Motor winding switching device, control method and motor system

Abstract

The present invention belongs to the technical field of six-phase motors and three-phase motors, and discloses a motor winding switching device, control method, and motor system. The motor is a six-phase motor, and the six-phase winding of the motor is divided into two parts, each of which is three-phase. Among them, three phases are high-speed and low-speed drive windings, and the other three phases are low-speed drive windings. The high-speed and low-speed drive windings are connected in series with the low-speed drive windings. One end of the high-speed and low-speed drive windings is connected to a three-phase bridge inverter 1, and the other end is connected to a three-phase bridge inverter 2; one end of the low-speed drive winding is connected to the three-phase bridge inverter 2, and the other end is connected to a winding switching circuit to form a speed switching circuit. It can switch between six phases and three phases, realize the function of a two-speed mechanical transmission, achieve high torque output at low speed, reduce the depth of weak magnetic field at high speed, and realize efficient drive over a wide speed range.

Description

Technical Field

[0001] The present invention belongs to the technical field of six-phase motors and three-phase motors, and particularly relates to a motor winding switching device, a control method and a motor system. Background Art

[0002] With the development of the times, multi-phase motors are gaining increasing attention in the industrial world. They are particularly suitable for applications requiring high power and high reliability, such as aerospace, ship propulsion, and electric vehicles. Because six-phase motors can eliminate sixth-order torque ripple through two sets of three-phase windings, they have a significant advantage over other multi-phase motors.

[0003] For new energy electric vehicles, the performance requirements for the drive motor system vary under different working conditions.

[0004] When a vehicle accelerates from zero or low speed, or when starting on a slope, the vehicle and motor speeds are relatively low, requiring high torque to overcome friction and the vehicle's own weight. Since the output electromagnetic torque of a permanent magnet synchronous motor is proportional to the flux linkage, which in turn is proportional to the number of coil turns, increasing the number of coil turns can help improve the motor's output torque.

[0005] When a car is cruising at high speeds, the system typically doesn't require high torque. However, to keep the car's drive motor running at high speeds, a controller must implement field weakening control of the motor. This is because the onboard battery voltage is limited, and the back EMF generated by the permanent magnets in the permanent magnet motor increases with speed. When the back EMF reaches the upper voltage limit, the motor speed cannot be increased further. At this point, field weakening control is required to increase the direct-axis demagnetization current. However, this increases losses, and even with deep field weakening, there is a risk of demagnetization of the permanent magnets. Therefore, the field weakening range should be selected appropriately.

[0006] Patent CN201310041277.4 proposes a technology for switching windings at high and low speeds. The stator coil is divided into two sections. During low-speed rotation, current flows through the entire coil, while during high-speed rotation, current flows through a portion of the coil. However, this technology uses fully controlled IGBTs, which are expensive and can generate overvoltage during active shutdown, damaging the winding insulation and the IGBT. The RC snubber circuit in the switching circuit increases system complexity, while capacitors are often large and fragile, posing a risk of failure under overvoltage shocks. Patent CN201810458487.6 proposes a three-phase motor winding switching device and control method. However, the winding switching circuit requires two three-phase uncontrolled rectifier bridges with thyristors. Thyristors are more expensive than ordinary diodes, and in the event of a fault, the presence of two thyristors can complicate repair and troubleshooting. Some solutions use two power supplies or two thyristors, which increases the cost and space required for actual circuit construction. Summary of the Invention

[0007] In response to the shortcomings of the prior art, the present invention provides a motor winding switching device, control method, and motor system that utilize electronic circuits to function as a two-speed mechanical transmission, enabling the motor to provide high torque in the lower speed range by increasing the number of turns. In the high-speed range, the six-phase motor is converted to a three-phase motor to reduce the number of winding turns, thereby reducing the back EMF generated by the motor, broadening the motor's constant torque operating range, and broadening the motor's speed regulation range without increasing the depth of field weakening, enabling the motor to operate normally in both the high-speed range (the speed range corresponding to the three-phase operating state, i.e., the n* to n4 range) and the low-speed range (the speed range corresponding to the six-phase operating state, i.e., the 0 to n* range). Simultaneously, the number of controllable switching devices T1 (such as thyristors, MOS transistors, IGBTs, bidirectional switches, etc.) and power supplies in the control circuit is reduced, thereby controlling costs and reducing the difficulty of repair, replacement, and troubleshooting.

[0008] The high-speed range is the speed range when the switching circuit controllable switch device T1 is disconnected, that is, the motor operates in a three-phase state, that is, the range n* to n4. The low-speed range is the speed range when the controllable switch device T1 is closed, that is, the motor operates in a six-phase state, that is, the range 0 to n*.

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] A motor winding switching device, wherein the motor is a six-phase motor, the six-phase winding of the motor is divided into two parts, each part has three phases, three of which are high-speed and low-speed drive windings, and the other three phases are low-speed drive windings, the high-speed and low-speed drive windings are connected in series with the low-speed drive windings, one end of the high-speed and low-speed drive windings is connected to a three-phase bridge inverter 1, and the other end is connected to a three-phase bridge inverter 2;

[0011] One end of the low-speed drive winding is connected to the three-phase bridge inverter 2, and the other end is connected to the winding switching circuit to form a speed switching circuit.

[0012] Furthermore, the three-phase bridge inverter 1 and the three-phase bridge inverter 2 are connected in parallel.

[0013] Furthermore, the three-phase bridge inverter 1 includes six transistors, which are divided into three groups, with two transistors in each group connected in series, and the three transistor groups are connected in parallel; the three-phase bridge inverter 2 has the same structure as the three-phase bridge inverter 1.

[0014] Furthermore, the winding switching circuit is composed of a three-phase uncontrolled rectifier bridge and a controllable switch device T1 in parallel;

[0015] The three-phase uncontrolled rectifier bridge includes six diodes, which are divided into three groups. Two diodes in each group are connected in series, and the three groups of diodes are connected in parallel.

[0016] Furthermore, the high-speed and low-speed driving windings are connected in series with the low-speed driving winding.

[0017] Furthermore, one end of the A-phase winding in the high- and low-speed drive windings is connected to the two transistors of the first group in the three-phase bridge inverter one, and the other end is connected to the two transistors of the first group in the three-phase bridge inverter two; one end of the B-phase winding in the high- and low-speed drive windings is connected to the two transistors of the second group in the three-phase bridge inverter one, and the other end is connected to the two transistors of the second group in the three-phase bridge inverter two; one end of the C-phase winding in the high- and low-speed drive windings is connected to the two transistors of the third group in the three-phase bridge inverter one, and the other end is connected to the two transistors of the third group in the three-phase bridge inverter two.

[0018] Furthermore, one end of the X-phase winding in the low-speed drive winding is connected to the two transistors of the first group in the three-phase bridge inverter 2, and the other end is connected to the two diodes of the first group in the three-phase uncontrolled rectifier bridge; one end of the Y-phase winding in the low-speed drive winding is connected to the two transistors of the second group in the three-phase bridge inverter 2, and the other end is connected to the two diodes of the second group in the three-phase uncontrolled rectifier bridge; one end of the Z-phase winding in the low-speed drive winding is connected to the two transistors of the third group in the three-phase bridge inverter 2, and the other end is connected to the two diodes of the third group in the three-phase uncontrolled rectifier bridge.

[0019] Furthermore, the high-speed and low-speed driving windings have the same number of turns as the low-speed driving winding.

[0020] A control method for a motor winding switching device is provided. When the motor is running at low speed, the motor controller sends a switching signal to the three-phase bridge inverter 1 and the three-phase bridge inverter 2, and at the same time sends a signal to the controllable switch device T1, turning on the controllable switch device T1. The neutral point of the low-speed drive winding is connected using the three-phase uncontrolled rectifier bridge. At this time, all windings participate in the operation, generating a large torque, and the maximum torque can reach T1.

[0021] When the motor speed rises to the range of n1 to n*, the motor back EMF value is equal to the supply voltage. At this time, it is necessary to increase the direct-axis demagnetization current to maintain the voltage balance during high-speed operation and increase the motor speed by means of magnetic weakening.

[0022] As the motor speed increases to n*, the controllable switch device T1 receives the signal and disconnects, the low-speed drive winding is immediately disconnected, and the high-speed and low-speed drive windings, three-phase bridge inverter 1 and three-phase bridge inverter 2 continue to work. The motor changes from six phases to three phases. Since the number of motor turns decreases at this time, the back EMF also decreases. The supply voltage value is greater than or equal to the back EMF value generated by the motor. The motor resumes working in the constant torque range, and there is no need to increase the speed through weak magnetic control.

[0023] When the motor speed is greater than n3, the three-phase motor needs to increase the direct-axis demagnetization current and use the weak magnetic control method again to reach the maximum speed n4.

[0024] A motor system comprising:

[0025] rotor; and

[0026] a stator including a low-speed drive winding used only during low-speed drive, a high-speed drive winding used during both low-speed drive and high-speed drive, and a plurality of slots provided for each pole of each phase,

[0027] The low-speed drive winding and the high-speed and low-speed drive winding are distributedly wound in different slots corresponding to each pole of each phase.

[0028] Beneficial effects of the present invention:

[0029] 1. Control the opening and closing of the controllable switch device T1 according to system requirements to realize the switching between the six-phase motor and the three-phase motor, playing the role of a two-speed gearbox, so that the motor can run at low speed and high torque, as well as high speed and high efficiency.

[0030] 2. The motor can operate in the constant torque range in both low-speed mode and high-speed mode, which can reduce the motor's magnetic weakening depth, expand the motor's operating speed range, and improve the motor's operating efficiency.

[0031] 3. Since the controllable switch device T1 automatically turns off when the current is zero, no snubber circuit is required, thus avoiding the risk of switching out of control and IGBT active shutdown causing overvoltage due to snubber circuit device failure.

[0032] 4. Since only one winding switching circuit is used, which only includes six diodes and the controllable switch device T1, the cost of control components is reduced. In addition, when a fault occurs in the winding switching circuit, the fault can be quickly eliminated and the faulty device can be replaced, reducing the difficulty of maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] Figure 1 This is a general framework diagram of a six-phase motor winding switching device and control system according to an embodiment of the present invention;

[0035] Figure 2 is a linear diagram of the output mechanical characteristics of a six-phase motor according to an embodiment of the present invention;

[0036] Figure 3 is a linear diagram of the output mechanical characteristics of the three-phase motor according to an embodiment of the present invention;

[0037] Figure 4 1 is a linear diagram of the output mechanical characteristics of the motor after the device is installed according to an embodiment of the present invention.

[0038] Description of the accompanying drawings: 1. Three-phase bridge inverter 1; 2. Three-phase bridge inverter 2; 3. Motor stator winding; 4. Winding switching circuit. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] In the description of the present invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inside", "around" and the like indicating orientation or positional relationship are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0041] Example 1

[0042] like Figure 1 As shown, a motor winding switching device is shown, the motor is a six-phase motor, the six-phase winding of the motor is divided into two parts, each part is three-phase, three phases of which are high-speed and low-speed drive windings, and the other three phases are low-speed drive windings, the high-speed and low-speed drive windings are connected in series with the low-speed drive winding, one end of the high-speed and low-speed drive windings is connected to a three-phase bridge inverter 1, and the other end is connected to a three-phase bridge inverter 2;

[0043] One end of the low-speed drive winding is connected to the three-phase bridge inverter 2 2, and the other end is connected to the winding switching circuit 4 to form a speed switching circuit.

[0044] Regarding the high-speed and low-speed drive windings and the low-speed drive windings, it should be noted that the six phases of the motor stator winding 3 are divided into two parts, each part is three-phase, one part of the three-phase winding is connected between the three-phase bridge inverter 1 and the three-phase bridge inverter 2 2, and the three-phase windings are respectively denoted as A, B, and C, and the whole is denoted as the high-speed and low-speed drive windings. The other part of the three-phase winding is connected between the three-phase bridge inverter 2 2 and the winding switching circuit 4, and the three-phase windings are respectively denoted as X, Y, and Z, and the whole is denoted as the low-speed drive winding.

[0045] In the diagrams of this application, three-phase bridge inverter 1 and three-phase bridge inverter 2 are connected in parallel. Three-phase bridge inverter 1 includes six transistors, divided into three groups, each with two transistors connected in series, and the three groups of transistors are connected in parallel. Similarly, three-phase bridge inverter 2 and three-phase bridge inverter 1 have the same structure.

[0046] In the diagram of this application, the winding switching circuit 4 is composed of a three-phase uncontrolled rectifier bridge and a controllable switch device T1 (such as a MOS tube, thyristor, IGBT, bidirectional switch tube, etc.) in parallel. The three-phase uncontrolled rectifier bridge includes six diodes, which are divided into three groups. The two diodes in each group are connected in series, and the three groups of diodes are connected in parallel.

[0047] In the drawings of the present application, the high-speed and low-speed driving windings are connected in series with the low-speed driving winding.

[0048] In the diagram of the present application, one end of the A-phase winding in the high- and low-speed drive windings is connected to the two transistors of the first group in the three-phase bridge inverter 1, and the other end is connected to the two transistors of the first group in the three-phase bridge inverter 2; one end of the B-phase winding in the high- and low-speed drive windings is connected to the two transistors of the second group in the three-phase bridge inverter 1, and the other end is connected to the two transistors of the second group in the three-phase bridge inverter 2; one end of the C-phase winding in the high- and low-speed drive windings is connected to the two transistors of the third group in the three-phase bridge inverter 1, and the other end is connected to the two transistors of the third group in the three-phase bridge inverter 2.

[0049] In the diagram of the present application, one end of the X-phase winding in the low-speed drive winding is connected to the two transistors of the first group in the three-phase bridge inverter 22, and the other end is connected to the two diodes of the first group in the three-phase uncontrolled rectifier bridge; one end of the Y-phase winding in the low-speed drive winding is connected to the two transistors of the second group in the three-phase bridge inverter 22, and the other end is connected to the two diodes of the second group in the three-phase uncontrolled rectifier bridge; one end of the Z-phase winding in the low-speed drive winding is connected to the two transistors of the third group in the three-phase bridge inverter 22, and the other end is connected to the two diodes of the third group in the three-phase uncontrolled rectifier bridge.

[0050] Specifically, the number of turns of the high-speed and low-speed driving windings is the same as that of the low-speed driving windings, which is N.

[0051] Specifically, the high-speed and low-speed drive windings are connected in series with the low-speed drive winding, and a winding switching circuit 4 including a three-phase uncontrolled rectifier bridge and a controllable switching device T1 (such as a MOS tube, a thyristor, an IGBT, a bidirectional switch tube, etc.) is used to complete the switching between the six-phase winding and the three-phase winding.

[0052] Figure 2 The figure shows the output mechanical characteristics of a six-phase motor with windings connected in series. Due to the large number of winding turns, a high back electromotive force is generated at high speeds. Under magnetic weakening control, the speed can only reach n2, and cannot reach the high speed n4 required by the application.

[0053] Figure 3The figure shows the output mechanical characteristics of a three-phase motor. Due to the small number of winding turns, the back EMF generated by the motor is smaller at the same speed, and the required high speed n4 can be achieved. However, it cannot output large torque T1 at low speed.

[0054] Example 2

[0055] like Figure 1 and Figure 4 The control method for a motor winding switching device of the present invention is shown. When the motor is running at low speed, the motor controller sends PWM operating signals to three-phase bridge inverter 1 and three-phase bridge inverter 2, while simultaneously sending a trigger signal to controllable switch device T1 in winding switching circuit 4. This causes controllable switch device T1 to be turned on by a positive voltage, and the lower end of the low-speed drive winding is short-circuited using a three-phase uncontrolled rectifier bridge. At this point, all windings are operational, and the motor operates as a six-phase motor, generating high torque, with the maximum torque reaching T1.

[0056] As the motor speed increases to the range n1 to n*, the motor's back EMF increases, and the six-phase motor enters a field-weakening state. By increasing the direct-axis demagnetizing current, the motor's back EMF is reduced, thereby increasing the motor speed. The maximum torque the motor can output begins to decrease from T1.

[0057] When the motor speed rises to n*, the six-phase motor characteristic curve intersects the three-phase motor characteristic curve. When the motor controller controls the current to decay to zero, the trigger signal to controllable switch device T1 is removed, reducing the current flowing through the controllable switch device to below the holding current. Controllable switch device T1 turns off, disconnecting the low-speed drive winding, and the motor becomes a three-phase motor. At this point, the high- and low-speed drive windings in the motor operate normally. Since the low-speed drive winding is disconnected, the number of turns is reduced, and the motor's back EMF also decreases. At this speed, there is no need to increase the speed through field weakening. The motor returns to operating in the constant torque range, with maximum torque reaching T2.

[0058] When the motor speed rises to n3, the motor back EMF value equals the supply voltage value, and the three-phase motor enters the field weakening speed expansion range. Since the number of turns is smaller at this time, the field weakening depth also decreases.

[0059] When the motor speed returns to n* or below, the motor controller sends an opening signal to T1 again, reconnects the low-speed drive winding, and returns the motor to the six-phase motor working state.

[0060] In the present invention, the controllable switching device T1 blocks the pulse through the inverter and is passively shut down, ensuring that the winding is always switched in the zero current state. Therefore, no buffer circuit is required, avoiding the risk of switching out of control and IGBT active shutdown causing overvoltage due to failure of the buffer circuit device.

[0061] Example 3

[0062] A motor system comprising:

[0063] rotor; and

[0064] a stator including a low-speed drive winding used only during low-speed drive, a high-speed drive winding used during both low-speed drive and high-speed drive, and a plurality of slots provided for each pole of each phase,

[0065] The low-speed drive winding and the high-speed and low-speed drive winding are distributedly wound in different slots corresponding to each pole of each phase.

[0066] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0067] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A control method for a motor winding switching device, wherein the motor is a six-phase motor, the six-phase winding of the motor is divided into two parts, each part has three phases, wherein three phases are high-speed and low-speed drive windings, and the other three phases are low-speed drive windings, and the high-speed and low-speed drive windings are connected in series with the low-speed drive winding, characterized in that: One end of the high-speed and low-speed drive winding is connected to the three-phase bridge inverter one (1), and the other end is connected to the three-phase bridge inverter two (2); One end of the low-speed drive winding is connected to the three-phase bridge inverter 2 (2), and the other end is connected to the winding switching circuit (4) to form a speed switching circuit; The three-phase bridge inverter 1 (1) and the three-phase bridge inverter 2 (2) are connected in parallel; The three-phase bridge inverter (1) includes six transistors, which are divided into three groups, each group has two transistors connected in series, and the three groups of transistors are connected in parallel; the three-phase bridge inverter (2) has the same structure as the three-phase bridge inverter (1); The winding switching circuit (4) is composed of a three-phase uncontrolled rectifier bridge and a controllable switch device T1 connected in parallel; The three-phase uncontrolled rectifier bridge includes six diodes, which are divided into three groups, with two diodes in each group connected in series, and the three groups of diodes are connected in parallel; The high-speed and low-speed driving windings are connected in series with the low-speed driving windings; One end of the A-phase winding in the high-low speed drive winding is connected to the two transistors of the first group in the three-phase bridge inverter (1), and the other end is connected to the two transistors of the first group in the three-phase bridge inverter (2); one end of the B-phase winding in the high-low speed drive winding is connected to the two transistors of the second group in the three-phase bridge inverter (1), and the other end is connected to the two transistors of the second group in the three-phase bridge inverter (2); one end of the C-phase winding in the high-low speed drive winding is connected to the two transistors of the third group in the three-phase bridge inverter (1), and the other end is connected to the two transistors of the third group in the three-phase bridge inverter (2); One end of the X-phase winding in the low-speed drive winding is connected to the two transistors of the first group in the three-phase bridge inverter (2), and the other end is connected to the two diodes of the first group in the three-phase uncontrolled rectifier bridge; one end of the Y-phase winding in the low-speed drive winding is connected to the two transistors of the second group in the three-phase bridge inverter (2), and the other end is connected to the two diodes of the second group in the three-phase uncontrolled rectifier bridge; one end of the Z-phase winding in the low-speed drive winding is connected to the two transistors of the third group in the three-phase bridge inverter (2), and the other end is connected to the two diodes of the third group in the three-phase uncontrolled rectifier bridge; The high-speed and low-speed driving windings have the same number of turns as the low-speed driving windings; When the motor is running at low speed, the motor controller sends a switching signal to the three-phase bridge inverter 1 (1) and the three-phase bridge inverter 2 (2), and at the same time sends a signal to the controllable switch device T1, so that the controllable switch device T1 is turned on, and the neutral point of the low-speed drive winding is connected by using the three-phase uncontrolled rectifier bridge. At this time, all windings participate in the work, generating a large torque, and the maximum torque can reach T1; When the motor speed rises to n1~n In the range, the motor back EMF value is equal to the supply voltage. At this time, it is necessary to increase the direct-axis demagnetization current to maintain the voltage balance during high-speed operation and increase the motor speed by means of magnetic weakening speed expansion. As the motor speed increases to n , the controllable switch device T1 receives the signal and disconnects, the low-speed drive winding is disconnected immediately, the high-speed and low-speed drive windings, the three-phase bridge inverter one (1) and the three-phase bridge inverter two (2) continue to work, and the motor is converted from six phases to three phases. Since the number of motor turns is reduced at this time, the back electromotive force is also reduced, and the supply voltage value is greater than or equal to the back electromotive force value generated by the motor. The motor works in the constant torque range again, and there is no need to increase the speed through weak magnetic control; When the motor speed is greater than n3, the three-phase motor needs to increase the direct-axis demagnetization current and use the weak magnetic control method again to reach the maximum speed n4.

2. A motor system, the system being used to implement the control method according to claim 1, characterized in that: include: rotor; and a stator including a low-speed drive winding used only during low-speed drive, a high-speed drive winding used during both low-speed drive and high-speed drive, and a plurality of slots provided for each pole of each phase; The low-speed drive winding and the high-speed and low-speed drive winding are distributedly wound in different slots corresponding to each pole of each phase.

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