit permanent magnet synchronous motor with an adjustable misalignment angle on-site. Its core feature is that the first unit motor and the second unit motor are coaxially mounted on the same rotating shaft or fixed hollow shaft, and a relative circumferential misalignment angle θ is provided between them, which can be adjusted on-site after the motor assembly is completed. n The misalignment angle θ n From formula θ n=180° / (n·LCM(Z, 2p)) is used to determine the angle, which is applicable to both integer slot fits and fractional slot fits. The motor is equipped with a shrink-fit coupling sleeve assembly. Through the operation window on the end cover, the entire process of loosening, adjusting and locking the misalignment angle can be completed without removing the end cover or pulling out the rotor.

[0040] Example 1 like Figure 1 As shown, this embodiment provides a dual-unit permanent magnet synchronous motor with an internal rotor topology.

[0041] The first permanent magnet rotor 12 is fixed on the rotating shaft 2. The center of the second permanent magnet rotor 22 is a stepped barrel hole. The left side of the stepped barrel hole is slidably connected to the rotating shaft, serving only to support the rotor. The middle section is open, and the right section is equipped with an expansion joint sleeve assembly 3. The second permanent magnet rotor 22 is fitted onto the rotating shaft 2 through the expansion joint sleeve assembly 3. The two stators are fixed to the inner wall of the housing 1.

[0042] An operating window 34 is provided on the right end cover 13 at the position corresponding to the tightening sleeve locking bolt 33. A torque wrench can be inserted through the operating window 34 to loosen or tighten the tightening sleeve locking bolt 33. The operating window 34 is equipped with a removable sealing cover 35, which remains sealed during normal operation to prevent dust and moisture from entering.

[0043] The right end cover 13 is provided with an end cover positioning pin hole 37, and a positioning pin groove 36 is opened on the right side of the second permanent magnet rotor. The two are locked with a positioning pin, which can fix the circumferential position of the second permanent magnet rotor and the end cover during the adjustment process. An anti-movement top pin screw hole 38 is provided. The top pin is screwed into the right end cover 13 to abut against the right side of the second permanent magnet rotor to prevent axial movement during the adjustment process.

[0044] The right end of the rotating shaft 2 is connected to the worm gear mechanism 40 via a clutch mechanism. The clutch mechanism is only used to connect the rotating shaft 2 to the worm gear mechanism 40 when adjusting the angle. The worm gear mechanism 40 is equipped with a manual crank 41, which has a self-locking function to prevent accidental rotation after adjustment. A scale 42 and a pointer 43 are located on the crank for reading and setting the misalignment angle; the minimum graduation value is no greater than 1 / 10 of the theoretical misalignment angle. Alternatively, a dial indicator / micrometer can be used to measure the circumferential arc length and convert the angle to eliminate axial parallax.

[0045] Axial thermal compensation mechanism: A disc spring assembly 4 is provided in the bearing chamber of the left end cover 5, sleeved on the rotating shaft 2, and installed between the outer ring of the left support bearing 11 and the bottom surface of the bearing chamber wall of the left end cover 5. It is in a pre-compressed state during final assembly. When the rotating shaft 2 thermally elongates to the right due to the temperature rise during operation, the disc spring assembly 4 is further compressed to absorb the thermal expansion displacement and maintain the misalignment angle between the first permanent magnet rotor and the second permanent magnet rotor constant throughout the entire temperature range.

[0046] Axial magnetic shielding structure: An annular magnetic shielding plate 14 is embedded in the inner wall of the housing 1, located between the adjacent end faces of the two stator units. Its inner diameter is larger than the outer diameter of the rotor. It is made of austenitic stainless steel or epoxy resin laminate and is used to block the axial leakage magnetic path between the two stator units and reduce end heating.

[0047] On-site adjustment operation procedure (taking motor shutdown maintenance scenario as an example): When the cogging torque of a motor increases due to factors such as accumulated assembly errors, material creep caused by thermal cycling, or bearing wear after long-term operation, the following steps can be taken for on-site adjustment: First, open the sealing cover plate 35 to expose the expansion joint sleeve assembly 3, the second permanent magnet rotor positioning pin groove 36 and the anti-movement top pin screw hole 38; The second step is to insert a positioning pin into the positioning pin slot 36 on the second permanent magnet rotor through the positioning pin hole 37 on the end cover to fix the circumferential position of the second permanent magnet rotor and the end cover; and screw in the anti-movement top pin to abut against the right side of the second permanent magnet rotor to prevent the second rotor from moving axially. Third step, insert the torque wrench through the operation window 34 to loosen the expansion sleeve locking bolt 33, so that the inner ring of the expansion sleeve is separated from the rotating shaft; Fourth step: Use the hand crank 41 to rotate the shaft 2. At this time, the second permanent magnet rotor disengages from the shaft and its circumferential position is locked. The shaft drives the first permanent magnet rotor to rotate freely, creating a relative misalignment angle between the two. Observe the scale 42 or dial indicator on the crank and rotate to the target angle θ. n (Determined by on-site vibration diagnosis and harmonic source analysis, with fine adjustments allowed within ±1° of the theoretical value); Fifth step, tighten the expansion sleeve locking bolt 33 to the predetermined torque, so that the expansion sleeve locks the rotating shaft and the misalignment angle is locked; Step 6: Remove the anti-movement top pin and positioning pin, and install the sealing cover plate 35.

[0048] The entire process requires no disassembly of the end caps or removal of the heavy rotor, reducing maintenance time from several days of traditional factory overhaul to hours of on-site operation.

[0049] Example 2 like Figure 2-4 As shown, this embodiment details the standard operating procedure for on-site adjustment of the misalignment angle under the inner rotor topology to ensure adjustment accuracy and operational safety: Step 1 (Opening the window): Turn off the motor power and execute the safety locking procedure. Open the sealing cover plate 35 on the end cover to expose the expansion joint sleeve assembly 3, the second permanent magnet rotor positioning pin groove 36 and the anti-slip top pin screw hole 38.

[0050] Step 2 (Positioning): Operate the clutch mechanism to connect the rotating shaft 2 with the worm gear mechanism 40. Rotate the rocker arm 41 to drive the rotating shaft 2, so that the positioning pin hole 37 of the end cover is aligned with the positioning pin groove 36 on the side of the second permanent magnet rotor. Insert the positioning pin to fix the circumferential position of the second permanent magnet rotor and the end cover. Screw in the anti-movement top pin to make it abut against the right side of the second permanent magnet rotor to eliminate the axial movement gap.

[0051] Step 3 (Loosening the sleeve): Insert the torque wrench through the operating window 34 and gradually loosen the tightening sleeve locking bolt 33 according to the prescribed sequence and number of turns, so that the inner ring of the sleeve disengages from the shaft. Note: The bolt should be loosened evenly to avoid the sleeve from becoming misaligned and jamming.

[0052] Step 4 (Angle Adjustment): Use the hand crank 41 to rotate the shaft 2. At this time, the second permanent magnet rotor 22 is fixed to the right end cover 13 by the positioning pin. The shaft 2 drives the first permanent magnet rotor 12 to rotate, changing the relative circumferential misalignment angle between the two. Observe the scale 42 or dial indicator reading on the crank and rotate to the target misalignment angle θ calculated by the on-site correction method. n For high-precision adjustment requirements, a dial indicator / micrometer can be used to measure the circumferential arc length on the outer circle of the shaft. The angle can then be converted from the arc length to eliminate axial parallax.

[0053] Step 5 (Locking): Tighten the expansion sleeve locking bolts 33 gradually according to the specified predetermined torque and cross sequence, so that the inner ring of the expansion sleeve contracts evenly and locks the shaft. The torque should be checked after tightening.

[0054] Step 6 (Unlocking the rotor and restoring it): Remove the anti-slip pin and the positioning pin, rotate the shaft to confirm that there is no jamming, install the sealing cover plate 35 and tighten the sealing cover plate fixing bolts, and operate the clutch mechanism to disengage the shaft 2 from the worm gear mechanism 40.

[0055] Step 7 (Verification): Re-power on and test run, monitoring dynamic signals using vibration and / or torque sensors to confirm that the cogging torque pulsation has decreased to the target value. If not, repeat steps 1 to 6 for fine-tuning (within ±1°).

[0056] Example 3 like Figure 5-8 As shown, this embodiment provides a dual-unit permanent magnet synchronous motor with an external rotor topology, including a split frame 51, a fixed hollow shaft 8, and a first unit motor 10 and a second unit motor 20 arranged sequentially along the axial direction.

[0057] Base Structure: The split base 51 is a horizontally split structure, consisting of an upper half 511 and a lower half 512 locked together by a locking bolt 513. A rectangular guide groove 515 is provided on the right side of the base 51, housing an upper slider 516 and a lower slider 517. The upper slider 516 and lower slider 517 are connected by a slider return spring 519, allowing them to slide relative to each other radially along the motor. The right end of the fixed hollow shaft 8 extends through the bearing bush 514 to the area of ​​the rectangular guide groove 515. The opposing surfaces of the upper slider 516 and lower slider 517 have arc-shaped clamping surfaces adapted to the outer wall of the fixed hollow shaft 8. Tightening the slider fastening bolt 518 allows the arc-shaped clamping surfaces to grip the fixed hollow shaft 8, achieving a rigid connection; when loosened, the slider return spring 519 separates the sliders, releasing the clamp and allowing the fixed hollow shaft 8 to rotate and adjust. Limit plates 520 are fixed on both sides of the rectangular guide groove 515.

[0058] Cantilever support structure: The left end of the fixed hollow shaft 8 is a cantilever structure, and only the right end is supported on the base 51 by the bearing 514. The cup-shaped outer rotor assembly, which is composed of the first bell housing 90 and the second bell housing 91, is rotatably mounted on the periphery of the fixed hollow shaft 8 through bearings.

[0059] Stator mounting structure: The first stator 23 is fixedly fitted onto the outer wall of the fixed hollow shaft 8; the second stator 24 is fitted onto the outer wall of the fixed hollow shaft 8 via the expansion coupling sleeve assembly 3. The expansion coupling sleeve assembly 3 includes an inner ring 31 and an outer ring 32, which are fitted together by a tapered surface. When the expansion sleeve locking bolt 33 is tightened, the inner ring contracts to hug the fixed hollow shaft, and the outer ring expands to tighten the inner wall of the second stator.

[0060] The outer rotor assembly consists of a first permanent magnet rotor 12 installed inside the first bell housing 90 and mounted on the periphery of the first stator 23 via a left-side support bearing 11; and a second permanent magnet rotor 22 installed inside the second bell housing 91 and mounted on the periphery of the second stator 24 via a right-side support bearing 21. The two bell housings are rigidly connected by a housing bolt 93 to form an integrated outer rotor assembly.

[0061] Axial magnetic shielding plate: A ring magnetic shielding plate 14 is installed on the fixed hollow shaft 8, located between the adjacent end faces of the first stator 23 and the second stator 24. It is made of austenitic stainless steel or epoxy resin laminate, and its outer diameter is smaller than the inner diameter of the bell shell, forming a safety gap of 1.5~3mm on one side, which not only blocks axial magnetic leakage, but also avoids collision and friction during operation.

[0062] Angle adjustment auxiliary mechanism: The right end of the fixed hollow shaft 8 extends out of the base 51 and is connected to the worm gear mechanism 40 via a clutch mechanism. A manual crank 41 is provided at the input end. The worm gear has a self-locking function to prevent accidental rotation after adjustment. The worm gear mechanism 40 has a dial 42, and a pointer 43 is fixed on the crank 41. The maximum rotational stroke of the worm gear mechanism 40 is limited to ±15° by a mechanical limit structure, ensuring that the flexible buffer sections of each lead wire are always within the elastic deformation range.

[0063] Conductor protection structure: The wire hole inside the fixed hollow shaft 8 is fitted with a wear-resistant bushing. The second stator lead wire has a flexible buffer section with a spiral or S-shaped bend inside the fixed hollow shaft. Its unfolded length is not less than twice the displacement corresponding to the maximum rotation stroke (±15° mechanical limit) of the worm gear mechanism, ensuring that the lead wire is always within the elastic deformation range during frequent adjustment, without plastic deformation, and avoiding wear of the insulation layer.

[0064] Working principle of external rotor on-site adjustment: During normal operation, the slider fastening bolt 518 is tightened to fix the hollow shaft 8 to the machine base 51.

[0065] When it is necessary to adjust the misalignment angle: 1. Activate the braking device on the motor itself or on the external load to lock the outer rotor assembly (the first bell housing 90 and the second bell housing 91 are rigidly connected) to prevent the rotor from rotating.

[0066] 2. Open the sealing cover plate 35, insert the positioning pin into the positioning pin groove 36 on the right side of the second stator through the positioning hole 37 of the end cover, and fix the second stator 24 and the end cover in the circumferential position; screw the top pin into the anti-movement top pin screw hole 38 to abut against the right side of the second stator.

[0067] 3. Loosen the slider fastening bolt 518 to release the slider from clamping the fixed hollow shaft; at the same time, loosen the expansion sleeve locking bolt 33 through the operation window 34.

[0068] 4. Shaking the rocker arm 41 drives the fixed hollow shaft 8 to rotate, causing the first stator 23 to rotate relative to the locked second stator 24, thus completing the misalignment angle adjustment (the angle reading method is the same as in Embodiments 1 and 2).

[0069] 5. Re-tighten the expansion sleeve locking bolt 33 and the slider fastening bolt 518, remove the positioning pin and top pin, install the sealing cover plate, and release the brake.

[0070] 6. Power-on trial operation to verify the adjustment effect.

[0071] The entire process does not require disassembling the end caps or pulling out the heavy outer rotor assembly, making the outer rotor motor available for field maintainability for the first time.

[0072] Example 4 like Figure 5-8 As shown, when the external rotor motor stops, the stopping position of the external rotor assembly is random, causing the operating window 34 on the end cover to be unable to align with the tightening sleeve locking bolt 33. This embodiment completely solves this problem through a stop positioning system.

[0073] (I) System Composition The system includes a cam 81, a proximity switch 82, and a controller 60. The cam 81 is fixedly mounted on the right side of the second bell housing 91 or the outer side of the end cover 13, and rotates synchronously with the outer rotor assembly. It is preferably secured with high-strength screws and a counterweight to ensure dynamic balance. The proximity switch 82 is fixed to the stationary base by a bracket, with its sensing end facing the cam's rotation trajectory.

[0074] (ii) Design of three overlapping lines The core of this invention lies in the spatial overlap of the following three angular position lines: • Angle position line A: The preset angle position line of the proximity switch 82 triggered by the cam 81; • Angle position line B: The angle position line in which the operating window 34 and the tightening sleeve locking bolt 33 are aligned in space; • Angle position line C: The angle position line (i.e., the electromagnetic positioning equilibrium point) that generates the maximum magnetic attraction between the second stator winding and the second permanent magnet rotor when DC current is applied.

[0075] Through structural layout design, the three elements overlap at the same spatial angle.

[0076] Pre-stop positioning control logic: A pre-stop positioning system and optimized braking adjustment strategy. For the external rotor topology, due to the randomness of the circumferential position of the bell-shaped rotating housing after shutdown, the operating window 34 and the tightening sleeve locking bolt 33 are often in a relatively misaligned state, making it impossible for on-site operators to directly access the bolt through the window. To solve this problem, this embodiment further includes a pre-stop positioning system.

[0077] The mechanical structure of the system is as follows: a cam 81 is fixedly installed on the outer wall or end face of the bell-shaped rotating housing, and a proximity switch 82 is fixedly installed on a stationary component such as the base. The cam has a specific trigger protrusion, the angle of which is set such that when the cam triggers the proximity switch, the operating window 34 and the tightening sleeve locking bolt 33 are exactly in circumferential alignment. At the same time, this angle is also designed such that when a DC current is applied to the second stator winding, the magnetic attraction between the stator magnetic field generated by it and the permanent magnet magnetic field of the second permanent magnet rotor reaches its maximum value (i.e., the d-axis coincides with the magnetic pole axis of the permanent magnet).

[0078] The control logic is as follows: When the on-site operator issues a stop and adjustment command, the controller 60 first reduces the motor speed to the set crawling speed (e.g., 0.1~0.5 r / min) through the frequency conversion speed regulation function. The motor continues to rotate at an extremely low speed. When the cam 81 rotates to the sensing area of ​​the proximity switch 82, the proximity switch is triggered and sends a trigger signal to the controller 60.

[0079] Upon receiving the trigger signal, the controller 60 first cuts off the motor power supply and enters a pre-stop state. Simultaneously, it injects DC current (from the inverter's DC bus) into the second stator 24 winding via the second inverter 62. This DC current establishes a static magnetic field in a fixed direction within the second stator 24 winding, interacting with the permanent magnet field of the second permanent magnet rotor 22 to generate magnetic attraction. This attraction further pulls the outer rotor assembly from the proximity switch trigger position (the critical point where the cam just enters the sensing zone) to the precise angle of maximum magnetic attraction. This maximum magnetic attraction angle is pre-designed to perfectly coincide with the angular position line of the operating window 34 aligned with the tightening sleeve locking bolt 33. Therefore, after DC traction is completed, the operating window 34 and the tightening sleeve locking bolt 33 are precisely aligned, achieving a positioning accuracy far exceeding that of relying solely on the proximity switch trigger signal.

[0080] Regarding the method of injecting DC current, those skilled in the art will understand that applying a DC component to the stator windings of the motor via an inverter to generate static positioning torque is a known electrical braking method in the field of vector control. Specifically, the controller, through its internal pulse width modulation (PWM) module, outputs a specific drive signal to the switching transistors of the three-phase inverter, causing the inverter to apply a DC voltage component from the DC bus voltage to the stator windings of the motor according to a space vector pulse width modulation (SVPWM) strategy. This generates a constant DC excitation current in the windings, forming the static magnetic field required for positioning. This invention does not limit the specific modulation algorithm of the DC current; any known control strategy capable of supplying DC to the stator windings can be used.

[0081] The controller 60 continuously monitors the trigger signal status of the proximity switch. When the proximity switch remains in the trigger state for more than the preset lock confirmation time t1 (preferably 0.5 to 1 second), the controller determines that the outer rotor assembly has stabilized at the preset angle, and then cuts off the DC current. At the same time, it controls the second inverter 62 to implement three-phase short-circuit braking (ASC, i.e., all upper bridge arms of the inverter are turned off and all lower bridge arms are turned on, or all upper bridge arms are turned on and all lower bridge arms are turned off, so that the three-phase leads of the second stator winding form a short-circuit loop).

[0082] Under three-phase short-circuit conditions, if the outer rotor assembly tends to rotate or deviate, the induced electromotive force generated by the second permanent magnet rotor 22 will induce a current in the short-circuited winding of the second stator 24. This induced current interacts with the permanent magnet magnetic field, generating a braking torque that opposes rotor movement. The magnitude of this braking torque increases with the increase of the rotor's deviation speed, exhibiting self-reinforcing characteristics. Since the second permanent magnet rotor 22 is fixed to the bell housing, this braking torque is transmitted to the entire bell housing through a mechanical connection, reliably locking the outer rotor assembly (including the first and second permanent magnet rotors) at a preset angle. During this locking phase, no continuous DC current is required; only an induced current exists in the stator winding, which is zero under static conditions. The winding generates almost no heat, and the locking time is unrestricted. Simultaneously with the three-phase short-circuiting of the second stator winding, the controller 60 activates the motor's built-in or load-side braking system to lock the outer rotor assembly, preventing it from rotating along with the first stator 23 during adjustment.

[0083] At this point, the operating window 34 and the tightening sleeve locking bolt 33 are precisely aligned, allowing the operator to directly observe and operate through the window. The operator first loosens the tightening connecting sleeve assembly 3, disengaging the second stator 24 from the fixed hollow shaft 8. The operator then rotates the hollow shaft 8 via the worm gear mechanism 40, causing the first stator to rotate. This changes the circumferential position of the slot of the first stator 23 relative to the second stator 24, thus altering the relative misalignment angle between the first unit motor 10 and the second unit motor 20.

[0084] After the misalignment angle is adjusted to the correct position, the operator locks the expansion coupling assembly 3 through the operation window 34 to fix the second stator 24 to the fixed hollow shaft 8. Finally, the controller exits the three-phase short-circuit braking state of the second stator winding (i.e., restores the inverter to normal standby mode), and the motor can then be put into normal operation according to the new misalignment angle.

[0085] The core advantages of the above solution are: DC traction ensures precise alignment of the operating window and fastening bolts (accuracy up to 0.1°), three-phase short-circuit braking plus mechanical braking achieves zero-energy, unlimited-time locking, the outer rotor assembly only needs to be positioned once, and there is no need to repeatedly start and stop the motor and re-search the cam trigger position during subsequent adjustments. The first stator can be freely rotated back and forth for trial adjustment until the misalignment angle precisely meets the requirements, which greatly improves the convenience and efficiency of on-site operation.

[0086] It should be noted that although DC traction and three-phase short-circuit braking are both known technologies in the field of motor control, in this invention, they are creatively combined and applied to the on-site adjustment of the misalignment angle of a dual-unit external rotor motor. First, precise positioning is achieved using DC traction, and then the ASC locking of the external rotor assembly is used as a reference, allowing the first stator to rotate freely to complete the "stator-side" misalignment angle adjustment. There is no prior art that combines "DC traction + ASC locking" with the positioning of the operating window of the expansion coupling sleeve assembly to achieve a "stator-side on-site adjustable" solution. Therefore, this combined solution is not an obvious simple superposition and has significant creative and practical value.

[0087] Example 5 like Figure 9 As shown, the present invention also provides a method for on-site adjustment of the misalignment angle of the above-mentioned motor. This method is performed on-site after the motor is assembled, transforming the misalignment angle from "one-time fixed" during the manufacturing stage to "adjustable as needed" throughout the entire operating life cycle.

[0088] Applicable scenarios: After a period of operation in the field (such as six months or a year), the tooth cogging torque increases due to factors such as accumulated assembly errors, thermal cycling creep, and bearing wear, or the load conditions change significantly. This method can be used for closed-loop correction in the field.

[0089] S1—On-site vibration diagnosis: At the actual installation site of the motor, install vibration sensors and / or torque sensors on the shaft 2 or the housing 1. Ensure the motor operates stably under rated conditions and collect dynamic signals (vibration acceleration, vibration velocity, or torque fluctuation signals) during operation. The acquisition duration should cover at least 10 complete mechanical rotation cycles to ensure sufficient frequency resolution for the FFT analysis.

[0090] S2 – Harmonic Source Analysis: The acquired dynamic signal is analyzed by a fast Fourier transform spectrum analysis using a data processing unit (which can be a portable data acquisition instrument or a motor controller with a built-in DSP) to obtain the spectral distribution of torque pulsation. The harmonic order n with the largest amplitude is identified (i.e., the main culprit causing the vibration). For low-speed, high-torque direct-drive motors, the fundamental frequency (n=1) or lower harmonics (n=2, 3, 6, etc.) are usually dominant.

[0091] S3 – Target Angle Calculation: According to the general formula θ n = 180° / (n · LCM(Z, 2p)) Calculate the target misalignment angle θ n ,in: • Z represents the number of slots in the stator of each unit motor; • 2p represents the number of poles of the rotor of each unit motor; LCM stands for least common multiple. • n represents the main harmonic order identified in step S2.

[0092] This formula applies to both integer slot coordination and fractional slot coordination. For complex situations with multiple harmonics, the optimal overall angle can be calculated based on amplitude weighting, or the order with the largest amplitude can be suppressed first.

[0093] S4 – On-site adjustment: By using the expansion joint sleeve assembly and end cap operation window, and following the adjustment operation procedures for the corresponding topologies in Examples 1 to 4, the misalignment angle is adjusted to the target value θ. n (Fine adjustments are allowed within ±1° of the theoretical value to compensate for nonlinear factors in actual operation). After adjustment, power on again for trial operation and repeat step S1 for verification. If the target is not met, further fine adjustments can be made within ±1°.

[0094] Method effectiveness verification: For a 12-pole, 72-slot low-speed, high-torque permanent magnet synchronous direct drive motor, after on-site correction using this method: • Peak cogging torque decreased from the original 2.8% of rated torque to below 0.4% of rated torque; • Total torque ripple decreased from ±6.5% to below ±1.2%; • The overall vibration acceleration level decreased by approximately 12 dB; The entire on-site operation takes about 4 hours, while the traditional return-to-factory overhaul solution takes 7 to 10 days.

[0095] Example 6 Verification of the effectiveness of the fault-tolerance mechanism. When any unit experiences an electrical control system failure, the control system blocks the inverter output of the faulty unit, and the healthy unit independently drives the entire rotor shaft system. The electromagnetic torque of the healthy unit only needs to overcome the load torque and mechanical losses (the peak torque of a single unit can reach 150% of the rated value, the fault-tolerance load is 50%, and the healthy unit has sufficient overload margin), ensuring that the whole machine does not lose synchronization or stop.

[0096] Analysis of the self-cancellation effect of misalignment angle on cogging torque under fault-tolerant conditions: The physical source of cogging torque is the interaction between the permanent magnet magnetic field and the stator cogging reluctance; the mathematical expression does not include the winding current term. After the first unit is de-energized, the permanent magnet still exists, and the cogging torque still exists; misalignment angle θ nIt is a mechanically fixed angle between the two permanent magnet rotors, which does not change due to the winding energization state. Under normal operating conditions: T_cog,total = T_cog,1 + T_cog,2 = T·sin(α) + T·sin(α + 180°) = 0. Under fault-tolerant conditions (first unit de-energized): T_cog,fault = T_cog,1,open + T_cog,2 = T·sin(α) + T·sin(α + 180°) = 0. The two equations are identical because the expression for T_cog is independent of the current.

[0097] The self-cancellation effect of the misalignment angle on the cogging torque is a purely mechanical and geometric effect, completely decoupled from the winding energization state. Under fault-tolerant conditions, this cancellation effect is fully maintained, achieving "power derating but no derating of cogging torque stability".

[0098] The fault-tolerant operation mechanism of this invention is applicable to motor operating conditions. Under normal operating conditions, the two units work together to achieve rated power output and self-cancellation of cogging torque. When any unit experiences an electrical control system failure (including but not limited to: damage to the inverter power devices corresponding to that unit, drive circuit failure, abnormal PWM output of the controller, bus voltage drop, loss of position sensor signal, etc., such failures account for more than 70% of electrical failures in permanent magnet synchronous motor drive systems), the control system immediately executes the following fault-tolerant operation: Step 1 (Fault Isolation): Block all PWM outputs of the inverter in this unit, turn off the power switching devices, and electrically isolate the unit from the DC bus.

[0099] Step Two (Passive Drive After Power Deactivation): The faulty unit stops outputting power, its stator windings are open (no current input), and its permanent magnet rotor, due to its rigid coaxial connection with the permanent magnet rotor of the healthy unit, is forcibly driven by the rotating magnetic field of the healthy unit to continue rotating at a synchronous speed strictly satisfying n = 60f / p. The physical mechanism lies in the fact that the synchronous operation of a permanent magnet synchronous motor depends on the "magnetic linkage locking" relationship between the stator rotating magnetic field and the permanent magnet rotor. Three-phase current is supplied to the stator windings of the healthy unit, generating a complete rotating magnetic field. This magnetic field continuously drags the entire coaxial rotor assembly (including the half of the permanent magnet from the faulty unit) to rotate synchronously. At this time, the permanent magnet of the faulty unit is essentially "carried" by the shaft system; although it does not generate active torque, it also does not generate significant resistance torque (because there is no induced circulating current due to the open windings).

[0100] Step 3 (Cogging Torque Self-Cancellation Maintenance): Although the faulty unit does not contribute output torque, its permanent magnet still retains the original misalignment angle θ with the permanent magnet of the healthy unit (this misalignment angle is mechanically fixed and unaffected by electrical faults). Therefore, the cogging torque waveforms of the two units continue to maintain a relationship of opposite phases and canceling amplitudes, ensuring that the whole machine maintains low torque pulsation characteristics even in half-power derating operation.

[0101] Step 4 (Derating Operation): At this point, the total output power is reduced to 50% of the rated value (only the healthy units are outputting). The whole machine continues to run, but it is not advisable to operate at full load for a long time. It is recommended to reduce the load request to below 50% of the rated power until the maintenance is completed.

[0102] Defining the applicable boundaries of fault tolerance mechanisms: The fault-tolerance mechanism described in this invention is mainly aimed at inverter / controller / sensor faults (i.e., electrical control system faults). Such faults account for more than 70% of drive system faults and are characterized by "the unit suddenly loses driving force but the motor body is intact". The "power-off passive drive" strategy of this invention is completely effective for such faults.

[0103] For severe motor failures (including but not limited to: inter-turn short circuits in windings, winding-to-ground breakdown, severe demagnetization of permanent magnets, bearing jamming, rotor rubbing, etc.), the faulty unit itself generates abnormal resistance torque or braking torque, making it difficult for the healthy unit to overcome this resistance torque and continue driving the entire machine. Such failures constitute severe motor failures and typically require immediate shutdown for repair, which is not the target scenario for the fault-tolerance mechanism of this invention. However, for winding short-circuit faults, this invention can be used in conjunction with an external rapid demagnetization circuit (or a thyristor short-circuit removal device) to short-circuit the ends of the three-phase windings of the faulty unit within milliseconds after the fault occurs, achieving rapid demagnetization and removal of braking torque, after which the healthy unit drives the machine under reduced derating. This external protection circuit is a well-known technology in the field and does not constitute an essential technical feature of this invention, but it can be used in conjunction with this invention to expand the scope of fault tolerance. Summary of the engineering significance of the fault-tolerant mechanism: For electrical control system faults, which account for over 70% of all faults, this invention achieves derating operation with "no shutdown, no loss of synchronization, and low pulsation." This has significant engineering value for scenarios where catastrophic shutdowns must be avoided, such as emergency propulsion in ships, slow elevator positioning, and emergency hoisting in mines. While this invention cannot achieve fault-tolerant operation for severe motor failures, such faults typically have gradual warning signs (abnormal temperature, increased vibration, decreased insulation resistance, etc.). Early warnings can be provided through online status monitoring, allowing for planned shutdowns without affecting the industrial applicability of this invention.

[0104] Application example – Low-speed, high-torque direct drive scenario: This invention is particularly suitable for low-speed, high-torque direct-drive motors (such as those used in hoisting, mine hoists, wind turbines, and industrial rolling mills). In these applications, the motor has a large number of pole pairs and slots, resulting in an extremely low fundamental frequency of the cogging torque. The high-frequency harmonic components are negligible in their contribution to the output torque pulsation due to the attenuation caused by eddy current damping on the rotor surface and mechanical impedance. The main vibration energy is concentrated in the fundamental frequency (n=1) and the second and third harmonics.

[0105] For the aforementioned low-order harmonics, the misalignment angle formula θ of this invention... n =180° / (n·LCM(Z,2p)) can accurately calculate a large and easily mechanically adjustable angle value (e.g., when LCM=48, θ1=3.75°, θ2=1.875°). High-precision alignment can be easily achieved through the expansion coupling assembly, which can theoretically completely cancel the target order. At the same time, this invention allows the optimal angle to be recalibrated on-site according to the actual load conditions, compensating for harmonic drift caused by material creep, thermal expansion and contraction, or bearing wear after long-term operation. This is an "active tracking" capability that fixed skewed slot / skewed pole structures cannot achieve.

[0106] Therefore, in a preferred embodiment of the present invention, the first unit motor and / or the second unit motor do not have skewed slots or skewed poles to avoid the weakening of the fundamental back EMF and the complexity of the winding process caused by skewed slots / poles, thereby maximizing the torque density and efficiency of the motor. Those skilled in the art will understand that even without skewed slots / poles, the dual-unit misalignment adjustment structure of the present invention is sufficient to achieve efficient suppression of cogging torque in direct-drive scenarios, achieving technical effects exceeding expectations.

[0107] Advantages: 1. Based on FFT spectrum analysis, accurately trace the source and avoid blind trial and error; 2. Form a complete closed loop of "diagnosis → source tracing → calculation → adjustment → verification"; 3. The entire process can be completed on-site without disassembling the end caps or removing the rotor; 4. It can be repeated periodically to achieve optimal gear cogging torque suppression effect throughout its entire life cycle.

[0108] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention from the specific circumstances.

[0109] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dual-unit permanent magnet synchronous motor with an adjustable offset angle, comprising a housing or base, a rotating shaft or a fixed hollow shaft, and a first unit motor and a second unit motor axially disposed within the housing or base; the first unit motor and the second unit motor each independently comprise a stator and a permanent magnet rotor, and are coaxially disposed on the same rotating shaft or fixed hollow shaft; characterized in that: The first unit motor and the second unit motor are provided with a relative circumferential misalignment angle θ that can be adjusted on-site after the motor assembly is completed. n The misalignment angle θ n Used to cancel target order harmonics caused by cogging torque; The motor is also equipped with a tensioning coupling sleeve assembly, which has a locked state and a loosened state. When in the loosened state, it can adjust the misalignment angle θ. n Perform on-site adjustments until the target value is reached, then switch to the locking state. It also includes an end cap, on which an operation window is provided corresponding to the position of the expansion coupling sleeve assembly, and a removable sealing cover is provided, through which the expansion coupling sleeve assembly can be loosened or locked.

2. The dual-unit permanent magnet synchronous motor with field-adjustable misalignment angle as described in claim 1, characterized in that, Displacement angle θ n From formula θ n =180° / (n · LCM(Z, 2p)) is determined, where Z is the number of slots in the stator of each unit motor, 2p is the number of poles in the rotor of each unit motor, LCM represents taking the least common multiple, and n is the harmonic order to be canceled, where n is a positive integer; this formula is applicable to both integer slot fits and fractional slot fits.

3. The dual-unit permanent magnet synchronous motor with field-adjustable misalignment angle according to claim 1, characterized in that: The first unit motor and / or the second unit motor have a skewed slot or skewed pole structure inside, serving as a first-stage suppression unit; the equivalent angle β of the skewed slot or skewed pole is related to the misalignment angle θ. n Each is determined independently.

4. The dual-unit permanent magnet synchronous motor with field-adjustable misalignment angle according to claim 1, characterized in that: The motor has an internal rotor topology: Two stators are fixed to the inner wall of the housing, the first permanent magnet rotor is fixedly connected to the shaft, and the second permanent magnet rotor is fitted onto the shaft through the expansion coupling assembly. The operation window is provided on the end cap at the position corresponding to the locking bolt of the expansion sleeve; An angle indicator component is provided at the extended end of the shaft or on the outside of the housing for reading and setting the misalignment angle θ. n ; The shaft is equipped with an axial thermal compensation mechanism to absorb the thermal expansion of the shaft caused by the temperature rise during operation and maintain a constant misalignment angle.

5. The dual-unit permanent magnet synchronous motor with field-adjustable misalignment angle according to claim 4, characterized in that: The axial thermal compensation mechanism is a disc spring assembly installed in the bearing chamber of the end cover, and its total compression stroke is greater than the maximum axial thermal expansion of the shaft. The end face of the second permanent magnet rotor is provided with a positioning pin groove, and the end cover is provided with a corresponding end cover positioning hole. The positioning pin forms a temporary circumferential locking structure to fix the relative position of the second permanent magnet rotor and the end cover during the adjustment process. On the end cap corresponding to the end face of the second permanent magnet rotor, an anti-movement top pin screw hole is provided. During the adjustment process, the top pin is screwed in to abut against the side of the second rotor to prevent the second rotor from moving axially. The end of the rotating shaft is connected to a worm gear mechanism, which has a self-locking function and a rocker arm at its input end.

6. The dual-unit permanent magnet synchronous motor with field-adjustable misalignment angle according to claim 1, characterized in that: The motor has an external rotor topology, including a split frame and a fixed hollow shaft. The two permanent magnet rotors are bell-shaped rotating shells and are coaxially arranged around the fixed hollow shaft. The first stator is fixedly mounted on the fixed hollow shaft, and the second stator is adjustablely mounted on the fixed hollow shaft via the expansion coupling assembly; The operation window is opened on the right side of the bell jar shell or on the end cover at the position corresponding to the fastening bolt; An annular magnetic shielding plate is fitted on the fixed hollow shaft, located between the adjacent end faces of the first stator and the second stator, to block the axial leakage magnetic path; The split base is a horizontally split structure, consisting of an upper half and a lower half locked together by locking bolts. The base is provided with a rectangular guide groove, within which are an upper slider and a lower slider. The upper and lower sliders are connected by a slider return spring and can slide relative to each other along the radial direction of the motor. The fixed hollow shaft extends into the rectangular guide groove area after passing through the bearing bush. The opposing surfaces of the upper and lower sliders are provided with arc-shaped clamping surfaces that fit the outer wall of the fixed hollow shaft. Tightening the slider fastening bolts allows the arc-shaped clamping surfaces to grip the fixed hollow shaft. When loosened, the slider return spring separates the upper and lower sliders. Limit plates are fixed on both sides of the rectangular guide groove.

7. The dual-unit permanent magnet synchronous motor with field-adjustable misalignment angle according to claim 6, characterized in that: It also includes a stop positioning system, which includes a cam fixed on a bell-shaped rotating housing, a proximity switch fixed on a stationary component, a controller, and an inverter; The preset angle position line for the cam to trigger the proximity switch, the angle position line for the operation window to align with the fastening bolt, and the angle position line for the second stator winding to generate the maximum magnetic attraction with the second permanent magnet rotor when DC power is applied, all three coincide at the same preset angle. When a shutdown adjustment is required, the controller reduces the motor to the crawling speed after receiving a shutdown command. In response to the trigger signal of the proximity switch, DC current is injected into the second stator winding through the inverter, and the outer rotor assembly is pulled to the preset angle by magnetic attraction. After the controller confirms the positioning is completed, it cuts off the DC current of the second stator winding and simultaneously controls the inverter to implement three-phase short-circuit braking and motor mechanical braking on the second stator winding, locking the outer rotor assembly at the preset angle; After the expansion coupling sleeve assembly is loosened, the first stator can rotate freely with the fixed hollow shaft to adjust the misalignment angle. After the adjustment is completed, the expansion coupling sleeve assembly is locked, and the controller exits the three-phase short-circuit braking.

8. The dual-unit permanent magnet synchronous motor with field-adjustable misalignment angle according to claim 6, characterized in that: The fixed hollow shaft is fitted with a wear-resistant bushing at the wire hole, and the second stator lead wire has a flexible buffer section with a spiral or S-shaped bend inside the fixed hollow shaft. The end of the second stator is connected to a worm gear mechanism, which has a self-locking function and a rocker arm at its input end.

9. A method for adjusting a dual-unit permanent magnet synchronous motor with an adjustable misalignment angle as described in any one of claims 1-8, characterized in that: The method is performed at the installation site after the motor is fully assembled, and includes the following steps: S1. At the actual installation site of the motor, the dynamic signals of the motor during operation are collected by vibration sensors and / or torque sensors installed on the shaft or housing; S2. Perform fast Fourier transform spectrum analysis on the acquired dynamic signal to identify the main harmonic order n that causes the vibration; S3. Based on formula θ n =180° / (n · LCM(Z, 2p)) Calculate the target misalignment angle θ n ; S4. Using the expansion coupling sleeve assembly and the operation window, adjust the misalignment angle between the first unit motor and the second unit motor to the target value θ. n The entire process does not require disassembling the end caps or removing the rotor.

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