FIELD OF THE INVENTION

This invention relates to wet grinders and, more particularly to the wet grinder includes Switched Reluctance motors with ingenious features.

BACKGROUND OF THE INVENTION

Wet Grinders are widely used in south indian families for preparing batter for idli, dosa, and vada etc. Due to the interaction of rotating stone and flat stone, food grain is grinded and batter is produced. At present wet grinders have several drawbacks like bulky in size (occupies more space), heavy weight, lacks user interface, unable to adapt to various type of power sources, no preselect option and no system to sense batter quality. More over the technology in wet grinder industry hasn't changed much for more than 30+ years. In order to build next generation wet grinders novel concepts should be implemented in every aspect.

At present Wet Grinders use Single Phase Induction Motors which use AC mains supply for their rotation. These motors run at constant speed and it is around 1440 rpm. So, the torque output is low. In order to increase the torque for grinding purpose the speed is reduced by means of pulley-belt or gear arrangement. Usage of belt pulley arrangement increases the size of the wet grinder. Since the entire setup is fixed, the output speed of the motor/drum remains constant. This problem can be addressed by using direct drive technology. The torque produced by the induction motor directly appears on the drum, the torque produced by the motor is not sufficient to grind. The torque can be increased by using complex power electronic control techniques. Moreover the construction of induction motor requires longer stack length which increases the size of the wet grinder vertically. This clears the point that induction motor is not a good choice for direct drive wet grinders.

The above discussed point concludes that the novelty should come from the motor technology first. On exploring other motor options special electrical machines seems to be promising solution to overcome the technological barrier. Special Electrical machine include both Permanent magnet and Non-Permanent magnet motors. Since Permanent magnets increases the motor construction cost, it is not suitable for appliances industry. Out of Non-Permanent magnet motors, the direct drive Reluctance Motor provides promising solution.

Switched Reluctance Motors produces torque which makes the rotor to align itself in minimum reluctance position. A drive circuit generates excitation sequence which ensures continuous rotation of motor. The construction of Switched Reluctance Motor is simple. Stator has plural salient poles. Rotor contains plural salient/Non-Salient poles. Stator has windings and the rotor has no windings.

In order to obtain continuous rotation, sequential excitation of the windings is required based on the rotor position data. This can be either obtained by using external position sensor or by applying sensor less techniques. External position sensor such as hall sensor/optical sensor/magnetic encoder/resolver can be used to sense the position data. This data is given to computational unit such as microcontroller/microprocessor or any computational device whatsoever. Based on the position data the computational unit excites the corresponding sequence which ensures continuous rotation of the motor.
Sensor less technique involves measuring of back electromotive force and calculating the angular position. Sensor less technique requires high computation power when compared with sensor based approach.

Many additional features can be incorporated in wet grinder containing Switched Reluctance Motor, since the computation unit is inherent in this system. User Interface can be incorporated which allows user to modify speed of the motor or set timer or other additional features according . to user requirement. The Wet Grinder will have a system where the batter quality can be checked by means of viscous sensor.

The Power supply required for driving Switched Reluctance Motor is DC supply. Since the domestic power supply available is AC, a Power Electronics circuitry is present in the Wet Grinder which can convert AC supply to DC supply. This Power supply is adaptable to various regions where the voltage and frequency of the supply vary.

Therefore the entire setup is made up of Switched Reluctance Motor, A drive assembly to excite the windings and a power electronics circuitry which converts AC main supply to DC. Additional to that the motor has user interface periphery which is used for interaction between entire system and user, thereby allowing user to change any modifications in the system.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1 is the front view of the wet grinder, where in the components are shown in exploded view.

Fig 2 is the bottom and top view of the drum and the rotor cover respectively.

Fig 3 is the bottom view of the rotor cover.

Fig 4 is the overall working block diagram of the motor drive system.

Fig 5. Is the front and isometric view of the motor.

Fig 6. Shows the Flux plots simulated in FEA software.

Fig 7. Shows dynamic torque vs speed response.

Fig 8. Shows Efficiency vs speed curve.

Fig 9. Shows Output power vs speed curve.

Fig 10. Shows voltage vs rotor position.

Fig 11. Shows current vs rotor position.

Fig 12. Shows Inductance vs Rotor position. .

Fig 13. Shows Flux linkage vs current graph for different rotor positions.

Fig 14. Control Algorithm Flow chart

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The Following detailed descriptions preferred exemplary embodiments only is not intended to limit the scope, applicability or configuration of the present invention. Rather, the detailed description of the preferred exemplary embodiments will provide those skilled in the art with an enabling description for implementing the preferred understood that various changes may be in the function and arrangement of the elements without departing from the spirit and scope of the invention as set forth in the appended claims.
A wet grinder according to the present invention includes a novel Switched Reluctance motor with plural number of poles. Switched Reluctance Motor includes plural number of stator and rotor poles. Stator poles have windings. Rotor has no windings. The Axis of rotation is vertical axis. Switched Reluctance Motor has high efficiency when compared to induction motor. Moreover the weight of Switched Reluctance motor is less when compared to induction motor thereby making the wet grinder more portable to carry.
With Initial reference to Fig 1 which is the front view of the wet grinder. Batter is prepared at 1 drum. The Drum contains roiling stone, a flat stone and a wiper arrangement. The 1 drum contains a coupler/periphery 8. It is coupled with 2 Rotor Cap. The 3 base height in this motor will be less compare to induction motor. The Rotor Cap contains 9 coupler/periphery. The Coupler 8 and 9 are coupled together. The Shape of coupler 8 and 9 can be of anything. The Drum 1 and Rotor cap 2 can also be coupled with snap action mechanism. The Rotor Cap 2 rotates which rotates the coupling arrangement 8 and 9, which in turn rotates the 1 drum. The Rotor Cap 2 contains rotor 12 and bearing 13.

Torque is produced due to interaction between Stator 4 and Rotor 12. The Stator has windings 11 wounded concentrically. The Drive circuitry is embedded in PCB 5, which ensures continuous rotation of motor. The PCB 5 has a computational unit 17 which is programmed to ensure continuous rotation of motor. The Computation Unit 17 also takes care of other features embedded in the wet grinder system.

The Weight of said 1 drum, 2 Rotor Cap and Rotor 13 is supported by the center shaft 10. The Shaft is supported by the Base Plate 6 and bush Assembly 7. The topology of the circuitry present in PCB 5 is shown in Fig 4. The Major components are Power Supply Management 14, Power electronics 15, Computational Unit 17, and User Interface 18.

Power Supply Management 14 converts AC/DC supply to constant different levels of DC. These DC supply is fed to power electronics 15 and Processing electronics 17 via PCB tracks 21, 22 and 23. The Power Electronics 15 consists of Power Switches which facilitates sequential excitation to the motor 16 windings. The Motor 16 contains a feedback system 21, based on which the processing electronics 17 will excite the power electronic components 15 via PCB track 24. A user interface system 18 is present in the current system which will act as a communication between 18 and 17 via communication channel 20. The Communication channel 20 is made of I2C/UART/CAN or other communication protocols. This Facilitates user to control speed, set timer, check batter quality etc.

Fig 7 to 13 shows performance characteristics of the motor. The Graph is plotted in Per

Unit (P.U) reference.

Fig 14 shows control algorithm flow chart.

WE CLAIM:

1. A Wet Grinder comprising of a drum and a Switched Reluctance Motor which rotates the drum. The Switched Reluctance Motor includes a stator and rotor. Stator contains plural number of poles. Rotor contains plural salient/Non-Salient poles. Winding is done in stator and rotor has no windings where in the said rotor is connected to shaft that is connected to drum. The rotor and drum is coupled through shaft without using pulley-belt/gear arrangement or any mechanical transmission. This motor construction is approximately half of the weight and less height when compared with existing induction motor. This wet grinder can also use any other type of motors . like Synchronous reluctance, flux switching, hybrid and axial Switched Reluctance Motor configurations.

2. The Wet Grinder of claim 1 is associated with power electronics controller circuitry to enable continuous rotation of the motor based on feedback from rotor position sensor such as Hall/Optical/Magnetic encoder/resolver or by using sensorless techniques.

3. The Wet Grinder of claim 1 can be started with full load using the control algorithms embed in the drive circuitry also it ensures constant speed operation for different load scenarios.

4. The Wet Grinder of claim 1 consists of a user interface system which allows user to select the preferred functionality such as food mode, auto start/stop timer & batter texture and any other functionality.

5. The Wet Grinder of claim I consists of a power source circuitry which converts supply from AC/DC, Battery or any other energy storage devices to the working voltage.

6. The Wet grinder of claim 1 includes over current & thermal protection unit to protect the motor. Also, this has protection for the user from electric shock.

7. The Wet Grinder of claim 1 can be table top/tiltable, industrial and other types. Additionally, it also has coupling of accessories like flour mixer/coconut scrubber.

8. The Wet Grinder of claim 1 includes viscosity based sensing system to sense the batter quality based on time and the control algorithm can adjust the speed, torque or other motor parameters according to batter. Once the required batter quality is achieved, the apparatus can shut down by itself at once the required time is reached.

9. The features mentioned above such as user interface, power electronics based voltage converter, batter quality check can also be implemented in any other type of wet grinder.