A three-phase permanent magnet synchronous motor and starting method thereof

Abstract

The present invention relates to the technical field of electric motors, and in particular to a three-phase permanent magnet synchronous motor and a starting method thereof. The three-phase permanent magnet synchronous motor comprises a stator, a control member, and a first rotor and a second rotor both rotatably connected to the stator. The control member is used to control the rotation and braking of the first rotor. The first rotor is provided with a first working winding for driving the second rotor to rotate, and the second rotor is a permanent magnet rotor. The starting method comprises step a: using the control member to drive the first rotor to rotate; step b: after the speed of the first rotor reaches the rated value, an alternating current is supplied to the first working winding of the first rotor, so that the speed difference between the speed of the rotating magnetic field generated by the first working winding and the speed of the first rotor is minimized; step c: using the control member to gradually reduce the speed of the first rotor to zero and keep it stationary. The present invention makes it easy to start the three-phase permanent magnet synchronous motor, reduces the cost required for starting the three-phase permanent magnet synchronous motor, and has a small starting impact.

Description

Technical Field

[0001] The present invention relates to the technical field of electric motors, and in particular to a three-phase permanent magnet synchronous motor and a starting method thereof. Background Art

[0002] Compared with squirrel cage asynchronous motors, permanent magnet synchronous motors have the advantages of high efficiency, high power factor, small size and energy saving. It can be seen that permanent magnet synchronous motors are more suitable for today's society that emphasizes conservation and green concepts.

[0003] The permanent magnet rotor does not need external energy to maintain its magnetic field, but this also makes it extremely difficult to adjust and control its magnetic field from the outside, so the three-phase permanent magnet synchronous motor is difficult to start by itself. In the prior art, a high-performance inverter dedicated to the three-phase permanent magnet synchronous motor is often used to control the alternating current in the stator winding to start the permanent magnet rotor, but the inverter that matches the current of the permanent magnet synchronous motor is large in power and cost. In the prior art, the permanent magnet synchronous motor is also started asynchronously by installing a squirrel cage device similar to the induction motor outside the permanent magnet rotor, but this method has a large starting impact current and impact torque, which can easily cause damage to the permanent magnet synchronous motor itself and subsequent equipment. Summary of the invention

[0004] The present invention aims at solving the problems in the prior art and provides a three-phase permanent magnet synchronous motor which is easy to start and has low starting cost and small starting impact.

[0005] The present invention adopts the following technical solution: a three-phase permanent magnet synchronous motor, including a stator, a control component, and a first rotor and a second rotor both rotatably connected to the stator, the control component is used to control the rotation and braking of the first rotor, the first rotor is provided with a first working winding for driving the second rotor to rotate, and the second rotor is a permanent magnet rotor.

[0006] Preferably, the control element comprises a second working winding arranged on the stator, and the second working winding is used for driving the first rotor to rotate and braking the first rotor.

[0007] Preferably, the control element includes a brake and a second working winding arranged on the stator, the second working winding is used to drive the first rotor to rotate, and the brake is used to brake the first rotor.

[0008] Preferably, the brake is a hysteresis brake, an electromagnetic slip clutch or a magnetic powder brake.

[0009] Preferably, the control component includes a frequency converter and a second working winding arranged on the stator, the second working winding is used to drive the first rotor to rotate, and the frequency converter is used to adjust the frequency of the alternating current in the second working winding.

[0010] The present invention also provides a method for starting the aforementioned three-phase permanent magnet synchronous motor, comprising the following steps performed in sequence: step a: using a control component to drive the first rotor to rotate; step b: after the speed of the first rotor reaches a rated value, alternating current is supplied to the first working winding of the first rotor, so that the speed difference between the speed of the rotating magnetic field generated by the first working winding and the speed of the first rotor is minimized, and the rotation direction of the rotating magnetic field generated by the first working winding is opposite to the rotation direction of the first rotor; step c: using a control component to gradually reduce the speed of the first rotor to zero and keep it stationary.

[0011] Preferably, the control element includes a second working winding arranged on the stator, and the second working winding is used to drive the first rotor to rotate and brake the first rotor; in step a, alternating current is supplied to the second working winding; in step c, the supply of alternating current to the second working winding is stopped, and direct current with a gradually increasing current value is supplied to the second working winding.

[0012] Preferably, the control element includes a brake and a second working winding arranged on the stator, the second working winding is used to drive the first rotor to rotate, and the brake is used to brake the first rotor; in step a, alternating current is supplied to the second working winding; in step c, the supply of alternating current to the second working winding is stopped, so that the braking torque of the brake gradually increases.

[0013] Preferably, the control component includes a frequency converter and a second working winding arranged on the stator, the second working winding is used to drive the first rotor to rotate, and the frequency converter is used to adjust the frequency of the alternating current in the second working winding; in step a, alternating current is passed into the second working winding; in step c, the frequency converter is used to gradually reduce the frequency of the alternating current in the second working winding.

[0014] The beneficial effects of the present invention are as follows: the three-phase permanent magnet synchronous motor is easy to start, the cost required for starting the three-phase permanent magnet synchronous motor is reduced, and the starting impact is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of embodiment 1 of the present invention.

[0016] Figure 2 It is a structural diagram of embodiment 2 of the present invention.

[0017] Figure 3 This is a schematic diagram of the structure of the third embodiment of the present invention.

[0018] The reference numerals in the drawings are: 1. stator; 2. control element; 3. first rotor; 31. first working winding; 4. second rotor; 5. second working winding; 6. brake; 7. frequency converter. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with the embodiments and drawings, and the contents mentioned in the embodiments are not intended to limit the present invention. The present invention is described in detail below in conjunction with the drawings.

[0020] Embodiment 1

[0021] like Figure 1 As shown, a three-phase permanent magnet synchronous motor includes a stator 1, a control component 2, and a first rotor 3 and a second rotor 4 both rotatably connected to the stator 1. The control component 2 is used to control the rotation and braking of the first rotor 3. The first rotor 3 is provided with a first working winding 31 for driving the second rotor 4 to rotate. The second rotor 4 is a permanent magnet rotor.

[0022] In a conventional three-phase permanent magnet synchronous motor, after AC is passed into the winding of the conventional stator, the rotating magnetic field generated by the conventional stator has a relatively fast speed, which is equivalent to the direction of the electromagnetic torque on the rotor changing rapidly. The direction of the torque changes once every half cycle of the AC current, so the average torque on the rotor is equal to zero, and thus the starting cannot be completed. In this embodiment, the speed n0 of the air gap magnetic field between the first rotor 3 and the second rotor 4 = the rotating magnetic field speed n1 generated by the first working winding 31 - the first rotor speed n2, and the speed of the air gap magnetic field between the first rotor 3 and the second rotor 4 gradually increases from the minimum value n0, and the first rotor 3 can provide sufficient electromagnetic torque to the second rotor 4 so that the speed of the second rotor 4 keeps up with the speed of the air gap magnetic field n0. The specific working process is as follows: the control part 2 drives the first rotor 3 to rotate. After the first rotor 3 rotates to the rated speed, an alternating current is supplied to the first working winding 31 of the first rotor 3, so that the first working winding 31 generates a rotating magnetic field, and the speed difference between the rotating magnetic field and the speed of the first rotor 3 is minimized. The rotating direction of the rotating magnetic field generated by the first working winding 31 is opposite to the rotating direction of the first rotor 3, which is equivalent to making the speed of the air gap magnetic field between the first rotor 3 and the second rotor 4 the minimum value. Then the control part 2 gradually reduces the speed of the first rotor 3, which is equivalent to gradually increasing the speed of the air gap magnetic field between the first rotor 3 and the second rotor 4. When the speed of the first rotor 3 is reduced to zero, the speed of the air gap magnetic field between the first rotor 3 and the second rotor 4 is the synchronous speed of the rotating magnetic field generated by the first working winding 31, so that the speed of the second rotor 4 also gradually increases and reaches the synchronous speed.

[0023] like Figure 1As shown, the control member 2 includes a second working winding 5 provided on the stator 1, and the second working winding 5 is used to drive the first rotor 3 to rotate and brake the first rotor 3. When driving the first rotor 3 to rotate, an alternating current is supplied to the second working winding 5; when the first rotor 3 needs to be gradually decelerated, a direct current with a gradually increasing current value is supplied to the second working winding 5, thereby realizing the driving and braking of the first rotor 3 with a simple structure. As the most preferred embodiment, the number of poles of the first working winding 31 and the second working winding 5 is equal.

[0024] Embodiment 2

[0025] like Figure 2 As shown, the difference between this embodiment and the first embodiment is that the control element 2 includes a brake 6 and a second working winding 5 provided on the stator 1, the second working winding 5 is used to drive the first rotor 3 to rotate, and the brake 6 is used to brake the first rotor 3. When driving the first rotor 3 to rotate, AC power is supplied to the second working winding 5; when the first rotor 3 needs to be gradually decelerated, the braking torque of the brake 6 is gradually increased, thereby realizing the control of the first rotor 3.

[0026] The braking torque of the brake 6 is adjustable. Specifically, the brake 6 is a hysteresis brake or an electromagnetic slip clutch or a magnetic powder brake.

[0027] Embodiment 3

[0028] like Figure 3 As shown, the difference between this embodiment and the first embodiment is that the control element 2 includes a frequency converter 7 and a second working winding 5 provided on the stator 1, the second working winding 5 is used to drive the first rotor 3 to rotate, and the frequency converter 7 is used to adjust the frequency of the alternating current in the second working winding 5. Since the frequency converter 7 is used to drive the first rotor 3 instead of the second rotor 4 connected to the load, the required power is relatively small, and an ordinary frequency converter can be used.

[0029] Embodiment 4

[0030] The present embodiment provides a method for starting the three-phase permanent magnet synchronous motor described in the first embodiment, characterized in that it includes the following steps performed in sequence: step a: using the control component 2 to drive the first rotor 3 to rotate; step b: after the speed of the first rotor 3 reaches the rated value, AC power is supplied to the first working winding 31 of the first rotor 3, so that the speed difference between the speed of the rotating magnetic field generated by the first working winding 31 and the speed of the first rotor 3 is minimized, and the rotation direction of the rotating magnetic field generated by the first working winding 31 is opposite to the rotation direction of the first rotor 3; step c: using the control component 2 to gradually reduce the speed of the first rotor 3 to zero and keep it stationary.

[0031] The minimum speed difference between the speed of the rotating magnetic field generated by the first working winding 31 and the speed of the first rotor 3 is equivalent to making the speed of the air gap magnetic field between the first rotor 3 and the second rotor 4 the minimum. Using the control part 2 to gradually reduce the speed of the first rotor 3 to zero is equivalent to gradually increasing the speed of the air gap magnetic field between the first rotor 3 and the second rotor 4. The first rotor 3 can provide sufficient electromagnetic torque to the second rotor 4 so that the speed of the second rotor 4 keeps up with the speed of the air gap magnetic field. When the speed of the first rotor 3 is reduced to zero, the speed of the air gap magnetic field between the first rotor 3 and the second rotor 4 is the synchronous speed of the rotating magnetic field generated by the first working winding 31, thereby realizing the starting of the three-phase permanent magnet synchronous motor.

[0032] Embodiment 5

[0033] The difference between this embodiment and the fourth embodiment is that: the control element 2 includes a second working winding 5 arranged on the stator 1, and the second working winding 5 is used to drive the first rotor 3 to rotate and brake the first rotor 3; in step a, AC is supplied to the second working winding 5; in step c, the supply of AC to the second working winding 5 is stopped, and DC with a gradually increasing current value is supplied to the second working winding 5. The AC makes the second working winding 5 generate a rotating magnetic field and drives the first rotor 3 to rotate, and the DC makes the second working winding 5 generate a static magnetic field, and the static magnetic field generates a braking torque on the first rotor 3 to decelerate the first rotor 3. The larger the current value, the greater the braking torque of the static magnetic field on the first rotor 3, thereby achieving the effect of gradually slowing down the first rotor 3.

[0034] Embodiment 6

[0035] The difference between this embodiment and the fourth embodiment is that: the control member 2 includes a brake 6 and a second working winding 5 arranged on the stator 1, the second working winding 5 is used to drive the first rotor 3 to rotate, and the brake 6 is used to brake the first rotor 3; in step a, AC is supplied to the second working winding 5; in step c, the supply of AC to the second working winding 5 is stopped, so that the braking torque of the brake 6 gradually increases. The AC makes the second working winding 5 generate a rotating magnetic field and drives the first rotor 3 to rotate. The braking torque of the brake 6 gradually increases, so that the first rotor 3 gradually slows down.

[0036] Embodiment 7

[0037] The difference between this embodiment and the fourth embodiment is that: the control element 2 includes a frequency converter 7 and a second working winding 5 arranged on the stator 1, the second working winding 5 is used to drive the first rotor 3 to rotate, and the frequency converter 7 is used to adjust the frequency of the alternating current in the second working winding 5; in step a, the alternating current is supplied to the second working winding 5; in step c, the frequency of the alternating current in the second working winding 5 is gradually reduced by the frequency converter 7. The alternating current enables the second working winding 5 to generate a rotating magnetic field and drives the first rotor 3 to rotate. When the frequency of the alternating current in the second working winding 5 is gradually reduced, the speed of the rotating magnetic field in the second working winding 5 is also gradually reduced, thereby gradually reducing the speed of the first rotor 3.

[0038] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention is disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments according to the technology of the present invention are within the scope of the technical solution of the present invention without departing from the content of the technical solution of the present invention.

Claims

1. A three-phase permanent magnet synchronous motor, Features: The invention comprises a stator (1), a control member (2), and a first rotor (3) and a second rotor (4) both of which are rotatably connected to the stator (1); the control member (2) is used to control the rotation and braking of the first rotor (3); the first rotor (3) is provided with a first working winding (31) for driving the second rotor (4) to rotate; and the second rotor (4) is a permanent magnet rotor; The control element (2) comprises a brake (6) and a second working winding (5) arranged on the stator (1), the second working winding (5) is used to drive the first rotor (3) to rotate, and the brake (6) is used to brake the first rotor (3); The speed n0 of the air gap magnetic field between the first rotor (3) and the second rotor (4) = the speed n1 of the rotating magnetic field generated by the first working winding (31) - the speed n2 of the first rotor, the speed of the air gap magnetic field between the first rotor (3) and the second rotor (4) gradually increases from a minimum value n0, and the electromagnetic torque of the first rotor (3) to the second rotor (4) makes the speed of the second rotor (4) keep up with the speed of the air gap magnetic field n0; the control component (2) drives the first rotor (3) to rotate, and after the first rotor (3) rotates to a rated speed, an alternating current is supplied to the first working winding (31) of the first rotor (3), so that the first working winding (31) generates a rotating magnetic field, and the speed difference between the speed of the rotating magnetic field and the speed of the first rotor (3) is minimized, and the rotation direction of the rotating magnetic field generated by the first working winding (31) is opposite to the rotation direction of the first rotor (3), which is equivalent to making the speed of the air gap magnetic field between the first rotor (3) and the second rotor (4) the minimum value; Subsequently, the control component (2) gradually reduces the rotation speed of the first rotor (3), which is equivalent to gradually increasing the rotation speed of the air gap magnetic field between the first rotor (3) and the second rotor (4). When the rotation speed of the first rotor (3) is reduced to zero, the rotation speed of the air gap magnetic field between the first rotor (3) and the second rotor (4) is the synchronous rotation speed of the rotating magnetic field generated by the first working winding (31), thereby causing the rotation speed of the second rotor (4) to gradually increase and reach the synchronous rotation speed.

2. A three-phase permanent magnet synchronous motor according to claim 1, Features: The brake (6) is a hysteresis brake, an electromagnetic slip clutch or a magnetic powder brake.

3. A method for starting the three-phase permanent magnet synchronous motor according to claim 1, Features: The process includes the following steps: Step a: using a control member (2) to drive the first rotor (3) to rotate; Step b: after the rotation speed of the first rotor (3) reaches a rated value, an alternating current is supplied to the first working winding (31) of the first rotor (3), so that the speed difference between the rotation speed of the rotating magnetic field generated by the first working winding (31) and the rotation speed of the first rotor (3) is minimized, and the rotation direction of the rotating magnetic field generated by the first working winding (31) is opposite to the rotation direction of the first rotor (3); Step c: using the control element (2) to gradually reduce the rotation speed of the first rotor (3) to zero and keep it stationary; The control element (2) comprises a brake (6) and a second working winding (5) arranged on the stator (1), the second working winding (5) is used to drive the first rotor (3) to rotate, and the brake (6) is used to brake the first rotor (3); In step a, an alternating current is supplied to the second working winding (5); In step c, the supply of alternating current to the second working winding (5) is stopped, so that the braking torque of the brake (6) gradually increases.

Images