CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the priority of the Indian Provisional Patent Application (PPA) with 202141009213 filed on March 05, 2021, with the title "AN IMPROVED SWITCHED RELUCTANCE MOTOR". The contents of abovementioned PPA are included in entirety as reference herein

BACKGROUND Technical field

[0002] The embodiments herein generally relate to switched reluctance motor (SRM). The embodiments herein are particularly related to a system and method of managing inductance in switched reluctance motor (SRM) in order to deliver the required torque at base and higher speeds thereby improving the performance efficiently. The embodiments herein are more particularly related to a system and method of achieving the required torque at a specific speed by managing the inductance.

Description of the Related art

[0003] High-performance motors are required for domestic, industrial, transport sectors and various other applications. In accordance with this trend, there is a great demand for a structure of an electric motor having a simple mechanical structure, a low price, and excellent efficiency and output characteristics compared to a conventional electric motor.

[0004] Switched Reluctance Motor or SRM is one among the currently known motors, which is being applied to industrial systems and home appliances due to its simple and robust mechanical structure, excellent traction torque, low manufacturing cost and minimal maintenance cost. In particular the SRM does not include a permanent magnet, a brush, and a commutator. Moreover, a SRM or a Switched Reluctance Motor has a stator, which includes salient poles and has a structure in which steels are stacked and winding around which coils connected in series with each other are wound are independently connected to the respective phases and enclose stator poles. A rotor does not include a winding, has a structure in which steels are stacked, and includes salient poles, similar to the stator. Therefore, since both of the stator and the rotor have the salient pole structure, the SRM may be considered as having a double salient pole type structure. Hence, due to the simple structure of the SRM, the reliability is increased, and production cost is decreased.

[0005] Unlike a typical AC motor, which obtains rotational force by a rotating magnetic field, SRM is a power device driven by pulse type excitation power and magnetic resistance due to the polarity of the rotor and stator which is reluctance torque. This is because continuous pulse excitation power supply is required every time. Furthermore, the inductance offered by the stator winding of a conventional SRM fundamentally determines the torque that is delivered. The inductance is a function of the size of the stator pole, number of turns and the flux in the coils. Moreover, a higher inductance leads to a higher torque and a lower inductance leads to a lower torque but facilitates high speed operation. Therefore, a high inductance SRM will deliver high torque at lower RPM and operates sub-optimally at higher speeds and vice-versa.

[0006] In the backdrop of emerging demand/trend there is a need for an alternative improved system and method of managing the inductance of an SRM in order to achieve the required torque at a specific speed. Further, there is a need for an improved system and method of managing the inductance of drive motors of any kind to achieve the required torque at a specific speed.

[0007] The above-mentioned shortcomings, disadvantages and problems are addressed herein, and which will be understood by reading and studying the following specification.

OBJECTIVES OF THE EMBODIMENTS HEREIN

[0008] The primary object of the embodiments herein is to provide a system and method of managing the inductance in switched reluctance motor (SRM) in order to deliver the required torque at base and higher speeds thereby improving the performance of the motor efficiently.

[0009] Another object of the embodiments herein is to system and method to achieve the required torque at a specific speed by switching the inductance, wherein the inductance has the same effect as changing the gears in a mechanical gear box. Hence, the method mimics a gearbox in an electronic fashion. [0010] Yet another object of the embodiments herein is to provide a driving circuit in order to achieve the required torque at specific speed by placing number of windings at each pole of a SRM or Switched Reluctance Motor thereby switching the inductance.

[0011] Yet another object of the embodiments herein is to arrange the windings dynamically in series or parallel in a driving circuit, thereby achieving the required torque at specific speed.

[0012] Yet another object of the embodiments herein is to provide the system with torque delivery at various speeds in order to match the various application requirements such as not limited to in electric vehicle motor, traction motors, industrial motors, home appliances, heavy duty home appliances and the like.

[0013] Yet another object of the embodiments herein is to provide the system for switching architectures not only with two inductances per phase but also include the switching architectures with three or more inductances per phase for finer control at an increased complexity of the switching logic.

[0014] Yet another object of the embodiments herein is to provide an improved system and method of managing the inductance of drive motors of any kind to achieve the required torque at a specific speed. [0015] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY

[0016] The following details present a simplified summary of the embodiments herein to provide a basic understanding of the several aspects of the embodiments herein. This summary is not an extensive overview of the embodiments herein. It is not intended to identify key /critical elements of the embodiments herein or to delineate the scope of the embodiments herein. Its sole purpose is to present the concepts of the embodiments herein in a simplified form as a prelude to the more detailed description that is presented later.

[0017] The other objects and advantages of the embodiments herein will become readily apparent from the following description taken in conjunction with the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. [0018] The various embodiments herein provide, a system for achieving required torque at a specific speed by switching inductance in a Switched Reluctance Motor (SRM) is provided. The system comprises a SRM configured with a plurality of stator poles and a plurality of rotor poles, and each of the plurality of stator poles comprises a plurality of windings and a driving circuit. The driving circuit includes a plurality of switches configured with the plurality of windings. The plurality of windings is further configured dynamically to achieve variable inductances. The dynamic configuration of the plurality of windings includes the plurality of windings arranged in series and parallel.

[0019] According to one embodiment herein, the plurality of windings at each of the plurality of stator poles further comprises a plurality of sub-windings. The plurality of sub-windings is dynamically configured in series or parallel or in combination mode to vary the inductance and torque or speed performance of the SRM.

[0020] According to one embodiment herein, the plurality of windings arranged in series produces higher torque, and the higher torque is achieved by higher inductance. The higher inductance is achieved by increasing the plurality of windings.

[0021] According to one embodiment herein, the plurality of windings arranged in parallel produces higher speed. The higher speed is achieved at lower inductance and higher rate of change of current, such that the higher rate of change of current provides an option to turn on and off each plurality of stator poles faster to achieve higher speed. [0022] Furthermore, in order to achieve higher ratios of lower and higher inductance, three or larger number of windings can be employed, such that the windings are arranged in series or parallel in order to provide wide range of inductance settings. [0023] According to one embodiment herein, the plurality of switches of the driving circuit includes mechanical switches, electronic relays or semiconductor switches like BJT, MOSFET or IGBTs. Furthermore, the system for achieving torque delivery at various speeds in order to match the various application requirements such as not limited to in electric vehicle motor, traction motors, industrial motors, home appliances, heavy duty home appliances and the like.

[0024] According to one embodiment herein, a method for achieving required torque at a specific speed by switching inductance in a Switched Reluctance Motor (SRM) is provided. The method includes configuring dynamically a plurality of windings of a SRM with a plurality of switches of a driving circuit. The plurality of windings is configured with in each of a plurality of stator poles of the SRM. The dynamic configuration of the plurality of windings includes the plurality of windings arranged in series and the plurality of windings arranged in parallel. The method further includes achieving required torque by switching between the plurality of windings arranged in series or the plurality of windings arranged in parallel or combination of both.

[0025] According to one embodiment herein, the method for achieving required torque is provided. The method includes measuring current torque and speed and estimating commanded torque. The commanded torque is the required torque in lower and higher speeds. The method further includes evaluating and continuing to function normally, if the current torque and speed is within the capability of current inductance. Switching to higher inductance by evaluating if the current torque is above maximum torque at current speed, and current speed is below maximum speed. Furthermore, the method includes switching to lower inductance by evaluating if the current speed is above the maximum speed at the current torque, and the current torque is below the maximum torque.

[0026] The example given in the embodiments of the present invention by way of illustration are not only limited to switching architectures with two inductances per phase but also include the switching architectures with three or more inductances per phase for finer control at an increased complexity of the switching logic.

[0027] According to an embodiment herein, the switching architectures with two or more inductances per phase for finer control at an increased complexity of the switching logic at any kind of drive motor, is provided.

[0028] Furthermore, an improved system and method are provided for managing the inductance of not only SRM motors but also drive motors of any kind to achieve the required torque at a specific speed.

[0029] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating the preferred embodiments and numerous specific details thereof, are given by way of an illustration and not of a limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The other objects, features, and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which: [0031] FIG. 1 illustrates a driving circuit for Switched Reluctance Motor or

SRM, according to an embodiment herein.

[0032] FIGS. 2A-2D depicts a configuration of sub-windings within the windings in various topologies in a SRM, according to an embodiment herein.

[0033] FIG. 3 illustrates a flow chart depicting a method for achieving required torque at a specific speed by switching inductance in a Switched Reluctance Motor (SRM), according to an embodiment herein.

[0034] FIG. 4A-4C depicts a system for switching architectures with three of more inductances per phase dynamically configured for finer control at an increased complexity of the switching logic, according to an embodiment herein. [0035] FIG. 5 illustrates a graph of torque vs speed performance of a SRM with

4 sub-windings per phase configured dynamically, according to an embodiment herein.

[0036] Although the specific features of the embodiments herein are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the embodiments herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS HEREIN [0037] In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense. [0038] The various embodiments herein provide a system and method of managing the inductance in a switched reluctance motor (SRM), to deliver the required torque at base and higher speeds thereby improving the performance of the motor efficiently. The embodiments herein, provides a system and method to achieve the required torque at a specific speed by switching the inductance, wherein the inductance has the same effect as changing the gears in a mechanical gear box. Hence, the method mimics a gearbox in an electronic fashion. The embodiments, herein also provides a driving circuit with dynamically arranged windings in series and parallel in order to achieve the required torque at specific speed by placing number of windings at each pole of a SRM or Switched Reluctance Motor thereby switching the inductance. [0039] The various embodiments herein provide, a system for achieving required torque at a specific speed by switching inductance in a Switched Reluctance Motor (SRM) is provided. The system comprises a SRM configured with a plurality of stator poles and a plurality of rotor poles, and each of the plurality of stator poles comprises a plurality of windings and a driving circuit. The driving circuit includes a plurality of switches configured with the plurality of windings. The plurality of windings is further configured dynamically to achieve variable inductances. The dynamic configuration of the plurality of windings includes the plurality of windings arranged in series and parallel. [0040] According to one embodiment herein, the plurality of windings at each of the plurality of stator poles further comprises a plurality of sub-windings. The plurality of sub-windings is dynamically configured in series or parallel or in combination mode to vary the inductance and torque or speed performance of the SRM. [0041] According to one embodiment herein, the plurality of windings arranged in series produces higher torque, and the higher torque is achieved by higher inductance. The higher inductance is achieved by increasing the plurality of windings connected in series. The torque produced by a switched reluctance motor at any given instant is given by: t= ½ I ² dL/dt [0042] It is to be noted that the inductance is minimum at unaligned position and maximum at aligned position of the rotor of the SRM. The rate of change of inductance from unaligned to aligned position of the rotor is proportional to the inductance of the plurality of windings. Hence, higher inductance of the plurality of windings produces higher gradient of inductance from unaligned to aligned position transition and hence, higher torque.

[0043] According to one embodiment herein, the plurality of windings arranged in parallel produces higher speed. The rate of current raise during turning on one phase of a switched reluctance motor is given by: di/dt = V/L where L represents the instantaneous inductance. When the inductance is less, the rate of change of current is higher, which provides an option to turn on and off each phase of the SRM faster and achieve higher speeds of operation.

[0044] According to one embodiment herein, the plurality of switches of the driving circuit includes mechanical switches, electronic relays or semiconductor switches like BJT, MOSFET or IGBTs. Furthermore, the system for achieving torque delivery at various speeds in order to match the various application requirements such as not limited to in electric vehicle motor, traction motors, industrial motors, home appliances, heavy duty home appliances and the like.

[0045] According to one embodiment herein, a method for achieving required torque at a specific speed by switching inductance in a Switched Reluctance Motor (SRM) is provided. The method includes configuring dynamically a plurality of windings of a SRM with a plurality of switches of a driving circuit. The plurality of windings is configured with in each of a plurality of stator poles of the SRM. The dynamic configuration of the plurality of windings includes the plurality of windings arranged in series and the plurality of windings arranged in parallel. The method further includes achieving required torque by switching between the plurality of windings arranged in series or the plurality of windings arranged in parallel or combination of both.

[0046] Each series-parallel combination of the plurality windings is considered as a gear setting, and wherein the settings with more plurality of windings in series is considered as a lower gear while the settings with more plurality of windings in parallel is considered as a higher gear.

[0047] According to one embodiment herein, the method for achieving required torque is provided. The method includes measuring current torque and speed and estimating commanded torque. The commanded torque is the torque required by the motor to continue to power the load as per the application demands. The method further includes evaluating and continuing to function normally, if the commanded torque and speed is within the capability of current gear setting. Switching to higher gear by evaluating if the commanded torque is above maximum torque at current speed, and the current speed is below maximum speed at the next higher gear. Furthermore, the method includes switching to lower gear by evaluating if the current speed is above the maximum speed at the commanded torque, and the commanded torque is below the maximum torque at the next lower gear. [0048] The example given in the embodiments of the present invention by way of illustration are not only limited to switching architectures with two inductances per phase but also include the switching architectures with three or more inductances per phase for finer control at an increased complexity of the switching logic.

[0049] According to one embodiment herein, the switching architectures with two or more inductances per phase for finer control at an increased complexity of the switching logic at any kind of drive motor, is provided. Consider the inductance of each sub-winding of a particular phase of the SRM as Lsw. Assume there are 2 ⁿ sub-windings for each phase. When all the sub-phases are connected together, the total inductance can vary from 2 ⁿ * Lsw to L _sw /2 ⁿ . Hence, the Table 1 below shows the different combinations that can be achieved in the case of 4 sub-windings per phase of the SRM. The same methodology is also be used for other sub-winding combinations of the SRM such as 2, 4, 8, 16 etc. Therefore, by changing the combination, the total inductance can be changed up to a total multiple of 2 ²ⁿ .

Table 1 showing the different combinations of windings achieved in case of 4 sub-windings per phase of SRM.

[0050] According to one embodiment herein, FIG. 1 illustrates a driving circuit for Switched Reluctance Motor or SRM. FIG. 1 illustrates a driving circuit comprising switches and windings arranged dynamically. The method of achieving the required torque at specific speed is achieved by two cases Case A and Case B, respectively. FIG. 1 illustrates Case A comprising windings arranged in series, wherein the switches SI and S3 are open and S2 is closed, which results in high torque generation at lower speeds in SRM. Case B comprises of windings arranged in parallel wherein the switch S2 is open and switches SI and S3 are closed which results in high-speed operation of the motor.

[0051] Furthermore, to achieve higher ratios of lower and higher inductance, three or larger number of windings can be employed, such that the windings are arranged in series or parallel, to provide wide range of inductance settings. [0052] According to one embodiment herein, FIGS. 2A-2D depicts a configuration of sub-windings within the windings in various topologies in an SRM.

[0053] FIG. 2A illustrates a 6-4 SRM. In 6-4 SRM each phase has two poles. The windings of each pole can be considered as a sub-winding and can be connected in series or parallel mode to vary the inductance and torque/speed performance of the machine. For example, phase A has A1 and A2 sub-windings which can be connected either in series or parallel to achieve torque speed variations.

[0054] FIG. 2B illustrates a 12-8 SRM. In 12-8 SRM each phase has four poles. The windings of each pole can be considered as a sub-winding and can be connected in series or parallel mode to vary the inductance and torque/speed performance of the machine. For example, phase A has Al, A2, A3 and A4 sub-windings which can be connected either in 4S, 2S2P and 4P arrangements to achieve torque speed variations.

[0055] FIG. 2C illustrates 12-8 SRM. In 12-8 SRM each pole winding has been split into two sub-windings. The half-winding of each pole can be considered as a sub- winding and can be connected in series or parallel mode to vary the inductance and torque/speed performance of the machine. For example, phase A has A1-A8 sub windings which can be connected either in 8S, 4S2P, 2S4P and 8P arrangements to achieve torque speed variations.

[0056] FIG. 2D illustrates 8-8 (Ns-Np) SRM. In 8-8 (Ns-Np) SRM all the 8 poles are connected as a single -phase machine. Here, all windings in the machine are excited simultaneously and can be considered as a single phase. The winding of each pole can be considered as a sub-winding and can be connected in series or parallel mode to vary the inductance and torque/speed performance of the machine. This is a single-phase machine - Phase A has A1-A8 sub-windings which can be connected either in 8S, 4S2P, 2S4P and 8P arrangements to achieve torque speed variations.

[0057] According to one embodiment herein, FIG. 3 illustrates a flow chart depicting a method for achieving required torque at a specific speed by switching inductance in a Switched Reluctance Motor (SRM). At step 302, current torque and speed is measured. At 304, commanded torque is measured, wherein the commanded torque is the torque required by the motor to continue to power the load as per the application demands. At step 306, commanded torque and speed is evaluated to check if the current torque and speed is within the capability of current gear setting. If the current torque and speed is within the capability of current gear setting, the motor continues to function normally. If not (If the current torque and speed is not within the capability of current gear setting), the commanded torque is evaluated to check if commanded torque is above maximum torque at current speed at step 308. At step 310, the current speed is evaluated to check if the current speed is below maximum speed at next higher gear setting. At step 312, switching to a higher gear setting is attained and which in turn increases the maximum torque available from the machine at the expense of maximum speed. At step 314, the current speed is evaluated to check if the current speed is above maximum speed at current torque. At step 316, commanded torque is evaluated to check if the commanded torque is below the maximum torque at a next gear setting. At step 318, switching to a lower gear is attained and which in turn increases the maximum speed available from the machine at the expense of maximum torque. In this manner, a wide range of torque-speed points of operation is delivered from the same motor. [0058] According to one embodiment herein, FIG. 4A-4C depicts a system for switching architectures with three of more inductances per phase dynamically configured for finer control at an increased complexity of the switching logic, according to an embodiment herein. [0059] FIG. 4A illustrates 4S combination of switching architecture. 4S includes 4 series sub-windings Wl, W2, W3 and W4 per phase connected in series.

[0060] FIG. 4B illustrates 2S2P combination of switching architecture. 2S2P includes 2 series sub-windings Wl, W2 are connected in series and W3, W4 are connected in series per phase and 2 combined windings W1&W2 and W3&W4 are connected in parallel per phase.

[0061] FIG. 4C illustrates 4P combination of switching architecture. 4P includes 4 parallel sub-windings Wl, W2, W3 and W4 are connected in parallel per phase.

[0062] According to one embodiment herein, FIG. 5 illustrates a graph of torque vs speed performance of a SRM with 4 sub-windings per phase configured dynamically. FIG. 5 shows torque vs speed performance of a motor with 4 sub windings per phase. The first curve 502 depicts highest torque and lowest speed range, achieved when all sub-windings are connected in series (4S). The second curve 504 depicts 2S2P arrangement (2 series and 2 parallel). The third curve 506 depicts highest speed and lowest torque range, achieved when all sub-windings are connected in parallel (4P) mode.

[0063] Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. [0064] The system and method for managing the inductance in a switched reluctance motor (SRM), to deliver the required torque at base and higher speeds thereby improving the performance of the motor efficiently disclosed in the embodiments herein have several exceptional advantages. The system helps to provide the torque delivery at various speeds, which in in turn matches various application requirements such as and not limited to in electric vehicle motor, traction motors, industrial motors, home appliances, heavy duty home appliances and the like.

[0065] The example given in the embodiments of the present invention by way of illustration are not only limited to switching architectures with two inductances per phase but also include the switching architectures with three or more inductances per phase for finer control at an increased complexity of the switching logic.

[0066] Furthermore, the embodiments herein provide a system by varying the inductances in SRM, such that the torque ratio is minimized from zero speed to maximum speed, wherein a flatter torque vs speed curve and a wider area of operation is achieved. Besides, switching the inductance in SRM, has the same effect as changing the gears in a mechanical gear box. Hence, the method mimics a gearbox in an electronic fashion. Furthermore, an improved system and method are provided for managing the inductance of not only SRM motors but also drive motors of any kind to achieve the required torque at a specific speed. [0067] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such as specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

[0068] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications. However, all such modifications are deemed to be within the scope of the claims.