DESC:SINGLE PHASE INDUCTION MOTOR SPEED REGULATION WITH VARIATION OF CAPACITANCE VALUE IN AUXILIARY WINDING WIITH PIANO SWTICH
FIELD OF INVENTION:
[001] The present subject matter described herein, relates to a Pedestal and Table/Desk Fan single phase induction motor speed regulation with controlling motor torque by varying auxiliary winding capacitance value with the help of capacitor. To control the capacitance value for each speed/switch operation, contact plate mechanism for piano switch is designed to select the terminals as per selection.
BACKGROUND AND PRIOR ART:
[002] The single phase induction motor has AC input. The single phase induction motor has rotor and stator. The single phase induction motor has only one phase on the stator winding. Hence the resulting magnetic field in a single phase induction motor does not rotate. For starting any type of motor there must be resulting magnetic field to create torque to rotate the rotor .In single phase induction motor without capacitor the field created by stator winding is positive in half cycle and negative in other half so resulting net field is zero so torque is also zero. Now when capacitor is added to the additional auxiliary winding of stator it creates field which leads by 90 degree to main winding field so the two fields which are 90 degrees to each other, resulting rotating field responsible for start of the fan motor. The capacitor used to start the motor after start may be taken out of circuit because as rotor is rotating each half field of stator creating field in rotor in same direction so producing net field not equal to zero and motor can run continuously if the switch off the power supply to the motor. In existing wall and pedestal fan single phase induction motor, speed of motor is controlled by tapping/looping points from different location of stator winding.
[003] Fig. 1 illustrates block diagram of existing system for speed/torque control in Wall and Pedestal fan single phase induction motor. The single phase induction motor has rotor and stator. The stator has run winding (main winding) 101 and auxiliary winding 102 with a capacitor 103 connected in series. During selection of low, medium and high speed, the AC input is tab in between the coils to vary current in the run winding 101. The main winding 101 has four coils R1, R2, R3, R4 or poles. Similarly the auxiliary winding 102 has four coils A1, A2, A3, A4 or poles. During Low speed selection 106, a supply live point or AC input is connected via switch 107 with tapping 106a between coil A2 and A3 in Auxiliary winding 102. Now coil A1 and A2 shifted to Run (Main) winding 101 which became 6 pole (coil), R1, R2, R3, R4, A1, A2, i.e., and Auxiliary (Start) winding left only with two (2) poles A3, A4 (coil). There is coil imbalance in between the main winding 101 and the auxiliary winding 102 which creates electrical imbalance between main winding 101 and the auxiliary winding 102 and generates noise in single phase induction motor.
[004] During medium speed point 105: when supply of live AC point is connected via switch 107 with tapping 105a between coil A1 and A2 in the auxiliary winding 102. Now coil A1 shifted to Run (Main) winding 101, i.e., Run winding became 5 pole (coil), i.e., R1, R2, R3, R4, A1 and the Auxiliary (Start) winding 102 left only 3 pole (coil), i.e., A2, A3, A4. There is coil imbalance in between the main winding 101 and the auxiliary winding 102 which creates electrical imbalance between main winding 101 and the auxiliary winding 102 and generates noise in single phase induction motor.
[005] During High speed point 104: when supply of live AC point connected via switch 107 with common terminal 104a of two windings. No Pole (Coil) shifting happens, i.e., Run winding remain with 4 pole (coil), i.e., R1, R2, R3, R4 and the auxiliary (Start) winding 102 remains with 4 pole (coil), i.e., A1, A2, A3, A4. There is no coil imbalance in between the main winding 101 and the auxiliary winding 102. Therefore, there is no electrical imbalance between Run and Start winding and noise is also not generated.
[006] In the existing system or induction motor, unwanted noise is generated in Low and Medium speed point due to electrical imbalance in between the run winding 101 and the auxiliary winding 102. Therefore, there is a requirement in the motor to have equal coil balance during low, medium and high speed point. Therefore, there is a need in the art to provide single phase induction motor with a mechanism to distribute equal coils in each speed point and varying flow of current in the windings depend upon the selection of speed point. Further, there is a need in the art to provide a single phase induction motor that is more simple and inexpensive, and which does not create noise and electrical imbalance.
OBJECTS OF THE INVENTION:
[007] The principal objective of the present invention is to provide a single phase induction motor having no electrical imbalance in both Run (Main) and Start (Auxiliary) winding.
[008] Another objective of the present subject matter is to reduce/eliminate noise in induction motor at low and medium speed point due to electrical imbalance.
[009] Another objective of the present subject matter is to provide a piano switch contact lever and circuit diagram for piano switch, so that capacitance value for different speed is controlled by this circuit.
[0010] Another object of the present subject matter is to increase number of contact points/contact area for each switch operation with the piano switch.
[0011] Yet another objective of the present subject matter is to provide a piano switch having capability to connect capacitor having different capacitance value such as the capacitor has three tapping points for supplying different capacitance value to motor for different speed operations in various combinations in series with the auxiliary winding of the single phase induction motor.
SUMMARY OF THE INVENTION:
[0012] The subject matter disclosed herein relates to a single phase induction motor with rotor torque/speed control with the help of variable capacitance value in auxiliary winding of the motor. The single phase induction motor has a stator and rotor. The stator is powered by a AC power source. The rotor rotates inside the stator upon generation of magnetic field. The stator has run winding (main winding) and an auxiliary winding (start winding). Further, a single capacitor having different capacitance value is provided to connect with the auxiliary winding in series upon selection of speed by a rotary switch. The single capacitor has three tapping points, such as C1, C2, and C3 (C3= C1+C2) for supplying different capacitance value to motor for different speed operations, such as low, medium, and high speed operations of the motor. The single capacitor is connected with the auxiliary winding in series upon selection of speed by a piano switch. The capacitance value of tapping point C2 is more than capacitance value of tapping point C1. The piano switch is provided for controlling current flow in the stator windings by varying capacitance value in the auxiliary winding by connecting capacitor with different capacitance value by tapping point C1 or tapping point capacitor C2 or combination of tapping point C1 and C2 of the capacitor in series. During low speed selection, the piano switch connects the capacitor tapping point C1 with low capacitance value in series with the auxiliary winding to operate the single phase induction motor at low speed. Due to low capacitance value, low current reaches to the stator. During medium speed selection, the piano switch connects the capacitor tapping point C2 with high capacitance value in series with the auxiliary winding to operate the single phase induction motor at medium speed. During high speed selection, the piano switch connects combination of the capacitor tapping point C1 and the capacitor tapping point C2 having combined capacitance value in series with the auxiliary winding to operate the single phase induction motor at high speed. In the present circuit, the coil distribution remains same in both windings, i.e., main winding and the auxiliary winding. Therefore, there is no electrical imbalance and no noise generation issue.
[0013] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0015] Fig. 1 illustrates block diagram of existing method for speed /torque control in Wall and Pedestal fan induction motor;
[0016] Fig. 2 illustrates block diagram of the present method with piano switch for capacitor regulation for speed/torque control in wall and pedestal fan single phase induction motor, in accordance with an embodiment of the present subject matter; and
[0017] Fig. 3 and 4 illustrates structure and functioning of piano switch for controlling the speed of single phase induction motor by varying capacitance value in the auxiliary winding, in accordance with an embodiment of the present subject matter.
[0018] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0019] The subject matter disclosed herein relates to a single phase induction motor with rotor torque/speed control with the help of variable capacitance value in auxiliary winding of the motor. The single phase induction motor has a stator and rotor. The stator is powered by a AC power source. The rotor rotates inside the stator upon generation of magnetic field. The stator has run winding (main winding) and an auxiliary winding (start winding). Further, a single capacitor having different capacitance value is provided to connect with the auxiliary winding in series upon selection of speed by a rotary switch. The single capacitor has three tapping points, such as C1, C2, and C3 (C3= C1+C2) for supplying different capacitance value to motor for different speed operations, such as low, medium, and high speed operations of the motor. The single capacitor is connected with the auxiliary winding in series upon selection of speed by a piano switch. The capacitance value of tapping point C2 is more than capacitance value of tapping point C1. The piano switch is provided for controlling current flow in the stator windings by varying capacitance value in the auxiliary winding by connecting capacitor with different capacitance value by tapping point C1 or tapping point capacitor C2 or combination of tapping point C1 and C2 of the capacitor in series. During low speed selection, the piano switch connects the capacitor tapping point C1 with low capacitance value in series with the auxiliary winding to operate the single phase induction motor at low speed. Due to low capacitance value, low current reaches to the stator. During medium speed selection, the piano switch connects the capacitor tapping point C2 with high capacitance value in series with the auxiliary winding to operate the single phase induction motor at medium speed. During high speed selection, the piano switch connects combination of the capacitor tapping point C1 and the capacitor tapping point C2 having combined capacitance value in series with the auxiliary winding to operate the single phase induction motor at high speed. In the present circuit, the coil distribution remains same in both windings, i.e., main winding and the auxiliary winding. Therefore, there is no electrical imbalance and no noise generation issue.
[0020] In another embodiment of the present subject matter, a piano switch is provided in the single phase induction motor for varying the capacitance value in the auxiliary winding for controlling motor torque/speed. The piano switch has a base plate, three contact lever, and four buttons to operate the contact levers. The three contact levers are connected with the corresponding buttons for couple and dis-coupling. The base plate has a three contact terminals for low speed, medium speed, and high speed. Each of the three contact terminals has contact points with the capacitor tapping points C1 or C2 or both capacitor tapping points C1 and capacitor C2, supply AC input, connection line, and blank contact point. The high speed terminal has contact points for capacitor tapping point C1, capacitor tapping point C2, supply AC input, and connection line. One contact lever is provided over each of the three contact terminals. Each contact lever is operated by up and down movement of corresponding button connected with the contact lever. The contact lever has four extending arms from base to make connection with the contact points of the corresponding contact terminal upon selection of speed. The base of the contact lever is connected with a vertical shaft operated by the button. During low speed selection, the contact lever of the low speed terminal is pressed and the four extending arms of the contact lever connects with Capacitor tapping point (C1), AC supply line (L), connection line (R), and blank contact to complete the circuit for low speed control. The contact lever connects the capacitor tapping point C1 with low capacitance value in series with the auxiliary winding along with AC supply line. During medium speed selection, the contact lever of the medium speed terminal is pressed, the four extending arms of the contact lever connects with Capacitor tapping point (C2), AC supply line (L), connection line (R), and blank line to complete the circuit for medium speed control. The contact lever of the medium speed terminal connects the capacitor tapping point C2 with high capacitance value in series with the auxiliary winding along with AC supply line. During high speed selection, the contact lever of the high speed terminal is pressed, the four extending arms of the contact lever connects with Capacitor tapping point (C1), Capacitor tapping point (C2), AC supply line (L), and connection line (R) to complete the circuit for high speed control. The contact lever of the high speed terminal connects the capacitor tapping point C1 and capacitor tapping point C2 in parallel combination in series with the auxiliary winding along with AC supply line.
[0021] The subject matter disclosed herein relates to a single phase induction motor with rotor torque/speed control by varying capacitance value and with specially designed piano switch. With the present system the electrical imbalance in main and auxiliary winding of single phase induction motor can be eliminated, reduce /elimination of noise of motor at low and medium speed.
[0022] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0023] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0024] Fig. 2 illustrates block diagram of the present method with piano switch for capacitor regulation for speed/torque control in wall and pedestal fan single phase induction motor, in accordance with an embodiment of the present subject matter. The single phase induction motor has a stator 200 and rotor. The stator 200 is powered by a AC power source 208. The rotor rotates inside the stator 200 upon generation of magnetic field. The stator 200 has run winding (main winding) 201 and an auxiliary winding (start winding) 202. The main winding 201 has four coils R1, R2, R3, R4 or poles. Similarly the auxiliary winding 202 has four coils A1, A2, A3, A4 or poles. Further, number of coils in both the winding can be increased and decreased as per requirement of the single phase induction motor. The single capacitor is provided with auxiliary winding. The single capacitor has three tapping points, such as C1, C2, and C3 (C3= C1+C2) for supplying different capacitance value to motor for different speed operations, such as low, medium, and high speed operations of the motor. Further, the single capacitor with three different tapping points connects with the auxiliary winding 202 in series upon selection of speed by a piano switch 300. The piano switch is provided for controlling current flow in the stator windings by varying capacitance value in the auxiliary winding by connecting capacitor tapping point C1 or capacitor tapping point C2 or combination of capacitor tapping points C1 and C2 in series. The capacitor has different capacitance value, where the capacitor taping point (C2) 204 has high capacitance value than capacitance value of capacitor tapping point (C1) 203. During Low speed point selection, supply of live AC point is connected via piano switch 300 with the capacitor tapping point (C1) 203 in the auxiliary winding 202. During low speed selection, the low capacitance value capacitor tapping point (C1) 203 is connected in series with the auxiliary winding 202. The motor torque and speed with the combination of capacitor tapping point (C1) 203 and the auxiliary winding 202 is achieved for running the single phase induction motor in low speed. The switch used for the selection is a piano type.
[0025] During Low speed point, supply live point connected via piano switch 300 with Capacitor tapping point C1 in Auxiliary winding. For low speed, low value capacitor tapping point (C1) is series with the auxiliary winding 202 in the circuit. Motor torque and speed with the present combination of capacitance value C1 is achieved. At low speed switch contact connected two points at a time. In this way both Run and Auxiliary winding remain with their 4 pole (Coil), no electrical imbalance happen and as a result noise problem was eliminated.
[0026] During Medium speed point 206, supply live point connected via switch with Capacitor tapping point C2 in Auxiliary winding. For medium speed high value capacitance capacitor tapping point (C2) is in circuit. More motor torque and speed with the present combination of capacitance value is achieved. At medium speed switch contact connected two points at a time. In this way both Run and Auxiliary winding remain with their 4 pole (Coil), no electrical imbalance happen and as a result noise problem is eliminated.
[0027] During High speed point 205, supply live AC point connected via the piano switch 300 with combination of Capacitor tapping point C1 and C2 in the auxiliary winding 202. For high speed, both capacitor tapping points adds their capacitance value (C3=C1+C2) is in series with the auxiliary winding 202. More motor torque and speed with the combination of capacitance value C1+C2 is achieved. At high speed, the piano switch contact connected four points of the base plate at a time, i.e., capacitor tapping point C1, Capacitor tapping point C2, connection line, and AC supply live. No electrical imbalance happens and as a result no noise is generated.
[0028] Fig. 2, Fig. 3, and Fig. 4 also illustrate functioning and working of piano switch for controlling the speed of wall and pedestal fan single phase induction motor structure, in accordance with an embodiment of the present subject matter. The piano switch 300 is provided in the single phase induction motor for varying the capacitance value in the auxiliary winding for controlling motor torque/speed. The piano switch 300 has a base plate 301, OFF terminal 302, three contact terminals 303, 304, 305 on the base plate 301, three contact levers 306, 307, 308, and four buttons (not shown in the figures) to operate the contact levers. The four button are OFF button, low speed button, medium speed button, and high speed button. Where the low speed button, medium speed button, and high speed button are coupled with the contact levers 306, 307, 308 to make connection with the contact terminals 303, 304, 305, respectively upon application of press force on the buttons. The three contact levers 306, 307, 308 are connected with the corresponding buttons for couple and dis-coupling with the contact terminals. If low speed contact lever 306 is coupled with the low speed contact terminal 303, the user presses the button of medium speed to connect the medium speed contact lever 307 with the medium speed contact terminal 304 on the base plate 301 of the piano switch. Upon pressing the medium speed button, the low speed contact lever 306 dis-coupled with the low speed contact terminal 303. Similarly, upon operation of different contact lever, the previously engaged contact lever dis-engaged with the plate. Upon pressing the Off button, no contact lever is in contact with the base plate, hence disengages the supply of live AC into the motor.
[0029] The base plate 301 has a three contact terminals for low speed 303, medium speed 304, and high speed 305. Each of the three contact terminals 303, 304, 305 has contact points for capacitor tapping point C1 or capacitor tapping point C2 or both capacitor tapping points C1 and C2, supply AC input, connection line, and blank contact point. For example, the low speed contact terminal 303 has capacitor tapping point C1 contact point 303a, connection line (R) contact point 303b, supply AC input (L) 303c, and blank contact point 303d. The high speed terminal 35 has contact points for capacitor tapping point C1 305b, capacitor tapping point C2 305b, supply AC input 305c, and connection line 305d. One contact lever 306, 307, 308 is provided over each of the three contact terminals 306, 307, 308. Each contact lever is operated by up and down movement of corresponding button connected with the contact lever.
[0030] Each of contact lever 306, 307, 308 has four extending arms from base to make connection with the contact points of the corresponding contact terminal upon selection of speed. For example, the low speed contact lever 306 has tapping point C1 contact point extending arm 306a, connection line (R) contact point extending arm 306b, supply AC input (L) contact point extending arm 306c, and blank contact point extending arm 306d. Similarly, each contact lever has four extending arms corresponding to contact points of the contact terminals of the base plate. Similarly, the high speed contact lever 308 has capacitor tapping point C2 contact point extending arm 308a, capacitor tapping point C1 contact point extending arm 308b, connection line (R) contact point extending arm 308d, supply AC input (L) contact point extending arm 308c. The base of the contact lever is connected with a vertical shaft operated by the button.
[0031] During low speed selection 207, the contact lever 306 of the low speed contact terminal 303 is pressed and the four extending arms 306a, 306b, 306c, 306d of the contact lever 306 connects with contact points 303a, 303b, 303c, 303d of the low speed contact terminal to complete the circuit for low speed control. The contact lever 306 connects the capacitor tapping point C1 in series with the auxiliary winding along with AC supply line.
[0032] During medium speed selection 206, the contact lever 307 of the medium speed terminal 304 is pressed, the four extending arms of the contact lever connects with Capacitor tapping point (C2), AC supply line (L), connection line (R), and blank line to complete the circuit for medium speed control. The contact lever of the medium speed terminal connects the capacitor tapping point C2 in series with the auxiliary winding along with AC supply line.
[0033] During high speed selection 205, the contact lever 308 of the high speed terminal 305 is pressed, the four extending arms of the contact lever connects with Capacitor (C1), Capacitor (C2), AC supply line (L), and connection line (R) to complete the circuit for high speed control. The contact lever 308 of the high speed terminal 305 connects the capacitor tapping point C1 and capacitor tapping point C2 in parallel combination in series with the auxiliary winding along with AC supply line. The piano switch 300 control speed of the motor by varying capacitance value in the auxiliary and main winding.
[0034] Fig. 3 illustrates connection of piano switch for low, medium and high speed of the fan motor. The piano switch 300 works and controls the speed/torque of the motor using varying capacitance value in the auxiliary and main winding. A single phase Induction motor for Pedestal and Table/Desk fan with Capacitor regulated torque/speed control of induction motor.

CONTINUITY WITH RESPECT TO TERMINAL "S" OF SWITCH
OPERATING CONDITION OF FAN SWITCH TERMINAL-LOW SWITCH TERMINAL-MED SWITCH TERMINAL-HIGH
OFF 1 1 0
LOW SPEED PT. 1 0 1
MED SPEED PT. 0 1 1
HIGH SPEED PT. 1 1 1
LOGIC TABLE OF NEW DEVELOPED SPECIAL TYPE COMBINATION SWITCH

[0035] In above table, ‘1’ is denoted for connection, and ‘0’ for disconnection.
[0036] In fan OFF condition: the OFF button is pressed which disconnect all connections with the base plate and hence there is no supply of live AC input in the motor. As HIGH terminal is disconnected, supply voltage also disconnected from fan or load and it act as in OFF condition.
[0037] In fan LOW speed point: the contact lever 306 is in contact with low speed contact terminal 303 and connects LOW and HIGH input but it remains disconnected with MED terminal (logic of switch terminal low, medium and high is 1, 0 and 1). The AC Supply live (L) voltage goes into the single phase induction motor through HIGH terminal of switch and at the same time connected with Capacitor tapping point C1 in series with the auxiliary winding. The capacitance value of capacitor tapping point C1 decided as per the speed requirement at that point.
[0038] In fan MED speed point: the contact lever 307 is in contact with the medium speed contact terminal 304 which connects the terminal of MED and HIGH but disconnected with LOW terminal (logic of switch terminal low, medium and high is 0, 1 and 1). The AC Supply live (L) voltage goes into the single phase induction motor through HIGH terminal of switch and at the same time connected with Capacitor tapping point C2 in series with the auxiliary winding. The capacitance value of capacitor tapping point C2 decided as per the speed requirement at that point.
[0039] In fan HIGH speed point: the contact lever 308 is in contact with the high speed contact terminal 305 which connects all the three terminals LOW, MED and HIGH (logic of switch terminal low, medium and high is 1, 1 and 1). The AC Supply live (L) voltage goes into the single phase induction motor through HIGH terminal of switch and at the same time connected with both the capacitor tapping point C1 and C2 in parallel combination in series with the auxiliary winding. The capacitance value of the capacitor become addition of C1 and C2, i.e., C= C1 + C2.
[0040] There is no electrical imbalance in the single phase induction motor and there is no noise generation in the single phase induction motor. A single phase Induction motor Pedestal & Table/Desk fan with Capacitor regulated torque/speed control of induction motor.
[0041] The present subject matter provides an electric motor with speed/torque of motor regulation with help of multi tapping from capacitor. Further, present subject matter provides an induction motor without imbalanced electrical load/Eliminated imbalanced electrical load. Specially designed piano switch contact leaver and circuit diagram for piano switch, so that capacitance value for different speed is controlled by this circuit.
[0042] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.
,CLAIMS:We claim:
1. A single phase induction motor with speed control by varying capacitance value in auxiliary winding by a piano switch, the single phase induction motor comprising:
a rotor;
a stator having running winding (201) and a auxiliary winding (202) powered by a power source (208);
single capacitor with variable capacitance value tapping points (C1, C2) (203, 204) provided to connect in series with the auxiliary winding (202);
a piano switch (300) is provided for controlling current flow in the stator (200) by varying capacitance value of the auxiliary winding,
wherein the piano switch (300) connects the capacitor tapping point (C1) in series with the auxiliary winding (202) during low speed selection;
wherein the piano switch (300) connects the capacitor tapping point (C2) in series with the auxiliary winding (202) during medium speed selection;
wherein the piano switch (300) connects the combination of the capacitor tapping point (C1) and the Capacitor tapping point (C2) in parallel combination (C1+C2) in series with the auxiliary winding (202) during high speed selection.

2. The single phase induction motor as claimed in claim 1, wherein the single capacitor has different capacitance value with tapping points C1 and C2.

3. The single phase induction motor as claimed in claim 1, wherein the capacitor tapping point (C2) has more capacitance value than Capacitor tapping point (C1).

4. The single phase induction motor as claimed in claim 1, wherein the running winding (201) and auxiliary winding (202) has equal number of poles.

5. A piano switch (300) for changing speed of induction motor by connecting capacitor with variable capacitance value with tapping points (C1, C2) in series with auxiliary winding (202), the piano switch (300) comprising:
a base plate (301) having a three contact terminals for low speed (303), medium speed (304), and high speed (305), wherein the three contact terminals (303, 304, 305) has four contact points for capacitor, supply AC input, connection line, and blank contact point;
one contact lever (306, 307, 308) is provided over each of the three contact terminals (303, 304, 304), wherein the contact lever (306, 307, 308) is operated by up and down movement of corresponding button connected with the contact levers (306, 307, 308),
wherein the contact levers (306, 307, 308) have four extending arms from base to make connection with the four contact points of the corresponding contact terminal (303, 304, 305) upon selection;
when the contact lever (306) of the low speed terminal (303) is pressed, the four extending arms (306a, 306b, 306c, 306d) of the contact lever (306) connects with four contact points Capacitor tapping point (C1) (303a), AC supply line (L) (303b), connection line (R) (303c), and blank contact point (303d) of the low speed contact terminal (303) to complete the circuit for low speed control and adding Capacitance value of capacitor tapping point (C1) in series with the auxiliary winding (202),
when the contact lever (307) of the medium speed terminal (304) is pressed, the extending arms (307a, 307b, 307c, 307d) of the contact lever (307) connects with Capacitor tapping point (C2) (304a), AC supply line (L) (304b), connection line (R) (304c), and blank contact point (304d) to complete the circuit for medium speed control and adding capacitance value of capacitor tapping point (C2) in series with the auxiliary winding (202), and
when the contact lever (308) of the high speed terminal (305) is pressed, the extending arms (308a, 308b, 308c, 308d) of the contact lever (308) connects with Capacitor (C1) (305a), Capacitor tapping point (C2) (305b), AC supply line (L) (305c), and connection line (R) (305d) to complete the circuit for high speed control, and adding combination of the capacitance value of capacitor tapping point (C1) and the Capacitor tapping point (C2) in parallel combination in series with the auxiliary winding (202).
6. The piano switch (300) as claimed in claim 5, wherein the high speed terminal (305) has four contact points for Capacitor tapping point C1, Capacitor tapping point C2, AC supply L, and connection line R.

7. The piano switch (300) as claimed in claim 5, wherein upon selection of new speed, the contact lever dis-coupled from initial coupling.

8. The piano switch (300) as claimed in claim 5, wherein the piano switch (300) is four contact point switch.

9. The piano switch (300) as claimed in claim 5, wherein the contact levers (306, 307, 308) is in shape of star with four arms, wherein the four arms of the contact levers (306, 307, 308) make connection with the four contact points of the contact terminals (303, 304, 305).

10. The piano switch (300) as claimed in claim 5, wherein the high speed contact terminal (305) has base plate (301) has contact points for capacitor tapping point C1, capacitor tapping point C2, supply AC input, and connection line.