TECHNICAL FIELD

[0001] The present subject matter, in general, relates to an induction motor with multiple voltage band operation and in particular, relates to an induction motor that can be operated at three or more different voltages with the same speed and similar torque characteristics.

BACKGROUND

[0002] Generally, electric motors operate by positioning a current carrying conductor in a magnetic field. An induction motor is a commonly employed electric motor that works on the principle of electromagnetic induction in which electromotive force is induced across a currentcarrying conductor when said current-carrying conductor is placed in a changing magnetic field. The mam components of an induction motor include a rotor that is provided with the bars and end rings and is configured to rotate with respect to a stationary member, i.e., a stator.

[0003] Motors that are capable of working with wide voltage bands are in high demand, particularly due to voltage variations, which are very common in many parts of India and other developing countries. Moreover, the voltage variations can happen within the same area at different times of the day especially in agriculture sector. However, increasing the voltage band requires higher core length, thereby increasing the active material, i.e., conductive material like copper or aluminium.

[0004] Various challenges are faced in agricultural fields due to fluctuation in voltage levels, especially in three phase supply systems. Agricultural pump sets operating in these conditions require an operating voltage band of at least 90 V to cater to the varying needs of users.

[0005] Conventionally, a three phase motor is designed with a single winding coil that can operate between 350V and 440V. Having a single motor with a wide voltage band is not necessarily an optimum design, as the voltage fluctuations within a certain period is not as broad as 90V. These fluctuations can be less than 60V for most of the operating periods.

[0006] A three phase motor is usually designed for 415V and cannot be operated in lower voltage. To deliver the same output power in low voltage, the motor draws high current. The effect of this is an increase in saturation level of the lamination. Once the saturation level is attained, increasing the magnetizing force does not help in changing the flux density. As a result, it is not possible to run the conventional motor at low voltages without the loss of power or increase in winding temperature. This may lead to motor failure when operated in low voltage.

[0007] Due to voltage fluctuations in the field condition, existing single voltage motors are not capable of meeting the user requirements. Another option is to design a motor for dual voltage, wherein the voltage ratio is 1:2. In such systems, the motor can operate either at 200V or 400V. However, this type of configuration cannot be operated for voltages in between 200 and 400V.

[0008] Figure la depicts a schematic representation of a conventional dual voltage motor comprising U-phase of UVW (RYB) circuit. As shown herein, the AC Induction motor is designed with slots in the stator that are multiples of 2. The number of slots may vary from 18 to 48 or more depending on the speed and power rating. Generally, agricultural motors have 24 or 36 stator slots.

[0009] Conventionally, dual voltage three phase motors, generally used for industrial applications have a voltage ratio of 1: 2 (e.g., 200V: 400 V). The construction of these motors is described below.

[0010] Two voltage bands are created by connecting the end points of the winding in series or parallel, depending on the voltage required, as shown in Figure lb, which depicts a schematic representation of the conventional dual voltage motor having existing dual voltage configuration (single winding). The circuit on the left side of Figure lb is a series connection and the one on the right represents a parallel connection. This type of winding construction, being a star connection, requires nine output leads that facilitate the formation of a series or parallel connection. The users need to change the connection based on their voltage requirement. In case of delta connection, twelve output leads are required to make a series / parallel arrangement.

[0011] The above construction generally provides a narrow voltage band. For example, this can be 190-220V in low voltage (parallel) and 380-440V in high voltage (series). Although, this is an acceptable operational voltage band, the reduction in speed and torque can be high in low voltage conditions. The main drawback of this technology is to operate the motor in either 200V or 400V main supply. Operating the motor at intermediate voltage is not possible. Also, the voltage ratio of 1:2 only is possible (Ex. 200:400, 100:200, 220:440...)

[0012] The other solution that is currently available is to provide two motors, each with an operating voltage band of 60V. This solution is more optimized for the voltage fluctuations. However, when the supply voltage conditions improve or deteriorate, these motors do not work for the intended needs. In the case of pump sets, the motor needs to be removed and replaced with a new motor with a different voltage band. The time lost in replacement is a loss in productivity. The two motors may have different voltage ratings. However, these motors work only in rated design conditions. For example, a low voltage motor will not work in high voltage conditions and vice versa.

[0013] Dual speed motors are also known in the art in which two windings are placed in each of the stator slots as shown Figure 2a and 2b. Figure 2a shows a schematic representation of U-phase of UVW (RYB) circuit in which solid lines represent high speed winding, and U1 and Ul’ denote the start and end of the winding respectively. The dashed lines in Figure 2a represent low speed winding, and U2 and U2’ denote the start and end respectively of the winding. In this figure, V & W phase is similar to U phase and displaced 120 degree between phases. These types of motors comprise two windings, each having separate pole configuration with different coil pitch. This arrangement helps in achieving two different speeds. Both windings are designed for the same rated voltage with a similar voltage band. However, the motor power achieved by the slow speed winding is lower than the power achieved by the high speed winding.

[0014] Therefore, there is a well felt need for a solution that overcomes the above constraints and shortcomings of conventional systems, particularly arising due to fluctuation in the voltage levels especially in three phase supply systems in agricultural fields.

SUMMARY

[0015] The present invention discloses an induction motor adapted to be operated at three or more different voltage bands. The induction motor includes a rotor that rotates in a housing about an axis of rotation, and a stator that is stationary and magnetically acts upon said rotor. The stator includes a stator core having a plurality of slots formed therein. Each of the plurality of slots includes two or more concentric windings configured therein. Each of the two or more concentric winding includes a coil extending between a starting lead towards an ending lead and having a variable number of winding turns. The two or more concentric windings are connected in one of at least three predetermined connection patterns so as to allow the induction motor to be operated in a respective voltage band depending upon the connection pattern when power is supplied there through.

[0016] Generally, the two or more windings have a phase difference that remains same in each of the selected connection patterns.

[0017] Particularly, the two or more concentric windings include a first winding having a first number of winding turns, and a second winding having a second number of windings turns. [0018] Further, each of the two or more concentric winding are arranged in a same slot and, have a similar core saturation.

[0019] Potentially, the winding can be energized on the basis of input voltage.

[0020] Optionally, the first number of windings turns is higher than the second number of windings turns.

[0021] Alternatively, the first number of winding turns is lower than the second number of windings turns.

[0022] Potentially, each of the two or more concentric windings have a same pole configuration and a same coil pitch.

[0023] Specifically, the first winding comprises a first starting lead (Ul, VI, Wl) that extend towards a first end lead (Ul’, VI’, Wl’) and the second winding comprises a second starting lead (U2, V2, W2) that extends towards a second end lead (U2’, V2’, W2’).

[0024] Particularly, the predetermined connection patterns comprise one or more of but not limited to a series connection, a star connection, and a delta connection.

[0025] In an embodiment, the predetermined connection pattern comprises first end leads of the first winding (Ul’, VI’, Wl’) being connected with second starting leads (U2, V2, W2) and the second end leads of the second winding being star connected.

[0026] In another embodiment, the predetermined connection pattern comprises first end leads of the first winding (Ul’, VI’, Wl’) being star connected and the second starting leads of the second winding (U2, V2, W2) kept open.

[0027] In yet another embodiment, the predetermined connection pattern comprises the first end leads of the first winding (Ul-Wl’, VI- Ul’, Wl- VI’) being delta connected and the second starting leads of the second winding (U2, V2, W2) kept open.

[0028] Specifically, the coil is formed of a conducting material selected from one or more of but not limited to copper or aluminium or Copper cladded Aluminium.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

[0029] The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description and the accompanying drawings. These and other details of the present invention will be described by reference to the accompanying drawings, which are furnished only by way of illustration and not in limitation of the invention, and in which drawings: [0030] Figures la and lb illustrate schematic representations of a dual voltage motor known in the art.

[0031] Figures 2a and 2b illustrate schematic representations of a dual speed motor known in the art.

[0032] Figure 3a illustrates a schematic representation of an induction motor in accordance with one embodiment of the present subject matter.

[0033] Figure 3b illustrates a schematic representation of the UVW (RYB) circuit of an induction motor in accordance with one embodiment of the present subject matter.

[0034] Figure 4 illustrates a schematic representation of the output terminal leads of two windings of the induction motor in accordance with one embodiment of the present subject matter.

[0035] Figure 5 illustrates a schematic representation of the terminal connection of 300-360V voltage band in accordance with one embodiment of the present subject matter.

[0036] Figure 6 illustrates a schematic representation of the terminal connection of 370-440V voltage band in accordance with one embodiment of the present subject matter.

[0037] Figure 7 illustrates a schematic representation of the terminal connection of 185-220V voltage band in accordance with one embodiment of the present subject matter.

[0038] Figure 8 illustrates a schematic representation of the terminal connection of 230-260V voltage band in accordance with one embodiment of the present subject matter.

[0039] Figure 9 illustrates a schematic representation of a circuit of two different windings, for high voltage (420V) in accordance with one embodiment of the present subject matter.

[0040] Figure 10 illustrates a schematic representation of a circuit of two different windings for an intermediate voltage (320V) in accordance with one embodiment of the present subject matter.

[0041] Figure 11 illustrates a schematic representation of a circuit of two different windings for a low voltage (200V) in accordance with one embodiment of the present subject matter.

[0042] Figure 12 illustrates a schematic representation of a circuit of two different windings for a fourth voltage (230V) in accordance with one embodiment of the present subject matter.

[0043] Figure 13a illustrates a chart displaying performance details for a 6 inch 3.7kW bore well submersible motor having a dual voltage winding, working in a variety of voltage bands, according to the present subject matter.

[0044] Figure 13b illustrates a chart displaying pump set characteristics for a 6 inch 3.7kW bore well submersible motor having a dual voltage winding, working in a variety of voltage bands, according to the present subject matter. [0045] Figure 13c illustrates a graphical representation of Pump set Characteristics displaying a comparison between overall efficiency of pumpset in relation to a discharge and head characteristics, for a 6 inch 3.7kWbore well submersible motor having a dual voltage winding, working in a variety of voltage bands, according to the present subject matter.

[0046] Figure 13d illustrates a graphical representation of a comparison between Efficiency and Voltage for a 6 inch 3.7kW bore well submersible motor having a dual voltage winding, working in a variety of voltage bands, according to the present subject matter.

[0047] Figure 14 illustrates a flow chart of a method of using the induction motor of current disclosure, in a variety of voltage bands, according to the present invention.

DETAILED DESCRIPTION

[0048] The following presents a detailed description of various embodiments of the present subject matter with reference to the accompanying drawings.

[0049] The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to a person skilled in the art. In the accompanying drawings, like reference numerals are used to indicate like components.

[0050] The specification may refer to “an”, “one”, “different” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

[0051] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “include”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/ or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “attached” or “connected” or “coupled” or “mounted” to another element, it can be directly attached or connected or coupled to the other element or intervening elements may be present. As used herein, the term “and/ or” includes any and all combinations and arrangements of one or more of the associated listed items. [0052] The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown.

[0053] The present invention provides an induction motor that is configured for multiple voltage bands. The present invention finds its application in sectors where voltage fluctuation and voltage drops are a common phenomenon, such as but not limited to agricultural sector.

[0054] Figure 3a illustrates schematic representation of an induction motor 100 in accordance with one embodiment of the present subject matter. This figure is simplified for the sake of explanation, as windings and other components are omitted. The induction motor 100 according to the present subject matter comprises a plurality of components. For example, and by no way limiting the scope of the present subject matter, major components of the induction motor 100 include but are not limited to a housing 105 having a rotor 102 adapted to be rotated about an axis of rotation R. The induction motor 100 further includes a stationary stator 104 encircled by the rotor 102. The housing 105 further includes an air gap 106 between the stator 104 and rotor 102. The air gap 106 is a free space sized to allow for relatively free rotation of the rotor 102 within the stator 104. Further, the airgap 106 is configured so as to obtain desirable levels of the magnetizing inductance and the leakage inductances between the rotor 102 and stator 104. In a preferred embodiment, the air gap 106 is at least 0.5 mm. However, in other embodiments, the airgap 106 may be sized in accordance to the requirements, without deviating from the scope of the present invention. The induction motor 100 further includes a shaft 108 coupled to the rotor 102. The shaft 108 is adapted to be coupled to downstream devices as required to be connected to the induction motor 100.

[0055] The stator 104 includes a stator core 110 having a plurality of slots 112 formed therein. The plurality of stator slots 112 includes two or more concentric windings 115 configured therein, adapted to rotate the rotor 102 with a number of magnetic poles P. In a preferred embodiment, the two or more concentric windings 115 includes a first winding 115a and a second winding 115b formed of a coil C, generally formed of a rectangular compressed wire. However, in other embodiments, the coil C may be made of any conducting material selected from one or more of but not limited to copper, aluminium, copper cladded aluminium and any other similar metal. In a preferred embodiment, the windings 115 are concentrically placed within successive slots such that phase difference, pole configuration and coil pitch remains same there through.

[0056] In an embodiment of the current disclosure, the first winding 115a comprises a first number of turns 116a extending between first starting leads (U, V, W) towards a first ending lead (U’, V’, W’). Further, the second winding 115b comprises a second number of turns 116b extending between second starting leads (Ul, VI, Wl) towards a second ending lead (Ul’, VI’, Wl’). The number of turns 116a, 116b are variable and may be varied in accordance to the voltage requirements of the induction motor 100. In some embodiments, the first number of turns 116a is higher than the second number of turns 116b. However, in some other instances, the first number of turns 116a is lesser than the second number of turns 116b. Accordingly, a voltage ratio V depending upon the ratio of first number of turns 116a and second number of turns 116b may be varied. For example, the voltage ratio V can range between as low as 1:1.20 to as high as 1:4 and even more.

[0057] The two or more concentric windings 115 are connected through one or more connection patterns CP so as to allow flow of current there through thereby enabling generation of poles, and magnetic reflux there through which in turn enables rotation of rotor 102. The connection patterns CP are further accommodated to determine voltage band of the induction motor 100.

[0058] The connection pattern CP determines connection between the two or more concentric windings 115a and 115b and may include one or more of series connection, a star connection, a delta connection and the like without limiting to any specific connection type. In some embodiments, as illustrated in Figure 4, the connection pattern CP includes connecting the first end leads (Ul’, VI’, Wl’) of the first winding 115a, being connected with the second starting leads (U2, V2, W2) while the second end leads (U2’, V2’, W2’) of the second winding 115b being star connected.

[0059] Alternatively, in some other embodiments, the first end leads (Ul’, VI’, Wl’) of the first winding 115a are star connected and the second starting leads (U2, V2, W2) of the second winding 115b are kept open.

[0060] In yet other embodiments, the connection pattern CP includes delta connecting the first end leads as mentioned below: (Ul-Wl’, VI- Ul’, Wl- VI’) and keeping the second starting leads (U2, V2, W2) of the second winding 115b as open.

[0061] In an exemplary embodiment, the induction motor of the present invention includes two windings (a, b) that are placed in the same slot. These two windings have two different coils, each coil having different number of turns. The ends of the winding are placed in successive slots in a concentric winding pattern. According to the present invention, the phase difference of the two windings according to the present invention remains the same. Based on the voltage ratio requirement, the number of turns in a coil with two windings can be varied to a ratio of 1: 4 or 1: 3, and so on. In this configuration, the winding ‘a’ has higher number of turns in a coil and winding V has lower number of turns in a coil. Hence, winding ‘a’ has higher resistance than winding V. However, each winding has the same pole configuration and coil pitch as shown in Figure 3b, which illustrates a schematic representation of the UVW (RYB) circuit of the induction motor in accordance with one embodiment of the present subject matter.

[0062] In some embodiments, the windings may be the combination of RL (Resistance- Inductance) elements. The voltage may be added when connecting the two circuits in series and the same current flows through two circuits.

Assuming, the induced emf for winding ‘a’ is ei and winding V is ez. el = N1 d$l/dt e2 = N2 d<j>2/dt

Total induced emf (e) = el + e2 (i.e. 11=12=1)

The potential across the phase RY, YB & BR is same.

[0063] Figure 4 illustrates, in general an exemplary representation of the output terminal leads of two windings of the induction motor according to an embodiment of the present invention. The winding ‘a’ includes three input terminals Ul, VI, Wl and three output terminals Ul’, VI’, Wl’. The winding V includes three input terminals U2, V2, W2 and three output terminals U2’, V2’, W2’. The end leads of second winding V are star connected.

[0064] Figure 5 illustrates a schematic representation of the terminal connection of 300-360V voltage band according to an embodiment of the present invention. The lower voltage band (I) 300 - 360V is obtained by connecting the end leads Ul’, VI’, Wl’ of winding ‘a’ in star mode, and the starting leads of winding V is open to run the motor in intermediate voltage zone. In some embodiments, the supply fed to winding ‘a’ and winding V are open. In some embodiments, the voltage ratio is obtained by the construction of winding ‘a’ end leads Ul’, VI’, Wl’ in star mode may be 1: 1.2 by selecting the voltage band based on the user requirement. In some exemplary embodiments, the input voltage of 320V is supplied to the starting leads of winding ‘a’ Ul, VI, Wl through the supply line LI, L2, L3.

[0065] Figure 6 illustrates a schematic representation of the terminal connection of 370-440V voltage band according to an embodiment of the present invention. The higher voltage band (II) 370 - 440V is obtained by connecting the winding ‘a’ and winding T>’ in series combination. The Resistance-Inductance (RL) values of winding ‘a’ and winding T>’ are different. The end leads of winding ‘a’ (Ul’, VI’, Wl’) is connected with starting leads of winding T>’ (U2, V2, W2) and the end leads of winding T>’ (U2’, V2’, W2’) is star connected to run the motor in high voltage zone. In some exemplary embodiments, the input voltage of 420V is supplied to the starting leads of winding ‘a’ (Ul, VI, Wl) through supply line LI, L2, L3, the induced electromotive force for winding ‘a’ is 3/ 4th of voltage and winding V is 1/ 4th of voltage. In some embodiments, the phase impedance is same for all three phases.

[0066] Figure 7 illustrates a schematic representation of the terminal connection of 185-220V voltage band according to an embodiment herein. A third operating voltage (III) of approximately 185 - 220V is obtained by connecting the winding ‘a’ in delta mode and the supply unit for winding ‘a’ and winding ID’ are open to run the motor in low voltage zone. The end leads of winding ‘a’ (Ul- WT, VI- Ul’, Wl- VI’) is delta connected and the starting leads of winding V (U2, V2, W2) is open. In some exemplary embodiments, the input voltage of 185V is supplied to the starting leads of winding ‘a’ (Ul, VI, Wl) through the supply line LI, L2, L3. In some embodiments, the motor may be operated at three different voltages with the same speed and similar torque characteristics.

[0067] Figure 8 illustrates a schematic representation of the terminal connection of 230-260V voltage band according to an embodiment herein. A fourth voltage of approximately 230 - 260V may be obtained by connecting twelve output terminal leads. In some embodiments, the motor may be operated at three different voltages with the same speed and similar torque characteristics. In some exemplary embodiments, the input voltage of 230V is supplied to the starting leads of winding ‘a’ (Ul, VI, Wl) through the supply line LI, L2, L3 by connecting winding ‘a’ and winding V as (U2-U1’, V2-V1’, W2-W1’) in series and linking winding ‘a’ and winding T>’ as (U2’-V1, V2’-W1, W2’-U1).

[0068] Figure 9 illustrates a schematic representation of two different windings connected in series for high voltage (420V) according to an embodiment herein. The different windings, winding ‘a’ and winding V are connected in series for a high voltage input of 420V. In this configuration, the RL values are different for both the windings. The user may run the motor in high voltage zone. The end leads of winding ‘a’ (Ul’, VI’, WL) is connected with starting leads of winding T>’ (U2, V2, W2) and the end leads of winding V (U2’, V2’, W2’) is star connected. In some exemplary embodiments, the input voltage is 420V and the induced electromotive force for winding ‘a’ is 3/ 4th of voltage and winding V is l/4th of voltage in this configuration. The phase impedance is same for all three phases.

[0069] Figure 10 illustrates a schematic representation of the circuit in which one winding is connected in star for intermediate voltage (320V) and the other winding is kept open according to an embodiment herein. The winding ‘a’ is connected in star mode and the input supply to winding ‘a’ and winding V is open. The user may run the motor in intermediate voltage zone (320V). In the configuration, the end leads of winding ‘a’ (Uf, VI’, Wl’) are star connected and starting leads of winding V (U2, V2, W2) are open.

[0070] Figure 11 illustrates a schematic representation of the circuit in which one winding is connected in delta for low voltage (200V) and the other winding is kept open according to an embodiment herein. The winding ‘a’ is connected in delta mode for low voltage (200V) and the input voltage to winding ‘a’ and winding V are open. The motor may run in low voltage zone. In the configuration, the end leads of winding ‘a’ (U1-W1’, Vi- Ui’, Wi- Vi’) are delta connected and starting leads of winding V (U2, V2, W2) are open.

[0071] In some embodiments, the motor is allowed to work for different voltage bands by having two winding coils with the voltage ratio as low as 1: 1.2. The two different operating voltages are obtained with the same power by different combination of winding. The voltage ratios that may be obtained using the windings is as low as 1: 1.2. In some embodiments, the voltage band of 300 V- 440

V is used by the agricultural customer. In some embodiments, the lower voltage of approximately 185

V - 220 V is possible by arranging the windings in different end connection and it provides the additional benefit of operating the motor at three different voltages with the same speed and torque characteristics.

[0072] Figure 12 illustrates a schematic representation of two different windings connected in series and formed as delta connection for a fourth voltage (230V) according to an embodiment herein. The different windings, winding ‘a’ and winding T>’ are connected in series and formed as delta connection. The user may run the motor in a fourth voltage zone ranging between the low voltage & the intermediate voltage zone. The end leads of winding ‘a’ (Ul’, VI’, Wl’) is connected with starting leads of winding T>’ (U2, V2, W2) and the starting leads of winding ‘a’ & end leads of winding V (Ui-W2’, Vi- U2’, Wi- V2) are delta connected.

[0073] Figure 13a through 13d illustrates an exemplary application of the dual winding of the current disclosure in a three phase, 2 pole 3.7kW, 2880rpm water-cooled borewell submersible induction motor suitable for bore well applications. The induction motor possesses below mentioned design characteristics:

Number of stator slots 24

Number of rotor slots 18

Diameter of the core 73 mm Length of the core 180 mm

Magnetic loading 0.6 Wb/m2

Electric loading 18000 ac/m

Turns per phase of first winding 96

Turns per phase of second winding 20

In an embodiment, the motor is designed for 4 different voltage levels and cover the wide voltage band. The rated voltage levels are 380V, 320V, 220V & 185V. The motor can be operated from three phase 170V, 50Hz input supply to three phase 440V, 50Hz input supply

Experimental Investigation:

[0074] In order to evaluate the performance, the developed motor is connected with 6-inch submersible pump for testing. The 12 leads are taken out from the winding for operating the motor with 4 different voltage levels.

Load test:

[0075] The developed three phase 3.7kW, 2 pole, 2880rpm, two winding squirrel cage induction motor (6 Inch borewell submersible motor) is coupled with 6-inch submersible pump to validate the motor performance as well as pumpset performance. The performance characteristics taken from full open to shutoff condition.

Connection 1:

[0076] The winding ‘A’ output leads Ul’, VI’ Wl’are connected with Winding ^C B’ input leads U2, V2, W2. The output leads of winding ‘B’ is linked (U2’, V2’ W2’). The three phase 380V input supply is fed to input terminals of winding ‘A’ (Ul, VI Wl). This is a series connection to operate the motor in high voltage zone

Connection 2:

[0077] The winding ‘A’ output leads Ul’, VI’ Wl’are star linked and Winding ‘B’ kept open. The three phase 320V input supply is fed to input terminals of winding ‘A’ (Ul, VI Wl). This is intermediate voltage zone. Connection 3:

[0078] The winding ‘A’ terminals are connected in delta and Winding ‘B’ kept open. The three phase 190V input supply is fed to input terminals of winding ‘A’ (Ul, VI Wl). This is very low voltage zone.

Connection 4:

[0079] The winding ‘A’ output leads Ul’, VI’ Wl’are connected with Winding ^C B’ input leads U2, V2, W2. The output leads of winding ‘B’ (U2’, V2’ W2’) & input terminals of winding ‘A’ (Ul, VI Wl) are delta connection. The three phase 220V input supply is fed to input terminals of winding ‘A’ (Ul, VI Wl). This is fourth voltage zone which is between intermediate voltage zone and very low voltage zone.

Results:

[0080] Testing has been carried out from 170V to 440V with different end connection. The optimum design points for each connection were highlighted in the Figure 13a. In the optimum point, the motor speed, input power & efficiency values are almost constant. The losses are almost similar at all optimum points (380V, 320V, 220V &190V). The magnetic saturation and current density values are similar. Also, the performances from 170V to 415V are almost similar. The 6-inch submersible pump is used as a load for motor. Hence the load percentage is slightly different for all voltage.

[0081] In the below experiment, we have changed the end connections through manually. This can be done through electronic control. According to the input voltage, the solid-state switch changes the connections (Connection 1, Connection 2, Connection 3 and Connection 4).

[0082] The same experiment done in 3.7Kw, 2 Pole, 3$ Monobloc pump set which is used for agricultural application. In that 12 leads terminal board were used and connection changes done through manually. The results were obtained in this model is similar to bore well submersible motor. [0083] Figure 13b illustrates a chart displaying pump set characteristics for a 6 inch 3.7 kW bore well submersible motor @5 HP motor having a dual voltage winding, working in a variety of voltage bands, according to the present subject matter. The overall efficiency & input power of pump set is almost common for all optimum voltage level. The graphical representation is given in below. [0084] Figure 13c illustrates a graphical representation of Pump set Characteristics displaying a comparison between overall efficiency of pumpset in relation to a discharge and head characteristics. Specifically, the representation displays Discharge (Q) Vs Head (H) & Discharge (Q) Vs Pump set overall efficiency (r|) characteristics as shown in below curve. Only 4% variations in Q-H characteristics & 2.5% variation in Q- r] characteristics from 170V to 440V voltage range.

[0085] Figure 13d illustrates a graphical representation of the comparison between Motor Input Voltage and Pumpset Overall Efficiency in a 6 inch 3.7kWbore well submersible motor @5 HP motor Dual Voltage Winding. The increase and decrease in voltages are represented in the graph.

Conclusion:

[0086] A 3.7Kw, 6 inch, 3-phase, 2-pole, two winding submersible motor has been designed, fabricated and tested successfully. The experimental results illustrate the performance of two winding motor. Based on the test results, the phase current, input power, motor & pumpset efficiency is almost similar in optimum voltage point of different end winding connections (Connection 1— 380V, Connection 2 -320V, Connection 3-220V & Connection 4— 190V). Also throughout the voltage range (3$, 170V to 440V), the performance of motor and pumpset is almost similar (Only 4 % variations in Q-H & 2.5% variation in Q-ip By using this technology, we can operate the motor in wide voltage condition.

[0087] This can be controlled by manual changing or electronic control. The two winding induction motor can be employed, where the induction motor runs continuously for a longer period of time like agricultural applications. Also, this can be adopted where the input voltage is continuously varying nature.

[0088] Figure 14 illustrates a flow chart of a method of using the induction motor of current disclosure, in a variety of voltage bands, according to the present invention. The method starts at step 1402 and proceeds to step 1404 where a connection pattern for connecting the two or more windings 115 is determined on the basis of the required voltage bands. Thereafter, the method proceeds to step 1406 where power is supplied to the induction motor based on the input voltage availability, and at step 1408 the induction motor is allowed to operate at the possible voltage bands depending upon the connection pattern selected to connect the two or more windings 115. The method ends at step 1410.

[0089] As can be seen from above, the induction motor according to the present invention is capable of working in multiple voltage bands. The present subject matter ensures that the active material is optimized, and the motor is allowed to work for different voltage bands by having two winding coils with a voltage ratio as low as 1: 1.2. With two different operating voltages, the present invention helps in achieving the same power with different combination of winding. The voltage ratios that can be achieved with the present invention of construction can be as low as 1: 1.2. Further, the voltage band of 300 V-440 V achieved by the present invention meets the needs of the agricultural customer. With the present invention, lower voltage of approximately 185 V - 220 V is possible by arranging the windings in different end connection. This gives the additional benefit of operating the motor at 3 different voltages with the same speed and torque characteristics.

[0090] The general characteristics of the geometry as known in the art of induction motor may be included. Such characteristic includes, but are not limited to, one or more of a variety of air gaps, width of stator slots, width of stator teeth, width and height of rotor teeth, density of stator core, number of stator slots per pole per phase, and an increased number of rotor slots, and so on.

[0091] The present subject matter ensures that foil allowable voltage band is increased from 90V to 140V. Another benefit of this configuration is the possibility of achieving a third operating voltage (III) of approximately 185 - 220V, as shown in Figure 7. This is possible by connecting the winding (a) in delta connection. This also gives the benefit of operating the motor at three different voltages with the same speed and similar torque characteristics. In addition to the above, there is a possibility for fourth operating voltage (IV) of approximately 230 - 260V, which can be achieved through twelve output terminal leads, as shown in Figure 8.

[0092] The voltage ratios that can be achieved with this type of construction can be as low as 1: 1.2, thereby allowing the voltage band to be selected based on the requirement. The lower voltage band (I) 300 - 360V is achieved through one set of winding (winding (a) as shown in figure 5), and the higher voltage band (II) 370 - 440V is achieved through the series combination of windings (a) and (b) as shown in the Figure 6. Both the voltage bands are in star connection. This can be achieved through nine output terminal leads.

[0093] The described embodiments are to be considered in all respects only as illustrative and not restrictive.

[0094] While the preferred embodiments of the present invention have been described hereinabove, it should be understood that various changes, adaptations, and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims. It will be obvious to a person skilled in the art that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.