EP4681319A1

EP4681319A1 - Drive system and method for induction motor

Info

Publication number: EP4681319A1
Application number: EP23712823.6A
Authority: EP
Inventors: Xiaobo Yang; Xing Huang; Minzhong YANG
Original assignee: Hitachi Energy Ltd
Current assignee: Hitachi Energy Ltd
Priority date: 2023-03-15
Filing date: 2023-03-15
Publication date: 2026-01-21
Also published as: CN120898363A; WO2024188461A1

Abstract

A drive system (10) for an induction motor (200) is provided. The drive system (10) includes a drive unit (12) coupled to the induction motor (200), and a control unit (11). The control unit (11) is configured to control the drive unit (12) to provide a first magnetizing current to the induction motor (200) in response to a trigger signal such that the drive unit (12) is operated for magnetization of the induction motor (200) during a first time period. The control unit (11) is further configured to control the drive unit (12) to provide a torque current to the induction motor (200) such that the drive unit (12) is operated for acceleration of the induction motor (200) during a second time period after the first time period.

Description

DRIVE SYSTEM AND METHOD FOR INDUCTION MOTOR

TECHNICAL FILED

[0001] The disclosure relates to the technical field of drive control of an induction motor during a start-up process of the induction motor.

BACKGROUND

[0002] An induction motor is a motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. Induction motors are more robust, more reliable, less expensive and more efficient than other types of motors. However, in the prior art, there is still problems regarding induction motors. For example, during a start-up process of an induction motor, the induction motors cannot be accelerated fast enough. This problem prevents the induction motor from being used in the scenario where starting the induction motor with a high acceleration is expected. One solution to overcome the above prior art problem is to improve the control of the induction motor, but due to the complex mathematical model and the nonlinear operation mode of devices of induction motor, the improvement of such control of induction motor becomes complicated.

SUMMARY

[0003] The disclosure provides methods and systems capable of rapidly increasing the rotational speed of an induction motor during a start-up process of the induction motor.

[0004] According to an embodiment of the disclosure, a drive system for an induction motor is provided. The drive system includes a drive unit coupled to the induction motor and a control unit. The control unit is configured to control the drive unit provide a first magnetizing current to the induction motor in response to a trigger signal such that the drive unit is operated for magnetization of the induction motor during a first time period. The control unit is further configured to control the drive unit to provide a torque current to the induction motor such that the drive unit is operated for acceleration of the induction motor during a second time period after the first time period.

[0005] According to another embodiment of the disclosure, a control system for an induction motor is provide. The control system includes a drive system and a central controller. The drive system includes a drive unit coupled to the induction motor and a control unit for controlling the drive unit, and a central controller in communication with the drive system. The central controller is configured to generate a trigger signal when a trigger event happens. The control unit is configured to control the drive unit to provide a first magnetizing current to the induction motor in response to the trigger signal such that the drive unit is operated for magnetization of the induction motor during a first time period. The control unit is further configured to control the drive unit to provide a torque current to the induction motor such that the drive unit is operated for acceleration of the induction motor during a second time period after the first time period.

[0006] According to yet another embodiment of the disclosure, a control method for an induction motor is provided. The method includes the steps of receiving a trigger signal; controlling a drive unit coupled with the induction motor to provide a first magnetizing current to the induction motor in response to the trigger signal such that the drive unit is operated for magnetization of the induction motor during a first time period; and controlling the drive unit to provide a torque current to the induction motor such that the drive unit is operated for acceleration of the induction motor during a second time period after the first time period.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The disclosed aspects will hereinafter be described in connection with the appended drawings that are provided to illustrate but not to limit the scope of the disclosure.

[0008] Figure l is a block diagram showing a drive system for an induction motor according to an embodiment of the disclosure.

[0009] Figure 2 shows an example of the drive system illustrated in Figure 1.

[0010] Figure 3 is a block diagram showing a drive unit of the drive system illustrated in Figure 1.

[0011] Figures 4A-4C show vector control performed by the drive unit illustrated in Figure 3.

[0012] Figure 5 shows an example of the drive unit illustrated in Figure 3.

[0013] Figure 6 shows another example of the drive system illustrated in Figure 1.

[0014] Figure 7 is a block diagram showing a control system for an induction motor according to an embodiment of the disclosure.

[0015] Figure 8 is a flowchart of a drive method for an induction motor according to an embodiment of the disclosure.

[0016] Figures 9A-9E show time-dependent changes in a magnetizing current, a torque current, magnetic flux, and a torque of the induction motor during a start-up process of the induction motor using the drive method illustrated in Figure 8.

[0017] Figure 10 is a flowchart of a drive method for an induction motor according to another embodiment of the disclosure.

[0018] Figures 11 A-l IE show time-dependent changes in a magnetizing current, a torque current, magnetic flux, and a torque of the induction motor during a start-up process of the induction motor using the drive method illustrated in Figure 10.

[0019] Figure 12 is a flowchart of a drive method for an induction motor according to yet another embodiment of the disclosure.

[0020] Figure 13A-13E show time-dependent changes in a magnetizing current, a torque current, magnetic flux, and a torque of the induction motor during a start-up process of the induction motor using the drive method illustrated in Figure 12.

[0021] Figure 14 is a flowchart of a drive method for an induction motor according to yet another embodiment of the disclosure.

[0022] Figures 15A-15C show an exemplary application scenario of a circuit breaker.

[0023] Figures 16A and 16B show simulation results of the proposed systems and methods during the magnetization process.

[0024] Figures 17 and 18 show simulation results of the proposed systems and methods during the acceleration process.

DETAILED DESCRIPTION

Overview

[0025] The inventors have found that the reason why an induction motor cannot achieve a sufficiently high acceleration during a start-up process is that a part of the drive capability of a drive unit for driving the induction motor is used for magnetization of the induction motor. Moreover, the magnetization needs to spend additional time.

[0026] In this regard, an embodiment of the disclosure provides a drive control solution for an induction motor, which independently controls the magnetization process and the acceleration process of the induction motor during the start-up process, so that the induction motor can obtain a higher acceleration during the start-up process. In this way, the induction motor can achieve a predetermined rotational speed, a predetermined rotational angle or a predetermined torque within a relatively shorter time period during the start-up process, which provides a beneficial effect to many industrial applications. For example, in a circuit breaker application where the circuit breaker is driven by the induction motor using the above-mentioned motor-drive control solution, the speed at the instant of contact separating is increased, which contributes to better arc extinguish during the fault current breaking. [0027] According to an embodiment of the disclosure, all or most of the drive capability of the drive unit is first used for the magnetization of the induction motor, and then all or most of the drive capability of the drive unit is used for the acceleration of the induction motor. Compared to a prior art solution that performs the magnetization and acceleration simultaneously during a start-up process, the induction motor can achieve a significantly higher acceleration during the start-up process by means of such independent control of the magnetization and acceleration.

[0028] According to an embodiment of the disclosure, the magnetization of the induction motor is performed before the acceleration of the induction motor, i.e., the so-called "early magnetization" solution. The magnetization is activated based on a trigger signal that can be implemented as different kinds of signals in different application scenarios. For example, the trigger signal is generated on a fault condition and causes the drive to power an opening or closing operation a circuit breaker, i.e. fault signal is used as a trigger in the circuit breaker application.

[0029] According to an embodiment of the disclosure, by providing the maximum driving current of the drive unit that can cause an overload operation state of the induction motor, the time period of the acceleration can be further reduced.

[0030] According to an embodiment of the disclosure, by adjusting a drive current and/or drive voltage of the drive unit, a magnetization time period (e.g., a first time period) and an acceleration time period (e.g., a second time period) can be controlled to meet customized requirements in different application scenarios.

Example systems

[0031] Figure 1 shows a drive system for an induction motor according to an embodiment of the disclosure. As shown in Figure 1, the drive system 10 includes a control unit 11 and a drive unit 12. The drive unit 12 includes a converter 122 and a converter controller 121. The control unit 11 receives a trigger signal (TS) and generates a control signal (CS) in response to the trigger signal. Then, the control unit 11 sends the control signal to the converter controller 121 and the converter controller 121 generates a drive control signal (e.g., a PWM signal) in response to the control signal. Then, the converter controller 121 sends the drive control signal to the converter 122 such that the converter provides a driving current (e.g., IABC) to the induction motor 200.

[0032] The control unit 11 can be embodied in hardware, software, a combination of hardware and software, firmware or microcode. Similarly, the converter controller 121 can be embodied in hardware, software, a combination of hardware and software, firmware or microcode. It is noted that although the control unit 11 and the converter controller 121 are illustrated as two modules, this does mean to limit their physical positions. In an example, as shown in Figure 2, the control unit 11 and the converter controller 121 can be provided in the same chip or circuit module. In another example, the control unit 11 and the converter controller 121 can be provided in different chips or circuits. In yet another example, one or both of control unit 11 and the converter controller 121 can be further functionally divided into sub-modules and one and more submodules can be provided as hardware or/and software modules integrated in a drive unit or provided separately to be operated together with a drive unit.

[0033] Figure 3 shows an example of a drive unit 12, and the operation of the induction motor and example drive unit are explained with help of Figure 3. In the example shown in Figure 3, the converter controller 121 includes a magnetizing current module 1211, a torque current module 1212, and a motor model 1213 configured in the converter controller 121.

[0034] The motor model 1213 includes a dynamic mathematical model of the induction motor 200. The dynamic mathematical model is able to calculate the magnetizing current IM and the torque current IT based on the motor stator current IABC which is input to the motor model 1213. The magnetic flux (e.g., rotor flux) in the induction motor 200 can be calculated based on the magnetizing current IT. By keeping the amplitude of the magnetic flux at a fixed value, the torque of the induction motor 200 can be determined based on the torque current IT because there is a linear relationship between the torque and the torque current. [0035] In an example, an input to the motor model 1213 may also include the one or more of the following parameters that can characterize the current state of the induction motor 200: a temperature parameter (e.g., the temperature of a motor housing of the induction motor 200 or the temperature of a surface of a semiconductor device disposed in the motor housing), a noise parameter (e.g., the noise emitted by the induction motor 200 when it is running), a vibration parameter (e.g., the vibration displacement, vibration velocity and vibration acceleration of a component disposed in the motor housing). The above mentioned parameters input to the motor model 1213 can improve the accuracy of the calculation by the motor model 1213. In an example, the motor model 1213 can be implemented by mean of using a flux observer module.

[0036] The magnetizing current module 1211 can control the magnetization process by means of an open-loop or closed-loop current loop. For example, the magnetizing current module 1211 receives a reference magnetizing current Iref M, and determines the magnetizing current IM by using the open-loop or closed-loop current loop with the reference magnetizing current Iref M as set point (a control target).

[0037] The reference magnetizing current Iref M is predetermined. For example, the reference magnetizing current Iref M is predetermined based on the maximum driving current that the converter 122 can provide. In this way, the maximum drive capability of the converter 122 can be used for the magnetization of the induction motor 200. The reference magnetizing current Iref M can be pre-stored in the magnetizing current module 1211.

[0038] The torque current module 1212 can control the acceleration process by means of an open-loop or closed-loop current loop. The control of the acceleration process can be embodied in multiple control modes including a speed control mode aiming at the induction motor reaching a predetermined rotational speed within a predetermined time period, a displacement control mode aiming at the induction motor 200 achieving a predetermined rotation angle within the predetermined time period, and a torque control mode aiming at the induction motor 200 achieving a predetermined torque within the predetermined time period. [0039] These exemplary three control modes can be applied to different application scenarios. For example, the speed control mode can be applied to an application scenario of an electric vehicle, which requires that the starting speed of the electric vehicle reaches a predetermined vehicle speed within the predetermined time period. The displacement control mode can be applied to an application scenario of a circuit breaker, which requires contacts of the circuit breaker to move a predetermined distance within the predetermined time period. The torque control mode can be applied to an application scenario of an industrial automation control system, which require precise torque force control of a rotatable mechanical part. For example, when a torque wrench is used during the installation of a special designed device in an industrial application, it is necessary to insure a predetermined torque is reached by using this wrench.

[0040] In the speed control mode, the torque current module 1212 in a drive unit receives a reference rotational speed w ref of the induction motor 200 and determines the torque current in this control mode based on the reference rotational speed and computations performed using the motor model 1213. Similarly, in the displacement control mode, the torque current module 1212 receives a reference rotation angle theta ref of the induction motor 200 (it is understood that the rotational angle of the induction motor 200 corresponds to a displacement of a load coupled to and driven by the induction motor 200), and determines the torque current in this control mode based on the reference rotational angle and computations performed using the motor model 1213. In the torque control mode, the torque current module 1212 receives a reference torque Te ref of the induction motor 200 and determines the torque current in this control mode based on the reference torque and computations performed using the motor model 1213.

[0041] The reference rotational speed, the reference rotational angle and the reference torque are predetermined in an embodiment. For example, each of these references is predetermined based on the maximum driving current that the converter 122 can provide. In this way, the maximum drive capability of the convert 122 can be used for the acceleration of the induction motor 200. These references can be seen as set points for the torque current module 1212 and are pre-stored in the torque current module 1212.

[0042] In an example, the converter controller 121 adopts vector control (e.g., FOC: field oriented control) to implement decoupled control of the magnetization process and the acceleration process. Figure 4A shows an example of the vector control. As shown in Figure 4A, the stator AC current IABC (i.e., a driving current) of the induction motor 200 in a three-phase coordinate system is equivalent to the magnetization component IM and the torque component IT in an M-T coordinate system. Because the rotor flux linkage is only generated by the magnetization component IM and is not related to the torque component IT at all, and the magnetization component IM and torque component IT are perpendicular to each other in the M-T coordinate system, the two components can be decoupled. Therefore, independent control of the magnetization process and the acceleration process can be achieved.

[0043] Such vector control enables the control of the induction motor 200 which is an AC machine can obtain advantages of the control of a DC machine, and thus accurate transient control as well as good dynamic performance both in terms of response time and power conversion are achieved.

[0044] According to an example of the disclosure, by independently controlling the magnetization process and the acceleration process of the induction motor 200 during a start-up process, the induction motor is first magnetized with all the drive capability or most of the drive capability of the converter 122, so that the magnetic field can be created quickly with such a large magnetizing current. Then, the acceleration process of the induction motor 200 is activated with all the drive capability or most of the drive capability of the converter 122, so that the induction motor 200 can be accelerated to a high rotational speed quickly.

[0045] Figure 5 shows an example of the converter controller 121.

[0046] Referring to Figure 5, the magnetizing current module 1121 includes multiple PI controllers. According to the PI controllers, the reference magnetizing current is used as a given value and the magnetizing current IM calculated by the motor model 1213 is used as an actual value to form a control deviation, thereby independently controlling the magnetization process. Then, a PWM signal is generated by a pulse generator (PWM) and output to the converter 122, so that the converter provides a driving current to the induction motor 200 according to the PWM signal. It is noted that, during the magnetization process, the magnetization component IM of the driving current should be much larger than the torque component IT (see Figure 4B).

[0047] The torque current module 1212 includes multiple PI controllers to form multiple control loops. These control loops take the reference rotational angle, the reference rotational speed, and the reference torque as given values and the measured rotational angle of the induction motor 200, the measured rotational speed of the induction motor 200, and the torque current calculated by the motor model 1213 as actual values to form control deviations, thereby independently controlling the acceleration process. Then, a PWM signal is generated by the pulse generator (PWM) and output to the converter 122, so that the converter provides a driving current to the induction motor 200 according to the PWM signal. It is noted that, during the acceleration process, the torque component IT should be much larger than the magnetization component IM (see Figure 4C).

[0048] Figure 6 shows another example of the drive system 10. In this example, a current sensor 302 (representing also electronic devices such Intelligent Electronic Device or Relays using a current sensor) is provided to detect whether there is an overcurrent fault in a power system 304 of the Load 300. For example, the current sensor 302 is arranged in a power supply circuit where the power system 304 supplies power to the load 300. Once the current sensor 302 detects that an overcurrent fault occurs in the power system 304, the current sensor 302 generates a fault signal and sends the fault signal to the control unit 11. The fault signal is used as the trigger signal for triggering the magnetization in this example and thereby operation of a circuit breaker for protecting line/equipment in the power system from the overcurrent situation.

[0049] According to examples of the disclosure, the drive system 10 can decouple the control of the magnetization process and the acceleration process, and thus can control the two processes independently.

[0050] Figure 7 shows a control system for an induction motor according to an embodiment of the disclosure. In this embodiment, a control system 100 is provided and the control system includes the above mentioned drive system 10 and a central controller 20 that is configured to coordinate with at least one another distributed controller along with the control unit 11 of the drive system 10 in a control system environment deployed in a power system, industrial automation system, electrical vehicle system or other applications using an induction motor-drive system.

[0051] The central controller 20 is in communication with the control unit 11. In an example, the central controller 20 could be a high-level controller, whereas the control unit 11 is a low-level controller. The central controller 20 communicates with devices, control nodes, power grid and loads in environment of the control system, and receives information regarding status and/or measurement of the devices, control nodes, power grid and loads. The central controller 20 can generate a trigger signal if the received information indicates a pre-defined trigger event happens, and send the trigger signal to the control unit 11, thereby triggering the magnetization process of the induction motor 200.

[0052] The central controller 20 can be communicatively coupled with the control unit 11 via a wired communication link. The central controller 20 can also be communicatively coupled with the control unit 11 via a wireless communication link, which is especially suitable for smart industrial applications with loT sensors.

[0053] In an example of the disclosure, an output shaft of the induction motor 200 can be directly coupled with a load 300 to drive the load to move or rotate. The output shaft of the induction motor can also be coupled to the load via a transmission system (e.g., a gear, a gearbox, etc.) to drive the load to move or rotate through the transmission system. Example methods

[0054] Example methods are now described. Such methods may be performed using the systems described above. It should be understood that the operations involved in the following methods need not be performed in the precise order described. Rather, various operations may be handled in a different order or simultaneously, and operations may be added or omitted.

Example 1 : “early magnetization” solution

[0055] Figure 8 is a flowchart of a drive method for an induction motor according to an embodiment of the disclosure.

[0056] In block 802, the control unit 11 receives a trigger signal.

[0057] In an example of a circuit breaker application (i.e., the load 300 driven by the induction motor 200 is a circuit breaker), a relay or an IED (Intelligent Electronic Device) associated with the circuit breaker generates an order for the opening or closing operation of the circuit breaker and the order is used as the trigger signal. In another example of the circuit breaker application, the central controller 20 generates the trigger signal when a trigger event of an opening or closing operation of the circuit breaker happens. That is to say, the trigger signal is generated once the opening or closing operation of the circuit breaker is triggered. For example, the central controller 20 is communicatively connected to the power grid, and determines that the circuit breaker needs to be operated to turn-on or turn-off based on state information of the grid side. Then, the central controller 20 generates the trigger signal and transmits the trigger signal to the control unit 11.

[0058] In an example of a circuit breaker application (e.g., the load 300 driven by the induction motor 200 is a transmission system of an electric vehicle), an instruction signal instructing the electric vehicle to start can be used as the trigger signal

[0059] In an example of an industrial automation application (e.g., the load 300 driven by the induction motor 200 is a movable part in an industrial automation production line), an instruction signal instructing a movable part to start moving can be used as the trigger signal.

[0060] In block 804, the control unit 11 outputs a control signal to the drive unit 12 in response to the trigger signal.

[0061] In block 806, under the control of the control signal, the drive unit 12 performs the above mentioned independent control of the magnetization process, so that a first magnetizing current is provided to the induction motor 200 during a first time period Atl . In the first time period, the first magnetizing current should be a larger component of the driving current IABC than the torque component, and thus the magnetic field can be created in the induction motor 200 very quickly.

[0062] The maximum value of the first magnetizing current is equal to the smaller one of the maximum magnetizing current that will lead to flux saturation of the induction motor 200 and a maximum drive current that the converter 122 can provide. In an example, for the induction motor 200, there is a maximum magnetizing current Im maxl that will lead to flux saturation. For the converter 122, there is a maximum converter output current Im_max2. The maximum value of the first magnetizing current Im max = minimum (Im maxl, Im_max2).

[0063] It is noted that the value of the first magnetizing current can be its maximum value, and can also be a value slightly smaller than the maximum value.

[0064] In an example, the converter controller 121 can determine the first time period based on a pre-defined level of motor flux indicating that the magnetic field has been created in the induction motor 200. For example, the pre-defined level of motor flux is stored in the converter controller 121. The actual level of motor flux can be obtained by integrating the first magnetizing current with respect to time, and thus whether the pre-defined level of motor flux is reached can be determined by comparing the actual level of motor flux with the pre-defined level of motor flux.

[0065] In block 808, the drive unit 12 performs the above mentioned independent control of the acceleration process, so that a torque current is provided to the induction motor 200 during a second time period At2 after the first time period Atl . In the second time period, the torque current should be a much larger component of the driving current IABC than the magnetizing component, and thus the induction motor 200 is accelerated to a high speed very quickly.

[0066] The maximum value of the torque current is equal to a maximum drive current that the converter 122 can provide. It is noted that the value of the torque can be its maximum value, and can also be a value slightly smaller than the maximum value.

[0067] In the second time period, a control target for the induction motor 200 such as the predetermined rotational speed, the predetermined rotational angle, or the predetermined torque is realized. Taking the circuit breaker application as an example, within the second time period, contacts of the circuit breaker need to move a predetermined displacement and stop after moving the predetermined displacement. Correspondingly, the induction motor 200 rotates through an angle corresponding to the predetermined displacement. In the whole process, the induction motor 200 first accelerates and then decelerates, and finally stops.

[0068] In Example 1, there is no time space between the first time period and the second time period. Although it is shown in Figure 1 that the second time period immediately follows the first time period, it is also possible that the second time period overlaps with the first time period. That is to say, “the second time period being after the first time period” should be understood as including the case where the second time overlaps the first time period. In this case, during the overlap period, the induction motor 200 could be magnetized and accelerated simultaneously.

[0069] In Example 1, the acceleration process of the induction motor 200 can be automatically triggered, that is to say, no further trigger signal is needed to trigger the acceleration process. For example, the drive unit 12 automatically triggers the acceleration process when it determines that the magnetic flux reaches the predetermined level or the first time period elapses after the induction motor 200 starts magnetizing.

[0070] In Example 1, during the first time period, the rotational speed of the induction motor 200 can be zero. The rotational speed of the induction motor 200 can also be a very small speed close to zero, for example, within the first period of time, 90% of the drive current is used as the magnetizing current of the and 10% of the drive current is used as the torque current.

[0071] Figures 9A-9E show time-dependent changes in the magnetizing current, torque current, magnetic flux, and torque of the induction motor 200 during the first time period and the second time period according to Example 1.

[0072] Referring to Figure 9A, Atl represents the first time period for the magnetization process, and At2 represents the second time period for the acceleration process. The second time period immediately follows the first time period. The magnetization process of the induction motor 200 is triggered based on the trigger signal TS, and the acceleration process is automatically performed immediately after the magnetization process.

[0073] Referring to Figure 9B, the x-axis represents time, the y-axis represents a magnetizing current, and the curve is a representation of the magnetizing current versus time waveform. In the first time period, the magnitude of the magnetizing current (e.g., a first magnetizing current) is large, for example, as large as the maximum driving current of the converter 122. In the second time period, the magnetizing current (e.g., a second magnetizing current) is small, for example, almost zero. The large magnetizing current (e.g., the first magnetizing current) is used to create the magnetic field in the induction motor 200 and the small magnetizing current (e.g., the second magnetizing current) is used to maintain the magnetic field.

[0074] Referring to Figure 9C, the x-axis represents time, the y-axis represents magnetic flux, and the curve is a representation of the magnetic flux versus time waveform. During the first time period, the magnetic flux gradually increases and reaches a maximum level when the magnetic field is created. Then, this maximum level of the magnetic field is maintained.

[0075] Referring to Figure 9D, the x-axis represents time, the y-axis represents torque current, and the curve is a representation of the torque current versus time waveform. During the first time period, the magnitude of the torque current is small, for example, zero. During the second time period, the magnitude of the torque current gradually increase and reaches a maximum value, for example, the maximum drive current of the converter 122.

[0076] Referring to Figure 9E, the x-axis represents time, the y-axis represents the torque of the induction motor 200, and the curve is a representation of the torque versus time waveform. Since there is a linear correspondence between the torque of the induction motor 200 and the torque current of the induction motor 200, the curve of the torque as shown in Figure 9E and the torque current as shown in Figure 9D have the same shape.

[0077] Example 2: “the earliest magnetization” solution

[0078] Figure 10 is a flowchart of a drive method for an induction motor according to another embodiment of the disclosure.

[0079] In block 1002, the control unit 11 receives a trigger signal.

[0080] In an example of the circuit breaker application, a power-up signal of the circuit breaker is used as the trigger signal. That is to say, once the circuit breaker is energized and starts to operate, the trigger for the magnetization is generated. In another example of the circuit breaker application, the central controller 20 generates the trigger signal when a trigger event of the circuit breaker enters an operation state happens. That is to say, in this “earliest magnetization” example, the magnetization of the induction motor 200 is triggered once the circuit breaker starts operation. For example, the operation state of the circuit breaker can be detected by an operating state sensor coupled with the circuit breaker. The operating state sensor sends the detection result of the circuit breaker starting operation to the central controller 20. Then, the central controller 20 generates the trigger signal and sends the trigger signal to the control unit 11.

[0081] In an example of a circuit breaker application (e.g., the load 300 driven by the induction motor 200 is a transmission system of an electric vehicle), an instruction signal instructing the electric vehicle to wait to start can be used as the trigger signal. [0082] In an example of an industrial automation application (e.g., the load 300 driven by the induction motor 200 is a movable part in an industrial automation production line), an instruction signal indicating that the movable part is about to be actuated to move can be used as the trigger signal.

[0083] In block 1004, the control unit outputs a control signal to the drive unit 12 in response to the trigger signal.

[0084] In block 1006, under the control of the control signal, the drive unit 12 performs the above mentioned independent control of the magnetization process, so that a first magnetizing current is provided to the induction motor 200 during a first time period Atl . In the first time period, the first magnetizing current should be a much larger component of the driving current IABC than the torque current, and thus the magnetic field is created in the induction motor 200 very quickly. It is noted that the above description about the maximum value of the first magnetizing current also applies here.

[0085] In block 1008, the control unit 11 waits for a further trigger signal. That is to say, after the magnetization in the first time period, the acceleration of the induction motor 200 is not performed immediately, but a waiting period is entered to wait for the further trigger signal for triggering the acceleration. In the waiting period, the converter 122 provides a second magnetizing current to the induction motor 200. The second magnetizing current is used for maintaining the magnetic field. The second magnetizing current is much smaller than the first magnetizing current. For example, the magnitude of the second magnetizing current is 3%~30% of that of the first magnetizing current.

[0086] In block 1010, the control unit 11 receives the further trigger signal.

[0087] In an example of the circuit breaker application, a relay or an IED (Intelligent Electronic Device) associated with the circuit breaker generates an order for the opening or closing operation of the circuit breaker and the order is used as the further trigger signal. In another example of the circuit breaker application, the central controller 20 generates the further trigger signal when a trigger event of an opening or closing operation of the circuit breaker happens. That is to say, the further trigger signal is generated once the opening or closing operation of the circuit breaker is triggered. For example, the central controller 20 is communicatively connected to the power grid, and determines that the circuit breaker needs to be operated to turn-on or turn-off based on state information of the grid side. Then, the central controller 20 generates the further trigger signal and transmits the further trigger signal to the control unit 11.

[0088] In an example of a circuit breaker application (e.g., the load 300 driven by the induction motor 200 is a transmission system of an electric vehicle), an instruction signal instructing the electric vehicle to start can be used as the further trigger signal.

[0089] In an example of an industrial automation application (e.g., the load 300 driven by the induction motor 200 is a movable part in an industrial automation production line), an instruction signal instructing a movable part to start moving can be used as the further trigger signal.

[0090] It can be seen that, in this “earliest magnetization” example, the further trigger signal is the trigger signal in the “early magnetization” example. Thus, in this “earliest magnetization” example, the magnetization of the induction motor 200 is performed earlier than in the “early magnetization” example. For example, in the circuit breaker application, according to the “early magnetization” example, the magnetization of the induction motor 200 is activated once an opening or closing operation of the circuit breaker is determined. However, according to the “earliest magnetization” example, the magnetization of the induction motor 200 is activated once the circuit breaker starts to operate, which is earlier than that happens in the “early magnetization” example.

[0091] It is understood that when the waiting time period ends depends on when the further trigger signal is received. During the waiting time period, the induction motor 200 only consumes a small amount of current for maintaining the magnetic field.

[0092] In block 1012, the control unit 11 outputs a further control signal to the 12 drive unit 12 in response to the further trigger signal.

[0093] In block 1014, the drive unit 12 performs the above mentioned independent control of the acceleration process, so that a torque current is provided to the induction motor 200 during a second time period At2 after the first time period Atl . In the second time period, the torque current should be a much larger component of the driving current IABC than the torque component, and thus the induction motor 200 is accelerated to a high speed very quickly. It is noted that the above description about the maximum value of the torque current also applies here.

[0094] In the second time period, a control target for the induction motor 200 such as the predetermined rotational speed, the predetermined rotational angle, or the predetermined torque is realized. Taking the circuit breaker application as an example, within the second time period, contacts of the circuit breaker need to move a predetermined displacement and stop after moving the predetermined displacement. Correspondingly, the induction motor 200 rotates through an angle corresponding to the predetermined displacement. In the whole process, the induction motor 200 first accelerates and then decelerates, and finally stops.

[0095] In Example 2, the waiting time period is provided between the first time period and the second time period to wait for the further trigger signal, and the acceleration process is triggered based on the further trigger signal to actuate the motor according to the motor-drive method

[0096] Figures 11 A-l IE show time-dependent changes in the magnetizing current, torque current, magnetic flux, and torque of the induction motor 200 during the first time period, the waiting period and the second time period according to Example 2.

[0097] Referring to Figure 11 A, Atl represents the first time period for the magnetization process, At_w represents the waiting time period for waiting for the further trigger signal, and At2 represents the second time period for the acceleration process. The waiting time period is between the first time period and the second time period. The magnetization process of the motor is triggered based on the trigger signal, and the acceleration process is triggered based on the further trigger signal.

[0098] Referring to Figure 1 IB, the x-axis represents time, the y-axis represents a magnetizing current, and the curve is a representation of the magnetizing current versus time waveform. In the first time period, the magnitude of the magnetizing current (e.g., a first magnetizing current) is large, for example, as large as the maximum driving current of the converter 122. In the waiting time period and the second time period, the magnetizing current (e.g., a second magnetizing current) is small, for example, almost zero. The large magnetizing current (e.g., the first magnetizing current) is used to create the magnetic field in the induction motor 200 and the small magnetizing current (e.g., the second magnetizing current) is used to maintain the magnetic field.

[0099] Referring to Figure 11C, the x-axis represents time, the y-axis represents magnetic flux, and the curve is a representation of the magnetic flux versus time waveform. During the first time period, the magnetic flux gradually increases and reaches a maximum level when the magnetic field is created. Then, this maximum level of the magnetic field is maintained.

[00100] Referring to Figure 1 ID, the x-axis represents time, the y-axis represents torque current, and the curve is a representation of the torque current versus time waveform. During the first time period and the waiting time period, the magnitude of the torque current is small, for example, zero. During the second time period, the magnitude of the torque current gradually increase and reaches a maximum value, for example, the maximum drive current of the converter 122.

[00101] Referring to Figure 1 IE, the x-axis represents time, the y-axis represents the torque of the induction motor 200, and the curve is a representation of the torque versus time waveform. Since there is a linear correspondence between the torque of the induction motor 200 and the torque current of the induction motor 200, the curve of the torque as shown in Figure 1 IE and the torque current as shown in Figure 1 ID have the same shape.

Example 3: “Second earliest magnetization” solution

[00102] Figure 12 is a flowchart of a drive method for an induction motor according to yet another embodiment of the disclosure.

[00103] In block 1202, the control unit 11 receives a trigger signal. [00104] With reference to Figure 6, in an example where the load 300 driven by the induction motor 200 is a circuit breaker, the trigger signal is generated when a fault (e.g., an overcurrent fault) happens in the power system 304 coupled with the circuit breaker. That is to say, in this “second earliest magnetization” example, the magnetization of the induction motor 200 is triggered once an overcurrent fault of the power system is detected by current sensor 302. The current senor 302 send an overcurrent fault signal to the control unit 11 once it detects the overcurrent fault. In this example, the overcurrent fault signal is used as the trigger signal.

[00105] In a prior art solution, the overcurrent fault signal will be provided to the central controller 20, and then the central controller 20 takes time to calculate and judge whether to an opening or closing operation of the circuit breaker should be triggered. Such calculation and judgment take time. The solution of block 902 of the disclosure can solve this issue. According to block 902, once the failure is detected, the magnetization of the induction motor 200 is performed immediately, and then a standby state is entered (i.e., the waiting time period is entered) for waiting for the further trigger signal. That is to say, the induction motor 200 can be magnetized before the decision of whether to perform an opening or closing operation of the circuit breaker is made. In this way, once the decision of the opening or closing operation of the circuit breaker is made by the central controller 20, the induction motor 200 can be accelerated with the maximum driving current, without spending time and a large magnetization component for magnetization.

[00106] In block 1204, the control unit 11 outputs a control signal to the drive unit 12 in response to the trigger signal.

[00107] In block 1206, under the control of the control signal, the drive unit 12 performs the above mentioned independent control of the magnetization process, so that a first magnetizing current is provided to the induction motor 200 during a first time period Atl . In the first time period, the first magnetizing current should be a much larger component of the driving current IABC than the torque component, and thus the magnetic field is created in the induction motor 200 very quickly. It is noted that the above description about the maximum value of the first magnetizing current also applies here.

[00108] In block 1208, the control unit 11 waits for a further trigger signal. That is to say, after the magnetization in the first time period, the acceleration of the induction motor 200 is not performed immediately, but a waiting period is entered to wait for the further trigger signal for triggering the acceleration. In the waiting period, the converter 122 provides a second magnetizing current the induction motor 200. The second magnetizing current is used for maintaining the magnetic field. The second magnetizing current is much smaller than the first magnetizing current. For example, the magnitude of the second magnetizing current is 3%~30% of that of the first magnetizing current.

[00109] In block 1210, the control unit 11 receives the further trigger signal.

[00110] In an example of the circuit breaker application, a relay or an IED (Intelligent Electronic Device) associated with the circuit breaker generates an order for the opening or closing operation of the circuit breaker and the order is used as the trigger signal. In another example of the circuit breaker application, the central controller 20 generates the further trigger signal when a trigger event of an opening or closing operation of the circuit breaker happens. That is to say, the further trigger signal is generated once the opening or closing operation of the circuit breaker is triggered. As the induction motor has been previously magnetized, the acceleration of the induction motor can be performed once the further trigger signal is received and the acceleration can be done without spending time and a large magnetizing current. In this way, the induction motor can be accelerated very quickly.

[00111] It is understood that when the waiting time period ends depends on when the further trigger signal is received. During the waiting time period, the induction motor 200 only consumes a small amount of current for maintaining the magnetic field.

[00112] In block 1212, the control unit 11 outputs a further control signal to the 12 drive unit in response to the further trigger signal.

[00113] In block 1214, the drive unit 12 performs the above mentioned independent control of the acceleration process, so that a torque current is provided to the induction motor 200 during a second time period At2 after the first time period Atl . In the second time period, the torque current should be a much larger component of the driving current IABC and thus the induction motor 200 is accelerated to a high speed very quickly. It is noted that the above description about the maximum value of the torque current also applies here.

[00114] In the second time period, a control target for the induction motor 200 such as the predetermined rotational speed, the predetermined rotational angle, or the predetermined torque is realized. Taking the circuit breaker application as an example, within the second time period, contacts of the circuit breaker need to move a predetermined displacement and stop after moving the predetermined displacement. Correspondingly, the induction motor 200 rotates through an angle corresponding to the predetermined displacement. In the whole process, the induction motor 200 first accelerates and then decelerates, and finally stops.

[00115] It is noted that the trigger of the magnetization in Example 2 is earlier than that in Example 3. For example, in Example 3, the magnetization of the motor is triggered once a fault of a circuit breaker is detected, while the magnetization of the motor is triggered once the circuit breaker starts to operate in Example 2.

[00116] Figures 13A-13E show time-dependent changes in the magnetizing current, torque current, magnetic flux, and torque of the induction motor 200 during the first time period, the waiting period and the second time period according to Example 2.

[00117] Referring to Figure 13 A, Atl represents the first time period for the magnetization process, At_w represents the waiting time period for waiting for the further trigger signal, and At2 represents the second time period for the acceleration process. The waiting time period is between the first time period and the second time period. The magnetization process of the motor is triggered based on the trigger signal, and the acceleration process is triggered based on the further trigger signal.

[00118] Referring to Figure 13B, the x-axis represents time, the y-axis represents a magnetizing current, and the curve is a representation of the magnetizing current versus time waveform. In the first time period, the magnitude of the magnetizing current (e.g., a first magnetizing current) is large, for example, as large as the maximum driving current of the converter 122. In the waiting time period and the second time period, the magnetizing current (e.g., a second magnetizing current) is small, for example, almost zero. The large magnetizing current (e.g., the first magnetizing current) is used to create the magnetic field in the induction motor 200 and the small magnetizing current (e.g., the second magnetizing current) is used to maintain the magnetic field.

[00119] Referring to Figure 13C, the x-axis represents time, the y-axis represents magnetic flux, and the curve is a representation of the magnetic flux versus time waveform. During the first time period, the magnetic flux gradually increases and reaches a maximum level when the magnetic field is created. Then, this maximum level of the magnetic field is maintained.

[00120] Referring to Figure 13D, the x-axis represents time, the y-axis represents torque current, and the curve is a representation of the torque current versus time waveform. During the first time period and the waiting time period, the magnitude of the torque current is small, for example, zero. During the second time period, the magnitude of the torque current gradually increase and reaches a maximum value, for example, the maximum drive current of the converter 122.

[00121] Referring to Figure 13E, the x-axis represents time, the y-axis represents the torque of the induction motor 200, and the curve is a representation of the torque versus time waveform. Since there is a linear correspondence between the torque of the induction motor 200 and the torque current of the induction motor 200, the curve of the torque as shown in Figure 13E and the torque current as shown in Figure 13D have the same shape.

Example 4: overload solution

[00122] According to an example of the disclosure, the induction motor 200 can be powered by different maximum driving currents in the case that the converter 122 has different rated power levels. For example, during the acceleration process, the maximum value of the torque current can be increased by providing a converter having a higher rated power level. During the magnetization process, the maximum value of the magnetizing current can also be increased by providing a converter having a higher rated power level if the maximum magnetizing current that will lead to flux saturation is big enough.

[00123] In an example, a converter with an increased rated power level is provided such that the induction motor 200 can be operated under an overload state. In this case, the torque of the induction motor 200 can be increased, and thus the acceleration of the motor during a start-up process is further increased.

[00124] Typically, a converter having the maximum drive capability (e.g., the rated power level) that matches with the rated power of the induction motor 200 will be selected as a driving deice for the induction motor 200. In this case, the converter will not be able to drive the induction motor 200 so that the induction motor 200 runs under an overload state. Therefore, for the purpose of the overload operation of the induction motor 200, it is necessary to provide a converter having an increased rated power level. This is the so called “oversize” (i.e., expanding the driving capability of the converter) solution.

[00125] Example 4 is particularly suitable for a circuit breaker application, because the circuit breaker does not perform opening or closing operations frequently in the entire life cycle. For example, only dozens of opening and closing operations might occur in the entire life cycle of the circuit breaker. This means that the number of times the induction motor 200 is operated in the overload state is only a few dozen times. In addition, the operation time for the opening or closing of the circuit breaker is usually very short, for example, only tens of milliseconds, which means that the induction motor 200 only needs to run in the overload state within these tens of seconds. From this point of view, Example 4 is also particularly suitable for the circuit breaker application.

[00126] Figure 14 is a flowchart of a drive method for an induction motor according to yet another example of the disclosure.

[00127] In block 1402, a maximum overload current for the induction motor 200 is determined. In general, the maximum overload current is determined by taking into account the lifetime and the design margin of the induction motor 200.

[00128] In an example, the maximum overload current of the induction motor 200 is determined based on the mechanical stress of an output shaft of the induction motor 200. That is to say, when the induction motor 200 is running at the maximum overload current, the output shaft of the induction motor 200 will not be damaged such as broken or deformed.

[00129] In block 1104, a rated power level of the converter 122 is determined based on the maximum overload current, so that the converter 122 having the determined rated power level can provide the maximum overcurrent to the induction motor 200. In this way, the acceleration of the induction motor 200 is maximized.

[00130] In block 1106, a converter having the determined rated power level is provided.

[00131] It is noted that Example 4 is applicable to the above exemplary systems and methods. For example, Example 4 can be combined with any of Examples 1-3.

Example applications

[00132] As described above, the methods and systems according to examples of the disclosure can be applied to various application scenarios such as an EV application, a circuit breaker application and an industrial automation production line application. In the following, the circuit breaker application is described in detail. The circuit breaker can be a vacuum circuit breaker, and can be also be a high-voltage circuit breaker.

[00133] Figure 15A shows an example of the circuit breaker application, in which an opening or closing operation of the circuit breaker is performed. Figure 15B shows an example of the opening operation of the circuit breaker. Figure 15C shows an example of the closing operation of the circuit breaker.

[00134] With reference to Figure 15 A, according to the above mentioned Example 1, once the drive system 10 receives an opening or closing order as the trigger signal (TS exl), the drive system 10 performs the drive control of the magnetization, and thus the magnetization process is triggered. Then, after the magnetization process, the acceleration process will be performed automatically.

[00135] Continuing with reference to Figure 15 A, according to the above mentioned Example 2, once the operating state sensor 308 detects the circuit breaker starts operating, the operating state sensor 308 sends an operating state signal as the trigger signal (TS_ex2) to the drive system 10. The drive system 10 performs the drive control of the magnetization in response to the operating state signal, and thus the magnetization process is triggered. After the magnetization, the drive system 10 will wait for a further trigger signal to trigger the acceleration process. In this example, the further trigger signal is aforesaid opening or closing order.

[00136] Continuing with reference to Figure 15 A, according to the above mentioned Example 3, once the current sensor 302 detects an overcurrent fault occurs in the power system 304, the current sensor 302 sends a fault signal as the trigger signal (TS_ex3) to the drive system 10. The drive system 10 performs the drive control of the magnetization in response to the fault signal, and thus the magnetization process is triggered. After the magnetization, the drive system 10 will wait for a further trigger signal to trigger the acceleration process. In this example, the further trigger signal is aforesaid opening or closing order.

[00137] In the circuit breaker application, during the start-up process of the induction motor 200, the opening operation as shown in Figure 15B or the closing operation as shown in Figure 15C can be completed very fast because, in the acceleration process, the induction motor 200 can obtain a large torque current and thus achieve a large torque.

[00138] To further illustrate the working of the motor-drive system, simulation results will be described below. Advantages of exemplary systems and methods of the disclosure are illustrated with the simulation results.

[00139] Figure 16A shows a magnetization for the induction motor 200 using a prior art solution where only a small part of the converter output current capability is used for the magnetization. In Figure 16A, the x-axis represents time, the black solid line represents the magnetizing current provided to the induction motor 200 over time, and the grey dotted line represents the flux over time. Figure 16B shows a magnetization for the induction motor 200 using the proposed solution of the disclosure where the full converter output current capability is used for the magnetization. In Figure 16B, the x- axis represents time, the black solid line represents the magnetizing current provided to the induction motor 200 over time, and the grey dotted line represents the flux over time. It can be seen that according to the solution of the present invention, by providing a large magnetizing current, the flux increases significantly faster (see Figure 16B), while according to the prior art solution, the flux increases very slowly due to a small magnetizing current (see Figure 16A). Therefore, the disclosure enables rapid establishment of a magnetic field in the induction motor 200.

[00140] Figure 17 shows, during the acceleration process, a comparison of a torque of the induction motor 200 according to the proposed solution and a torque of the induction motor 200 according to the prior art solution. In Figure 17, the x-axis represents time, the black solid line represents the rotational angle over time according to the proposed solution, and the grey dotted line represents the rotational angle over time according to the prior art solution. It can be seen that, according to the solution of the disclosure, the rotational angle of the induction motor 200 can reach the predetermined value faster, because almost all of the driving current capability can be provided as the torque current without the need of a large magnetizing current for the magnetization.

[00141] Figure 18 shows, during the acceleration process, a comparison of a rotational speed of the induction motor 200 according to the proposed solution and a rotational speed of the induction motor 200 according to the prior art solution. In Figure 18, the x-axis represents time, the black solid line represents the rotational speed over time according to the proposed solution, and the grey dotted line represents the rotational speed over time according to the prior art solution. It can be seen that, according to the solution of the disclosure, the rotational speed of the induction motor 200 can reach the predetermined value faster, because almost all of the driving current capability can be provided as the torque current without the need of a large magnetizing current for the magnetization.

[00142] It is noted that, in Figures 17 and 18, the value of each axis increases along the axis within a range corresponding to the applied scenario. For example, in the case that the simulation of Figures 17 and 18 is implemented in a circuit breaker application, the value of the x-axis of either Figure 17 or 18 increases along the x-axis and is from Os to 0.15s, the value of y-axis of Figure 17 increases along the y-axis and is from 0 degree to 150 degrees, and the value of y-axis of Figure 18 increases along the y-axis and is from Ormp to 1200rmp.

[00143] It is noted that all the operations described above are merely exemplary, and the disclosure is not limited to any operations or sequence orders of these operations, and should cover all other equivalents under the same or similar concepts.

[00144] The described systems and method can be implemented by mean of one or more processors. These processors can be implemented using electronic hardware, computer software, or any combination thereof. Whether these processors are implemented as hardware or software will depend on the specific application and the overall design constraints imposed on the system. By way of example, a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented as a microprocessor, a micro-controller, a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic device (PLD), state machine, gate logic, discrete hardware circuitry, and other suitable processing components configured to perform the various functions described in this disclosure. The functions of a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented as software executed by a microprocessor, a micro-controller, a DSP, or other suitable platforms.

[00145] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein. All structural and functional equivalent transformations to the elements of the various aspects of the disclosure, which are known or to be apparent to those skilled in the art, are intended to be covered by the claims.

Claims

WHAT IS CLAIMED IS:

1. A drive system (10) for an induction motor (200), comprising: a drive unit (12) coupled to the induction motor (200); and a control unit (11) configured to control the drive unit (12) to provide a first magnetizing current to the induction motor (200) in response to a trigger signal such that the drive unit (12) is operated for magnetization of the induction motor (200) during a first time period, the control unit (11) being further configured to control the drive unit (12) to provide a torque current to the induction motor (200) such that the drive unit (12) is operated for acceleration of the induction motor (200) during a second time period after the first time period.

2. The drive system (10) according to claim 1, wherein the control unit (11) is configured to send a control signal to the drive unit in response to the trigger signal; and the drive unit is configured to generate the first magnetizing current based on a reference magnetizing current under the control of the control signal such that a magnetic field is created in the induction motor (200) during the first time period, wherein the first magnetizing current is equal to the smaller one of the maximum magnetizing current that will lead to flux saturation of the induction motor (200) and a maximum drive current that the drive unit (12) can provide.

3. The drive system (10) according to any one of claims 2-3, wherein the control unit (11) is configured to send a further control signal to the drive unit (12) in response to a further trigger signal; and the drive unit (12) is configured to generate the torque current based on one of a reference rotational angle, a reference rotational speed and a reference torque of the induction motor (200) under the control of the further control signal such that the induction motor (200) is operated to achieve the reference rotational angle, the reference rotational speed or the reference torque within the second time period, wherein the torque current is equal to a maximum drive current that the drive unit (12) can provide.

4. The drive system (10) according to any one of claims 1-3, wherein the first magnetizing current causes an overload operation state of the induction motor (200); and/or wherein the torque current causes an overload operation state of the induction motor (200).

5. The drive system (10) according to claim 1, wherein the trigger signal is generated once an opening or closing operation of a circuit breaker driven by the induction motor (200) is triggered.

6. The drive system (10) according to claim 5, wherein the drive unit (12) is configured to automatically perform the acceleration of the induction motor (200) once since the magnetization starts the first time period elapses or magnetic flux in the induction motor reaches a predetermined level.

7. The drive system (10) according to claim 3, wherein the trigger signal is generated once a state indicating a circuit breaker driven by the induction motor (200) starts to operate is detected.

8. The drive system (10) according to claim 7, wherein the further trigger signal is generated once an opening or closing operation of the circuit breaker is triggered.

9. The drive system (10) according to claim 3, wherein the trigger signal is generated once a fault in a power system coupled with a circuit breaker driven by the induction motor (200) is detected.

10. The drive system (10) according to claim 9, wherein the further trigger signal is generated once an opening or closing operation of the circuit breaker is triggered.

11. The drive system (10) according to any one of claims 7-11, wherein a waiting time period is provided between the first time period and the second time period for waiting for the further trigger signal.

12. The drive system (10) according to claim 11, wherein the control unit (11) is configured to control the drive unit (12) to provide a second magnetizing current to the induction motor (200) for maintain a magnetic field in the induction motor (200) during the waiting time period, the second magnetizing current being less than of the first magnetizing current.

13. The drive system (10) according to any one of claims 1-12, wherein the first time period and the second time period are included in a start-up process of the induction motor (200), and wherein the rotational speed of the induction motor (200) is substantially zero or below a predetermined low speed during the first time period.

14. The drive system (10) according to claim 3, wherein the reference rotational angle is predetermined based on a target displacement which is a displacement corresponding to a position change of a contact of the circuit breaker driven by the induction motor during the opening or closing operation.

15. The drive system (10) according to claim 3, wherein the reference rotational speed is predetermined such that the induction motor (200) drives a movable member coupled to the induction motor (200) to move with a target moving speed corresponding to the reference rotational speed.

16. The drive system (10) according to claim 3, wherein the reference torque is predetermined such that the induction motor (200) drives a rotational member coupled to the induction motor (200) to rotate by a target torque force corresponding to the reference torque.

17. A control system (100) for an induction motor (200), comprising: a drive system (10) comprising a drive unit (12) coupled to the induction motor (200) and a control unit (11) for controlling the drive unit (12); and a central controller (20) in communication with the drive system (10), the central controller being configured to generate a trigger signal when a trigger event happens, the control unit (11) being configured to control the drive unit (12) to provide a first magnetizing current to the induction motor (200) in response to the trigger signal such that the drive unit (12) is operated for magnetization of the induction motor (200) during a first time period, the control unit (11) being further configured to control the drive unit (12) to provide a torque current to the induction motor (200) such that the drive unit (12) is operated for acceleration of the induction motor (200) during a second time period after the first time period.

18. The control system (100) of claim 17, wherein the drive unit (17) comprise a converter (122) coupled with the induction motor (200) and a converter controller (121) in communication with the control unit (11), and wherein the converter is provided such that the maximum drive current provided by the converter causes an overload operation state of the induction motor (200).

19. A drive method for an induction motor (200), comprising: receiving a trigger signal; controlling a drive unit (12) coupled with the induction motor (200) to provide a first magnetizing current to the induction motor (200) in response to the trigger signal such that the drive unit (12) is operated for magnetization of the induction motor (200) during a first time period; and controlling the drive unit (12) to provide a torque current to the induction motor (200) such that the drive unit (12) is operated for acceleration of the induction motor (200) during a second time period after the first time period.

20. The drive method according to claim 19, further comprising: providing the drive unit having a maximum drive current that can cause an overload operation state of the induction motor (200).

21. The drive method according to any one of claims 19-20, further comprising: receiving an instruction for instructing the opening or closing of a circuit breaker driven by the induction motor (200); and generating the trigger signal in response to the received order.

22. The drive method according to claim 21, further comprising: automatically performing the acceleration of the induction motor (200) once since the magnetization starts the first time period elapses or magnetic flux in the induction motor reaches a predetermined level.

23. The drive method according to any one of claims 19-20, further comprising: receiving an operating state signal indicating a circuit breaker driven by the induction motor (200) starts to operate; and generating the trigger signal in response to the received operating state signal.

24. The drive method according to claim 23, further comprising: receiving an instruction for instructing the opening or closing of a circuit breaker driven by the induction motor (200); and generating a further trigger signal in response to the received order to trigger the acceleration of the induction motor (200).

25. The drive method according to any one of claims 19-20, further comprising: receiving a fault signal indicating a fault occurs in a power system coupled with a circuit breaker driven by the induction motor (200); and generating the trigger signal in response to the received fault signal.

26. The drive method according to claim 25, further comprising: receiving an instruction for instructing the opening or closing operation of a circuit breaker driven by the induction motor (200); and generating a further trigger signal in response to the received order to trigger the acceleration of the induction motor (200).

27. The drive method according to claim 19, further comprising: providing a waiting time period is provided between the first time period and the second time period for waiting for a further trigger signal for triggering the acceleration of the induction motor (200).

28. The drive method according to claim 27, further comprising: controlling the drive unit (12) to provide a second magnetizing current to the induction motor (200) for maintain a magnetic field in the induction motor (200) during the waiting time period, wherein the second magnetizing current is less than the first magnetizing current.