Method and apparatus for driving a motor of an environmentally friendly vehicle

Abstract

A method and apparatus for driving a motor of an environmentally friendly vehicle are provided. The apparatus includes: a motor having a rotor and a stator; and a controller for operating the motor. The motor includes a plurality of stator coils and a stator relay and the controller operates the stator relay based on an operation mode to adjust the number of turns of the stator coil.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Application No. 10-2018-0128178, filed on October 25, 2018, which is hereby incorporated by reference in its entirety as if fully set forth herein. Technical Field

[0003] The present invention relates to a method and apparatus for driving a motor of an environmentally friendly vehicle, and more particularly, to a method and apparatus for driving a motor by changing the number of turns of a stator coil through on / off control of a stator relay. Background Art

[0004] Generally, environmentally friendly vehicles such as electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and fuel cell electric vehicles (FCEV) use electric drive power as the main driving source and have a motor system including a motor, an inverter and a battery as a main power source. The motor may include a rotating body (rotor) with a permanent magnet inserted therein and a stator including a stator coil in which current flows. The inverter controls the current flowing in the motor and the battery is the main source of electrical energy.

[0005] In the related art, various methods are used to operate the motor at optimal efficiency. Techniques such as optimal arrangement of permanent magnets for reducing leakage flux and a laminated structure of thin steel plates have been applied to the rotor. In addition, techniques such as application of a stator coil having an optimal shape for increasing a space factor, a structure for reducing end loss, and increasing the number of turns of the stator coil for reducing current flowing in the stator coil have been applied to the stator.

[0006] Specifically, a technique of increasing the number of turns (e.g., the number of windings) of a stator coil is one method that can more effectively increase motor efficiency. Fundamentally, if there is no problem with vehicle mountability, the number of turns of the stator coil can be increased to reduce the current flowing in the stator coil, thereby reducing the so-called copper loss (I 2 R). In addition, the reduced current reduces the conduction loss in the inverter, thereby maximizing the fuel efficiency of the motor system and increasing the fuel efficiency of an environmentally friendly vehicle. However, once the number of turns of the stator coil for high-efficiency operation is increased according to the related art, the torque / output in the low-speed range can be increased, but the high output cannot be maintained from the medium-speed range to the highest-speed range. Summary of the invention

[0007] Therefore, the present invention provides a method and apparatus for driving a motor of an environmentally friendly vehicle that substantially avoids one or more problems due to limitations and disadvantages of the related art. More specifically, the present invention provides a configuration of a stator coil of a motor of an environmentally friendly vehicle and a vehicle operation strategy. An object of the present invention is to provide a method for changing the number of turns of a stator coil by on / off control of a stator relay and a vehicle using the method.

[0008] In an exemplary embodiment, an apparatus for driving a motor of an environmentally friendly vehicle may include: a motor having a rotor and a stator; and a controller configured to operate the motor. The motor may include a plurality of stator coils and a stator relay and the controller may be configured to operate the stator relay according to an operation mode to adjust the number of turns of the stator coil.

[0009] In some exemplary embodiments, the controller may be configured to select an operating mode based on vehicle drive mode information. In addition, the controller may be configured to select any one of a first operating mode in which the number of turns of the stator coil is increased and a second operating mode in which the number of turns of the stator coil is reduced as the operating mode. In some exemplary embodiments, the motor may include three phases.

[0010] The motor may further include a series circuit, wherein at least two stator coils in each phase are connected in series, and at least two series circuits may be connected in parallel. The number of stator relays may be determined by the following equation 1:

[0011] Equation 1

[0012] Number of relays in each phase: [(S-1)*2]*P

[0013] Therein, S denotes the number of stator coils per series circuit and P denotes the number of series circuits connected in parallel.

[0014] Further, the motor may include a first stator coil, a second stator coil, a first stator relay connected in parallel to the second stator coil, and a second stator relay connected in series to the second stator coil, and the first stator coil, the second stator relay and the second stator coil may be connected in series, and the first stator relay and the second stator relay may be connected in parallel.

[0015] The controller may be configured to: when the operation mode is the first operation mode, turn off the first stator relay and turn on the second stator relay. In addition, when the operation mode is the second operation mode, the controller may be configured to turn on the first stator relay and turn off the second stator relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Arrangements and exemplary embodiments will be described in detail with reference to the following drawings, in which like reference numerals refer to like elements, and in which:

[0017] Figure 1 is a block diagram of a vehicle according to an exemplary embodiment of the present invention;

[0018] Figure 2 is a diagram illustrating an apparatus for driving a motor of an environmentally friendly vehicle according to an exemplary embodiment of the present invention;

[0019] Figure 3 is a graph showing a motor driving characteristic based on the number of turns of a stator coil according to an exemplary embodiment of the present invention;

[0020] Figure 4 is a view showing motor control characteristics according to an exemplary embodiment of the present invention;

[0021] Figure 5 is a diagram showing a configuration of a stator coil and a relay of a motor according to an exemplary embodiment of the present invention; and

[0022] Figure 6 is a flowchart illustrating a method of driving a motor of an environmentally friendly vehicle according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0023] It should be understood that the term "vehicle" or "vehicular" or other similar terms as used herein generally encompass motor vehicles, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including various boats and ships, aircraft, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, for example, gasoline-powered and electric vehicles.

[0024] Although the exemplary embodiment is described as using multiple units to perform the exemplary process, it should be understood that the exemplary process can also be performed by one or more modules. In addition, it should be understood that the term controller / control unit refers to a hardware device including a memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more processes described further below.

[0025] In addition, the control logic of the present invention may be implemented as a non-volatile computer-readable medium containing executable program instructions executed by a processor, a controller / control unit, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disk (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable recording medium may also be distributed in a network-coupled computer system so that, for example, a telematics server or a controller area network (CAN) stores and executes the computer-readable medium in a distributed manner.

[0026] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. Unless the context clearly indicates otherwise, as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well. It should also be understood that when the terms "comprises" and / or "comprising" are used in this specification, the presence of the features, integers, steps, operations, elements, and / or parts described are indicated, but the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or combinations thereof are not excluded. As used herein, the term "and / or" includes any and all combinations of one or more of the relevant listed items.

[0027] Unless otherwise specified or apparent from the context, as used herein, the term "about" is understood to be within the normal tolerance range in the art, such as within 2 standard deviations of the mean. "About" may be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the value. Unless otherwise apparent from the context, all numerical values ​​provided herein may be modified by the term "about".

[0028] With reference to the accompanying drawings hereinafter, the equipment and the various methods of exemplary embodiments of the present invention will now be described more comprehensively. The suffixes "module" and "unit" of the elements herein are used for ease of description, and therefore, can be used interchangeably and without any distinguishable meaning or function. In the following description of exemplary embodiments, it should be understood that when each element is referred to as being formed on another element "on" (above) or "under (below)" or "before" (in front) or "after" (behind), it can be directly formed on another element "on" (above) or "under (below)" or "before" (in front) or "after" (after) or with one or more intermediate elements intervening therebetween indirectly.

[0029] It should be understood that although the terms "first", "second", "A", "B", "(a)", "(b)", etc. may be used herein to describe various elements of the present invention, these terms are only used to distinguish one element from another element and these terms do not limit the nature, order or sequence of the corresponding elements. It should be understood that when an element is referred to as being "connected to", "coupled to" or "accessed to" another element, although an element may be directly connected to or directly accessed to another element, an element may be "connected to", "coupled to" or "accessed to" another element via another element.

[0030] The method and apparatus for driving a motor of an environmentally friendly vehicle according to the present invention can adjust the number of turns of the stator coil wound in phases U, V and W of the stator of the motor using the stator coil, and the number of turns can be changed by the on / off control of the stator relay. At this time, the on / off control of the stator relay can change the number of turns according to the operation mode of the vehicle.

[0031] Figure 1 is a block diagram of a vehicle according to an exemplary embodiment of the present invention, and Figure 2 is a diagram showing an apparatus for driving a motor of an environmentally friendly vehicle according to an exemplary embodiment of the present invention. Figure 1 , the vehicle 100 may include an engine 10, a motor 20, an inverter 30, a transmission 40, a battery 60, a hybrid starter generator (HSG) 50, and wheels 70. The motor 20 and the inverter 30 may collectively serve as a device for driving a motor of an environmentally friendly vehicle.

[0032] The engine 10 may be configured to generate power by burning fuel. The motor 20 may be configured to assist the power of the engine 10 and operate as a generator during braking or deceleration of the vehicle, thereby generating electrical energy. In some exemplary embodiments, the motor 20 may be implemented as an internal permanent magnet (IPM) type motor, in which permanent magnets are inserted into the rotor core. The electrical energy generated by the motor 20 may be stored in the battery 60.

[0033] The characteristics of the motor 20 may be changed based on the configuration of the stator coil. The motor 20 may have a plurality of motor characteristics according to the driving control of the motor of the environmentally friendly vehicle. The acceleration performance and fuel efficiency of the vehicle may be determined based on the characteristics of the motor 20.

[0034] refer to Figure 2 The motor 20 may be a three-phase (U, V, and W) motor. The motor 20 may include a stator coil in which current flows in the three phases U, V, and W. The inverter 30 may include a voltage source Vdc and a plurality of switching elements SW1 to SW6. The inverter 30 may convert the current I U ,I V and IW Provided to the motor for operation of the switching element.

[0035] Back to Figure 1 , the inverter 30 may include a controller 35 configured to operate the motor 20. The controller 35 may be configured to receive vehicle drive mode information. The vehicle drive mode may include an automatic mode and a manual mode. The automatic mode may be a mode that receives real-time driving conditions, loads, etc. The manual mode may be a mode in which a user selects an operating mode. The controller 35 may be configured to select an operating mode based on the vehicle drive mode information.

[0036] The operation mode may include an eco-mode and a power mode. The eco-mode may be a first operation mode that increases the number of turns of the stator coil in the motor 20. The power mode may be a second operation mode that reduces the number of turns of the stator coil in the motor 20. The controller 35 may be configured to operate the stator relay in the motor according to the operation mode. For example, in the first operation mode, the controller 35 may be configured to turn on and off the stator relay to increase the number of turns of the stator coil. In the second operation mode, the controller 35 may be configured to turn on and off the stator relay to reduce the number of turns of the stator coil.

[0037] Further, the transmission 40 may be connected in series to the motor 20 and may be configured to convert the power generated by the engine 10 into a required rotational force based on the speed and transmit the rotational force to the wheels 70. The HSG 50 may be configured to start the engine 10 or generate power by the rotational force of the engine 10. The high-voltage battery 60 may be connected to charge and discharge and may be charged during power generation.

[0038] Figure 3 is a graph showing motor driving characteristics based on the number of turns of a stator coil according to an exemplary embodiment of the present invention, and Figure 4 is a view showing motor control characteristics according to an exemplary embodiment of the present invention. Figure 3 A first graph shows a relationship between torque and motor speed according to first and second motor types and a second graph shows a relationship between output and motor speed according to first and second motor types.

[0039] The horizontal axis of the first graph 310 represents an increase in motor speed and the vertical axis of the first graph 310 represents an increase in torque. The horizontal axis of the second graph 320 represents an increase in motor speed and the vertical axis of the second graph 320 represents an increase in output. The first motor type indicates a motor having fewer turns of stator coils than the second motor type. In other words, the second motor type may have more turns of stator coils than the first motor type.

[0040] refer to Figure 3, when the motor speed is the first speed 301, the first motor type can obtain a greater torque than the second motor type and the first motor type can obtain a greater output than the second motor type. When the motor speed is the second speed 302, the first motor type and the second motor type can obtain the same torque and output. When the motor speed is the third speed 303, the first motor type can obtain a smaller torque than the second motor type and the first motor type can obtain a smaller output than the second motor type.

[0041] In other words, the first motor type can obtain the same torque as the second motor type with a relatively small current based on the same torque, thereby reducing motor losses (for example, stator coil copper loss I 2 R) and inverter losses (e.g., conduction losses). Therefore, the first motor type can be configured to operate the vehicle with higher fuel efficiency than the second motor type. However, as the motor speed increases to the medium speed 302 and the high speed 303 (e.g., the second and third speeds), the motor 20 can be configured to be Figure 4 The motor control characteristics shown in FIG.

[0042] refer to Figure 4 , the region in which the motor can be operated at medium and high speeds (eg, second and third speeds) may be limited by a voltage-limited elliptical region V s1 、V s2 and V s3 The voltage limiting elliptical region 410 of the motor 20 can be adjusted along with the inductance L d Magnetic flux interlinkage with permanent magnets ψ m In other words, in the size of the pressure-limiting elliptical area, V s3 >V s2 >V s1 .

[0043] When the number of turns of the stator coil increases, the inductance and magnetic flux linkage increase. Therefore, the voltage limiting elliptical area V s1 、V s2 and V s3 can be reduced, and the motor 20 may not be able to obtain a larger torque. In other words, in the equal torque curve according to the pressure-limited elliptical area, T 3 >T 2 >T 1 Therefore, the output of the motor 20 decreases at medium and high speeds (e.g., the second and third speeds). The first motor type having a relatively small number of turns of the stator coil may show difficulty in high-efficiency operation even though it can perform high-output operation at high speed (e.g., the third speed).

[0044] Therefore, the first motor type has an advantage in that the low-speed torque performance can be improved and the initial swing performance of the vehicle can be increased. In addition, the first motor type has an advantage in that the efficiency of the motor 20 and the inverter 30 can be increased due to the reduction of the phase current. However, the first motor type has a disadvantage in that the output may be reduced when the speed of the vehicle is medium and high speeds (e.g., the second and third speeds) as the inductance and the magnetic flux linkage increase.

[0045] In addition, the second motor type has the advantage that the acceleration performance of the vehicle at medium and high speeds (e.g., the second and third speeds) can be improved and thus high power performance can be obtained. For example, the second motor type can achieve a performance improvement of about 0 to 100 KPH in terms of vehicle speed due to the improved acceleration performance of the vehicle at medium and high speeds (e.g., the second and third speeds). However, in the second motor type, due to the increase in phase current, the efficiency of the motor 20 and the inverter 30 may be reduced. Therefore, the fuel efficiency of the vehicle may be reduced.

[0046] Figure 5 is a diagram showing a configuration of a stator coil and a relay of a motor according to an exemplary embodiment of the present invention. Figure 5 , the motor 20 may include three phases U, V and W. Each phase of the motor 20 may include two series circuits. The series circuits may be arranged in parallel with each other. Therefore, in the circuit connected to phase U, the first series circuit 510 may include a first stator coil CU1, a second stator coil CU2, a first stator relay RU1 and a second stator relay RU2.

[0047] Specifically, the first stator relay RU1 may be connected in parallel to the second stator coil CU1. The second stator relay RU2 may be connected in series to the second stator coil CU2. Therefore, the first stator relay RU1 and the second stator relay RU2 may be connected in parallel. The second series circuit 520 connected in parallel to the first series circuit 510 may include a third stator coil CU3, a fourth stator coil CU4, a third stator relay RU3 and a fourth stator relay RU4. The third stator relay RU3 may be connected in parallel to the third stator coil CU3. The fourth stator relay RU4 may be connected in series to the fourth stator coil CU4. Therefore, the third stator relay RU3 and the fourth stator relay RU4 may be connected in parallel.

[0048] In addition, the motor 20 may include the same circuit as the circuit connected to each phase. The motor 20 having such a structure can change the motor type according to the operation mode. The motor 20 can be configured to adjust the number of turns of the stator coil by operating the stator relay that can be turned on / off in a series / parallel structure based on the motor type. In other words, the number of turns of the stator coil can be changed by the on / off control of the stator relay to reflect the characteristics of the motor 20 suitable for the operation mode.

[0049] The operation of controlling the stator relay according to the motor type is shown in the following table.

[0050] Table 1

[0051]

[0052] Referring to Table 1, when high-efficiency operation is required, the first operating mode can be selected. Therefore, R1 and R3 of the stator relay of each phase can be disconnected and R2 and R4 can be turned on. Therefore, the number of turns of the coil connected in series in each phase is set to 2T and the first motor type can have a relatively large number of turns of the stator coil. Therefore, the number of turns of the stator coil can be increased. At this time, R1 can be the first stator relay RU1, RV1 or RW1 arranged in each phase, R2 can be the second stator relay RU2, RV2 or RW2 arranged in each phase, R3 can be the third stator relay RU3, RV3 or RW3 arranged in each phase, and R4 can be the fourth stator relay RU4, RV4 or RW4 arranged in each phase.

[0053] In addition, when high dynamic performance of the vehicle is required without considering high fuel efficiency operation, the second operating mode can be selected. Therefore, R1 and R3 of the stator relay of each phase can be turned on and R2 and R4 can be disconnected. Therefore, the number of turns of the coils connected in series in each phase can be set to 1T and the second motor type can have a relatively small number of turns of the stator coil. Therefore, the second motor type can improve the acceleration performance of the vehicle at medium and high speeds (e.g., the second and third speeds). Therefore, with the increase in the number of turns of the stator coil, the vehicle can be driven with higher dynamic characteristics than the first motor type.

[0054] In another example, when the number of series / parallel structures is added to one of the three phases U, V, and W, the number of relays configured in the motor coil is shown in the following Equation 1.

[0055] Equation 1

[0056] Number of relays in each phase: [(S-1)*2]*P

[0057] Therein, S denotes the number of stator coils of each series circuit and P denotes the number of series circuits connected in parallel.

[0058] Thus, in various embodiments, various series circuits and parallel connection combinations may be possible depending on the use and packaging type of the motor 20, and therefore modified stator relays may be incorporated.

[0059] Figure 6 is a flowchart illustrating a method of driving a motor of an environmentally friendly vehicle according to an exemplary embodiment of the present invention. Figure 6 , the controller 35 may be configured to receive vehicle driving mode information. When the vehicle driving mode is the manual mode, the user may select and input the operation mode (S610 and S620). In other words, the controller may be configured to receive a user selection related to the operation mode.

[0060] After step S620, when the first operation mode is selected, the controller 35 may be configured to perform on / off control of the stator relay based on the first operation mode (S630). Specifically, for the control of the stator relay corresponding to the first operation mode, the controller 35 may be configured to turn on the relay switches R2 and R4 arranged in each phase of the motor 20 and turn off the relay switches R1 and R3. Therefore, the number of turns of the stator coil of the motor 20 can be increased.

[0061] After step S630, control parameters for current control according to the first motor type may be received (S640). Thus, the controller 35 may be configured to adjust the inductance, back electromotive force constant, current control gain, maximum torque, and output of the motor 20. After step S640, the vehicle 100 may be operated by the motor 20 of the first motor type (S650).

[0062] In addition, after step S620, if the second operation mode is selected, the controller 35 may be configured to perform on / off control of the stator relay based on the second operation mode (S660). Specifically, for the control of the stator relay corresponding to the second operation mode, the controller 35 may be configured to disconnect the relay switches R2 and R4 arranged in each phase of the motor 20 and connect the relay switches R1 and R3. Therefore, the number of turns of the stator coil of the motor 20 can be reduced.

[0063] After step S660, control parameters for current control according to the second motor type may be received (S670). Thus, the controller 35 may be configured to adjust the inductance, back electromotive force constant, current control gain, maximum torque, and output of the motor 20. After step S640, the vehicle 100 may be operated by the motor 20 of the second motor type (S680).

[0064] The method and apparatus for driving a motor for an environmentally friendly vehicle according to the present invention have the following effects. If the method and apparatus for driving a motor for an environmentally friendly vehicle according to the present invention are used, two types of vehicle operation can be selected. When high fuel efficiency is required, the number of turns of the stator coil can be set to 2T to reduce the applied current, thereby reducing losses. On the contrary, when high output power performance is required, the number of turns of the stator coil can be set to 1T so as to obtain high output even at high speeds.

[0065] The method according to the exemplary embodiment can be implemented as a program for execution on a computer and stored in a non-volatile computer-readable recording medium. Examples of non-volatile computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage device. The non-volatile computer-readable recording medium can be distributed on multiple computer devices connected to a network so that computer-readable code is written thereto and executed therefrom in a decentralized manner. Functional programs, codes, and code segments that need to implement the exemplary embodiments herein can be interpreted by those of ordinary skill in the art.

Claims

1. A device for driving a motor of an environmentally friendly vehicle, include: The motor comprises a rotor and a stator; as well as a controller configured to operate the motor, Wherein, the motor includes a plurality of stator coils and a stator relay, and wherein the controller is configured to operate the stator relay based on an operation mode to adjust the number of turns of the stator coil, The motor includes three phases, each phase of the motor includes two series circuits, the two series circuits are arranged in parallel with each other, and the two series circuits include a first series circuit and a second series circuit. The first series circuit comprises: a first stator coil; a second stator coil; a first stator relay connected in parallel to the second stator coil; and a second stator relay connected in series to the second stator coil, and wherein the first stator coil, the second stator relay and the second stator coil are connected in series, and Wherein, the first stator relay and the second stator relay are connected in parallel, The second series circuit comprises: a third stator coil; a fourth stator coil; a third stator relay connected in parallel to the fourth stator coil; and a fourth stator relay connected in series to the fourth stator coil, and The third stator coil, the fourth stator relay and the third stator coil are connected in series, and Wherein, the third stator relay and the fourth stator relay are connected in parallel, The number of stator relays is determined by: Number of relays in each phase: [(S-1)*2] * P Therein, S denotes the number of stator coils of each series circuit and P denotes the number of said series circuits connected in parallel.

2. The device according to claim 1, in, The controller is configured to select the operating mode based on vehicle drive mode information.

3. The device according to claim 1, in, The controller is configured to select, as the operation mode, any one of a first operation mode in which the number of turns of the stator coil is increased and a second operation mode in which the number of turns of the stator coil is decreased.

4. The device according to claim 1, in, The electric machine comprises a series circuit, wherein in each phase at least two stator coils are connected in series, and wherein at least two of the series circuits are connected in parallel.

5. The device according to claim 1, in, When the operation mode is a first operation mode, the controller is configured to turn off the first stator relay and turn on the second stator relay.

6. The device according to claim 1, in, When the operation mode is a second operation mode, the controller is configured to turn on the first stator relay and turn off the second stator relay.

7. A method of driving a motor of an environmentally friendly vehicle, The following steps are involved: The operating mode is selected by the controller; operating, by the controller, a stator relay in the motor based on the operating mode; as well as operating the motor by the controller based on the operation of the stator relay, The motor includes three phases, each phase of the motor includes two series circuits, the two series circuits are arranged in parallel with each other, and the two series circuits include a first series circuit and a second series circuit. The first series circuit comprises: a first stator coil; a second stator coil; a first stator relay connected in parallel to the second stator coil; and a second stator relay connected in series to the second stator coil, and wherein the first stator coil, the second stator relay and the second stator coil are connected in series, and Wherein, the first stator relay and the second stator relay are connected in parallel, The second series circuit comprises: a third stator coil; a fourth stator coil; a third stator relay connected in parallel to the fourth stator coil; and a fourth stator relay connected in series to the fourth stator coil, and The third stator coil, the fourth stator relay and the third stator coil are connected in series, and Wherein, the third stator relay and the fourth stator relay are connected in parallel, The number of stator relays is determined by: Number of relays in each phase: [(S-1)*2] * P Here, S represents the number of the stator coils of each of the series circuits and P represents the number of the series circuits connected in parallel.

8. The method according to claim 7, in, Selecting the operating mode includes selecting, by the controller, the operating mode based on vehicle drive mode information.

9. The method according to claim 8, in, Selecting the operation mode includes selecting, by the controller, any one of a first operation mode in which the number of turns of the stator coil is increased and a second operation mode in which the number of turns of the stator coil is decreased as the operation mode.

10. The method according to claim 9, in, The electric machine comprises a series circuit, wherein in each phase at least two stator coils are connected in series, and wherein at least two of the series circuits are connected in parallel.

11. The method according to claim 9, in, Operating the stator relay of the motor includes, when the operation mode is a first operation mode, turning off the first stator relay and turning on the second stator relay by the controller.

12. The method according to claim 9, in, Operating the stator relay of the motor includes, when the operation mode is a second operation mode, turning on the first stator relay and turning off the second stator relay by the controller. 13 . A non-volatile computer-readable recording medium on which a program for realizing the method according to claim 7 is recorded.

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