A three-phase hybrid-excited doubly salient motor and its control method

Abstract

The present invention discloses a three-phase hybrid excitation doubly salient motor and its control method. The minimum unit of the motor includes 9 armature teeth and 3 excitation teeth, and 1 excitation tooth is distributed every 3 armature teeth. The excitation elements are arranged on the dedicated excitation teeth, and the armature windings are arranged on the independent armature teeth; all armature coils are wound on the armature teeth in the same winding direction, and the in-phase armature coils are connected in series to form a phase armature winding; the excitation coils are wound on the excitation teeth, the adjacent excitation coils are wound in the same direction, and all the excitation coils are connected in series to form a single-phase excitation winding. The permanent magnets are surface-mounted on the surface of the excitation teeth facing the rotor, each permanent magnet is radially magnetized, and the magnetization directions are the same. In the three-phase hybrid excitation doubly salient motor of the present invention, the excitation teeth and the armature teeth are completely separated, with higher reliability, and the problem of tight slot fill factor of the armature-excitation slots in the doubly salient motor is solved. The shapes of the armature teeth in each phase are completely the same, and the magnetic circuits of each phase are symmetrical, improving the electromagnetic characteristics of the motor.

Description

Technical Field

[0001] The present invention relates to the technical field of motor equipment, and particularly relates to a three-phase hybrid excitation doubly salient motor structure. Background Art

[0002] Permanent magnet doubly salient motors have the advantages of simple structure, flexible control, and high efficiency. However, such motors cannot adjust the air-gap magnetic field, it is difficult to expand the speed regulation range, and when a short-circuit fault occurs, it is difficult to demagnetize. While the electric excitation doubly salient motor can conveniently control the motor magnetic field by adjusting the excitation current, so as to realize the requirements of field weakening speed regulation, power generation voltage regulation, and fault demagnetization. However, the existence of excitation loss in the electric excitation doubly salient motor reduces the system efficiency and limits its use in various occasions. Combining the advantages of the two types of motors, the hybrid excitation doubly salient motor has two magnetic potential sources, namely permanent magnet and electric excitation, which better solves the problems of difficult magnetic field regulation of the permanent magnet doubly salient motor and low efficiency of the electric excitation doubly salient motor, and has broad application prospects in the fields of aerospace, wind power generation, automotive ships, etc.

[0003] Chinese Patent CN203289210U discloses a "hybrid excitation type stator surface-mounted doubly salient motor", which includes a stator, a rotor and a rotating shaft. The permanent magnets are mounted on the surface of the stator permanent teeth facing the rotor. Each pair of permanent magnets appears in pairs, is radially magnetized, and the magnetization directions of two adjacent permanent magnets are opposite. The rotor is composed of a U-shaped magnetic-conducting rotor core and a magnetic isolation mechanism. The U-shaped magnetic-conducting rotor core is embedded in the magnetic isolation mechanism, and a connecting bridge is required to connect between the U-shaped magnetic-conducting cores, which reduces the mechanical strength of the motor to a certain extent and increases the manufacturing process difficulty.

[0004] Chinese Patent CN100424967C discloses a "radial magnetic steel doubly salient hybrid excitation motor". The stator is composed of an annular stator back yoke and an E-shaped stator tooth yoke. The permanent magnets are placed between the stator tooth yoke and the stator back yoke. An excitation winding is wound in the stator slots formed by adjacent E-shaped stator tooth yokes. The principle of this motor is that it has an even number of permanent magnetic steels, and there is at least one pair of stator poles with an excitation source provided by electric excitation. Although this technology can achieve the effect of hybrid excitation, the distribution positions of each stator coil of each phase stator winding from the excitation element are different, resulting in problems such as asymmetric magnetic circuit and unbalanced counter electromotive force of each phase, which easily causes an increase in motor torque ripple. Summary of the Invention

[0005] Aiming at the problems existing in the above-mentioned prior art, the object of the present invention is to provide a three-phase hybrid excitation doubly salient motor with a compact structure, high material utilization rate, small torque ripple and high reliability. By reasonably arranging the distribution of the armature winding, excitation winding and permanent magnet, the excitation teeth and armature teeth are completely separated, and the excitation elements are arranged on the dedicated excitation teeth, so the reliability is higher, and the problem of tight slot fill factor of the armature-excitation slots in the doubly salient motor is solved. The shape of each phase of armature teeth is exactly the same, and the overall magnetic circuit of each phase is symmetric, solving the problem of asymmetric magnetic circuit of each phase in the traditional three-phase doubly salient motor.

[0006] The technical solution adopted by the present invention is as follows: a three-phase hybrid excitation doubly salient motor, comprising a stator and a rotor; characterized in that: the stator is composed of a stator core, an armature winding and an excitation element; the rotor is composed of a rotor core and a rotating shaft; the stator core and the rotor core are of salient pole structure and are coaxially arranged; the minimum stator unit of the three-phase hybrid excitation doubly salient motor is provided with 12 stator teeth, including 9 armature teeth and 3 excitation teeth, and 1 excitation tooth is distributed every 3 armature teeth, and the excitation teeth and armature teeth are completely separated; the excitation element includes an excitation winding and a permanent magnet, and is arranged on the independent excitation teeth; the armature coils are wound around the stator armature teeth, and all the armature coils are wound in the same direction, that is, the armature coils on the minimum stator unit of the three-phase hybrid excitation doubly salient motor are distributed in the circumferential direction as: A1+A1-C1+C1-B1+B1-C2+C2-B2+B2-A2+A2-B3+B3-A3+A3-C3+C3-, and the coils of the same phase are connected in series with each other to form an armature winding; the arrangement mode of the armature winding on the minimum stator unit of the three-phase hybrid excitation doubly salient motor is ACB—CBA—BAC, each phase occupies 3 armature teeth, and the relative positions of the armature teeth and the excitation teeth of each phase are the same as a whole. The excitation coils are wound around the stator excitation teeth, the winding directions of adjacent excitation coils are the same, and all the excitation coils are connected in series to form a single-phase excitation winding. The excitation coils on the minimum stator unit of the three-phase hybrid excitation doubly salient motor are arranged in the circumferential direction as: F1-F1+F2-F2+F3-F3+; the permanent magnets are mounted on the surface of the excitation teeth facing the rotor, and each permanent magnet is radially magnetized and has the same magnetization direction; the number of rotor poles satisfies N r ≠3k1, where k1 is a positive integer; the slot pitch electrical angle of the three-phase hybrid excitation doubly salient motor is N s is the number of stator teeth, and k2 is a positive integer.

[0007] Further, both the excitation winding and the armature winding are concentrated windings; the magnetic flux generated by the excitation winding can be in the same direction or in the opposite direction as the magnetic flux of the permanent magnet.

[0008] Further, both the permanent magnet and the excitation winding are located on the same excitation tooth.

[0009] Further, both the stator and the rotor are made of silicon steel sheets by stamping.

[0010] Further, the three-phase hybrid excitation doubly salient motor can operate as a generator or a motor.

[0011] Beneficial effects:

[0012] 1. In the motor of the present invention, the smallest unit single machine includes 9 armature teeth and 3 excitation teeth, and the excitation elements are arranged on the dedicated excitation teeth, and the number is 3, breaking the design idea that the excitation elements of the conventional doubly salient motor are arranged in an even number along the circumferential direction.

[0013] 2. In the motor of the present invention, the shapes of the armature teeth of each phase are exactly the same, and the overall magnetic circuits of each phase are symmetrical, solving the problem of asymmetry of the magnetic circuit of each phase in the traditional three-phase doubly salient motor and improving the electromagnetic characteristics of the motor. The excitation elements are arranged on the dedicated excitation teeth, and the armature windings are arranged on the independent armature teeth, solving the problem that the excitation winding and the armature winding of the traditional doubly salient motor share the same stator slot, resulting in a tight slot fill factor of the armature-excitation slot, and there are many heat sources in the slot and a large temperature rise. Especially taking the traditional three-phase doubly salient motor as an example, in order to solve the tight slot fill factor of the armature-excitation slot, a parallel tooth structure is adopted, resulting in different shapes of the armature teeth of each phase, and the left and right sides of the parallel teeth are acute angle and obtuse angle structures respectively, resulting in asymmetry of the magnetic chain on the left and right. In the present invention, the excitation teeth and the armature teeth are completely independent, and the shapes of the armature teeth are the same.

[0014] 3. In the motor of the present invention, the permanent magnet is surface-mounted on the surface of the excitation tooth facing the rotor, reducing the leakage of the permanent magnet and improving the material utilization rate.

[0015] 4. In the motor of the present invention, both the armature winding and the excitation winding adopt the form of concentrated windings, and the winding ends are shorter, reducing the manufacturing cost.

[0016] 5. In the motor of the present invention, without introducing a ferromagnetic bridge, the integrity of the stator core of the motor is maintained, the process difficulty is reduced, and the mechanical strength of the motor is improved. Description of the drawings

[0017] Figure 1 It is an axial sectional view of a 12 / 8-pole three-phase hybrid excitation doubly salient motor in an embodiment of the present invention;

[0018] Figure 2 It is a slot electromotive force star diagram of a 12 / 8-pole three-phase hybrid excitation doubly salient motor in an embodiment of the present invention;

[0019] Figure 3 It is the winding method of a 12 / 8-pole three-phase hybrid excitation doubly salient motor in an embodiment of the present invention;

[0020] Figure 4This is the working principle diagram of the 12 / 8-pole three-phase hybrid excitation doubly salient motor in the embodiment of the present invention;

[0021] Figure 5 This is the flux linkage waveform diagram of the 12 / 8-pole three-phase hybrid excitation doubly salient motor in the embodiment of the present invention;

[0022] Figure 6 This is the back electromotive force waveform diagram of the 12 / 8-pole three-phase hybrid excitation doubly salient motor in the embodiment of the present invention;

[0023] Figure 7 This is the connection diagram of the excitation bidirectional converter of the three-phase hybrid excitation doubly salient motor of the present invention;

[0024] Figure 8 This is the no-load magnetic flux density distribution diagram of the 12 / 8-pole three-phase hybrid excitation doubly salient motor under different excitation currents in the embodiment of the present invention;

[0025] Figure 9 This is the no-load air-gap magnetic flux density waveform diagram of the 12 / 8-pole three-phase hybrid excitation doubly salient motor under different excitation currents in the embodiment of the present invention;

[0026] Figure 10 This is the connection diagram of the stator winding of the three-phase hybrid excitation doubly salient motor of the present invention and the full-bridge converter;

[0027] Figure 11 This is the connection diagram of the stator winding of the three-phase hybrid excitation doubly salient motor of the present invention and the H-bridge converter;

[0028] Figure 12 This is the conduction schematic diagram of the control strategy when the three-phase hybrid excitation doubly salient motor of the present invention operates in the electric mode;

[0029] Figure 13 This is the wiring mode of the armature winding when the three-phase hybrid excitation doubly salient motor of the present invention operates in the generating mode;

[0030] In the figure, the labels are: 1 - stator core, 2 - rotor core, 3 - armature winding, 4 - excitation winding, 5 - permanent magnet, 6 - rotating shaft. Specific embodiments

[0031] The technical solution of the present invention will be described below with reference to the accompanying drawings. The described embodiments and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0032] This embodiment adopts a unit motor with a new stator structure - a 12 / 8-pole three-phase hybrid excitation doubly salient motor, as Figure 1 shown, the motor includes a coaxial stator and rotor.

[0033] The stator includes a stator core, an armature winding, and an exciting element; the rotor includes a rotor core and a rotating shaft; the stator core and the rotor core are of salient pole structure.

[0034] There are 12 stator teeth provided on the stator core, among which 9 are armature teeth and 3 are exciting teeth. One exciting tooth is distributed every three armature teeth, and the exciting teeth and the armature teeth are independent of each other.

[0035] The exciting element is composed of an exciting winding and a permanent magnet, and they are jointly arranged on independent exciting teeth;

[0036] The armature coils are wound on the stator armature teeth, and all the armature coils are wound in the same direction. That is, in this embodiment, the three-phase armature winding coils are arranged in the circumferential direction as: A1+A1-C1+C1-B1+B1-C2+C2-B2+B2-A2+A2-B3+B3-A3+A3-C3+C3-. The armature coils of the same phase are connected in series to form the armature winding. In this embodiment, the armature winding is distributed in the circumferential direction as ACB—CBA—BAC. Each phase occupies 3 armature teeth, and the relative positions of the armature teeth of each phase and the exciting teeth are the same as a whole.

[0037] The number of exciting coils is 3. The exciting coils are wound on the stator exciting teeth, and the winding directions of adjacent exciting coils are the same. That is, all the exciting coils are distributed in the circumferential direction as: F1-F1+F2-F2+F3-F3+. All the exciting coils are connected in series to form a single-phase exciting winding. The magnetic flux generated by the exciting winding can be the same as or opposite to the magnetic flux direction of the permanent magnet.

[0038] The number of permanent magnets is 3, and they are surface-mounted on the surface of the exciting teeth facing the rotor. All the permanent magnets are radially magnetized and have the same magnetization direction.

[0039] Figure 2 It is the slot electromotive force star diagram of a 12 / 8-pole three-phase hybrid-excited doubly salient motor. According to Figure 2 The winding method of the 12 / 8-pole three-phase hybrid-excited doubly salient motor can be obtained, as shown in Figure 3As shown in the figure. The A-phase armature winding is distributed in the circumferential direction as: A1+A1-A2+A2-A3+A3-; the B-phase armature winding is arranged in the circumferential direction as: B1+B1-B2+B2-B3+B3-; the C-phase armature winding is arranged in the circumferential direction as: C1+C1-C2+C2-C3+C3-; that is, the incoming line ends of the armature windings are located on the same side of the stator armature teeth, and the winding directions are the same. The armature windings of the same phase are connected in series to form a phase winding. In addition, in the A-phase armature winding, there are 4 armature teeth between the A1 winding coil and the A2 winding coil, 1 armature tooth between the A2 winding coil and the A3 winding coil, and 1 armature tooth between the winding coils A3 and A1; in the B-phase armature winding, there is 1 armature tooth between the B1 winding coil and the B2 winding coil, 1 armature tooth between the B2 and B3 winding coils, and 4 armature teeth between the B3 and B1 winding coils; for the C-phase armature winding, there is 1 armature tooth between the winding coils C1 and C2, 4 armature teeth between the C2 and C3 winding coils, and 1 armature tooth between the C3 and C1 winding coils. On the other hand, the excitation winding of this motor is arranged in the circumferential direction as: F1-F1+F2-F2+F3-F3+; that is, the incoming line ends of the excitation windings are located on the same side of the stator excitation teeth, and the winding directions of adjacent excitation windings are the same. All the excitation windings are connected in series to form a single-phase excitation winding.

[0040] Figure 4 Describes the working principle of a 12 / 8-pole three-phase hybrid excitation doubly salient motor. As Figure 4 (a) shows that when the rotor teeth are opposite to the stator armature teeth of the A-phase winding, the excitation winding F1 and the permanent magnet on the excitation tooth where it is located jointly provide an excitation magnetic field for the A-phase winding; there is a 180° interval between the excitation tooth where the excitation winding F1 is located and the armature tooth where the A3 winding coil is located, and there are 2 armature teeth between the A1 and A2 winding coils. Figure 4 (b) is a schematic diagram when the rotor teeth are opposite to the stator armature teeth of the B-phase winding. Figure 4 (b), the excitation winding F3 and the permanent magnet on the excitation tooth where it is located jointly provide a magnetic field for the B-phase winding. There is a 180° interval between this excitation tooth and the armature tooth where the winding coil B2 is located, and there are 2 armature teeth between the winding coils B1 and B2. The situation when the rotor teeth are directly opposite to the stator armature teeth of the C-phase winding is as Figure 4 (c) shows that the excitation coil F2 and the permanent magnet on the excitation tooth where it is located jointly provide an excitation magnetic field for the C-phase winding. There is a 180° difference between this excitation tooth and the armature tooth where the C1 winding coil is located, and there are 2 armature teeth between the C2 and C3 winding coils respectively.

[0041] Figure 5 is the magnetic flux waveform of the 12 / 8-pole three-phase hybrid excitation doubly salient motor in this embodiment. Figure 6 is the three-phase back electromotive force waveform of the 12 / 8-pole three-phase hybrid excitation doubly salient motor in this embodiment. FromFigure 5 and 6 It can be seen that the magnetic fluxes of each phase in the 12 / 8-pole three-phase hybrid-excitation doubly salient motor in this embodiment are symmetric, and the back electromotive force amplitudes of each phase are equal, solving the asymmetry problem caused by different positions of each armature winding from the excitation element in the traditional three-phase doubly salient motor.

[0042] Figure 7 This is the connection diagram of the excitation bidirectional converter and the excitation winding of a three-phase hybrid-excitation doubly salient motor of the present invention. By changing the direction of the excitation current through this circuit, the internal magnetic field of the motor can be magnetized or demagnetized. The excitation bidirectional converter of the three-phase hybrid-excitation doubly salient motor consists of two bridge arms, namely the first bridge arm and the second bridge arm. The first bridge arm includes the first switch tube Q F1 , the second switch tube Q F2 , the first diode D F1 and the second diode D F2 . Among them, the first pole of the first switch tube Q F1 is connected to the closed switch S1, the second pole of the first switch tube Q F1 is connected to the first pole of the second switch tube Q F2 and serves as the neutral point of the first bridge arm, and the second pole of the second switch tube Q F2 is connected to the DC power supply. The other end of the DC power supply is connected to the closed switch S1. The cathode of the first diode D F1 is connected to the first pole of the first switch tube Q F1 , and the anode of the first diode D F1 is connected to the second pole of the first switch tube Q F1 . The first pole of the second diode D F2 is connected to the first pole of the second switch tube Q F2 , and the anode of the second diode D F2 is connected to the second pole of the second switch tube Q F2 .

[0043] The second bridge arm includes the third switch tube Q F3 , the fourth switch tube Q F4 , the third diode D F3 and the fourth diode D F4 . Among them, the first pole of the third switch tube Q F3 is connected to the closed switch S1, the second pole of the third switch tube Q F3 is connected to the first pole of the fourth switch tube Q F4 and serves as the neutral point of the second bridge arm, and the second pole of the fourth switch tube Q F4 is connected to the DC power supply. The cathode of the third diode D F3 is connected to the first pole of the third switch tube Q F3 , and the anode of the third diode D F3 is connected to the third switch tube QF3 is connected to the second pole. The fourth diode D F4 's first pole is connected to the fourth switching transistor Q F4 's first pole, and the anode of the fourth diode D F4 is connected to the second pole of the fourth switching transistor Q F4 . The exciting winding of the three-phase hybrid excitation doubly salient motor is connected between the neutral point of the first bridge arm and the neutral point of the second bridge arm. In addition, Figure 7 where R f is the exciting winding resistance, L f is the exciting winding inductance, and e f is the induced electromotive force of the exciting winding.

[0044] Close the switch S1. When the switching transistors Q F1 and Q F4 are conducting, the current flowing through the exciting winding is positive, and the magnetic field formed by the exciting winding is in the same direction as the magnetic field of the permanent magnet. The magnetomotive force of the motor is the sum of the permanent magnet magnetomotive force and the exciting magnetomotive force, that is, F = F PM +N f i f . Among them, F PM is the permanent magnet magnetomotive force, N f is the number of turns of the exciting winding, and i f is the magnitude of the exciting current. At this time, the magnetic field enhancement inside the motor is realized. When the switching transistors Q F2 and Q F3 are conducting, the current flowing through the exciting winding is negative, and the magnetic field formed by the exciting winding is in the opposite direction to the magnetic field of the permanent magnet. The magnetomotive force of the motor is the difference between the permanent magnet magnetomotive force and the exciting magnetomotive force, that is, F = F PM -N f i f . At this time, the magnetic field demagnetization inside the motor is realized. As Figure 8 shown, it is the no-load magnetic flux density distribution diagram of the 12 / 8-pole three-phase hybrid excitation doubly salient motor under different exciting currents in the embodiment of the present invention, Figure 9 is the comparison diagram of the no-load air-gap magnetic flux density of the 12 / 8-pole three-phase hybrid excitation doubly salient motor under different exciting currents in this embodiment.

[0045] As a further optimization scheme of a three-phase hybrid excitation doubly salient motor of the present invention, when the three-phase hybrid excitation doubly salient motor operates as a motor, the three-phase stator armature windings are connected to the three-phase full-bridge converter in a Y-shaped connection manner, as Figure 10 shown. According to the principle of minimum magnetic resistance and the position signals of each phase, when the stator teeth and rotor teeth are not aligned, the switching transistors are controlled to turn on each phase, and when the stator teeth and rotor teeth are aligned, the switching transistors are controlled to turn off each phase, so as to realize the rotational movement of the motor by sequentially conducting each phase.

[0046] As a further optimization scheme of a three-phase hybrid excitation doubly salient motor according to the present invention, when the three-phase hybrid excitation doubly salient motor operates electrically, an H-bridge converter can be used for control. Among them, the three-phase stator armature windings are respectively connected to the midpoints of the three arms of the H-bridge converter, as Figure 11 shown.

[0047] As a further optimization scheme of a three-phase hybrid excitation doubly salient motor according to the present invention, when the three-phase hybrid excitation doubly salient motor operates electrically, the control logic of the three-phase armature windings is as Figure 12 shown.

[0048] As a further optimization scheme of a three-phase hybrid excitation doubly salient motor according to the present invention, when the three-phase hybrid excitation doubly salient motor operates as a generator, the three-phase stator armature windings are connected to a full-bridge rectifier, as Figure 13 shown.

[0049] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A three-phase hybrid-excited doubly salient motor, comprising a stator and a rotor arranged coaxially, characterized in that: The stator includes a stator core, an armature winding and an excitation element, and the rotor includes a rotor core and a rotating shaft; the stator core and the rotor core are of salient pole structure; The three-phase hybrid-excited doubly salient motor comprises k minimum stator units, where k is a positive integer; The minimum stator unit includes 12 stator teeth, and the minimum stator unit is composed of 9 armature teeth and 3 excitation teeth. One excitation tooth is distributed every 3 armature teeth, and the excitation teeth and the armature teeth are completely separated; The excitation element includes an excitation winding and a permanent magnet, which are arranged on independent excitation teeth; where The excitation coils are wound on the excitation teeth, and all the excitation coils are wound in the same direction. All the excitation coils are connected in series to form a single-phase excitation winding. The excitation coils on the minimum stator unit of the three-phase hybrid-excited doubly salient motor are arranged in the circumferential direction as: F1-F1+F2-F2+F3-F3+; The armature coils are wound on the stator armature teeth of each phase, and all the armature coils are wound in the same direction, that is, the armature coils on the minimum stator unit of the three-phase hybrid-excited doubly salient motor are distributed in the circumferential direction as: A1+A1-C1+C1-B1+B1-C2+C2-B2+B2-A2+A2-B3+B3-A3+A3-C3+C3-, and the armature coils of the same phase are connected in series with each other to form a single armature winding; the arrangement mode of the armature winding on the minimum stator unit of the three-phase hybrid-excited doubly salient motor is ACB—CBA—BAC, each phase occupies 3 armature teeth, and the relative positions of the armature teeth of each phase and the excitation teeth are the same as a whole; The permanent magnets are mounted on the surface of the excitation teeth facing the rotor, and each permanent magnet is radially magnetized and the magnetization directions are the same; The number of rotor poles N r satisfies N r not equal to a multiple of 3; The slot pitch electrical angle of the three-phase hybrid excitation doubly salient motor is , where n satisfies that n is not a multiple of 4, and N s is the number of stator teeth.

2. The three-phase hybrid-excitation doubly salient motor according to claim 1, wherein Both the armature winding and the excitation winding adopt concentrated windings; the magnetic flux generated by the excitation winding is the same as or opposite to the magnetic flux direction of the permanent magnet.

3. The three-phase hybrid excitation doubly salient motor according to claim 1, wherein, Both the stator and the rotor are made of silicon steel sheets by stamping.

4. The three-phase hybrid-excitation doubly salient motor according to any one of claims 1 to 3, characterized in that, The motor can operate as a generator or a motor.

5. A three-phase hybrid excitation doubly salient motor control system, characterized in that The system includes an excitation winding, switching transistors Q F1 to Q F4 , a power supply, and a switch S1. In the system, the excitation winding of the doubly salient motor is connected in the following manner: Switching transistor Q F1 in series with Q F2 Switching transistor Q F3 in series with Q F4 Switching transistor Q F1 Q F2 the midpoint of the branch, switching transistor Q F3 Q F4 the midpoints of the two branches are connected, and the two midpoints are connected to both ends of the excitation winding in the three-phase hybrid excitation doubly salient motor; the power supply and the switch S1 are connected to both ends of the branch formed by the switching transistors.

6. The control method of the three-phase hybrid excitation doubly salient motor according to claim 5, characterized in that, Close switch S1. When the switching transistors Q F1 and Q F4 are turned on, the current flowing through the excitation winding is positive. The magnetic field formed by the excitation winding is in the same direction as the magnetic field of the permanent magnet. The magnetomotive force of the motor is the sum of the magnetomotive force of the permanent magnet and the magnetomotive force of the excitation, that is, F = F PM +N f i f ; where F PM is the magnetomotive force of the permanent magnet, N f is the number of turns of the excitation winding, and i f is the magnitude of the excitation current. At this time, the magnetic field inside the motor is enhanced; When the switching transistors Q F2 and Q F3 are turned on, the current flowing through the excitation winding is negative, and the magnetic field formed by the excitation winding is opposite to the direction of the permanent magnet magnetic field. The magnetomotive force of the motor is the difference between the permanent magnet magnetomotive force and the excitation magnetomotive force, that is, F = F PM -N f i f . At this time, demagnetization of the internal magnetic field of the motor is achieved.

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