Claims:CLAIMS

I/We claim:

1. A switched reluctance motor (SRM) comprising:
a stator is made of a silicon steel lamination comprises a plurality of stator poles, wherein the stator poles comprising a plurality of coil windings to generate a magnetic field in the stator poles;
a rotor is made of the silicon steel lamination comprises a plurality of rotor poles, wherein the stator and the rotor are stacked on to a shaft;
a Hall effect rotary smart angler position sensor to measure the position orientation of the stator and the rotor;
an energy switching circuit to attach a voltage supply to the coil windings to produce current and drive the switched reluctance motor (SRM), wherein the energy switching circuit provides a substitute path for the current to flow when the energy switching circuit is turned off;
an isolated gate driver circuit (IGBT) to protect a switched reluctance motor (SRM) drive at the time of variable load condition and voltage and current spikes current;
a microcontroller to control the SRM motor through a PWM pulse, wherein the microcontroller facilitates the Hall effect rotary smart angler position sensor to measure the position orientation of the stator and the rotor and commutates the coil windings to attain a variable speed and a torque-speed; and
a motor housing having a body made of aluminum gravity die-casting to house the stator, the rotor, the Hall effect rotary smart angler position sensor, the energy switching circuit, the isolated gate driver circuit (IGBT), and the microcontroller.
2. The switched reluctance motor of claim 1, wherein the measured position commutates an overlapped dwell angle firing to minimize a torque ripple and vibration of the switched reluctance motor.
3. The switched reluctance motor of claim 1, wherein the coil windings are constructed in a pair of five copper wire having seventeen standard wire gauge (SWG).
4. The switched reluctance motor of claim 1, wherein the energy switching circuit comprises an asymmetric converter topology to drive the switched reluctance motor (SRM).
5. The switched reluctance motor of claim 1, wherein the isolated gate driver circuit (IGBT) is designed by a galvanic isolated driver that uses magnetically-coupled coreless transformer (CT) to provide signal transfer across galvanic isolation from an input to an output.
6. The switched reluctance motor of claim 1, wherein the microcontroller having a computational capability of at least fifty Million Instructions Per Second (MIPS).
7. The switched reluctance motor according to claim 1, wherein the microcontroller commutates to attain the variable speed and the torque-speed from about 1 revolution per minute (RPM) to base speed.
8. The switched reluctance motor according to claim 1 mounds with a foot mount for a chain drive and a flange mount for a differential gear arrangement in a vehicle.
, Description:SWITCHED RELUCTANCE MOTOR (SRM)

TECHNICAL FIELD
[0001] The present invention relates to an electrical machine, in particular to a switched reluctance motor (SRM).

BACKGROUND
[0002] The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in-and-of-themselves may also be inventions.
[0003] Typically, a switched reluctance motor (SRM) is operated by reluctance torque and power is delivered to windings in a stator rather than the rotor. Switched reluctance motor (SRM) is a type of motor doubly salient with phase coils mounted around diametrically opposite stator poles. Switched reluctance motors (SRM) have a simple and robust structure, thus they are generally suitable for high-speed applications such as electric vehicles (EV). High-speed motors have the advantage of high power density, which is an important issue of traction motors in electric vehicles (EV).
[0004] European patent application EP0814558A2 filed by Ki-Bong, Kim discloses a switched reluctance motor that includes a stator and a rotor, each having a plurality of poles, characterized in that the poles of the rotor are configured to smooth output torque as a function of rotor angular position. US patent number US8541920B2 filed by Krishnan Ramu talks about a switched reluctance motor that includes four stator poles and an electrically conductive material around each of the stator poles. The geometric outline, on one side of the stator pole, of at least one of the conductive materials is not rectangular, as viewed from a cross-section of the switched reluctance motor showing each of the stator poles.
[0005] However, the existing switched reluctance motors (SRM) do not provide high motor-drive efficiency, reliability, and increased performance. Therefore, there is a need for a switched reluctance motor (SRM) that can provide high motor-drive efficiency, reliability, and increased performance.
[0006] The above-mentioned shortcomings, disadvantages, and problems are addressed herein and which will be understood by reading and studying the following specification.

SUMMARY
[0007] The various embodiments herein provide a switched reluctance motor (SRM).
[0008] According to an embodiment herein, a switched reluctance motor (SRM) includes a stator, a rotor, a Hall effect rotary smart angler position sensor, an energy switching circuit, an isolated gate driver circuit (IGBT), a microcontroller, and a motor housing. The stator is made of a silicon steel lamination. The stator includes a plurality of stator poles. The stator poles include a plurality of coil windings to generate a magnetic field in the stator poles. The rotor is made of silicon steel lamination. The rotor includes a plurality of rotor poles. The stator and the rotor are stacked on to a shaft. The Hall effect rotary smart angler position sensor measures the position orientation of the stator and the rotor. The energy switching circuit attaches a voltage supply to the coil windings to produce current and drive the switched reluctance motor (SRM). The energy switching circuit provides a substitute path for the current to flow when the energy switching circuit is turned off. The isolated gate driver circuit (IGBT) protects a switched reluctance motor (SRM) drive at the time of variable load condition and voltage and current spikes current. The microcontroller controls the SRM motor through a PWM pulse. The microcontroller facilitates the Hall effect rotary smart angler position sensor to measure the position orientation of the stator and the rotor and commutates the coil windings to attain a variable speed and a torque-speed. The motor housing having a body made of aluminum gravity die-casting to house the stator, the rotor, the Hall effect rotary smart angler position sensor, the energy switching circuit, the isolated gate driver circuit (IGBT), and the microcontroller.
[0009] In an aspect, the measured position commutates an overlapped dwell angle firing to minimize a torque ripple and vibration of the switched reluctance motor.
[0010] In an aspect, the coil windings are constructed in a pair of five copper wire having seventeen standard wire gauge (SWG).
[0011] In an aspect, the energy switching circuit includes an asymmetric converter topology to drive the switched reluctance motor (SRM) and also provides a minimal switching of a semiconductor.
[0012] In an aspect, the isolated gate driver circuit (IGBT) is designed by a galvanic isolated driver that uses magnetically-coupled coreless transformer (CT) to provide signal transfer across galvanic isolation from an input to an output.
[0013] In an aspect, the microcontroller has a computational capability of at least fifty Million Instructions Per Second (MIPS).
[0014] In an aspect, the microcontroller commutates to attain the variable speed and the torque-speed from about 1 revolution per minute (RPM) to base speed.
[0015] In an aspect, the switched reluctance motor mounds with a foot mount for a chain drive and a flange mount for a differential gear arrangement in a vehicle.
[0016] According to an embodiment herein, the design parameter and dimension is optimized with the efficiency of the present switched reluctance motor (SRM).
[0017] Accordingly, one advantage of the present invention is that the silicon steel lamination of the stator and rotor provides good hysterias property in the magnetizing and demagnetizing.
[0018] Accordingly, one advantage of the present invention is that the stator and rotor rugged and reduce the vibration and noise.
[0019] Accordingly, one advantage of the present invention is that it uses a Hall effect principle to measure the absolute position of the stator and rotor orientation. The Hall effect rotary smart angler position sensor is construed with low cost.
[0020] Accordingly, one advantage of the present invention is that the overlapped dwell angle firing minimizes the torque ripple and vibration of the motor.
[0021] Accordingly, one advantage of the present invention is that the asymmetric converter topology is utilized for a minimal switching of a semiconductor and low cost.
[0022] According to an embodiment herein, the SRM is a type of electrical machine. The stator has coil windings. The rotor contains no conductors or permanent magnets. The rotor and stator are constructed by silicon steel lamination that is stacked on to a shaft. The SRM is electronically commutated. The current pass through one of the stator’s coil windings. The torque is generated by the tendency of the rotor to align with the excited stator pole. The direction of torque generated is a function of the rotor position with respect to the energized phase and is independent of the direction of current flow through a phase winding. The continuous torque is produced by intelligently synchronizing each phase's excitation with the position orientation of the rotor.
[0023] Other features of embodiments of the present invention will be apparent from accompanying drawings and from the detailed description that follows.
[0024] Yet other objects and advantages of the present invention will become readily apparent to those skilled in the art following the detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated herein for carrying out the invention. As we realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In the figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description applies to any one of the similar components having the same first reference label irrespective of the second reference label.
[0026] FIG. 1 illustrates an exploded view of various components of a switched reluctance motor (SRM), in accordance with one embodiment of the present invention.
[0027] FIG. 2 illustrates a perspective view of a stator, in accordance with one embodiment of the present invention.
[0028] FIG. 3 illustrates a perspective view of a rotor, in accordance with one embodiment of the present invention.
[0029] FIG. 4 illustrates a circuit diagram of an asymmetric converter topology, in accordance with one embodiment of the present invention.
[0030] FIG. 5 illustrates a graphical representation of the operation performed by IGBT 1 and IGBT 2, in accordance with one embodiment of the present invention.
[0031] FIG. 6 illustrates a graphical representation to depict that the voltage across the winding becomes zero if the diode and transistor voltage drops are neglected, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION
[0032] The present invention is best understood with reference to the detailed figures and description set forth herein. Various embodiments have been discussed with reference to the figures. However, those skilled in the art will readily appreciate that the detailed descriptions provided herein with respect to the figures are merely for explanatory purposes, as the methods and systems may extend beyond the described embodiments. For instance, the teachings presented and the needs of a particular application may yield multiple alternative and suitable approaches to implement the functionality of any detail described herein. Therefore, any approach may extend beyond certain implementation choices in the following embodiments.
[0033] Although the present invention describes the switched reluctance motor (SRM), it should be appreciated that the same has been done merely to illustrate the invention in an exemplary manner and to highlight any other purpose or function for which explained structures or configurations could be used and is covered within the scope of the present invention.
[0034] According to an embodiment herein, the switched reluctance motor is constructed in various configurations such as 6 stator poles and 4 rotor pole, and 8 stator poles and 6 rotor poles. With respect to the base speed, the number of stator poles and rotor poles is configured. This motor configuration is designed for the based speed of 3000 rpm and a maximum speed of 6000 rpm. A motor shaft is directly coupled to the differential gearbox or chain drive of the vehicle. This configuration of the motor commutated to attain variable speed and torque-speed from 1 RPM to Base speed.
[0035] The basic operating principle of the SRM the stator consists of laminated iron silicon with stator poles and winding. The rotor consists of laminated iron silicon steel. By exciting pair of opposite winding in the stator poles, the current is passed through the stator windings. The torque is generated by the tendency of the rotor to align with the excited stator pole. The direction of torque generated is a function of the rotor position with respect to the energized phase and is independent of the direction of current flow through the phase winding. Continuous torque can be produced by intelligently synchronizing each phase's excitation with the rotor position.
[0036] FIG. 1 illustrates an exploded view of various components of a switched reluctance motor (SRM) 100, in accordance with one embodiment of the present invention. The switched reluctance motor (SRM) 100 includes a stator (shown and explained in conjunction with FIG. 2), a rotor (shown and explained in conjunction with FIG. 3), a Hall effect rotary smart angler position sensor (8), an energy switching circuit, an isolated gate driver circuit (IGBT), a microcontroller, and a motor housing (1). The stator is made of a silicon steel lamination. The stator includes a plurality of stator poles. The stator poles include a plurality of coil windings (16) to generate a magnetic field in the stator poles. The rotor is made of silicon steel lamination. The rotor includes a plurality of rotor poles. The stator and the rotor are stacked on to a shaft (6) (mild steel material). In an embodiment, the coil windings (16) are constructed in a pair of five copper wire having seventeen standard wire gauge (SWG). In an embodiment, the coil windings (16) are designed with respect to operating voltage and current to archive the rated torque and speed for a 3 kW machine. The multiple pair of wire reduces the skin effect in the copper wire.
[0037] The Hall effect rotary smart angler position sensor (8) measures the position orientation of the stator and the rotor. In an embodiment, the measured position commutates an overlapped dwell angle firing to minimize a torque ripple and vibration of the switched reluctance motor. According to an embodiment herein, the overlapped dwell angle firing is a variable parameter depends on the torque ripple. The angle is adjusted from 0 to 30% of the overlapped dwell angle firing to reduce the torque ripple and manages the demand of the overall torque to drive the load.
[0038] The Hall effect rotary smart angler position sensor (8) has an output of 0-5V (for 0-360 degrees) with respect to the absolute position of the rotor. The output interfaces with the controller to understand the orientation of the stator and rotor. The speed of the rotor is calculated from the ramp output from the sensor. This sensing arrangement is constructed with standard shaft 6 mm and 13 mm length. This sensor home position and the rotor and stator are mechanically oriented with the position .this will leads the controller will understand the position of the rotor accurately and commutate the stator coils. The main advantage of the Hall effect rotary smart angler position sensor (8) is to provide the position reading to commutate the overlapped dwell angle firing.
[0039] The optical sensor is will give pules per rotation the position and the speed of the rotor is only mathematically evaluated one. This optical sensor or encoder to understand the home position is difficult at starting. In an embodiment, the present SRM utilizes a linear Hall effect sensor to overcome the above problem.
[0040] The energy switching circuit attaches a voltage supply to the coil windings to produce current and drive the switched reluctance motor (SRM). The energy switching circuit provides a substitute path for the current to flow when the energy switching circuit is turned off. In an embodiment, the energy switching circuit includes an asymmetric converter topology (shown in FIG. 4) to drive the switched reluctance motor (SRM) and also provides a minimal switching of a semiconductor.
[0041] The isolated gate driver circuit (IGBT) protects a switched reluctance motor (SRM) drive at the time of variable load condition and voltage and current spikes current. In an embodiment, the isolated gate driver circuit (IGBT) is designed by a galvanic isolated driver that uses magnetically-coupled coreless transformer (CT) to provide signal transfer across galvanic isolation from an input to an output.
[0042] The microcontroller controls the SRM motor through a PWM pulse. The microcontroller facilitates the Hall effect rotary smart angler position sensor (8) to measure the position orientation of the stator and the rotor and commutates the coil windings to attain a variable speed and a torque-speed. In an embodiment, the microcontroller has a computational capability of at least fifty Million Instructions Per Second (MIPS). In an embodiment, the microcontroller commutates to attain the variable speed and the torque-speed from about 1 revolution per minute (RPM) to base speed. In an embodiment, the switched reluctance motor mounds with a foot mount for a chain drive and a flange mount for a differential gear arrangement in a vehicle. The foot mount 4 numbers of M10 holes are provided to mount on the chassis. The flange mount 4 numbers of 13 mm holes are provided to mount with M12 bolt in the differential gear arrangement.
[0043] The description further describes the principle of the commutation of the microcontroller. The present SRM is controlled by the electronic commutation of stator poles. Each pair of opposite stator poles are excited by the electronic switching through a converter. The pair of poles are A A’, B B’, C C’, D D’ (shown in FIG. 2). The A pole is exited as the North Pole and A’ pole is exited in the South Pole the electromagnetic field is passed from the north pole to south pole through rotor pole. The rotor is attracted by the start pole. At initial condition the reluctance of the pole is high and it will draw the minimum current to attract the rotor pole. Once the rotor pole is alien with stator pole the reluctance is low the current high. The rotor will move from the unaligned position to align position depends on the sensor feedback the stator coils are fired to create rotation rotational magnetic field. This rotational magnetic field rotates the rotor in 360 degrees. The above firing scheme is the normal operation of the switched reluctance motor. But it will create the more torque ripple in the rotor shaft. To overcome this to minimize the torque ripple by overlap the firing angle of the stator coil pair. An optimized overlapping angle is estimated by the speed and torque demand by the system. This closed-loop control is activated without compromise the efficiency of the system. This will be implemented by the absolute position sensor feedback control system.
[0044] The motor housing (1) having a body made of aluminum gravity die-casting to house the stator, the rotor, the Hall effect rotary smart angler position sensor (8), the energy switching circuit, the isolated gate driver circuit (IGBT), and the microcontroller. In an embodiment, the body of the motor is the aluminum gravity die-casting for 3 kW design the outer diameter of the housing is 166 mm. Depends on the power rating the diameter of the motor housing is varied. According to an embodiment herein, the length of the motor housing (1) is 152 mm for 3 kW. The length of the motor housing (1) also varies with respect to the power rating of the motor. The cooling fence is projected outside of the motor housing (1) for 10 mm height. The rotor shaft is supported with bearing. The motor flange arrangement is directly coupled with a differential gear mechanism or chain drive of the mechanical drive system. According to an embodiment herein, the motor housing (1) is an aluminium body with a fence and the motor housing (1) also has a back end cover (2) and a front cover with flange mount (3) made of aluminium. Aluminum front and rear motor flange end cover are holding with bearing. In an embodiment, the bearing is sealed ball bearings 204PP (11) for front and rear.
[0045] According to an embodiment herein, the switched reluctance motor (SRM) 100 includes a rotor lamination stamping stack (4) and stator lamination stamping stack (5) to eliminate welding or riveting of the switched reluctance motor (SRM) 100. In an embodiment, the rotor lamination stamping stack (4) and stator lamination stamping stack (5) are made of electrical steel sheet (M22) having 0.35 mm thickness.
[0046] FIG. 2 illustrates a perspective view 200 of a stator, in accordance with one embodiment of the present invention. The stator is constructed by silicon steel laminations are stacked. Depend on the power rating the stator stack length is constructed with a 0.35 mm thickness laminated steel sheet. A “V “crew or a welding provision (20) is formed in the stator. The stator is welded to form the solid stator to avoid vibration and good magnetic poles. Each pole ends are projected with a coil holding arrangement or a holding clamp (21). The lamination silicon steel M22 grade to minimize the watt loss in the stator. The width of each stator poles (22) is 13 mm for 3 kW rating and the 8 stator poles are symmetric with each pole to make a perfect alignment. The stator pole and rotor pole width are optimized design to flow the electromagnetic field a pair of the opposite pole. In an embodiment, the lamination material of the stator and rotor is constructed by Non-Grain Oriented Electrical Steel IS 648 standard: 35C300 Former AISI standard: M22 IEC 60404-8-4 standard: M300-35 A5. The material core loss is 1.15 watts/ kg. C-5 type inorganic coating which provides good insulation resistance, very good temperature capability and a high stacking factor. This property of the steel leads the motor efficiency.
[0047] FIG. 3 illustrates a perspective view 300 of a rotor, in accordance with one embodiment of the present invention. The rotor is constructed by silicon steel laminations are stacked on to a shaft. The silicon steel lamination has a good hysterias property in the motoring operation. Because the lamination steel contains highly silicon material to activating and deactivating magnetic property. Depend on the power rating the stack length is constructed with a 0.35 mm thickness laminated steel sheet. The rotor lamination and the locking arrangement of the keyway (24) are constructed to avoid the slip. The silicon steel lamination is M22 grade to minimize the watt loss in the rotor. The rotor is perfectly balanced to rotate freely. The rear side of the motor shaft is extended to mount for a cooling fan (10) (shown in FIG. 1) and a position sensor. The cooling fan (10) is covered by a back end fan cover (7) made of mild steel. In an embodiment, the rotor poles (23) are constructed with 6 poles or 4 poles depends on the configuration of the motor. In an embodiment, the stack length is 112 mm for 3 kW rated.
[0048] FIG. 4 illustrates a circuit diagram 400 of an asymmetric converter topology, in accordance with one embodiment of the present invention. The asymmetric bridge converter topology considers only one phase of the SRM. The rest of the phases are similarly connected. The IGBT1 and IGBT2 shown in FIG. 4 circulate a current in phase A of the SRM. If the current rises above the commanded value, IGBT1 and IGBT2 are turned off. The energy stored in the motor winding of phase A keeps the current in the same direction until it is depleted. Hence, diodes D1 and D2 become forward biased leading to recharging of the source. That decreases the current, rapidly bringing it below the commanded value. This operation is explained with the waveforms of FIG. 5. FIG. 5 illustrates a graphical representation 500 of the operation performed by IGBT 1 and IGBT 2, in accordance with one embodiment of the present invention. In FIG. 5, it is assumed that a current of magnitude Ip is desired during the positive inductance slope for motoring action, the A-phase current command is generated with a linear inductance profile. Here, phase advancing both at the beginning and during commutation is neglected. The current command, i?, is enforced with a current feedback loop where it is compared with the phase current, ia. The current error is presumed to be processed through a hysteresis controller with a current window of ?i. When the current error exceeds ??i, the switches IGBT1 and IGBT2 are turned off simultaneously. Hysteresis current controller is considered here due to its simplicity in concept and implementation. At that time, diodes, D1 and D2 take over the current and complete the path through the dc source.
[0049] In an embodiment, the voltage of phase A is then negative and will equal the source voltage, Vdc. During this interval, the energy stored in the machine inductance is sent to the source, thus exchanging energy between the load and source repeatedly in one cycle of phase current. After the initial startup, during turn-on and turn-off of IGBT1 and IGBT2, the machine phase winding experiences twice the rate of change of dc-link voltage, resulting in a higher deterioration of the insulation. This control strategy (a strategy I) hence puts more ripples into the dc-link capacitor, thus reducing its life and also increasing the switching losses of the power switches due to frequent switching necessitated by energy exchange. These can be ameliorated with an alternate switching strategy.
[0050] The energy stored in the phase A can be effectively circulated in itself by turning off, say, IGBT2 only (strategy II). In that case, the current will continue to flow through IGBT1, phase A, and D1, the latter having forward-biased soon after IGBT2 is turned off. The voltage across the winding becomes zero if the diode and transistor voltage drops are neglected as shown in a graphical representation 600 of FIG. 6. That takes the phase current from Ip ? ?i to Ip ? ?i in a time greater than had it been forced against the source voltage using the previous strategy. This particular fact reduces the switching frequency and hence the switching losses. When the current command goes to zero, both IGBT1 and IGBT2 are turned off simultaneously. During this interval, the voltage across the winding is ?Vdc as long as D1 and D2 conduct (i.e., until ia goes to zero) and thereafter the winding voltage is zero. The voltage across IGBT2 during its off time and when IGBT1 is on is equal to the source voltage, Vdc. Hence, the power switches and diodes have to be rated to a minimum of source voltage at least. The current ratings of the switches are equal to or less than ip by interchanging the off times between IGBT1 and IGBT2 in one cycle of phase conduction. Similarly, the current rating of the diodes can be evaluated. While such a self-circulation will keep the current going for a longer time compared to recharging the source voltage, it has the advantage of converting the stored energy to useful mechanical work. While this form of control can be used for current control, the recharging of the source is advantageous when the current has to be turned off rapidly. Such an instance arises when the inductance profile becomes flat or is starting to have a negative slope. Any further conduction of current in such regions entails a loss of energy or production of negative torque, thus reducing the average motoring torque. Note that this converter requires two IGBT and two diodes for each phase, resembling the conventional ac motor drives.
[0051] In an embodiment, the energy switching circuit uses an asymmetric converter topology to drive the switched reluctance motor (SRM) and also provides a minimal switching of a semiconductor. The energy switching circuit is a converter that uses resistance in the demagnetization path for faster commutation. The control of the converter is very simple. During freewheeling and commutation the stored energy is dumped into the asymmetric converter topology. The main advantages of the converter include but not limited to i) lower number of switching devices, and simple commutation required and therefore very low cost, ii) simple control of the switches, and iii) faster demagnetization of phases.
[0052] While embodiments of the present invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the scope of the invention, as described in the claims.