Rotor and asynchronous electric machine having the same

Abstract

The application discloses a rotor and an asynchronous motor with the same. The rotor comprises a rotor core, end rings, a plurality of first rotor bars and a plurality of second rotor bars. The plurality of first rotor bars are arranged in a plurality of first mounting slots of the rotor core and are connected in series between the end rings at the two axial ends to form a first rotor squirrel cage. The plurality of second rotor bars are arranged in a plurality of second mounting slots of the rotor core and are connected in series between the end rings at the two axial ends to form a second rotor squirrel cage. The first rotor squirrel cage is closer to the stator than the second rotor squirrel cage. The number of the first mounting slots is not equal to the number of open slots on the stator for winding the winding, and the number of the second mounting slots is equal to the number of the open slots. The rotor of the embodiment of the application forms a double squirrel cage structure based on the first rotor squirrel cage and the second rotor squirrel cage, and can effectively improve the performance related to the starting and normal operation of the asynchronous motor and meet the requirements of the starting and operation efficiency of the asynchronous motor.

Description

Technical Field

[0001] This application relates to the field of electric motor manufacturing, specifically to a rotor and an asynchronous motor having the rotor. Background Technology

[0002] In related technologies, the rotor of an asynchronous motor (also known as a short-circuit rotor or squirrel-cage rotor) includes a rotor core, rotor windings, and a shaft. The rotor core is part of the magnetic circuit and is generally made of stacked silicon steel sheets. The rotor core is fixed on the shaft. Multiple mounting slots are opened at intervals along the circumferential direction of the rotor core. Guide bars are set in each mounting slot. An end ring is formed at each end of the rotor core. The parts of all the guide bars that extend out of the mounting slots are connected to form a short-circuit circuit.

[0003] If the number of mounting slots on the rotor is not equal to the number of open slots on the stator (i.e., unequal slot matching), it easily leads to greater high-frequency current loss and pulsation loss, resulting in reduced efficiency of the asynchronous motor. If the number of mounting slots on the rotor is equal to the number of open slots on the stator (i.e., equal slot matching), although it reduces operating losses, it generates additional synchronous torque at the moment of motor startup, preventing the motor from starting. Therefore, existing asynchronous motors often employ the less efficient unequal slot matching.

[0004] Application content

[0005] In view of this, embodiments of this application provide a rotor and an asynchronous motor having the same, which are intended to effectively improve the operating performance of the asynchronous motor.

[0006] The technical solution of this application embodiment is implemented as follows:

[0007] This application provides a rotor, including:

[0008] A rotor core is fitted onto the rotor shaft. The rotor core has multiple first mounting slots and multiple second mounting slots that are spaced apart along the circumference of the rotor core. The multiple first mounting slots and multiple second mounting slots all extend through the rotor core along its axial direction.

[0009] End rings are disposed at both axial ends of the rotor core;

[0010] Multiple first rotor guide bars are disposed in the multiple first mounting slots and connected in series between the end rings at both ends of the axial direction to form a first rotor cage;

[0011] Multiple second rotor guide bars are disposed in the multiple second mounting slots and connected in series between the end rings at both ends of the axial direction to form a second rotor cage;

[0012] The first rotor squirrel cage is closer to the stator than the second rotor squirrel cage. The number of the first mounting slots is not equal to the number of opening slots on the stator used for winding. The number of the second mounting slots is equal to the number of opening slots.

[0013] In some implementations, the number of the first mounting slots is less than the number of the opening slots.

[0014] In some embodiments, the first mounting slots are evenly spaced along the circumference of the rotor core; and / or, the second mounting slots are evenly spaced along the circumference of the rotor core.

[0015] In some implementations, the resistivity of the first rotor bar is greater than that of the second rotor bar.

[0016] In some embodiments, the first rotor bar is made of brass, aluminum, or bronze, and the second rotor bar is made of copper.

[0017] In some embodiments, there are two end rings; the first end of the first rotor bar and the second rotor bar along the axial direction of the rotor core are each connected to one of the two end rings, and the second end of the first rotor bar and the second rotor bar along the axial direction of the rotor core are each connected to the other of the two end rings.

[0018] In some embodiments, the number of end rings is four; the first rotor guide bar connects to two of the four end rings at its first and second ends along the axial direction of the rotor core, and the second rotor guide bar connects to the remaining two of the four end rings at its first and second ends along the axial direction of the rotor core.

[0019] This application also provides an asynchronous motor, including the rotor described in this application embodiment.

[0020] In some embodiments, the asynchronous motor further includes a stator, with the rotor sleeved outside the stator.

[0021] In some embodiments, the asynchronous motor further includes a stator, which is fitted outside the rotor.

[0022] The technical solution provided in this application embodiment includes multiple first rotor guide bars disposed in multiple first mounting slots and connected in series between end rings at both axial ends to form a first rotor squirrel cage; multiple second rotor guide bars disposed in multiple second mounting slots and connected in series between end rings at both axial ends to form a second rotor squirrel cage; wherein, the first rotor squirrel cage is closer to the stator than the second rotor squirrel cage, the number of first mounting slots is not equal to the number of open slots on the stator used for winding, and the number of second mounting slots is equal to the number of open slots. The rotor of this application embodiment, based on a double-squirrel cage structure formed by the first and second rotor squirrel cages, can effectively improve the performance related to the starting and normal operation of the asynchronous motor, and is compatible with the starting and operating efficiency requirements of the asynchronous motor. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the asynchronous motor according to an embodiment of this application;

[0024] Figure 2 This is a cross-sectional schematic diagram of an asynchronous motor according to an embodiment of this application.

[0025] Explanation of reference numerals in the attached figures:

[0026] 10. Stator; 11. Stator core; 12. Open slot; 13. Winding;

[0027] 20. Rotor; 21. Rotor core; 211. First mounting slot; 212. Second mounting slot. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] In the description of this application, references are made to "some embodiments," which describe a subset of all possible embodiments. However, it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0030] In the description of this application, the terms "first," "second," etc., are used merely to distinguish similar objects and do not represent a specific ordering of the objects. It is understood that "first," "second," etc., may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein. Unless otherwise stated, "a plurality of" means at least two.

[0031] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0032] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0033] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] In related technologies, asynchronous motors generate a rotating magnetic field by feeding alternating current into the stator, which in turn induces a magnetic field in the rotor. The combined effect of these two magnetic fields causes the rotor to rotate following the stator's rotating magnetic field. However, the rotor rotates slower than the stator's rotating magnetic field, exhibiting slip and asynchrony, hence the name asynchronous motor. The rotor of an asynchronous motor consists of short-circuited windings that generate current through electromagnetic induction. Asynchronous motors are simple, low-cost, and easy to install and maintain. Their disadvantages include low efficiency and a low power factor, which is detrimental to the power grid. Furthermore, since the rotor's magnetic field originates from the stator excitation, copper losses occur, resulting in a lower energy conversion rate compared to permanent magnet synchronous motors.

[0035] This application provides a rotor for an asynchronous motor, which effectively improves the starting and normal operation performance of the asynchronous motor. The rotor includes: a rotor core, end rings, multiple first rotor guide bars, and multiple second rotor guide bars. The rotor core is mounted on the rotor shaft. Multiple first mounting slots and multiple second mounting slots are spaced circumferentially along the rotor core, and both the first and second mounting slots extend axially through the rotor core. End rings are located at both axial ends of the rotor core. Multiple first rotor guide bars are disposed within the multiple first mounting slots and connected in series between the end rings at both axial ends, forming a first rotor cage. Multiple second rotor guide bars are disposed within the multiple second mounting slots and connected in series between the end rings at both axial ends, forming a second rotor cage. The first rotor cage is closer to the stator than the second rotor cage. The number of first mounting slots is not equal to the number of open slots on the stator used for winding, and the number of second mounting slots is equal to the number of open slots.

[0036] Understandably, when the motor starts, the first rotor squirrel cage engages with the stator, which is equivalent to an unequal slot engagement. This avoids the synchronous additional torque generated at the moment of motor startup and facilitates motor startup. When the motor is running, the second rotor squirrel cage engages with the stator, which is equivalent to an equal slot engagement. This effectively reduces high-frequency current loss and pulsation loss, and improves the motor's operating efficiency.

[0037] It should be noted that the second rotor squirrel cage is matched with the stator in equal slots, meaning the number of second mounting slots equals the number of open slots on the stator. The induced electromotive force generated by the stator tooth harmonic flux in adjacent second rotor bars is equal in magnitude and phase. Therefore, no current (including lateral current) is generated between them. This indicates that with equal slot matching, the stator tooth harmonic flux does not generate high-frequency current losses (including lateral current losses) in the rotor. Furthermore, when the second rotor squirrel cage is matched with the stator in equal slots, the width of the rotor tooth tip is very close to the wavelength of the stator tooth harmonics. Therefore, the pulsation caused by the stator tooth harmonic flux in the rotor teeth is smaller, and the pulsation loss is also smaller. Similarly, the pulsation loss caused by the rotor tooth harmonic flux in the stator teeth is also smaller. Thus, based on the equal slot matching method of the second rotor squirrel cage and the stator, the motor operating losses can be greatly reduced, and the operating efficiency can be improved.

[0038] Furthermore, based on the unequal slot fit between the first rotor squirrel cage and the stator, that is, the number of the first mounting slots is not equal to the number of open slots on the stator, the motor's inability to start due to the synchronous additional torque during motor startup can be effectively avoided.

[0039] For example, when the first rotor squirrel cage is fitted with the stator unequal slots, the number of the first mounting slots can be greater than or less than the number of open slots.

[0040] When the number of mounting slots on the rotor differs from the number of open slots on the stator, the impact of whether the number of mounting slots on the rotor is greater or less than the number of open slots on the additional losses depends on the rotor type. For copper bar cage rotors or straight-slot cast aluminum rotors, the additional losses on the stator and rotor sides are similar in magnitude. However, when using a multi-slot rotor (i.e., the number of mounting slots on the rotor is greater than the number of open slots on the stator), although the harmonic losses in the rotor are higher than when using a low-slot rotor (i.e., the number of mounting slots on the rotor is less than the number of open slots on the stator), the amplitude of the rotor tooth harmonic losses is reduced, and the pulsation losses generated in the stator teeth are also smaller. Therefore, the total additional losses are about the same as when using a low-slot rotor. However, for skew-slot cast aluminum rotors, the corresponding losses caused by the transverse current between the conductor bars are larger and increase rapidly with the increase of the number of slots. Therefore, the additional losses on the rotor side are much larger than those on the stator side.

[0041] In one embodiment, the number of first mounting slots is less than the number of opening slots, which helps to reduce additional losses when the motor starts.

[0042] In some embodiments, the first mounting slots are evenly spaced along the circumference of the rotor core; and / or, the second mounting slots are evenly spaced along the circumference of the rotor core.

[0043] It is understandable that by evenly spaced first and second mounting slots on the rotor core, the magnetic field strength and induced current generated by electromagnetic induction on the rotor are evenly distributed, which is beneficial to the reliable operation of the motor.

[0044] To reliably achieve motor starting based on the unequal slot fit between the first rotor squirrel cage and the stator, and to reduce motor operating losses based on the equal slot fit between the second rotor squirrel cage and the stator, in one embodiment, the resistivity of the first rotor bars is greater than that of the second rotor bars. Thus, the first rotor squirrel cage has a high resistance and low leakage reactance, while the second rotor squirrel cage has a low resistance and high leakage reactance.

[0045] When the motor starts, the high slip of the rotor and stator of the asynchronous motor results in a high rotor current frequency. At this high frequency, the location of the rotor current concentration is primarily determined by the leakage reactance. Due to the skin effect (current tends to concentrate on the surface of a conductor), the current distribution between the first and second rotor cages depends mainly on their leakage reactance. The first rotor cage has a small leakage reactance, while the second rotor cage has a large leakage reactance. Therefore, the current at startup is mainly concentrated in the unequal-slot first rotor cage, meaning only the unequal slots of the first rotor cage are functioning. Because the unequal-slot structure does not produce harmful synchronous additional torque, the motor can start normally.

[0046] When the motor starts and operates normally, the slip of the rotor and stator of the asynchronous motor decreases, the rotor current frequency is low, and the leakage reactance is small. The resistance plays a major role in the leakage impedance of the first and second rotor cages, and the current distribution between them depends primarily on their resistance. Because the resistance of the second rotor cage is low, the current is mainly concentrated in the second rotor cage during normal operation, meaning only the second rotor cage is functioning. The equal-slot configuration of the second rotor cage has the advantage of high efficiency. Therefore, the double-cage unequal-slot structure of this embodiment balances normal startup with high operating efficiency.

[0047] For example, the first rotor bar is made of brass, aluminum or bronze, which have relatively high resistivity, and the second rotor bar is made of copper, which has relatively low resistivity, so that the first rotor cage has high resistance and low leakage reactance, and the second rotor cage has low resistance and high leakage reactance.

[0048] Understandably, when the motor starts, the rotor current frequency is relatively high. Due to the skin effect, the current distribution between the first and second rotor cages depends primarily on their leakage reactance. The first rotor cage has a smaller leakage reactance, while the second rotor cage has a larger one. Therefore, the current at startup is mainly concentrated in the unequal-slot first rotor cage, meaning only the unequal slots of the first rotor cage are functioning. Since the unequal-slot structure does not produce harmful synchronous additional torque, the motor can start normally.

[0049] It is understandable that when the motor starts and operates normally, the rotor current frequency is low and the leakage reactance is small. The resistance plays a major role in the leakage impedance of the first and second rotor cages, and the current distribution between them depends primarily on their resistance. Because the resistance of the second rotor cage is low, the current is mainly concentrated in the second rotor cage during normal operation, meaning only the second rotor cage is functioning. Furthermore, the equal-slot structure of the second rotor cage has the advantage of high efficiency. Therefore, the double-cage unequal-slot structure of this embodiment balances normal startup with high operating efficiency.

[0050] In some embodiments, there are two end rings; the first ends of the first rotor bar and the second rotor bar along the axial direction of the rotor core are each connected to one of the two end rings, and the second ends of the first rotor bar and the second rotor bar along the axial direction of the rotor core are each connected to the other of the two end rings.

[0051] Here, an end ring can be set at each end of the rotor core along the axial direction, and the first rotor guide bar and the second rotor guide bar are connected in series between the two end rings, which can simplify the structural setup.

[0052] In some embodiments, the number of end rings is four; the first rotor guide bar connects to two of the four end rings at its first and second ends along the axial direction of the rotor core, and the second rotor guide bar connects to the remaining two of the four end rings at its first and second ends along the axial direction of the rotor core.

[0053] Here, two end rings can be set at both ends of the rotor core axial direction to form two sets of opposite end ring assemblies. The first rotor guide bar and the second rotor guide bar are connected in series between different end ring assemblies, so that the first rotor squirrel cage and the second rotor squirrel cage are independent of each other.

[0054] This application also provides an asynchronous motor, including the rotor of this application embodiment.

[0055] In some embodiments, the asynchronous motor further includes a stator, with the rotor sleeved outside the stator, i.e., the asynchronous motor adopts an external rotor structure.

[0056] In some embodiments, the asynchronous motor further includes a stator, which is sleeved outside the rotor, i.e., the asynchronous motor adopts an internal rotor structure.

[0057] The following explanation uses an asynchronous motor with an internal rotor structure as an example. Figure 1 and Figure 2 As shown, the asynchronous motor includes a stator 10 and a rotor 20 disposed within the stator 10. The stator 10 includes a stator core 11, an open slot 12 formed on the stator core 11, and a winding 13 wound within the open slot 12. The rotor 20 includes a rotor core 21, on which a plurality of first mounting slots 211 and a plurality of second mounting slots 212 are formed and distributed circumferentially along the rotor core 21. The plurality of first mounting slots 211 and the plurality of second mounting slots 212 are all axially connected along the rotor core 21. The rotor 20 also includes end rings disposed at both ends of the rotor core 21 along the axial direction, a plurality of first rotor guide bars, and a plurality of second rotor guide bars (not shown in the figure). Multiple first rotor guide bars are disposed within multiple first mounting slots 211 and connected in series between end rings at both ends of the axial direction to form an upper squirrel cage (i.e., the first rotor squirrel cage). Multiple second rotor guide bars are disposed within multiple second mounting slots 212 and connected in series between end rings at both ends of the axial direction to form a lower squirrel cage (i.e., the second rotor squirrel cage). The upper squirrel cage is the first rotor squirrel cage slot with a number of slots slightly less than the number of open slots (12 slots), and the material can be brass, aluminum, bronze, etc., which have relatively high resistivity. The lower squirrel cage is the second rotor squirrel cage slot with a number of slots equal to the number of open slots (12 slots), and the material can be copper, which has relatively low resistivity. Due to the different positions and materials of the upper and lower squirrel cages, the upper squirrel cage has a high resistance and low leakage reactance; the lower squirrel cage has a low resistance and high leakage reactance.

[0058] When the motor starts, the rotor current frequency is relatively high. Due to the skin effect, the current distribution between the upper and lower squirrel cages mainly depends on their leakage reactance. The upper squirrel cage has a smaller leakage reactance, while the lower squirrel cage has a larger leakage reactance. Therefore, at the moment of startup, the current is mainly concentrated in the upper squirrel cage with unequal slots, which is equivalent to only the unequal slots of the upper squirrel cage being active. Since the unequal slot structure does not have harmful synchronous additional torque, the motor can start normally.

[0059] When the motor starts and runs normally, the rotor current frequency is low and the leakage reactance is small. The resistance in the leakage impedance of the upper and lower squirrel cages plays a major role, and the current between the upper and lower squirrel cages depends on their respective resistances. Because the resistance of the lower squirrel cage is small, the current is mainly concentrated in the lower squirrel cage during normal operation, which is equivalent to only the lower squirrel cage being effective. The equal slot configuration of the lower squirrel cage has the advantage of high efficiency. Therefore, this double-cage unequal slot structure takes into account both the normal starting of the motor and high operating efficiency.

[0060] It should be noted that the technical solutions described in the embodiments of this application can be combined arbitrarily without conflict.

[0061] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A rotor, characterized in that, include: A rotor core is fitted onto the rotor shaft. The rotor core has multiple first mounting slots and multiple second mounting slots spaced apart along the circumference of the rotor core. The multiple first mounting slots and multiple second mounting slots all extend through the rotor core along its axial direction. End rings are disposed at both axial ends of the rotor core; Multiple first rotor guide bars are disposed in the multiple first mounting slots and connected in series between the end rings at both ends of the axial direction to form a first rotor cage; Multiple second rotor guide bars are disposed in the multiple second mounting slots and connected in series between the end rings at both ends of the axial direction to form a second rotor cage; The first rotor squirrel cage is closer to the stator than the second rotor squirrel cage. The number of the first mounting slots is not equal to the number of opening slots on the stator used for winding. The number of the second mounting slots is equal to the number of opening slots.

2. The rotor according to claim 1, characterized in that, The number of the first mounting slots is less than the number of the opening slots.

3. The rotor according to claim 1, characterized in that, The first mounting slots are evenly spaced along the circumference of the rotor core; and / or, The second mounting slots are evenly spaced along the circumference of the rotor core.

4. The rotor according to claim 1, characterized in that, The resistivity of the first rotor bar is greater than that of the second rotor bar.

5. The rotor according to claim 4, characterized in that, The first rotor bar is made of brass, aluminum or bronze, and the second rotor bar is made of copper.

6. The rotor according to claim 1, characterized in that, The number of end rings is two; the first end of the first rotor guide bar and the second rotor guide bar along the axial direction of the rotor core are each connected to one of the two end rings, and the second end of the first rotor guide bar and the second rotor guide bar along the axial direction of the rotor core are each connected to the other of the two end rings.

7. The rotor according to claim 1, characterized in that, The number of end rings is four; the first rotor guide bar connects to two of the four end rings at its first and second ends along the axial direction of the rotor core, and the second rotor guide bar connects to the remaining two of the four end rings at its first and second ends along the axial direction of the rotor core.

8. An asynchronous motor, characterized in that, Includes the rotor as described in any one of claims 1 to 7.

9. The asynchronous motor according to claim 8, characterized in that, The asynchronous motor also includes: The stator, with the rotor sleeved outside the stator.

10. The asynchronous motor according to claim 8, characterized in that, The asynchronous motor also includes: The stator is fitted outside the rotor.

Images