FIELD OF INVENTION

The present invention in general relates to the field of motors for electric submersible pumps, and in particular to ferrite semi-modular spoke-type brushless DC motor for bore-well submersible water pumps. BACKGROUND

Photovoltaic powered submersible electric water pumps are becoming popular in the rural areas due to the non-availability of grid connectivity. The initial cost of a photovoltaic (PV) system is high though it is environmental friendly compared to a diesel-electric system. In general, usually bore-well submersible induction motors are employed for a solar water pump.

Reference has been made to W02017106318A1, disclosing a permanent magnet submersible motor with a one-piece rotor and resin embedded magnets. The safe retention of magnets is ensured by a shape form closure on the yoke, even under high centrifugal loads, while an exterior cladding tube and a cast resin filler material are used to further secure the magnets around the yoke periphery providing hermetic sealing against the working fluid. Reference has been made to WO2017155778A1, relating to an electric submersible pump with sealed stator windings. The invention is related to methods for reducing or preventing degradation of electrical insulation that separates the windings of a motor for use in the submersible pump system by providing a hermetic seal that prevents the ingress of well bore fluids into the motor's stator chamber. The stator core sections are formed of a soft magnetic composite material to form a single-piece unit. The stator core sections are positioned end-to-end with seals at each end to form a plurality of stator slots, where each of the stator slots extends through each of the stator core sections and is in fluid communication with the others to form a sealed stator chamber. The sealed stator chamber can have an expansion chamber to allow expansion and contraction of dielectric fluid in the stator chamber while maintaining separation of the dielectric oil from lubricating oil which is within the motor but external to the stator chamber. The sealed stator chamber can prevent well fluids that leak into the motor from reaching the stator windings and degrading their insulation.

Reference has been made to US20070096571A1, pertaining to a three phase permanent magnet down hole electric motor for a submersible pump. The adjacent coils of each pair of phase windings extend through opposite parts of the respective one of the slots, so that these coils extend alongside one another in the slot, either being separated by a gap through which cooling fluid may be pumped to cool the coils. The invention focuses around cooling the motor windings and improving the motor life.

Further reference has been made to US 20090142207A1, disclosing a bottom hole hollow core electric submersible pumping system. The pump output is directed through the hollow core output shaft and into the hollow core motor rotor.

Yet another reference has been made to US20100288501A1, relating to an electric submersible pumping system for dewatering of gas wells, a method of unloading liquid from a reservoir deploying the system into a well bore to a location proximate the reservoir using a cable.

The efficiency of these motors is poor which reflects in the overall Watt-peak rating of the solar panel, and thus increases the initial cost. On the other hand, ferrite permanent magnet brushless dc motors are efficient compared to an induction motor and are also economical. Further, unlike the costly rare-earth magnets, ferrite magnets are manufactured in India which allows for indigenisation of the technology.

Accordingly, there is a need for a cost effective ferrite magnet based submersible brushless DC, BLDC, motor having reduced flux leakage and with the features of flux concentration and structural integrity of a conventional spoke -type rotor. SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

An object of the present invention is to provide a ferrite magnet semi -modular brushless DC motor, BLDC, motor assembly according to the present invention.

An object of the present invention is to provide a submersible pumping system comprising a ferrite magnet semi-modular brushless DC motor, BLDC, motor assembly according to the present invention.

In accordance with an aspect of the present disclosure, is to provide a ferrite magnet semi-modular brushless DC, BLDC motor assembly comprising a submersible motor, operably coupled to a centrifugal pump, said motor comprising a semi-modular rotor disposed radially outwards on a motor shaft, said rotor having a plurality of stacks, a stator fitted into a motor frame, wherein the stator circumferentially encloses the rotor along the length of the motor shaft and a submersible sensorless controller electrically coupled to a three phase inverter power module, wherein the motor is operably disposed between the pump and the controller and the motor is electrically coupled to the pump and the controller, wherein the inverter module is electronically coupled to the motor.

In another aspect of the present invention, is to provide a bore-well submersible pumping system comprising a ferrite magnet semi-modular brushless DC, BLDC motor assembly comprising a submersible motor, operably coupled to a centrifugal pump, said motor comprising a semi-modular rotor disposed radially outwards on a motor shaft, said rotor having a plurality of stacks; a stator fitted into a motor frame, wherein the stator circumferentially encloses the rotor along the length of the motor shaft; and a submersible sensorless controller electrically coupled to a three phase inverter power module, a DC power generating source electrically coupled to provide power to the pumping system; wherein the motor is operably disposed between the pump and the controller and the motor is electrically coupled to the pump and the controller, wherein the inverter module is electronically coupled to the motor.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features and advantages of the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates a voltage source inverter interfaced between the photovoltaic panel and the submersible BLDC motor and the motor control thereof, according to an implementation of the present invention.

Figure 2 illustrates three-dimensional schematic of the submersible deep bore-well BLDC motor with the sensorless drive, according to an implementation of the present invention.

Figure 3 illustrates cross-sectional view of the submersible BLDC motor, according to an implementation of the present invention.

Figures 4 illustrates two-dimensional axial view of the pump-side flange, according to an implementation of the present invention. Figure 5 illustrates two-dimensional axial view of the controller side flange, according to an implementation of the present invention.

Figures 6 illustrates the two-dimensional cross-section of stator of the submersible BLDC motor, according to an implementation of the present invention.

Figure 7 illustrates the two-dimensional cross-section of the rotor of the submersible BLDC motor, according to an implementation of the present invention.

Figure 8 illustrates the axial three-dimensional isometric view of the stainless steel motor shaft, according to an implementation of the present invention.

Figure 9 illustrates the axial three-dimensional axial view of the submersible spoke type BLDC motor with non-magnetic isolation between the rotor stacks, according to an implementation of the present invention.

Figures 10 (a)-(h) illustrate the 15 slot, 10 pole submersible ST BLDC motor, according to an implementation of the present invention.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense, but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure. The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the various embodiments set forth herein, rather, these various embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the present disclosure. Furthermore, a detailed description of other parts will not be provided not to make the present disclosure unclear. Like reference numerals in the drawings refer to like elements throughout.

The subject invention lies in providing a bore-well submersible semi-modular spoke type ferrite magnet brushless motor and a pumping system thereof.

According to one embodiment of the present invention a ferrite magnet semi- modular brushless DC, BLDC motor assembly comprising a submersible motor (2), operably coupled to a centrifugal pump (1), said motor (2) comprising a semi-modular rotor (25) disposed radially outwards on a motor shaft (24), said rotor having a plurality of stacks; a stator (26) fitted into a motor frame (22), wherein the stator (26) circumferentially encloses the rotor (25) along the length of the motor shaft (24); and a submersible sensorless controller (3) electrically coupled to a three phase inverter power module (28), wherein the motor (2) is operably disposed between the pump (1) and the controller (3) and the motor is (2) electrically coupled to the pump (1) and the controller (3), wherein the inverter module (28) is electronically coupled to the motor (2).

According to another embodiment of the present invention a submersible pumping system comprising a ferrite magnet semi-modular brushless DC, BLDC motor assembly comprising a submersible motor (2), operably coupled to a centrifugal pump (1), said motor (2) comprising a semi-modular rotor (25) disposed radially outwards on a motor shaft (24), said rotor having a plurality of stacks; a stator (26) fitted into a motor frame (22), wherein the stator (26) circumferentially encloses the rotor (25) along the length of the motor shaft (24); and a submersible sensorless controller (3) electrically coupled to a three phase inverter power module (28), a DC power generating source (4) electrically coupled to provide power to the pumping system; wherein the motor (2) is operably disposed between the pump (1) and the controller (3) and the motor is (2) electrically coupled to the pump (1) and the controller (3), wherein the inverter module (28) is electronically coupled to the motor (2). In an embodiment in accordance to the subject matter of the present invention, it provides a ferrite magnet semi-modular dual-stack brushless dc (BLDC) motor based deep bore-well submersible water pumping system as illustrated in figure 1. The system has the submersible motor (2) coupled beneath a submersible centrifugal pump (1), and a submersible sensorless controller along with a three phase inverter (3) is coupled beneath the submersible motor. A photovoltaic, PV panel (4) provides power to the submersible water pumping system. The motor, controller and pump are placed inside a j[aigMM2]bore- well (5). The water table of the ground water (6) is substantially belowja3] the overhead tank (8), where the tank is mounted on the ground level (7). In another embodiment in accordance to the subject matter of the present invention, a single-stage power conversion along with maximum power point tracking, MPPT (9), and sensorless control (10) has been disclosed. The line voltages of the motor (11) are sensed and fed to the controller (3), and thus the gating pulses (12) are generated. The PV voltage (13) and current (14) are sensed and fed to the controller for MPPT. DC link capacitance (15) is interfaced to the PV panel. A microcontroller (43) is configured to process the sensed data and control the motor (2) and implementing MPPT. The DC link current (16) is also sensed for MPPT operation. Insulated Gate Bi-Polar Transistors, IGBT (17), based switches are used for the three phase inverter. The inverter electronically commutates the motor and the phase currents (18) are forced through the motor (2).

Referring to figure 2, three dimensional schematic diagram of the submersible BLDC motor along with the submersible controller has been illustrated. The submersible controller and inverter (3) are assembled inside a stainless steel, SS-304 grade controller frame (19). The three phase inverter along with the gate driver circuit are mounted on the power printed circuit board, PCB, (20) inside the controller frame (19). The controller side flange (21) made up of SS 304 grade is mounted inside the controller frame (19) on one end. The motor frame (22) is also made of SS 304 and is affixed on the controller end by a controller flange (21), and on the other end using a pump side flange (23). A SS 304 stainless steel shaft having a key-way slot is used for holding the semi-modular dual-stack rotor (25) having a key, into position using the key and key-way arrangement.

The stator frame (26) is press fitted inside the motor frame (22). Cold rolled non grain oriented, CRNGO, silicon steel of 0.5 mm lamination thickness is used for both the rotor (25) and stator (26). Three SS-304 keys (27), substantially placed 120 degrees apart in the key-way slots within the controller frame, are used for holding the power and controller PCBs. The three phase inverter power module (28) is mounted on the power circuit PCB (20). The DC link capacitor (29) is mounted beneath the power PCB (20). The sensing circuit PCB (30) is placed at the extreme end of the controller frame (19). The two dimensional axial cross-sectional view of the motor assembly as shown in figure 3 refers to the ferrite magnet semi-modular submersible brushless dc motor (2) hermetically sealed to the controller (3) using nitrile rubber based O-rings (31). An oil- seal (32) is used for sealing the driving end of the motor. Provision is provided for controller side fitting (33) with the controller side flange (21). The stator winding terminals are placed through a passage (34) in the controller side flange (21), for driving the motor with the sensorless controller and inverter circuit. The constructional features and design of the pump side flange (23) and the controller side flange (21) are illustrated in figures 4 and 5. The perspective views of a fifteen-slot stator (26) and a ten-pole semi modular dual stack rotor (25) along with the motor shaft (24) are illustrated in figures 6, 7 and 8 respectively.

The three dimensional view of the rotor as illustrated in figure 9, the semi- modular dual-stack spoke-type submersible BLDC rotor has one fixed rotor module (35) on one rotor stack (39), which supports the floating rotor module (37) on the other rotor stack (41), through non-magnetic SS 304 based rivets (42). The ferrite magnets are placed inside the slots (36). The fixed rotor stack has a magnetic bridge (38) which is fixed on the motor shaft (24). Non-magnetic SS 304 based circular discs (40) of 2 mm thickness are used at either end of the rotor stacks and in between them for supporting the whole rotor structure, through which the rivets (42) end-by. The various parts of the fabricated of the ferrite magnet based semi-modular dual-stack motor prototype (2) is shown in Fig.

10

In all the embodiments of the submersible self-modular motor (2) herein above, the motor comprises of a plurality of stacks in the rotor (25).

Some of the non-limiting advantages of the present invention are:

1. Higher efficiency compared to an existing bore-well submersible induction motor.

2. Reduced flux leakage and higher air-gap flux density compared to the conventional spoke-type rotor.

3. Improved mechanical integrity compared to the completely modular spoke-type motor.

4. Safe retention of magnets inside the rotor from centrifugal forces and from the pump working fluid.

5. Reduced overall Watt-peak requirement of solar panel compared to an induction motor based pump.

6. Lower cost of the BLDC motor compared to a rare-earth magnet based BLDC motor or permanent magnet synchronous motor (PMSM)

7. Single-stage three phase inverter based sensorless control of the submersible motor without boost converter stage between the photovoltaic, PV, source and the motor along with maximum power point tracking, MPPT.

Although a ferrite magnet based Semi-Modular spoke type ferrite magnet, submersible BLDC motor has been described in language specific to structural features, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific methods or devices described herein. Rather, the specific features are disclosed as examples of implementations of a ferrite magnet based Semi-Modular spoke type ferrite magnet, submersible BLDC motor.