Permanent magnet synchronous motor, starting method thereof, and air conditioner

Abstract

The present invention discloses a permanent magnet synchronous motor, a starting method thereof, and an air conditioner. The permanent magnet synchronous motor comprises: a motor body, a controller, a first bridge arm switching device, a second bridge arm switching device, a third bridge arm switching device, and a bus capacitor. The first bridge arm switching device comprises a first upper bridge arm switching device and a first lower bridge arm switching device, the second bridge arm switching device comprises a second upper bridge arm switching device and a second lower bridge arm switching device, and the third bridge arm switching device comprises a third upper bridge arm switching device and a third lower bridge arm switching device. The controller is configured to output a pulse signal with a preset duty cycle to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device, and the third lower bridge arm switching device, obtain a bus voltage across the bus capacitor during a low level period of the pulse signal, and control the starting of the permanent magnet synchronous motor according to the bus voltage. The motor starting can be controlled without adding hardware circuits, and the method is low in cost, simple, and convenient.

Description

Technical Field

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

[0002] When not in operation, permanent magnet synchronous motors (PMSMs) used in electric fans and air conditioner outdoor fans rotate clockwise or counterclockwise due to the influence of external airflow. However, these applications typically lack rotor position sensors, making it impossible to detect the motor's rotational speed before starting, and consequently, to control the PMSM's startup process. Prior art methods typically incorporate a back-EMF sampling circuit into the hardware to detect the motor's rotational speed based on its back-EMF before starting. Based on the speed, the system then determines whether to start the motor from a standstill or bypass the startup process and directly operate in a closed-loop manner. Alternatively, position observers, such as those used for low and zero speeds, such as high-frequency injection, are used to measure the motor's rotational speed and position before starting. These methods are costly and complex. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention aims to provide a permanent magnet synchronous motor and a starting method thereof, and an air conditioner.

[0004] A permanent magnet synchronous motor proposed in the present invention includes: a motor body, a controller, a first bridge arm switching device, a second bridge arm switching device, a third bridge arm switching device and a bus capacitor, wherein the first bridge arm switching device, the second bridge arm switching device, the third bridge arm switching device and the bus capacitor are connected in parallel with each other, and a three-phase motor winding is provided in the motor body; the first bridge arm switching device includes a first upper bridge arm switching device and a first lower bridge arm switching device, the second bridge arm switching device includes a second upper bridge arm switching device and a second lower bridge arm switching device, and the third bridge arm switching device includes a third upper bridge arm switching device and a third lower bridge arm switching device; the first upper bridge arm switching device, the first lower bridge arm switching device, the second upper bridge arm switching device, the second lower bridge arm switching device The device, the third upper bridge arm switching device and the third lower bridge arm switching device are each connected in reverse parallel with a diode; the connection point between the first upper bridge arm switching device and the first lower bridge arm switching device, the connection point between the second upper bridge arm switching device and the second lower bridge arm switching device and the connection point between the third upper bridge arm switching device and the third lower bridge arm switching device are respectively connected to one end of the three-phase motor winding of the permanent magnet synchronous motor; the controller is configured to: output a pulse signal with a preset duty cycle to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device and the third lower bridge arm switching device, obtain the bus voltage across the bus capacitor during the low level period of the pulse signal, and control the start-up of the permanent magnet synchronous motor according to the bus voltage.

[0005] In addition, the permanent magnet synchronous motor according to the embodiment of the present invention may also have the following additional technical features:

[0006] Furthermore, the controller is specifically configured to: determine the rotational speed of the permanent magnet synchronous motor according to the bus voltage; and control the permanent magnet synchronous motor to start when it is determined that the rotational speed of the permanent magnet synchronous motor is zero.

[0007] Furthermore, the controller is specifically configured to: obtain a change in the increase amplitude of the bus voltage; and when the increase amplitude of the bus voltage decreases to zero, determine that the speed of the permanent magnet synchronous motor is zero.

[0008] Furthermore, the increase in the bus voltage is proportional to the rotational speed of the permanent magnet synchronous motor.

[0009] Furthermore, the controller is specifically configured to: establish a data table, wherein the data table is used to record the mapping relationship between the bus voltage and the speed of the permanent magnet synchronous motor; input the bus voltage into the data table to query and obtain the corresponding speed of the permanent magnet synchronous motor.

[0010] Furthermore, the controller is specifically configured to: receive the multiple sets of mapping relationship data between the bus voltage and the motor speed; and calibrate the data table according to the multiple sets of mapping relationship data between the bus voltage and the motor speed.

[0011] Furthermore, it also includes: a voltage sampling unit, which is connected in parallel with the bus capacitor, and the controller is specifically configured to: during the low level period of the pulse signal, sample the bus voltage across the bus capacitor through the voltage sampling unit.

[0012] Furthermore, the voltage sampling unit includes a first sampling resistor and a second sampling resistor connected in series, and the controller is specifically configured to: use the voltage at the connection point of the first sampling resistor and the second sampling resistor as the bus voltage.

[0013] According to the permanent magnet synchronous motor of an embodiment of the present invention, before the permanent magnet synchronous motor is started, a pulse signal with a preset duty cycle is output to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device and the third lower bridge arm switching device. During the low level period of the pulse signal, the bus voltage across the bus capacitor is obtained, and the starting of the permanent magnet synchronous motor is controlled according to the bus voltage. There is no need to add a back electromotive force detection circuit, and the starting of the permanent magnet synchronous motor can be controlled according to the bus voltage. This has the advantages of low cost, simplicity and convenience.

[0014] A further embodiment of the present invention also discloses a method for starting a permanent magnet synchronous motor, comprising: outputting a pulse signal with a preset duty cycle to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device, and the third lower bridge arm switching device; obtaining the bus voltage across the bus capacitor during the low level period of the pulse signal; and controlling the starting of the permanent magnet synchronous motor according to the bus voltage.

[0015] According to the starting method of a permanent magnet synchronous motor in an embodiment of the present invention, before the permanent magnet synchronous motor is started, a pulse signal with a preset duty cycle is output to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device and the third lower bridge arm switching device. During the low level period of the pulse signal, the bus voltage across the bus capacitor is obtained, and the starting of the permanent magnet synchronous motor is controlled according to the bus voltage. There is no need to add a back electromotive force detection circuit, and the starting of the permanent magnet synchronous motor can be controlled according to the bus voltage. This has the advantages of low cost, simplicity and convenience.

[0016] A further embodiment of the present invention also discloses an air conditioner, comprising the permanent magnet synchronous motor as described in any of the above embodiments.

[0017] According to the air conditioner of an embodiment of the present invention, before the permanent magnet synchronous motor is started, a pulse signal with a preset duty cycle is output to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device and the third lower bridge arm switching device. During the low level period of the pulse signal, the bus voltage across the bus capacitor is obtained, and the starting of the permanent magnet synchronous motor is controlled according to the bus voltage. There is no need to add a back electromotive force detection circuit, and the starting of the permanent magnet synchronous motor can be controlled according to the bus voltage. This has the advantages of low cost, simplicity and convenience.

[0018] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0020] Figure 1 is a structural schematic diagram of a permanent magnet synchronous motor according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of the induced current flow direction of a permanent magnet synchronous motor according to an embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of the induced current flow direction of a permanent magnet synchronous motor according to another embodiment of the present invention;

[0023] Figure 4 is a flowchart of a method for starting a permanent magnet synchronous motor according to an embodiment of the present invention;

[0024] Figure 5 is a flow chart of controlling the startup of a permanent magnet synchronous motor according to one embodiment of the present invention;

[0025] Figure 6 is a flow chart for determining the speed of a permanent magnet synchronous motor according to one embodiment of the present invention;

[0026] Figure 7 is a flowchart of establishing a data table according to one embodiment of the present invention. DETAILED DESCRIPTION

[0027] The embodiments of the present invention will be described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present invention will be described in detail below.

[0028] Reference below Figure 1-Figure 7 A permanent magnet synchronous motor, a starting method thereof, and an air conditioner according to embodiments of the present invention are described.

[0029] Figure 1FIG. 1 is a structural diagram of a permanent magnet synchronous motor according to an embodiment of the present invention. Figure 1 As shown, a permanent magnet synchronous motor includes: a motor body M, a controller (not shown in the figure), a first bridge arm switch device, a second bridge arm switch device, a third bridge arm switch device and a bus capacitor C1. The first bridge arm switch device, the second bridge arm switch device, the third bridge arm switch device and the bus capacitor C1 are connected in parallel with each other, and a three-phase motor winding is provided in the motor body M; the first bridge arm switch device includes a first upper bridge arm switch device Q1 and a first lower bridge arm switch device Q4, the second bridge arm switch device includes a second upper bridge arm switch device Q2 and a second lower bridge arm switch device Q5, and the third bridge arm switch device includes a third upper bridge arm switch device Q3 and a third lower bridge arm switch device Q6; the first upper bridge arm switch device Q1, the first lower arm switch device A diode is connected in reverse parallel to each of the first upper-arm switching device Q4, the second upper-arm switching device Q2, the second lower-arm switching device Q5, the third upper-arm switching device Q3, and the third lower-arm switching device Q6. The connection point between the first upper-arm switching device Q1 and the first lower-arm switching device Q4, the connection point between the second upper-arm switching device Q2 and the second lower-arm switching device Q5, and the connection point between the third upper-arm switching device Q3 and the third lower-arm switching device Q6 are respectively connected to one end of the three-phase motor winding of the permanent magnet synchronous motor, namely, U, W, and Y. The controller is configured to output a pulse signal with a preset duty cycle to at least two of the first lower-arm switching device, the second lower-arm switching device, and the third lower-arm switching device; during the low-level period of the pulse signal, obtain the bus voltage across the bus capacitor C1, and control the starting of the permanent magnet synchronous motor based on the bus voltage.

[0030] Specifically, before the permanent magnet synchronous motor is started, when it is in a rotating state due to the influence of external forces, such as external airflow, there will be an induced electromotive force between the three-phase motor windings. At this time, if a pulse signal with a preset duty cycle is output to at least two of the first lower bridge arm switch device Q4, the second lower bridge arm switch device Q5 and the third lower bridge arm switch device Q6, such as the first lower bridge arm switch device Q4 and the second lower bridge arm switch device Q5, during the high level period of the pulse signal, the first lower bridge arm switch device Q4 and the second lower bridge arm switch device Q5 are in the on state, then an induced current will be generated between U-Q4-Q5-W (such as Figure 2As shown), during the low level period of the pulse signal, the first lower bridge arm switch device Q4 and the second lower bridge arm switch device Q5 are in the off state. When the first lower bridge arm switch device Q4 and the second lower bridge arm switch device Q5 are switched from the on state to the off state, the loop between U and W is cut off. However, due to the existence of the motor winding inductance, the induced current cannot drop to zero immediately, but continues to flow in the original direction. At this time, the voltage at the U terminal will be raised above the bus voltage, causing the diode in anti-parallel connection with the first upper bridge arm switch device Q1 to conduct, and the induced current charges the bus capacitor C1 through the diode in anti-parallel connection with the first upper bridge arm switch device Q1 (as shown). Figure 3 As shown), the voltage across the bus capacitor C1 is raised. At the same time, during the high level period of the pulse signal, due to the presence of the on-resistance of the first lower bridge arm switch device Q4 and the second lower bridge arm switch device Q5 and the three-phase motor winding resistance of the motor body M, the motor speed will gradually decrease. When the motor speed drops to zero, the bus voltage across the bus capacitor C1 will not be raised. At this time, the permanent magnet synchronous motor can be started according to the static starting method, for example, the permanent magnet synchronous motor can be started by open-loop starting control, and then switched to closed-loop vector control after the permanent magnet synchronous motor rotor is pulled into synchronization and reaches the target speed. This method of starting the permanent magnet synchronous motor does not require the addition of a back electromotive force detection circuit, and can control the starting of the permanent magnet synchronous motor according to the bus voltage, which has the advantages of low cost, simplicity and convenience.

[0031] In one embodiment of the present invention, the controller is specifically configured to: determine the speed of the permanent magnet synchronous motor according to the bus voltage; and control the permanent magnet synchronous motor to start when it is determined that the speed of the permanent magnet synchronous motor is zero.

[0032] Specifically, when the speed of the permanent magnet synchronous motor is zero, the permanent magnet synchronous motor can be started according to the static starting method, that is, when the speed of the permanent magnet synchronous motor is zero, the permanent magnet synchronous motor is started. Before the motor starts, there is no need to distinguish whether the motor is in a downwind rotation state or a headwind rotation state, and the starting method is simple.

[0033] In one embodiment of the present invention, the controller is specifically configured to: obtain the change in the increase amplitude of the bus voltage; when the increase amplitude of the bus voltage decreases to zero, determine that the speed of the permanent magnet synchronous motor is zero.

[0034] Specifically, when the motor is rotating due to an external force, the bus voltage increases. When the controller detects that the increase in bus voltage has dropped to zero, it assumes the permanent magnet synchronous motor is stationary and can start the permanent magnet synchronous motor using the stationary starting method.

[0035] In a specific embodiment, the magnitude of the bus voltage increase is proportional to the speed of the permanent magnet synchronous motor. That is, the greater the magnitude of the bus voltage increase, the greater the speed of the permanent magnet synchronous motor due to the influence of the external force. In particular, when the magnitude of the bus voltage increase is zero, the speed of the permanent magnet synchronous motor before startup is zero.

[0036] In one embodiment of the present invention, the controller is specifically configured to: establish a data table, wherein the data table is used to record the mapping relationship between the bus voltage and the speed of the permanent magnet synchronous motor; input the bus voltage into the data table to query and obtain the corresponding speed of the permanent magnet synchronous motor.

[0037] Specifically, when a permanent magnet synchronous motor is subjected to an external force, the bus voltage increases. A mapping relationship exists between the bus voltage and the motor's speed. Therefore, the motor's speed can be obtained from the bus voltage. Specifically, before determining the motor's speed, a data table can be created that shows a one-to-one correspondence between the bus voltage and the motor's speed. Once the bus voltage is obtained, the motor's speed can be retrieved from the table based on the current bus voltage.

[0038] In one embodiment of the present invention, the controller is specifically configured to: receive multiple sets of mapping relationship data between bus voltage and motor speed; and calibrate the data table according to the multiple sets of mapping relationship data between bus voltage and motor speed.

[0039] In a specific embodiment, when establishing a data table, it is necessary to receive multiple sets of mapping relationship data between bus voltage and motor speed. These mapping relationship data can be determined experimentally, i.e., the motor speed can be calibrated for different bus voltages. Furthermore, a relationship curve between bus voltage and motor speed can be fitted based on the multiple sets of mapping relationship data between bus voltage and motor speed. After the bus voltage is obtained, the target motor speed corresponding to the bus voltage can be obtained based on the fitted relationship curve.

[0040] In one embodiment of the present invention, the permanent magnet synchronous motor further comprises: a voltage sampling unit connected in parallel with the bus capacitor, and the controller is specifically configured to: during the low level period of the pulse signal, sample the bus voltage across the bus capacitor through the voltage sampling unit. Specifically, Figure 1-3 As shown, the voltage sampling unit includes a first sampling resistor R1 and a second sampling resistor R2 connected in series, and the voltage at the connection point of the first sampling resistor R1 and the second sampling resistor R2 is used as the bus voltage.

[0041] According to the permanent magnet synchronous motor of an embodiment of the present invention, before the permanent magnet synchronous motor is started, a pulse signal with a preset duty cycle is output to at least two of the first lower bridge arm switching device Q4, the second lower bridge arm switching device Q5 and the third lower bridge arm switching device Q6. During the low level period of the pulse signal, the bus voltage across the bus capacitor C1 is obtained, and the starting of the permanent magnet synchronous motor is controlled according to the bus voltage. Without adding a back electromotive force detection circuit, the starting of the permanent magnet synchronous motor can be controlled according to the bus voltage, which has the advantages of low cost, simplicity and convenience.

[0042] A further embodiment of the present invention further discloses a method for starting a permanent magnet synchronous motor, which is used for the permanent magnet synchronous motor described in any of the above embodiments. Figure 4 FIG. 1 is a flow chart of a method for starting a permanent magnet synchronous motor according to an embodiment of the present invention. Figure 4 As shown, a method for starting a permanent magnet synchronous motor includes the following steps:

[0043] Step S1: outputting a pulse signal with a preset duty cycle to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device, and the third lower bridge arm switching device.

[0044] Step S2: During the low level period of the pulse signal, the bus voltage across the bus capacitor is obtained.

[0045] Step S3: Control the startup of the permanent magnet synchronous motor according to the bus voltage.

[0046] In one embodiment of the present invention, Figure 5 As shown, controlling the startup of the permanent magnet synchronous motor according to the bus voltage includes: determining the speed of the permanent magnet synchronous motor according to the bus voltage; and controlling the startup of the permanent magnet synchronous motor when it is determined that the speed of the permanent magnet synchronous motor is zero.

[0047] In one embodiment of the present invention, a change in the increase amplitude of the bus voltage is obtained; when the increase amplitude of the bus voltage decreases to zero, it is determined that the speed of the permanent magnet synchronous motor is zero.

[0048] In one embodiment of the present invention, the increase amplitude of the bus voltage is proportional to the rotation speed of the permanent magnet synchronous motor.

[0049] In one embodiment of the present invention, Figure 6 As shown, the speed of the permanent magnet synchronous motor is determined according to the bus voltage, including: establishing a data table, wherein the data table is used to record the mapping relationship between the bus voltage and the speed of the permanent magnet synchronous motor; the bus voltage is input into the data table to query and obtain the corresponding speed of the permanent magnet synchronous motor.

[0050] In one embodiment of the present invention, Figure 7As shown, establishing a data table includes: receiving multiple sets of mapping relationship data between bus voltage and motor speed; and calibrating the data table according to the multiple sets of mapping relationship data between bus voltage and motor speed.

[0051] In one embodiment of the present invention, the permanent magnet synchronous motor further includes a voltage sampling unit connected in parallel with the bus capacitor. Acquiring the bus voltage across the bus capacitor includes sampling the bus voltage across the bus capacitor via the voltage sampling unit during a low level period of the pulse signal.

[0052] In one embodiment of the present invention, the voltage sampling unit includes a first sampling resistor and a second sampling resistor connected in series. During a low-level period of the pulse signal, sampling the bus voltage across the bus capacitor by the voltage sampling unit includes: using the voltage at the connection point of the first sampling resistor and the second sampling resistor as the bus voltage.

[0053] It should be noted that the specific implementation method of the starting method of the permanent magnet synchronous motor in an embodiment of the present invention is similar to the specific implementation method of the control method of the permanent magnet synchronous motor controller in an embodiment of the present invention. Please refer to the description of the method part for details. In order to reduce redundancy, it will not be repeated here.

[0054] According to the starting method of a permanent magnet synchronous motor in an embodiment of the present invention, before the permanent magnet synchronous motor is started, a pulse signal with a preset duty cycle is output to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device and the third lower bridge arm switching device. During the low level period of the pulse signal, the bus voltage across the bus capacitor is obtained, and the starting of the permanent magnet synchronous motor is controlled according to the bus voltage. There is no need to add a back electromotive force detection circuit, and the starting of the permanent magnet synchronous motor can be controlled according to the bus voltage. This has the advantages of low cost, simplicity and convenience.

[0055] A further embodiment of the present invention also discloses an air conditioner, comprising the permanent magnet synchronous motor as described in any of the above embodiments.

[0056] It should be noted that when the air conditioner in the embodiment of the present invention starts the permanent magnet synchronous motor, its specific implementation method is similar to the specific implementation method of the control method of the permanent magnet synchronous motor controller in the embodiment of the present invention. Please refer to the description of the method part for details. In order to reduce redundancy, it will not be repeated here.

[0057] According to the air conditioner of an embodiment of the present invention, before the permanent magnet synchronous motor is started, a pulse signal with a preset duty cycle is output to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device and the third lower bridge arm switching device. During the low level period of the pulse signal, the bus voltage across the bus capacitor is obtained, and the starting of the permanent magnet synchronous motor is controlled according to the bus voltage. There is no need to add a back electromotive force detection circuit, and the starting of the permanent magnet synchronous motor can be controlled according to the bus voltage. This has the advantages of low cost, simplicity and convenience.

[0058] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0059] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A permanent magnet synchronous motor, characterized in that: include: A motor body, a controller, a first bridge arm switching device, a second bridge arm switching device, a third bridge arm switching device and a bus capacitor, wherein the first bridge arm switching device, the second bridge arm switching device, the third bridge arm switching device and the bus capacitor are connected in parallel with each other, and a three-phase motor winding is provided in the motor body; The first bridge arm switching device includes a first upper bridge arm switching device and a first lower bridge arm switching device, the second bridge arm switching device includes a second upper bridge arm switching device and a second lower bridge arm switching device, and the third bridge arm switching device includes a third upper bridge arm switching device and a third lower bridge arm switching device; A diode is connected in reverse parallel to each of the first upper bridge arm switching device, the first lower bridge arm switching device, the second upper bridge arm switching device, the second lower bridge arm switching device, the third upper bridge arm switching device, and the third lower bridge arm switching device; The connection point between the first upper bridge arm switching device and the first lower bridge arm switching device, the connection point between the second upper bridge arm switching device and the second lower bridge arm switching device, and the connection point between the third upper bridge arm switching device and the third lower bridge arm switching device are respectively connected to one end of the three-phase motor winding of the permanent magnet synchronous motor; The controller is configured to: output a pulse signal with a preset duty cycle to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device, and the third lower bridge arm switching device; obtain a bus voltage across the bus capacitor during a low level period of the pulse signal; and control the start-up of the permanent magnet synchronous motor according to the bus voltage; The controller is further configured to: obtain a change in the increase amplitude of the bus voltage; when the increase amplitude of the bus voltage decreases to zero, determine that the speed of the permanent magnet synchronous motor is zero; determine the speed of the permanent magnet synchronous motor based on the bus voltage; and when it is determined that the speed of the permanent magnet synchronous motor is zero, control the permanent magnet synchronous motor to start.

2. The permanent magnet synchronous motor according to claim 1, characterized in that: The increase amplitude of the bus voltage is proportional to the rotation speed of the permanent magnet synchronous motor.

3. The permanent magnet synchronous motor according to claim 1, characterized in that: The controller is specifically configured to: Establishing a data table, wherein the data table is used to record a mapping relationship between the bus voltage and the speed of the permanent magnet synchronous motor; The bus voltage is input into the data table to query and obtain the corresponding speed of the permanent magnet synchronous motor.

4. The permanent magnet synchronous motor according to claim 3, characterized in that: The controller is specifically configured to: Receive multiple sets of mapping relationship data between bus voltage and motor speed; The data table is obtained by calibrating multiple sets of mapping relationship data between the bus voltage and the motor speed.

5. The permanent magnet synchronous motor according to claim 1, characterized in that: Also includes: A voltage sampling unit is connected in parallel with the bus capacitor, and the controller is specifically configured as follows: During the low level period of the pulse signal, the bus voltage across the bus capacitor is sampled by the voltage sampling unit.

6. The permanent magnet synchronous motor according to claim 5, characterized in that: The voltage sampling unit includes a first sampling resistor and a second sampling resistor connected in series, and the controller is specifically configured to use a voltage at a connection point between the first sampling resistor and the second sampling resistor as the bus voltage.

7. A method for starting a permanent magnet synchronous motor, characterized in that: include: Outputting a pulse signal with a preset duty cycle to at least two of the first lower bridge arm switching device, the second lower bridge arm switching device, and the third lower bridge arm switching device; During the low level period of the pulse signal, obtaining the change in the increase amplitude of the bus voltage at both ends of the bus capacitor; when the increase amplitude of the bus voltage decreases to zero, determining that the speed of the permanent magnet synchronous motor is zero; When the rotation speed of the permanent magnet synchronous motor is zero, the permanent magnet synchronous motor is controlled to start.

8. An air conditioner, characterized in that: It comprises the permanent magnet synchronous motor as described in any one of claims 1 to 6.

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