阅读说明：本技术 用于车辆的控制系统 (Control system for vehicle ) 是由 库马尔 拉查巴特尼 V·拉格亨特 S·杰贝兹迪纳加 于 2018-04-04 设计创作，主要内容包括：本发明涉及一种车辆(100)的电机,并且更具体地,本发明涉及一种配备有用于车辆(100)电机的开关的控制器。旋转磁场以60°电角的阶跃产生,其导致转子扭矩选择为扭矩相对于角度波形的60°的组合,其具有峰值扭矩,从而产生六个重复的扭矩波形。通过本配置,可以增加输出扭矩波形的最低扭矩,这进而增加了转子的平均扭矩并且仍然保持峰值扭矩不变。(The present invention relates to a motor of a vehicle (100), and more particularly, to a controller equipped with a switch for the motor of the vehicle (100). The rotating magnetic field is generated in 60 ° electrical angle steps, which results in rotor torque being selected as a 60 ° combination of torque versus angle waveform, with peak torque, resulting in six repeating torque waveforms. With the present configuration, the lowest torque of the output torque waveform can be increased, which in turn increases the average torque of the rotor and still keeps the peak torque unchanged.)

1. A control system (200) for assisting an internal combustion engine of a vehicle (100) and achieving a higher average torque during starting of the vehicle (100) and during high-speed operation, the control system (200) having an electric machine (101) and a power supply, the electric machine (101) being compact and capable of being housed in the vehicle (100), and the control system (200) being capable of achieving a reduction in exhaust emissions at high-speed operation, the control system (200) comprising:

a motor (101) of the BLDC type, the motor (101) comprising a stator (102) having a plurality of teeth (112), each tooth of the plurality of teeth (112) being wound with a wire to form a winding connected in a star winding configuration, the motor (101) comprising a rotor (104) having a plurality of magnets (108), the plurality of magnets (108) being arranged to face the plurality of teeth (112) of the stator (102); and

a motor controller (202) comprising at least one microcontroller (204), the motor controller (202) comprising a first set of switch configurations having six switches arranged in a first, second and third switch configurations, the first, second and third switch configurations respectively comprising two switches connected in series between terminals of the power source, the first set comprising three top switches and three bottom switches, a first junction of each of the two switches connected in series being connected to a connector end of a first phase of the star winding configuration and a second junction of each of the two switches connected in series being connected to a connector end of a second phase of the star winding configuration and a third junction of each of the two switches connected in series being connected to a connector end of a third phase of the star winding configuration, the motor controller (202) comprises a second set of switch configurations arranged in a fourth switch configuration having two switches connected in series between terminals of the power supply, the second set comprising a fourth junction connected to a neutral point of the star winding configuration.

2. The control system (200) of claim 1, wherein the at least one microcontroller (204) turns on a predetermined sequence of switch configurations causing a 30 ° electrical angle step of the rotating magnetic field.

3. The control system (200) of claim 1 or claim 2, wherein the at least one microcontroller (204) switches on top switches of the first switch configuration and bottom switches of the fourth switch configuration causing current to flow through the first phase to obtain a first 30 ° electrical angle of the rotating magnetic field, the at least one microcontroller (204) switches on top switches of the first switch configuration and bottom switches of the second switch configuration causing current to flow through the first phase and the second phase to obtain a second 30 ° electrical angle of the rotating magnetic field.

4. The control system (200) of claim 3, wherein the at least one microcontroller (204) causes a 30 ° angular step of the rotating magnetic field by turning on the first and second sets of switch configurations in a predetermined sequence.

5. The control system (200) of claim 1, wherein the plurality of magnets (108) of the motor (101) are mounted on a surface of the rotor (104) facing the stator (102).

6. The control system (200) of claim 1, wherein the plurality of magnets (108) of the motor (101) are embedded inside the rotor (104).

7. The control system (200) according to claim 1, wherein the electric motor (101) is a brushless direct current motor having the rotor (104) arranged inside the stator (102).

8. The control system (200) of claim 1, wherein the motor (101) is a brushless direct current motor having the rotor (104) arranged outside the stator (102).

9. The control system (200) of claim 1 or claim 2, wherein the first and second sets of switch configurations are constituted by a parallel combination of a plurality of power electronic switching circuit elements.

10. The control system (200) of claim 1, wherein the power source is for supplying energy to the electric machine (101) when the electric machine (101) operates as a motor, and for storing energy generated by the electric machine (101) when the electric machine (101) operates as a generator.

11. The control system (200) of claim 1 or claim 2, wherein the control system (200) further comprises one or more sensors configured to sense an operating position of the rotor (104).

12. The control system (200) of claim 1 or claim 10, wherein the rotor (104) is rotatable by interaction with a magnetic field generated by the stator (102) when receiving electrical energy from at least one energy storage device, the rotor (104) is separated from the stator (102) by an air gap, and the magnetic field is perpendicular to an axis of rotation of the rotor (104).

13. The control system (200) of claim 1 or claim 10, wherein the rotor (104) is rotatable by interaction with a magnetic field generated by the stator (102) when receiving electrical energy from at least one energy storage device, the rotor (104) being separated from the stator (102) by an air gap (110), and wherein the magnetic field is parallel to an axis of rotation of the rotor (104).

14. The control system (200) according to claim 1, wherein the electric machine (101) is capable of reaching a peak torque at an operating current, the peak torque being in the range of 45Nm to 50Nm both during the engine start and when providing power assistance to the internal combustion engine during driving of the vehicle (100).

Technical Field

The present invention relates to a motor of a vehicle, and more particularly, to a controller for a motor of a vehicle.

Background

Electric machines are generally composed of a stator and a rotor. Typically, BLDC motors have a star winding configuration and the controller for such motors is also equipped with six power electronic switches that control the current through the three phases of the motor in such a way that at any instant current flows through two phases. The switches are arranged such that two of the switches are connected in series between the power supplies, and three such configurations are repeated. Furthermore, the middle part of each configuration is connected to the phase terminals of the star winding configuration.

This results in six stable positions for the magnetic field, resulting in six ripples in the torque waveform with a full mechanical rotation of the rotor. The ripple will have a negative effect on the average torque, which further reduces the available load torque that can be applied to the load. Therefore, in such motors, in order to meet the load torque requirement, the overall size of the motor is generally large, which may prevent placing the motor in a vehicle, especially in a small vehicle such as a two-wheeled vehicle or a three-wheeled vehicle.

Therefore, there is a need to provide a compact electric machine that can deliver more average torque to meet the load torque requirements of the vehicle.

Drawings

The embodiments are described with reference to the accompanying drawings. Throughout the drawings, the same reference numerals are used to refer to like features and components.

Fig. 1 illustrates a left side view of an exemplary two-wheeled vehicle, in accordance with an embodiment of the present subject matter.

Fig. 2 shows a typical cross section of an electrical machine according to an embodiment of the invention.

FIG. 3 depicts a block diagram of a control system for assisting an internal combustion engine of a vehicle during start-up and during high speed operation, according to an embodiment of the present invention.

Fig. 4 shows a phase diagram representation of three of six possible states of a switch of a three-phase switching network providing a power electronic switch according to an embodiment of the invention.

Fig. 5 shows a six-switch network of the power electronic switches depicted in fig. 4, which results in the switching of the three-phase motor depicted in fig. 2.

Fig. 6 provides a phase diagram representation of six possible states of switches in a three-phase switching network of power electronic switches according to an embodiment of the invention.

Fig. 7 shows a six-switch network of power electronic switches with an additional switching branch electrically connected to the neutral point of the coils of the star winding of the electrical machine depicted in fig. 2.

Fig. 8 depicts torque waveforms for a conventional electric machine according to the network connection shown in fig. 5.

Fig. 9 depicts torque waveforms for the motor of the present invention according to the network connection depicted in fig. 7.

Detailed Description

The present invention describes an electric machine that exceeds the ISG in terms of function. The present invention is also designed to provide assistance to the engine at high speed, high load conditions so that vehicle and engine operation can be performed to reduce emissions of CO2 and NOx.

Furthermore, the present invention may be implemented with a variety of motor topologies, such as induction motors, Switched Reluctance Motors (SRMs), and BLDC (brushless direct current) motors. The induction motor and the switched reluctance motor operate with corresponding power electronic controllers that regulate torque based on input conditions, such as current rotational speed.

Although the speed of the induction motor and the SRM is not limited by the induced back electromotive force (electromotive force), the speed range of the BLDC is affected due to the induced voltage. This is due to the rate of change of magnetic flux in the coil created by the presence of the rotating magnet, thereby inducing a voltage in the winding coil. This voltage limits the current flowing into the motor, limiting the possible torque at speeds greater than zero, depending on the voltage supplied.

When the motor is designed for starting and power-assisted operation, the requirements are contradictory. Launch requires a high torque constant, while power assist requires high speed/power operation and in turn requires a low torque constant.

The invention provides a BLDC motor and a controller for the same, the controller for the BLDC motor has eight power electronic switches, wherein the switches are arranged in the following manner: two of the switches (top one and bottom one) are connected in series between the power supplies and four such configurations are repeated. Furthermore, the middle portions of the first three configurations are connected to the phase terminals of the star winding configuration, while the middle portion of the fourth configuration is connected to the neutral point of the star winding configuration.

Furthermore, each of the switches is operated by the microcontroller via a power electronic switching circuit, respectively. Each of the switches is composed of a parallel combination of a plurality of power electronic switching circuit elements.

A conventional BLDC motor and its controller are provided with three configurations, having six switches, wherein the switches from two different configurations are operated, wherein one of the switches is a top switch and the other is a bottom switch, when operated in a predetermined sequence, a rotating magnetic field is established in the stator of the BLDC motor. Typically, the rotating magnetic field causes the rotor to follow the magnetic field to establish a rotational movement of the rotor.

In such BLDC motors, the rotating magnetic field is generated in 60 ° electrical angle steps, which results in the rotor torque being selected as a 60 ° combination of torque versus angle waveforms, which has a peak torque, resulting in six repeating torque waveforms. This will produce six torque ripples within a 360 electrical rotation of the rotor. The average torque of the rotor is typically the average of the peak torque and the lowest torque of the output torque waveform. In this case, the average torque of the rotor is lower than the peak torque, which results in the motor meeting only the lower load torque requirement.

Thus, in the present invention, a dedicated switch configuration is implemented as the fourth switch configuration, such that a middle portion of the fourth configuration is connected to the neutral point of the star winding configuration of the electric machine. By this configuration, the present invention achieves a possible switching configuration that may result in finer steps of less than 60 ° electrical angle, for example, finer steps of 30 ° electrical angle of the rotating magnetic field.

For example, in one embodiment, the invention involves turning on the top switch of the first switch configuration and the bottom switch of the fourth switch configuration to cause current to flow through only one of the phases to obtain the first 30 electrical angle of the rotating magnetic field. To obtain the next 30 electrical angle of the rotating magnetic field, the top switch of the first switching configuration and the bottom switch of the second switching configuration are turned on, resulting in current flowing through two of the phases of the stator winding. Similarly, a 30 ° angular step of the rotating magnetic field can be achieved. With this configuration, the lowest torque of the output torque waveform can be increased, which in turn increases the average torque of the rotor, and still keeps the peak torque constant. In this case, since the average torque is high, it is possible for the BLDC motor to satisfy a high load torque requirement.

In one embodiment, the resulting phase of the magnetic field in the air gap of the machine is rotated by 30 ° in each step. Accordingly, a greater number of hall effect sensors may be placed on the stator of the motor to detect 30 ° rotation of the rotor. In another embodiment, the position of the rotor is predicted based on a previously known position of the rotor and a calculated speed derived from conventional three hall effect sensors mounted on the stator.

During the time when only one of the phases is switched, the current limit of the controller is increased so that the peak amplitude of the induced magnetic field will remain the same.

In one embodiment, the present invention enables a compact-sized and lightweight BLDC motor, thereby enabling it to be fitted in a small-sized vehicle. In addition, the present invention also facilitates higher average torque, thereby enabling the electric machine to meet higher load torque requirements of the vehicle. For BLDC motors designed for high speed driving operation, the starting torque is typically low. However, the present invention provides a BLDC motor configured to achieve higher starting torque that can satisfy vehicle startability requirements, for example, startability requirements of a powertrain (such as an internal combustion engine of a vehicle), in addition to satisfying high-speed driving operations.

In one embodiment, the proposed electric machine is used to assist the rotation of the crankshaft of an internal combustion engine, wherein the peak torque at operating current is limited to about 50Nm when powering the internal combustion engine during vehicle start-up and during vehicle driving. Further, the peak torque of the electric machine of the present invention at operating current is less than the operating requirements of the traction motor of a hybrid and/or electric vehicle.

In one embodiment, the present subject matter provides a control system for assisting an internal combustion engine of a vehicle and achieving a higher average torque during startup and high speed operation. The control system of the present invention is provided with a motor and a power supply that are compact and can be housed in a small vehicle. The control system also enables reduction of exhaust emissions at high speed operation.

In one embodiment, the control system of the present invention comprises a BLDC type motor. The motor includes a stator having a plurality of teeth, each tooth of the plurality of teeth wound with wire to form windings connected in a star winding configuration. The motor includes a rotor having a plurality of permanent magnets arranged to face a plurality of teeth of the stator.

In one embodiment, the control system of the present invention comprises a motor controller comprising at least one microcontroller. The motor controller includes a first set of switch configurations having six switches arranged in a first switch configuration, a second switch configuration, and a third switch configuration, wherein the first switch configuration, the second switch configuration, and the third switch configuration each include two switches connected in series between terminals of the power source. The first group comprises three top switches and three bottom switches, wherein the first junction of each of the two switches connected in series is connected to the connector end of the first phase of the star winding configuration. The second junction of each of the two switches connected in series is connected to the connector end of the second phase of the star winding configuration. The third junction of each of the two switches connected in series is connected to the connector end of the third phase of the star winding configuration. The motor controller comprises a second set of switch configurations arranged in a fourth switch configuration having two switches connected in series between terminals of the power source, the second set comprising a fourth junction connected to a neutral point of the star winding configuration.

In one embodiment, the control system comprises at least one microcontroller that switches on a predetermined sequence of switch configurations causing a 30 ° electrical angle step of the rotating magnetic field.

Furthermore, in one embodiment the control system is provided with at least one microcontroller, which switches on the top switch of the first switch configuration and the bottom switch of the fourth switch configuration, causing a current to flow through said first phase to obtain the first 30 ° electrical angle of the rotating magnetic field. At least one microcontroller switches on the top switch of the first switching arrangement and the bottom switch of the second switching arrangement, causing a current to flow through the first phase and the second phase to obtain a second 30 ° electrical angle of the rotating magnetic field.

Further, in one embodiment, the at least one microcontroller causes a 30 ° angular step of the rotating magnetic field by turning on the first set of switch configurations and the second set of switch configurations in a predetermined sequence.

In one embodiment, the plurality of permanent magnets of the BLDC motor are mounted on a surface of the rotor facing the stator. In an alternative embodiment, the plurality of permanent magnets of the BLDC motor are embedded inside the rotor.

Furthermore, in one embodiment, the motor is a brushless dc motor having the rotor disposed inside the stator. In another embodiment, the motor is a brushless dc motor having said rotor arranged outside said stator.

In one embodiment, the first set of switch configurations and the second set of switch configurations are comprised of a parallel combination of a plurality of power electronic switching circuit elements. In one embodiment, the power source is for supplying energy to the electric machine when the electric machine is operating as a motor, and for storing energy generated by the electric machine in the power source when the electric machine is operating as a generator.

In one embodiment, the control system includes one or more sensors configured to sense an operating position of the rotor. In one embodiment, the rotor is rotatable by interaction with a magnetic field generated by a stator, the rotor being separated from the stator by an air gap, and wherein the magnetic field is perpendicular to an axis of rotation of the rotor, when receiving electrical energy from at least one energy storage device.

In an alternative embodiment, the rotor is rotatable by interaction with a magnetic field generated by a stator, the rotor being separated from the stator by an air gap, and wherein the magnetic field is parallel to the axis of rotation of the rotor, when receiving electrical energy from at least one energy storage device.

In one embodiment, the electric machine is capable of reaching a peak torque at the operating current, said peak torque being at most 50Nm both during engine start-up and when powering the internal combustion engine during vehicle driving. In an alternative embodiment, the peak torque is at most 10Nm to 30Nm in the case of a three-wheeled vehicle. Similarly, in the case of a two-wheeled vehicle, such as a motorcycle and scooter-type vehicle having an engine capacity of about 110cc, the peak torque may be in the range of up to 7 Nm. In one embodiment, peak torque may be up to 10mm for a higher capacity two-wheeled vehicle, such as a motorcycle with an engine capacity of about 200 cc.

These and other advantages of the present subject matter will be described in more detail in the following description, taken in conjunction with the accompanying drawings.

Fig. 1 illustrates a left side view of an exemplary two-wheeled vehicle, in accordance with embodiments of the present subject matter. The vehicle 100 has a frame assembly 105, the frame assembly 105 serving as a structural member and skeleton of the vehicle 100. The frame assembly 105 includes a head tube 105A, and the steering assembly is rotatably journaled by the head tube 105A. The steering assembly includes a handlebar assembly 111 connected to a front wheel 115 by one or more front suspensions 120. The front fender 125 covers at least a portion of the front wheel 120. Further, the frame assembly 105 includes a main tube (not shown) extending rearward and downward from the head tube 105A. The fuel tank 130 is mounted to the main pipe 105A. Further, a down tube (not shown) extends substantially horizontally rearward from the rear of the main tube. Additionally, the frame assembly includes one or more rear tubes (not shown) extending obliquely rearward from the rear of the down tube. In the preferred embodiment, the frame assembly 105 is a single tube type that extends from the front F to the rear R of the vehicle 100.

In one embodiment, power unit 135 is mounted to the down tube. In one embodiment, power unit 135 includes an Internal Combustion (IC) engine. The fuel tank 130 is functionally connected to the power unit 135 to supply fuel. In a preferred embodiment, the IC engine is tilted forward, i.e. the piston axis of the engine is tilted forward. Further, the IC engine 135 is functionally coupled to the rear wheel 140. The swing arm 140 is swingably connected to the frame assembly 105, and the rear wheel 145 is rotatably supported by the swing arm 140. One or more rear suspensions 150 are connected to the swing arm 145 at an angle that takes up the radial and axial forces due to wheel reactions. The rear fender 155 is disposed above the rear wheel 145. The seat assembly 160 is disposed at the rear R of the walk-in portion defined by the frame assembly 105. In one embodiment, seat assembly 160 includes a driver seat 160A and a rear seat 160B. Further, the rear seat 160B is positioned above the rear wheel 145. In addition, the vehicle 100 is supported by a center bracket (not shown) mounted to the frame assembly 105. A floor 165 is mounted to the downtube and disposed at the step-in portion. The floor 165 covers at least a portion of the power unit 135. The vehicle 100 is equipped with an auxiliary power unit (not shown), e.g., an energy storage device such as a battery, supported by the frame assembly 105. Additionally, the vehicle 100 is provided with at least one set of foot pedals 180 to enable the driver/rear seat passenger to rest their feet.

Fig. 2 shows a cross section of an electrical machine in relation to an embodiment of the invention. In one embodiment, the motor is an external rotating BLDC motor. In one embodiment, an external rotating BLDC motor is used as an Integrated Starter Generator (ISG). The subject electric machine 101 includes a rotor 104, the rotor 104 further including a back iron 106 and a plurality of magnets 108 disposed on an inner surface of the rotor 104. In one embodiment, back iron 106 rotates as rotor 104 rotates. In one embodiment, the plurality of magnets 108 are permanent magnets.

Additionally, back iron 106 may be made of any of iron, silicon steel, which may be made as a single piece of iron or silicon steel. Alternatively, back iron 106 is fabricated as a layer of iron or silicon steel with a plurality of electrically insulating layers therebetween. In one embodiment, the plurality of magnets 108 may be any one of arc magnets and planar magnets. Further, in one embodiment, the plurality of magnets 108 are arranged circumferentially adjacent to each other without any gaps. Alternatively, the plurality of magnets 108 may be arranged circumferentially adjacent to each other with a circumferential air gap between two adjacent magnets of the plurality of magnets 108.

Further, the electric machine 101 includes a stator 102, the stator 102 having a centrally disposed stator core 118, a plurality of stator teeth 112 circumferentially arranged about the stator core 118 forming a plurality of stator slots 114 therebetween. In one embodiment, the plurality of stator slots 114 are further filled with a plurality of windings 116. In one embodiment, the stator 102 is enclosed within the rotor 104 and radially separated by an air gap 110. In one embodiment, each of the plurality of stator teeth 112 includes a shank. In one embodiment, the stems of the teeth of the plurality of stator teeth 112 are provided with equal widths at both ends of the stems, i.e., at a first end toward the stator core 118 and a second end away from the stator core 118. In an alternative embodiment, each of the plurality of stator slots 114 is formed to have equal widths at both ends, i.e., at an end closer to the stator core 118 and at an end further from the stator core 118, by two adjacent teeth of the plurality of stator teeth 112 having different widths at both ends thereof. In another alternative embodiment, each of the plurality of stator teeth 112 and each of the plurality of stator slots 114 are formed such that the widths of the teeth and slots at the two ends are not equal. In one embodiment, the shank of each of the plurality of stator teeth 112 terminates with a head facing rotor 104, and the head has a width wider than the shank.

FIG. 3 depicts a block diagram of a control system for assisting an internal combustion engine of a vehicle during start-up and during high speed operation, according to an embodiment of the present invention. In one embodiment, the control system 200 includes a motor controller 202, the motor controller 202 further including at least one microcontroller 204 and a plurality of switches 214. The motor controller 202 is powered by an energy storage device (e.g., a battery 212) and is capable of receiving input from one or more sensors 208. Based on the input received from the one or more sensors 208, the motor controller 202 controls the motor 101 to operate efficiently by providing a boosted voltage to the motor 101 during vehicle start-up and by providing a voltage from the battery 212 during vehicle travel operation.

In one embodiment, the microcontroller 204 is capable of processing signals received from one or more sensors 208 to effectively initiate operation of the vehicle.

Fig. 4 shows a phase diagram representation of three of six possible states of switches of a three-phase switching network of power electronic switches according to an embodiment of the invention. In one embodiment, phase diagram 402 depicts the generated magnetic field as represented along a two-dimensional vector of the magnetic field due to phase A of motor 101 and the magnetic field due to phase-B of motor 101. In one embodiment, phase map 404 depicts the generated magnetic field as represented along a two-dimensional vector of the magnetic field due to phase a and the magnetic field due to phase-C of motor 101. Similarly, in one embodiment, phase diagram 406 depicts the generated magnetic field as represented along a two-dimensional vector of the magnetic field due to phase B of motor 101 and the magnetic field due to phase-C of the motor. In one embodiment, the three sequences ABD, ACD and BCD are 60 apart in a clockwise rotation sequence.

Fig. 5 shows a six-switch network of the power electronic switches depicted in fig. 4, which results in switching of the three-phase motor depicted in fig. 2. In one embodiment, the power electronics circuit 300 of the motor controller 202 includes a first top switch 314 and a first bottom switch 316 arranged in series, the first top switch 314 and the first bottom switch 316 forming a first junction 308 therebetween. First top switch 314 is connected to the positive pole of battery 212 and first bottom switch 316 is connected to the negative pole of battery 212. Similarly, the power electronics circuit 300 of the motor controller 202 further includes a second top switch 318 and a third top switch 322, which are arranged in series with a second bottom switch 320 and a third bottom switch 324, respectively, forming a second joint 310 and a third joint 312 at their respective joints. First top switch 314 and first bottom switch 316 are arranged in parallel with second top switch 318 and second bottom switch 320 and third top switch 322 and second bottom switch 324. The first, second and third joints 308, 310, 312 are also connected to phase terminals of the motor 101, such as the phase terminals A, B, C302, 304, 306 of the motor 101, such that an electrical connection is established between the motor controller 202 and the motor 101.

Fig. 6 provides a phase diagram representation of six possible states of the switches of a three-phase switching network of power electronic switches according to an embodiment of the invention. In one embodiment, phase diagram 402 depicts the generated magnetic field as represented along a two-dimensional vector of the magnetic field due to phase A of motor 101 and the magnetic field due to phase-B of motor 101. In one embodiment, phase map 404 depicts the generated magnetic field as represented along a two-dimensional vector of the magnetic field due to phase a and the magnetic field due to phase-C of motor 101. Similarly, in one embodiment, phase diagram 406 depicts the generated magnetic field as represented along a two-dimensional vector of the magnetic field due to phase B of motor 101 and the magnetic field due to phase-C of the motor. Similarly, the present subject matter provides a phase map 602 in which the magnetic field that is generated along the magnetic field due to phase-B of motor 101. In one embodiment, the magnetic field due to phase-B and the generated magnetic field of phase map 402 are separated by 30 in a clockwise rotational sequence. Similarly, phase maps 604 and 606 provide magnetic fields due to phase A and phase-C. Further, the magnetic field due to phase A is separated from the generated magnetic field of phase diagram 404 by 30 in a clockwise rotating order, while the magnetic field due to phase-C is separated from the generated magnetic field of phase diagram 406 by 30 in a clockwise rotating order.

Fig. 7 shows a six-switch network of power electronic switches with an additional switching branch electrically connected to the neutral point of the coils of the star winding of the electrical machine depicted in fig. 2. In one embodiment, the power electronic circuit 700 of the present invention further includes a fourth top switch sw 7704 and a fourth bottom switch sw 8706 arranged in series forming a fourth junction N708 therebetween. In one embodiment, the fourth junction N708 is also connected to a phase terminal of the electric machine 101, e.g. the neutral point N702 of the star winding configuration of the electric machine 101, such that when a current flows through one of the above switches to the neutral point N702, the magnetic fields generated are 30 ° apart, thereby reducing the average value.

Fig. 8 depicts a torque waveform 500 for a conventional electric machine according to the network connection shown in fig. 5. In one embodiment, the rotating magnetic field is created in steps of 60 ° electrical angle, which results in the rotor torque being selected as a 60 ° combination of torque versus angle waveform, with peak torque, resulting in six repeating torque waveforms. This will produce six torque ripples within a 360 electrical rotation of the rotor of the motor 101. The average torque of the rotor is typically the average of the peak torque and the lowest torque of the output torque waveform. In this case, the average torque of the rotor is lower than the peak torque, which results in the motor 101 meeting only the lower load torque requirement. For example, waveform 508 includes ripple 1 contributed by the top switch of phase a and the bottom switch of phase B. Similarly, ripple 2 is contributed by the top switch of phase a, the bottom switch of phase C. At the same time, ripple 3 is contributed by the top switch in phase B, the bottom switch in phase C. Similarly, ripple 4 is contributed by the top switch of phase B, the bottom switch of phase a, and ripple 5 is contributed by the top switch of phase C and the bottom switch of phase a. Finally, ripple 6 is contributed by the top switch of phase C and the bottom switch of phase B. The cycle repeats in this order.

Fig. 9 depicts a torque waveform 600 for an electric machine of the present invention according to the network connection depicted in fig. 7. In one embodiment, an additional switch configuration is introduced as shown in fig. 7 as a fourth switch configuration, such that a middle portion of the fourth configuration is connected to the neutral point of the star winding configuration of the electric machine 101. By this configuration, the present invention enables a possible switching configuration that may result in finer steps of less than 60 ° electrical angle, for example, a finer step of 30 ° electrical angle of the rotating magnetic field, involving turning on the top switch of the first switching configuration and the bottom switch of the fourth switching configuration to cause current to flow through only one of the phases to obtain the first 30 ° electrical angle of the rotating magnetic field. To obtain the next 30 electrical angle of the rotating magnetic field, the top switch of the first switching configuration and the bottom switch of the second switching configuration are turned on, resulting in current flowing through two of the phases of the stator winding. Similarly, a 30 ° angular step of the rotating magnetic field can be achieved. With this configuration, the lowest torque of the output torque waveform can be increased, which in turn increases the average torque of the rotor, and still keeps the peak torque constant. In this case, since the average torque is high, it is possible for the BLDC motor 101 to satisfy a high load torque request. For example, in one embodiment, torque waveform 602 includes ripple 7, which is contributed by the top switch of the N-phase, the bottom switch of the B-phase. Similarly, ripple 8 is contributed by the top switch of phase a, the bottom switch of phase B. Ripple 9 is contributed by the top switch of phase a, the bottom switch of phase N, and ripple 10 is contributed by the top switch of phase a, the bottom switch of phase C. Similarly, ripple 11 is contributed by the top switch of the N-phase, the bottom switch of the C-phase, and ripple 12 is contributed by the top switch of the B-phase, the bottom switch of the C-phase. In a similar manner, ripple 13 is contributed by the top switch of phase B, the bottom switch of phase N, and ripple 14 is contributed by the top switch of phase B, the bottom switch of phase a. Similarly, ripple 15 is contributed by the top switch of the N-phase, the bottom switch of the a-phase, while ripple 16 is contributed by the top switch of the C-phase, the bottom switch of the a-phase. Finally, ripple 17 is contributed by the top switch of phase C, the bottom switch of phase N, and ripple 18 is contributed by the top switch of phase C and the bottom switch of phase B. The cycle repeats in this order so that the lowest torque of the output torque waveform can be increased, thereby increasing the average torque of the rotor, and still keeping the peak torque constant. In this case, the average torque is higher.

Many modifications and variations of the present subject matter are possible in light of the above disclosure. Therefore, within the scope of the claims of the present subject matter, the disclosure may be practiced other than as specifically described.