High-torque permanent magnet motor and control method

Abstract

The present invention relates to a high-torque permanent magnet motor and a control method. The high-torque permanent magnet motor comprises a stator and a rotor; a plurality of pole teeth are uniformly arranged on the stator in the circumferential direction; a winding is wound on each pole tooth; a plurality of permanent magnets are uniformly arranged on the rotor in the circumferential direction; N poles and S poles of the plurality of permanent magnets are alternately arranged; each winding is connected to a direct-current power supply by means of a switch control circuit; the magnitude and direction of the current flowing through each winding are independently adjustable; N poles and S poles can be alternately formed on the windings in the circumferential direction; and magnetic fields generated by the windings can interact with the permanent magnets of the rotor to drive the rotor to rotate. The present invention can effectively increase the output torque of motors.

Description

High-torque permanent magnet motor and control method Technical Field

[0001] The present invention relates to an electric motor, in particular to a large-torque permanent magnet electric motor and a control method thereof. Background Art

[0002] A traditional three-phase AC motor inputs three-phase current into the stator windings. This current excites the stator windings, generating a magnetic field. This interacts with the rotor's magnetic field, causing a cycle of attraction and repulsion, generating a rotating magnetic field that propels the rotor. The three-phase current input varies over time. At any given moment, one-third to two-thirds of the stator windings receive current, while the remaining stator windings receive no current. Consequently, the mutual push-pull force between the stator and rotor can only reach approximately 30% to 60% of the maximum possible force. Technical issues

[0003] The object of the present invention is to provide a high-torque permanent magnet motor and a control method thereof, which can effectively improve the output torque of the motor.

[0004] Based on the same inventive concept, the present invention has two independent technical solutions:

[0005] 1. A high-torque permanent magnet motor, comprising a stator and a rotor, wherein the stator is uniformly provided with a plurality of pole teeth along the circumferential direction, each pole tooth being wound with a winding, and the rotor is uniformly provided with a plurality of permanent magnets along the circumferential direction, wherein the plurality of permanent magnets have alternating north and south poles. The motor is characterized in that: each winding is connected to a DC power supply via a switch control circuit, the magnitude and direction of the current passing through each winding are independently adjustable and controllable, the windings can alternately generate north poles or south poles along the circumferential direction, and the magnetic field generated by each winding can interact with the rotor permanent magnets to drive the rotor to rotate.

[0006] Furthermore, the switch control circuit is an H-bridge switch circuit, which is composed of four switch transistors, MOS transistors, FET transistors or IGBT transistors. The H-bridge switch circuit can control the direction of the winding input current.

[0007] 2. A control method for the above-mentioned high-torque permanent magnet motor, wherein the stator windings can be evenly grouped, each group has the same number of windings, and each group adopts the same winding current control method; multiple grouping methods are adopted, and the corresponding grouping method is selected according to the load condition to perform winding current control.

[0008] When the number of windings in each group is less than 6, the input current of one winding in each group must be lower than that of other windings in the same group or zero. The current input value of one winding in the same group is in a certain proportion to the rated current value of a single winding, and the current input of the remaining windings is the rated current of a single winding.

[0009] Furthermore, when the number of windings in each group is greater than or equal to 6, the input current of one winding in each group must be lower than or zero than the input current of other windings in the same group, the current input value of one winding in the same group is in a first proportion to the rated current value of the single winding, the current input value of one winding in the same group is in a second proportion to the rated current value of the single winding, and the current input of the remaining windings is the rated current of the single winding.

[0010] Furthermore, the rated current of a single winding = the rated current of the motor / 2 / (M / t-2), where M is the number of stator windings, and t is the greatest common divisor of the number of stator windings and the number of rotor permanent magnet poles. The rated current of the motor can be the rated current at full load or no load depending on the load conditions.

[0011] Furthermore, when the rotor rotation speed is inconsistent with the set value, the ratio of the winding current input value to the rated current value of a single winding can be adjusted.

[0012] Furthermore, when the rotor rotation speed is lower than the set value, the ratio of the winding current input value to the rated current value of a single winding is increased; when the rotor rotation speed is higher than the set value, the ratio of the winding current input value to the rated current value of a single winding is decreased.

[0013] When the ratio of the winding current input value to the rated current value of a single winding cannot reach the set value, other grouping methods are selected for winding current control; when the rotor rotation speed is lower than the set value, a grouping method in which the number of windings in each group is greater than the current number of windings in each group is selected for winding current control; when the rotor rotation speed is higher than the set value, a grouping method in which the number of windings in each group is less than the current number of windings in each group is selected for winding current control.

[0014] In each set of windings, the current directions of the two adjacent windings are opposite.

[0015] The present invention has the beneficial effects:

[0016] The present invention includes a stator and a rotor. The stator is evenly provided with multiple pole teeth along the circumferential direction, and a winding is wound around each pole tooth. The rotor is evenly provided with multiple permanent magnets along the circumferential direction. The north poles and south poles of the multiple permanent magnets are alternately arranged. Each winding is connected to a DC power supply via an H-bridge switch control circuit. The current magnitude and direction passing through each winding are independently adjustable. Each winding can alternately generate north poles or south poles along the circumferential direction. The magnetic field generated by each winding can interact with the rotor permanent magnet to drive the rotor to rotate.

[0017] Each stator winding in the present invention is connected to a DC power supply, and the current magnitude and direction are independently adjustable. For example, in a motor with 18 stator slots, a conventional three-phase motor can have current input to at most 12 stator windings at a time, while the present invention can have current input to 16 stator windings at a time. If the same current is input to the motor, the present invention can increase torque by 25%. The torque increase for motors with other numbers of stator slots is as follows:

[0018] This is different from the traditional three-phase motor winding connection method of Y connection or △ connection. If Y connection or △ connection is used, as long as one phase is missing, the motor will become single-phase powered, which will increase the current and cause the motor to burn out. Since each stator winding of the present invention is connected to a DC power supply and is independently controlled, if one of the stator windings fails in power supply, the motor can still operate normally. Each stator winding of the present invention is connected to a DC power supply, which facilitates variable speed operation control. While the volume of the stator slot remains unchanged, the single coil winding structure can be used to flexibly change the coil wire diameter and the number of winding turns to reduce the coil resistance, reduce the temperature rise of the motor, and extend the service life of the motor.

[0019] The switch control circuit described in the present invention is an H-bridge switching circuit, composed of four switching transistors, MOS transistors, FET transistors, IGBT transistors, or equivalent electronic components. The H-bridge switching circuit controls the direction of the winding input current. This switch control circuit further effectively ensures reliable control of the stator winding power supply.

[0020] The stator windings of the present invention can be evenly grouped, with the same number of windings in each group and the same winding current control method used in each group. Multiple grouping methods can be used, and the corresponding grouping method can be selected according to the load conditions for winding current control. When the number of windings in each group is less than 6, the input current of one winding in each group must be lower than or zero compared to the input currents of the other windings in the same group, the current input value of one winding in the same group is a certain ratio to the rated current value of the single winding, and the current input of the remaining windings is the rated current of the single winding. When the number of windings in each group is greater than or equal to 6, the input current of one winding in each group must be lower than or zero compared to the input currents of the other windings in the same group, the current input value of one winding in the same group is a first ratio to the rated current value of the single winding, the current input value of one winding in the same group is a second ratio to the rated current value of the single winding, and the current input of the remaining windings is the rated current of the single winding. Through the above control method, the present invention can effectively improve torque output and perform winding current control according to load conditions to ensure the reliability of motor operation.

[0021] The rated current of a single winding of the present invention is calculated as follows: motor rated current / 2 / (M / t-2), where M is the number of stator windings, and t is the greatest common divisor of the number of stator windings and the number of rotor permanent magnet poles. When the rotor rotation speed is inconsistent with the set value, the ratio of the winding current input value to the rated current value of the single winding can be adjusted. When the rotor rotation speed is lower than the set value, the ratio of the winding current input value to the rated current value of the single winding is increased; when the rotor rotation speed is higher than the set value, the ratio of the winding current input value to the rated current value of the single winding is decreased. If the ratio of the winding current input value to the rated current value of the single winding cannot reach the set value after adjusting the ratio, another grouping method is selected for winding current control; when the rotor rotation speed is lower than the set value, a grouping method in which the number of windings in each group is greater than the current number of windings in each group is selected for winding current control; when the rotor rotation speed is higher than the set value, a grouping method in which the number of windings in each group is less than the current number of windings in each group is selected for winding current control. In each winding group, the current directions of two adjacent windings are opposite. The present invention further ensures that the winding current is controlled according to the load conditions through the above control method, thereby ensuring the reliability of the motor operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a schematic diagram of a single stator winding connection circuit of the present invention;

[0023] FIG2 is a control principle diagram of a motor with 18 stator slots according to the present invention;

[0024] FIG3 is a control principle diagram of the first grouping mode of 18 stator slot windings according to the present invention;

[0025] FIG4 is a control principle diagram of the second grouping mode of 18 stator slot windings according to the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in this field based on these embodiments are all within the scope of protection of the present invention. Example

[0027] High torque permanent magnet motor

[0028] As shown in Figure 2, the motor comprises a stator 1 and a rotor 2. The stator 1 is circumferentially provided with multiple pole teeth 3, a technique known in the prior art. Each pole tooth 3 is wound with a winding 4. The rotor 2 is circumferentially provided with multiple permanent magnets, each with alternating north and south poles. As shown in Figures 1 and 2, each winding 4 is connected to a DC power supply via a switching control circuit. The magnitude and direction of the current passing through each winding are independently adjustable. Each winding can alternately generate north and south poles along the circumference. The magnetic field generated by each winding interacts with the rotor permanent magnets to drive the rotor's rotation. The switching control circuit is an H-bridge switching circuit composed of four switching transistors, MOS transistors, FET transistors, IGBT transistors, or equivalent electronic components. The H-bridge switching circuit controls the direction of the current input to the windings. In this embodiment, four switching transistors T1 through T4 are used.

[0029] In specific implementations, each winding is equipped with a control unit. This control unit can be an MCU, DSP, or a chip with equivalent computing capabilities. The first signal output terminal of the control unit is connected to the control terminal of the switch control circuit to control the direction and on / off of the winding current. The second signal output terminal of the control unit is connected to the DC power supply control terminal to control the output current of the DC power supply. The signal input terminal of each winding control unit is connected to the central control unit, which is responsible for the overall control of each winding. Example

[0030] Control method of high-torque permanent magnet motor according to embodiment 1

[0031] The stator windings can be evenly grouped, with each group having the same number of windings and using the same winding current control method. Multiple grouping methods can be used, and the appropriate grouping method is selected for winding current control based on load conditions. Within each winding group, the currents of adjacent windings flow in opposite directions. The number of rotor permanent magnet poles is two less than the number of stator windings.

[0032] When the number of windings in each group is less than 6, the input current of one winding in each group must be lower than or zero compared to the input currents of the other windings in the group. The input current value of one winding in the group must be proportional to the rated current of the individual winding, and the input current of the remaining windings must be the rated current of the individual winding. When the number of windings in each group is greater than or equal to 6, the input current of one winding in each group must be lower than or zero compared to the input currents of the other windings in the group. The input current value of one winding in the group must be proportional to the rated current of the individual winding, and the input current value of one winding in the group must be proportional to the rated current of the individual winding. The input current of the remaining windings must be the rated current of the individual winding.

[0033] The rated current of a single winding = motor rated current / 2 / (M / t-2), where M is the number of stator windings, and t is the greatest common divisor of the number of stator windings and the number of rotor permanent magnet poles. The rated current of the motor can be the rated current at full load or no load depending on the load conditions.

[0034] When the rotor speed is inconsistent with the set value, the ratio of the winding current input value to the rated current value of each winding can be adjusted. When the rotor speed is lower than the set value, the ratio is increased. When the rotor speed is higher than the set value, the ratio is decreased. If the set value cannot be achieved by adjusting the ratio of the winding current input value to the rated current value of each winding, another grouping method is used for winding current control. When the rotor speed is lower than the set value, a grouping method with more windings per group than the current number of windings per group is selected for winding current control. When the rotor speed is higher than the set value, a grouping method with fewer windings per group than the current number of windings per group is selected for winding current control.

[0035] The control method of the present invention is further described in detail below by taking a motor with 18 stator slots as an example.

[0036] As shown in Figure 2, a motor with 18 stator slots and 16 rotor poles has 18 corresponding stator slots, each with 18 pole teeth. Each tooth is wound with a winding, resulting in 18 windings (corresponding to L1 through L18 in the diagram). This means M = 18, R = 16, and the greatest common factor of the number of stator windings and the number of rotor permanent magnet poles is t = 2. When stationary, two stator slots must be aligned with the rotor poles (as shown at positions L1 and L10 in Figure 1). The remaining 14 slots are positioned at varying angles relative to the rotor magnets.

[0037] As described above, the stator windings can be controlled in groups, with each group using the same winding current control method. In this embodiment, as shown in FIG3 , three slots (three stator windings) can be used. As shown in FIG4 , six slots (six stator windings) or nine slots (nine stator windings) can be used as a group for group control. The number of slots in each group is determined by the total number of stator slots and its prime factor. By controlling the winding current in each group, each stator winding generates a thrust or pull magnetic field of different magnitude, causing the rotor to rotate.

[0038] As mentioned above, the rated current of a single winding = motor rated current / 2 / (M / t-2), where M is the number of stator windings, M=18, and t is the greatest common factor of the number of stator windings and the number of rotor permanent magnet poles, t=2. The motor rated current is the current required to drive the motor at its rated torque. In this embodiment, the rated current of the 18-stator slot motor is 140A. Therefore, the rated current of a single winding = 140 / 2 / (18 / 2-2) = 10A.

[0039] As described above, when the number of windings in each group is less than 6, the input current of one winding in each group must be lower than or zero compared to the input currents of the other windings in the group. The input current value of one winding in the group must be a certain ratio to the rated current of the individual winding. In practice, the ratio can be 25%, 50%, 75%, etc. The input current of the remaining windings is the rated current of the individual winding. When the number of windings in each group is greater than or equal to 6, the input current of one winding in each group must be lower than or zero compared to the input currents of the other windings in the group. The input current value of one winding in the group must be a first ratio to the rated current of the individual winding, and the input current value of one winding in the group must be a second ratio to the rated current of the individual winding. In practice, the ratio can be 25%, 50%, 75%, etc. The input current of the remaining windings is the rated current of the individual winding.

[0040] In this embodiment, if the torque required to drive the load of the motor is half of the rated torque, the required current is 140A / 2=70A. Assuming that the current tolerance is + / -0.5A, the input current is given by first setting the 3-slot winding as a group. The total current is (10+0.25*10=12.5A / group)*6 groups=75A, which exceeds the required current of 70A. At this time, the input current percentage of the L2 stator winding is reduced to 10%, and the total current is ( 10+0.1*10=11A / group)*6 groups=66A. Since the current is lower than the required current, the input current of the L2 stator winding is increased to 16%. The total current is (10+0.16*10=11.6A / group)*6 groups=69A, which is still less than 70A. Therefore, the input current of the L2 stator winding is increased to 16.5%. The total current is (10+0.165*10=11.65A / group)*6 groups=69.9A.

[0041] The total current of 6 slots per group (3 groups in total) is

[0042] (10*3+0.25*10+0.75*10=40A / group)*3 groups=120A

[0043] The total current of a group of 9 slots (2 groups in total) is

[0044] (6*10*1+10*0.25+10*0.75=70A / group)*2groups=140A

[0045] When the motor starts, it is first controlled in groups of three slots, with one aligned slot as the reference, as shown in Figure 3. The current of the L1 stator winding (hereinafter referred to as L1) is set to be lower than or zero compared to the input current of other windings in the same group. The current of the L2 stator winding (hereinafter referred to as L2) is set to 25% input, and the current of the L3 stator winding (hereinafter referred to as L3) is set to 100% output (in and out here represent different current directions, and 100% represents the rated current of a single winding). The magnetic fields generated by the L2 and L3 currents have different directions (for example, L1 in Figure 3 has an uncertain polarity, represented by the symbol "X", L2 is the N pole, and L3 is the S pole). The rest are similar (L4=0; L5=25%, generating S pole; L6=100%, produces N pole), the magnetic field directions generated by the stator windings on both sides of the stator winding (such as L1, L4...) whose current is lower than or zero than the input current of other windings in the same group are the same, but the current magnitudes are different. For example, L3 and L5 are both S poles, and L6 and L8 are both N poles. When the rotor starts to rotate and the magnet moves to the next magnetic pole and aligns with the reference slot L1 (as shown in Figure 3, the magnet corresponding to L1 is the S pole at this time), the direction of the stator winding current changes, but the current magnitude remains unchanged, that is, the current in L1 is still lower than the input current of other windings in the same group or is zero. L2 becomes 25% current out, and L3 changes to 100% current in. The directions of the magnetic fields generated by the currents in L2 and L3 are different (as shown in Figure 3, L2 becomes the S pole and L3 is the N pole). The same applies to the rest (L4~0%, L5=25% out, L6=100% in / L7~0%, L8=25% out, L9=100% in, and so on).

[0046] While the current is changing, the position sensor checks the rotor's position, direction, and speed for correctness. If the position is incorrect, that is, when the rotor speed is inconsistent with the set value, the ratio of the winding current input value to the rated current of each winding is adjusted. When the rotor speed is below the set value, the ratio of the winding current input value to the rated current of each winding is increased. When the rotor speed is above the set value, the ratio is decreased. If the set value cannot be achieved by adjusting the ratio of the winding current input value to the rated current of each winding, another grouping method is used for winding current control. When the rotor speed is below the set value, a grouping method with more windings per group is selected for winding current control. When the rotor speed is above the set value, a grouping method with fewer windings per group is selected for winding current control. In this embodiment, if the current is increased to the upper limit of the phase current but still does not reach the correct position (lags behind), it means that the speed is insufficient, that is, the input current cannot drive the load. In this case, the number of winding groups needs to be changed (changing the blank group of 3 slots to a group of 6 slots, and if the current is insufficient, increasing it to a group of 9 slots, and so on, up to a maximum of 9 slots per group).

[0047] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

[0048] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A high torque permanent magnet motor, comprising a stator and a rotor, wherein the stator is evenly provided with a plurality of pole teeth along the circumferential direction, each pole tooth is wound with a winding, and the rotor is evenly provided with a plurality of permanent magnets along the circumferential direction, wherein the plurality of permanent magnets have N poles and S poles arranged alternately, and characterized in that: Each winding is connected to a DC power supply via a switch control circuit. The current size and current direction passing through each winding can be independently adjusted and controlled. Each winding can alternately generate an N pole or an S pole along the circumferential direction. The magnetic field generated by each winding can interact with the rotor permanent magnet to drive the rotor to rotate.

2. The high torque permanent magnet motor according to claim 1, characterized in that: The switch control circuit is an H-bridge switch circuit, which is composed of four switch transistors, MOS tubes, FET tubes, or IGBT tubes. The H-bridge switch circuit can control the direction of the winding input current.

3. A control method for a high torque permanent magnet motor according to claim 1, characterized in that: The stator windings can be evenly grouped, with the same number of windings in each group, and each group adopts the same winding current control method; multiple grouping methods are adopted, and the corresponding grouping method is selected for winding current control according to the load conditions.

4. The control method of the large torque permanent magnet motor according to claim 3, characterized in that: When the number of windings in each group is less than 6, the input current of one winding in each group must be lower than or zero than that of other windings in the same group. The current input value of one winding in the same group is in a certain proportion to the rated current value of a single winding, and the current input of the remaining windings is the rated current of a single winding.

5. The control method of the large torque permanent magnet motor according to claim 3, characterized in that: When the number of windings in each group is greater than or equal to 6, the input current of one winding in each group must be lower than or zero than the input currents of other windings in the same group, the current input value of one winding in the same group is in a first proportion to the rated current value of a single winding, the current input value of one winding in the same group is in a second proportion to the rated current value of a single winding, and the current inputs of the remaining windings are the rated currents of the single windings.

6. The control method of the large torque permanent magnet motor according to claim 4 or 5, characterized in that: Rated current of a single winding = rated current of the motor / 2 / (M / t-2), where M is the number of stator windings, and t is the greatest common factor of the number of stator windings and the number of rotor permanent magnet poles. The rated current of the motor can be the rated current at full load or no load depending on the load conditions.

7. The control method of the large torque permanent magnet motor according to claim 4 or 5, characterized in that: When the rotor rotation speed is inconsistent with the set value, the ratio of the winding current input value to the rated current value of a single winding can be adjusted.

8. The control method of the large torque permanent magnet motor according to claim 7, characterized in that: When the rotor rotation speed is lower than the set value, the ratio of the winding current input value to the rated current value of a single winding is increased; when the rotor rotation speed is higher than the set value, the ratio of the winding current input value to the rated current value of a single winding is decreased.

9. The control method of the large torque permanent magnet motor according to claim 7, characterized in that: When the ratio of the winding current input value to the rated current value of a single winding cannot reach the set value, other grouping methods are selected for winding current control; when the rotor rotation speed is lower than the set value, a grouping method in which the number of windings in each group is greater than the current number of windings in each group is selected for winding current control; when the rotor rotation speed is higher than the set value, a grouping method in which the number of windings in each group is less than the current number of windings in each group is selected for winding current control.

10. The control method of the large torque permanent magnet motor according to claim 3, characterized in that: In each set of windings, the current directions of two adjacent windings are opposite.

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