Intravascular blood pump with multilayer air-core coil

Abstract

To provide an intravascular blood pump for insertion into the patient's heart.SOLUTION: A blood pump comprises a slotless permanent magnet motor contained in a housing, the motor having p magnet pole pairs and n phases, where p is an integer greater than zero, and n is an integer greater than or equal to 3. The motor comprises a stator extending along a longitudinal axis of the housing and having 2np coils wound to form two coils per phase per magnet pole pair. The stator comprises inner and outer windings each comprising np coils electrically connected such that a current flowing through the coils is in a same direction, the coils of the outer winding arranged on an outer surface of the coils of the inner winding.SELECTED DRAWING: None

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 62 / 868,530, filed on June 28, 2019, which is incorporated herein by reference.

[0002] Technical Field The present technology relates to an intravascular blood pump system having a permanent magnet motor and a stator having coils.

Background Art

[0003] Background Intravascular blood pumps, such as the Impella® pump by Abiomed, Inc. of Danvers, MA, are rapidly becoming the current standard for ventricular assist devices. Currently, there are the Impella 2.5® pump, the Impella 5.0® pump, the Impella CP® pump, and the Impella LD® pump. These pumps can be inserted percutaneously into a patient's body through a single access point (e.g., radial access, femoral access, axillary access) so that the pump head can be placed into the left ventricle of the patient's heart through a small - diameter (6 - 7 Fr) catheter. The pump head includes an electric motor having a stator configured to interact magnetically with a rotor to rotate the rotor, thereby providing a volumetric flow rate of blood through the rotor and thus through the patient's heart.

[0004] Currently, Impella® pumps can deliver blood at flow rates of approximately 1.0 to 6.0 liters per minute (lpm). However, with the increasing use of Impella® in more and more surgical procedures, there is a growing demand to increase the blood flow rate generated beyond these levels. This essentially means that the rotor speed of the electric motor needs to be increased. However, due to the small geometry involved, increasing the rotor speed has several implications that can affect the operation of such small pumps. For example, increasing the rotor speed may involve increased heat generation (Joule heating) within the electric motor. Since the device is inserted percutaneously into the heart, such increased heat generation can have serious consequences. Another point to consider is the resistive load placed on the device; modifications made to the electric motor to achieve higher flow rates may lead to higher resistive losses.

[0005] Various techniques have been employed to increase the torque coefficient and / or efficiency of a motor, including increasing the number of turns and mounting density of the coils within the motor. However, such topologies are limited by constraints imposed on the motor, such as its size (e.g., diameter and / or length). This has led to the implementation of post-processing methods, such as mechanically squeezing the coils, to adhere to motor dimensional constraints; however, such methods compromise motor reliability, for example, by damaging the insulation of the wires forming the coils, leading to short circuits.

[0006] Given the shortcomings of the current technological situation described above, there is a significant need to increase the flow rate generated by electric motors while maintaining or increasing the efficiency of the motors. [Overview of the Initiative]

[0007] Brief Overview Devices for addressing various problems and shortcomings of the aforementioned technical status are disclosed herein. More specifically, an intravascular blood pump for insertion into a patient's heart is disclosed herein. The blood pump of the present invention comprises an elongated housing having a proximal end connected to a catheter and a distal end connected to a pump; the housing has a longitudinal axis. The blood pump comprises a slotless permanent magnet motor housed within the housing, the motor having p pairs of magnetic poles and n phases, where p is an integer greater than zero and n is an integer greater than or equal to 3. The motor comprises a stator extending along the longitudinal axis of the housing and having 2np coils wound to form two coils per phase per permanent pole pair. The stator comprises an inner winding having np coils, in which one coil for each phase is arranged next to a coil for a different phase in phase order for each pole pair, and this arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator, and the inner winding has an outer surface. The stator also comprises an outer winding having np coils, arranged on the outer surface of the inner winding, and each coil of the outer winding is also arranged so that each coil of the outer winding spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator, and each coil of the outer winding is circumferentially aligned with the coils of the inner winding having the same phase for each pole pair. Within the stator, the coils of the same phase for each pole pair are connected such that the current flowing through the coils is in the same direction. The coil windings described herein are formed from magnet wire. Magnet wire is well known to those skilled in the art and will not be described in detail herein. In addition, the motor is equipped with a magnet that is supported to rotate when it magnetically interacts with the stator, thereby facilitating the flow of blood through the pump.

[0008] In another embodiment, a slotless permanent magnet electric motor is provided having p pairs of poles and n phases, where p is an integer greater than zero and n is an integer greater than or equal to 3, and the motor has a longitudinal axis. The motor comprises a stator having 2np coils that extend along the longitudinal axis of the housing and are wound to form two coils per phase per permanent pole pair. The stator comprises an inner winding having np coils, in which one coil for each phase is arranged next to a coil for a different phase in phase order for each pole pair, and this arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) around the cross-section of the stator, and the inner winding has an outer surface. The stator also comprises an outer winding having np coils arranged on the outer surface of the inner winding, and each coil of the outer winding is circumferentially aligned with the coils of the inner winding, which are in phase with each pole pair, such that each coil of the outer winding spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator. Within the stator, the in-phase coils of each pole pair are connected such that the current flowing through them is in the same direction. In addition, the motor comprises magnets supported to rotate when they magnetically interact with the stator, thereby promoting the rotation of the rotor.

[0009] In some embodiments, the outer winding has at least the same number of winding turns as the inner winding. In certain embodiments, each coil comprises two layers of magnet wire, each extending longitudinally along the length of the stator. In some embodiments, the magnet wires within each coil are arranged sequentially next to each other along the span of the coil. In further embodiments, the inner winding of the coil establishes a uniform base upon which the outer winding of the coil is superimposed. In other embodiments, one phase of coil is connected to the other phase of coil in either a star or delta configuration. In some embodiments, the coils of each phase are connected in either series or parallel.

[0010] In certain embodiments, the 2np coils comprise one of helical windings, diamond windings, conventional windings, and hybrid windings. In further embodiments, the motor comprises a three-phase, one-pole machine. In other embodiments, the motor comprises a six-coil, two-pole machine, with each coil spanning a mechanical angle of 120 degrees around the cross-section of the stator. In some embodiments, the rotor pumps blood at a flow rate of about 1.0 lpm to about 6.0 lpm. In other embodiments, the pump may be inserted into the right ventricle of the patient's heart. In further embodiments, the pump may be inserted into the left ventricle of the patient's heart.

[0011] The arrangement in which 2np coils are wound as a double winding comprising np coils in the inner winding and np coils in the outer winding, forming two coils per phase per pole pair, allows for the use of more wire within the available space in the electric motor, thereby enabling better utilization of the motor space design. This improves the efficiency of the motor compared to a motor using a single-winding stator.

[0012] In a further embodiment, a method is provided for forming a stator for use in a slotless permanent magnet motor having p pairs of poles and n phases, where p is an integer greater than zero and n is an integer ≥ 3, and the stator has 2np coils that extend longitudinally and are wound to form two coils per phase per permanent pole pair. The method includes the step of forming an inner winding comprising np coils, wherein in the np coils, one coil for each phase is placed next to a coil for a different phase in phase order for each pole pair, and the arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator, and the inner winding has an outer surface. The method then includes the step of forming an outer winding comprising np coils arranged on the outer surface of an inner winding, wherein each coil of the outer winding is circumferentially aligned with the coils of the inner winding having the same phase for each pole pair, such that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator. The method then includes the step of electrically connecting the coils of the same phase for each pole pair so that current flows through the coils in the same direction.

[0013] In some embodiments, the method further includes the step of forming the outer winding such that the outer winding has at least the same number of winding turns as the inner winding. In certain embodiments, the method also includes the step of forming the coils such that each coil has two layers of magnet wire, each extending longitudinally along the length of the stator. In other embodiments, the magnet wires in each coil are arranged sequentially next to each other along the span of each coil. This allows for a precise and compact arrangement of the magnet wires within the stator coils, which leads to a minimum coil thickness that does not require mechanical squeeze to fit within the yoke of the electric motor. A stator is a combination of coils and a yoke. The thickness of the stator is the sum of the coil thickness and the yoke thickness. The coil thickness described herein excludes the yoke thickness. The precise and compact arrangement of the coils increases the reliability of the double-wound stator because there is no risk to the integrity of the insulation around the wires forming the windings. This minimal coil thickness also allows for the use of larger rotor magnets and / or thicker magnet steel yokes within the electric motor, thereby enabling the motor to achieve higher efficiency compared to motors using stators with randomly wound multilayer magnet wires.

[0014] In some embodiments, the method includes the step of connecting coils of one phase to coils of other phases in either a star configuration or a delta configuration. In certain embodiments, the method includes the step of connecting coils of each phase in either series or parallel. In other embodiments, the method includes the step of forming 2np coils using coil windings selected from any one of helical, rhombic, conventional, and hybrid. In some embodiments, the stator is suitable for use in a motor having three phases and one pair of poles. In certain embodiments, the stator is suitable for use in a 6-coil, 1-pole-pair motor where each coil spans a mechanical angle of 120 degrees around the cross-section of the stator. [Brief explanation of the drawing]

[0015] The above and other purposes and benefits will become clear upon consideration of the following detailed description in conjunction with the attached drawings; throughout the attached drawings, similar reference numerals refer to similar parts.

[0016] [Figure 1] An exemplary cross-section of an intravascular blood pump, based on one aspect of this disclosure, is shown. [Figure 2] Figures 2A–2D show exemplary winding patterns for individual turns within a coil, known in the art and which may be used in the blood pump of Figure 1. Figures 2E–2H show exemplary completed coil winding patterns formed by a coil having the individual turns shown in Figures 2A–2D. [Figure 3] Figure 1 shows an exemplary cross-section of a three-phase single-wound stator, in which each phase is implemented with a single-helix coil, for use in the blood pump. [Figure 4] Figure 1 shows an exemplary cross-section of a three-phase double-wound stator, based on one aspect of the present disclosure, for use in a blood pump, in which each phase is carried out by a double helix coil. [Figure 5] An exemplary cross-section of the stator shown in Figure 4, used in the blood pump of Figure 1, is shown according to one aspect of this disclosure. [Figure 6] Figure 6A shows an exemplary circuit diagram illustrating the lead wire connections in the single-winding stator of Figure 3. Figure 6B shows an exemplary circuit diagram illustrating the lead wire connections in the double-winding stator of Figure 4, where in-phase coils are connected in series, based on one aspect of the present disclosure. Figure 6C shows an exemplary circuit diagram illustrating the lead wire connections in the double-winding stator of Figure 4, where in-phase coils are connected in parallel, based on one aspect of the present disclosure. [Figure 7] Figure 1 shows an exemplary cross-section of a blood pump using a double-wound stator for an electric motor having three phases and two pairs of poles, according to one aspect of the present disclosure. [Figure 8] FIG. 1 shows an exemplary cross-section of a blood pump using a dual-wound stator for an electric motor having five phases and a pair of pole pairs, according to one aspect of the present disclosure. [Figure 9] FIG. 9A shows an exemplary random wound multi-layer stator in which a wire winding sequence is used for its formation. FIG. 9B shows an exemplary dual-wound stator of FIG. 4 in which a wire winding sequence is used for its formation, according to one aspect of the present disclosure. [Figure 10] FIG. 10A shows an image of a random wound multi-layer stator formed using the wire winding sequence of FIG. 9A. FIG. 10B shows an image of a dual-wound stator formed using the wire winding sequence of FIG. 9B, according to one aspect of the present disclosure. [Figure 11] FIG. 10 shows an exemplary flowchart of a method of forming the dual-wound stators of FIGS. 4 and 9B, according to one aspect of the present disclosure. DETAILED DESCRIPTION

[0017] The various aspects of the present disclosure will be described in detail with reference to the drawings, in which like reference numerals refer to the same or similar elements. It should be understood that the disclosed aspects are merely examples of the present disclosure and can be embodied in various forms. To avoid obscuring the present disclosure with unnecessary details, well-known functions or construction styles will not be described in detail. Accordingly, the specific structural and functional details disclosed herein should not be construed as limiting, but should be construed only as a basis for the claims and as a representative basis for teaching those skilled in the art how to use the present disclosure in virtually any structure that is properly detailed.

[0018] ​​To provide a general understanding of the devices described herein, certain illustrative aspects will be described. The aspects and features described herein are particularly described with respect to use in an intravascular blood pump, but as will be understood, all components and other features outlined below may be combined with each other in any suitable manner and may be adapted and applied to other types of procedures that require an efficient electric motor.

[0019] The devices and methods described herein relate to an intravascular blood pump for insertion into a patient's heart. The blood pump of the present invention comprises an elongated housing having a proximal end connected to a catheter and a distal end coupled to the pump, the housing having a longitudinal axis. The blood pump comprises a slotless permanent magnet motor housed within the housing, the motor having p pairs of magnetic pole pairs and n phases, where p is an integer greater than zero and n is an integer ≧3. The motor comprises a stator having 2np coils wound to form two coils per phase per permanent magnetic pole pair and extending along the longitudinal axis of the housing. The stator comprises an inner winding having np coils, in which one coil per phase in order of phase per pole pair is arranged next to a coil of a different phase, the arrangement being repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator, the inner winding having an outer surface. The stator also comprises an outer winding having np coils arranged on the outer surface of the inner winding, each coil of the outer winding also spanning a mechanical angle of 360 / (np) degrees around the cross-section of the stator, the coils of each phase of the outer winding being circumferentially aligned with the coils of the inner winding having the same phase per pole pair. Within the stator, the coils of the same phase per pole pair may be connected in series or in parallel such that the current flowing through the coils is in the same direction. In addition, the motor comprises a magnet supported to rotate upon magnetic interaction with the stator and thereby facilitate the flow of blood through the pump.

[0020] The intravascular blood pump of this disclosure uses an electric motor with a unique stator. Such a stator features a double-wound (or four-layer) coil, which leads to improved utilization of the motor design space. This facilitates the motor's use of copper wire compared to a stator with a single-wound (or two-layer) coil, and therefore significantly increases the motor's torque capacity. The stator of this invention also allows the motor to achieve higher motor constants and higher motor efficiency. It should be noted that, due to the fixed geometry of the motor, when a double-wound stator is implemented instead of a single-wound stator, the stator coils become thicker, requiring the use of smaller magnets and / or thinner yokes. Thus, increasing the number of magnet wires in a double-wound stator involves the compromise of using smaller magnets in the rotor and / or reducing the yoke thickness. This leads to a decrease in magnetic flux density. However, the effect of having more magnet wires more than compensates for the reduction in magnetic flux density due to the smaller rotor magnets and thinner magnetic yoke. In some embodiments, thicker magnet wires may be used in the double-wound stator to maintain coil resistance equivalent to that of a single-wound stator. Such a double-wound stator comprises two coils per phase per pole pair, connected in the configuration described above. This can increase the motor torque coefficient by about 20% to about 50% compared to a blood pump using a single-wound stator with one coil per phase per pole pair. In certain embodiments, the motor torque coefficient may be increased by about 25%, about 30%, about 35%, about 40%, or about 45%.

[0021] Furthermore, conventional attempts to increase the number of magnet wires in the stator of an electric motor have resulted in non-uniform multilayer stators. The irregular arrangement of wires in such stators leads to overly large random-winding stators, particularly in thickness. Such random-winding stators often require mechanical squeezing to reduce the thickness of the coils by reducing the coil diameter and / or increasing the coil inner diameter before they can be used in an electric motor. In contrast, the double-winding stators based on embodiments of this disclosure allow for the sequential arrangement of magnet wires in each coil of the stator, thereby resulting in a stator with more compact coils. Because the coils of the double-winding stator are relatively thinner compared to random-winding multilayer stators, pre-use mechanical squeezing may be required or minimal, which enhances the reliability of the motor by maintaining the integrity of the wire insulation.

[0022] The following description of a stator uses the following terms: A stator comprises at least one winding, electrically connected together, such as an inner winding and an outer winding. Each winding extends 360° around the cross-section of the stator. In addition, each winding comprises multiple coils, evenly spaced circumferentially around the entire 360° span of the stator, such as coils A, B, and C for a three-phase electric motor. For example, coils A, B, and C may each extend 120° around the cross-section of the stator. Each coil comprises multiple turns N. For example, each coil may have 65 winding turns. Each of the N turns comprises a magnet wire having a forward portion extending longitudinally from the proximal end to the distal end of the winding and a return portion extending from the distal end to the proximal end. Each winding (inner or outer winding) consisting of coils A, B, and C forms a two-layer coil upon completion. Therefore, the double-wound stator forms a total of four coil layers.

[0023] Figure 1 illustrates an exemplary intravascular blood pump 100 for insertion into a patient's heart, based on one aspect of the present disclosure. The blood pump 100 comprises a motor unit 110 and a pump unit 120, arranged along a longitudinal axis 105. The motor unit 110 comprises an electric motor including a stator 140 and a rotor 150 housed in a housing 112. The stator 140 extends along the length of the motor unit 110 from a proximal end 142 to a distal end 143 and comprises a wire 144 wound in a specific pattern, which will be described in detail later. The stator 140 defines a central lumen 145 in which the rotor 150 is positioned. The stator 140 is slotless so that the wire 144 is wound on the wire itself rather than on a stratified stator core. For the operation of the motor unit 110, power supply lines 146 and 147 provide the necessary electrical connections from outside the pump 100 to the stator 140. Each of the wires 144 may have an insulating coating (not shown), and the stator 140 may be enmolded with a synthetic epoxy resin (also not shown).

[0024] In Figure 1, the stator 140 and the housing 112 are depicted as separate components, but it should be understood that the stator 140 may be enclosed within the housing 112 to form a single component. The housing 112 comprises a proximal end 114 and a distal end 116. The proximal end 114 of the housing 112 is connected to the distal end 134 of a catheter 130, which may comprise a flexible tube. The catheter 130 comprises a lumen 132 extending toward the physician (i.e., proximal) for the control and operation of the blood pump 100.

[0025] The rotor 150 comprises a permanent magnet 152 rotatably supported around a shaft 153 within the lumen 145 of the stator 140. The magnet 152 may comprise a cylindrical permanent magnet 152 surrounding the shaft 153 within the motor unit 110. The shaft 153 extends from the motor unit 110 into the pump unit 120 and facilitates the rotation of the impeller 160 to pump blood. In certain embodiments, the rotor 150 may comprise several permanent magnets attached to the shaft 153, or an electromagnet having its own rotor winding. Furthermore, although Figure 1 shows the rotor 150 as rotatable within the stator 140, the electric motor 110 may be configured such that the stator 140 is kept stationary around the shaft 153, and the rotor 150 is configured as a cylinder that rotates around the stator 140. The shaft 153 extends along the length of the motor unit 110 and into the cylindrical housing 122 of the pump unit 120. In some embodiments, the shaft 153 may be hollow and have a lumen 154, for example, to allow the passage of a guide wire.

[0026] The distal end of the shaft 153 is connected to an impeller 160 located within the pump housing 122. The interaction between the stator 140 and rotor 150 of the motor unit 110 generates torque within the rotor 150, causing the shaft 153 to rotate, which in turn rotates the impeller 160 within the cylindrical pump housing 122. When this occurs, blood is drawn into the pump through the axial intake opening 124 to be transported axially, and then exits laterally through the opening 126, flowing axially along the housing 112. In this manner, the pump 100 generates a blood flow within the patient's heart.

[0027] The electric motor also comprises a yoke 113 housed within a housing 112. The yoke 113 carries the magnetic flux generated by the permanent poles of the rotor 150. In some cases, the housing 112 may serve as the yoke 113. Since the yoke 113 is the outermost component of the electric motor, its inner diameter limits the size of the stator 140.

[0028] Figures 2A–2D illustrate exemplary winding patterns 210–213 based on one aspect of the present disclosure. Figures 2A–2D show individual winding turn structures of different winding patterns, such as wire 142 in Figure 1, but it will be understood that a finished stator, such as stator 140 in Figure 1, is obtained by arranging multiple wire turns axially and at angles around the longitudinal axis of the motor unit, such as the longitudinal axis 105 in Figure 1. Figures 2E–2H illustrate the coil winding patterns for a finished stator for each of the coil winding types in Figures 2A–2D. In Figures 2E–2H, the horizontal axis of each plot represents the angular position along the circumference of the respective stator, and the vertical axis represents the longitudinal length of the respective stator from the distal end to the proximal end.

[0029] Figures 2A–2D illustrate exemplary winding patterns for individual turns within a coil used in an electromechanical device. The winding patterns in Figures 2A–2D may be used to form the stator 140 of the motor unit 110 in Figure 1. Figure 2A shows an individual coil winding pattern 210 in which each wire 214 in the coil extends from a proximal end 221 along the length of the coil to a distal end 225. At the distal end 225, the wire 214 traverses the outer circumference of the stator over a mechanical angle of 180 degrees and returns to the proximal end 221. Since both endpoints of the wire 214 end at the proximal end 221, the coil winding pattern 210 may face an end-turn stack-up problem, where each of the multiple leads must be electrically connected to the stator power supply circuit at the proximal end 221 of the coil winding 210, which can lead to congestion and connection problems. Figure 2E shows the completed coil winding pattern formed by the coils having the turns illustrated in Figure 2A. Figure 2B shows individual diamond coil winding patterns 211 in which each wire 215 is arranged in a bent configuration. Unlike the coil winding pattern 210 in Figure 2A, the diamond coil winding pattern comprises a single continuous wire that has been wound several times; each completed turn is shifted in the angular direction to form the completed coil winding pattern as shown in Figure 2F. If a bent configuration of the diamond coil winding pattern is adopted in the stator, post-assembly of each individual phase coil may be required.

[0030] Figure 2C shows an individual helical coil winding pattern 212 in which each wire 216 is arranged in an elliptical configuration. The helical coil winding pattern 212 is similar to the diamond coil winding pattern 211 in Figure 2B, but without bends, which simplifies the coil winding process. Helical coil winding is a one-step winding that can be easily formed without requiring a post-assembly stage. Figure 2G shows a completed coil winding pattern having the helical coil winding pattern illustrated in Figure 2C. Figure 2D shows an individual hybrid coil winding pattern 213 comprising a coil winding that is a mixture of the coil winding shown in Figure 2A and the diamond coil winding shown in Figure 2B. Such hybrid coil windings allow for an optimal ratio of torque to resistance by adjusting the horizontal-to-vertical aspect ratio of the coil. Figure 2H shows a completed coil winding comprising the hybrid coil winding pattern illustrated in Figure 2D.

[0031] In the following disclosure, the individual helical coil winding patterns in Figure 2C and the associated completed coil winding patterns in Figure 2G are used in each stator. However, it should be understood that the stators in this disclosure may use any of the winding patterns described with respect to Figures 2A-2D. Furthermore, in some embodiments of this disclosure, any other arbitrary winding patterns may be used.

[0032] Figures 3 and 4 illustrate cross-sections of exemplary stators for use in electric motors, such as the stator 140 of the motor unit 110 in Figure 1. The cross-sections of the stators shown in Figures 3 and 4 are the cross-sections along the line X-X' shown in Figure 1. Figure 3 shows a stator 300 for use in a three-phase electric motor having one pair of poles, comprising one coil per phase per pole pair. In this configuration, the stator 300 is a single-winding stator (or two-layer coil stator). In this disclosure, the three phases of the electric motor are referred to as phases A, B, and C. In the single-winding stator 300, each phase comprises one coil—coil 310 for phase A (labeled "A"), coil 311 for phase B (labeled "B"), and coil 312 for phase C (labeled "C"). Each of the coils 310-312 comprises a winding having a plurality of N turns, where N is an integer and N > 1, and each coil has the same number of turns. The winding is formed from wire wound in a specific manner, such as the manner described with respect to Figures 2A-2D, thereby resulting in each coil having a start point and an end point, as shown by the lead wires 320-325 in Figure 3. In some embodiments, the winding is formed from insulated magnet wire. The embodiments of this disclosure will be described with respect to a stator having a helical coil as illustrated in Figures 2C and 2G, but it will be understood that any winding type may be used.

[0033] As shown in Figure 3, the angular distribution of coils 310 to 312 is such that they are equally distributed around the stator 300, with each coil spanning a mechanical angle of 120 degrees around the circumference of the cross-section of the stator 300. The stator 300 is used in a three-phase electric motor having one coil per pole pair, but for a typical electric motor with n phases and p pole pairs, each coil of a single-winding stator with one coil per phase per pole pair spans a mechanical angle of 360 / (np) degrees around the circumference of the cross-section of the stator. Regarding the axial distribution of the coils around the longitudinal axis of the single-winding stator 300, the windings of coils 310 to 312 are configured to extend longitudinally from the proximal end of the stator 300 (e.g., the proximal end 142 of stator 140 in Figure 1) to the distal end (e.g., the distal end 143 of stator 140 in Figure 1) and then return to the proximal end. In this configuration, each of the coils 310 to 312 of the stator 300 effectively has a single winding. In the configuration shown in Figure 3, the lead wires for each of the coils 310 to 312 are located at the proximal end of the stator 300 to facilitate connection to the power supply lines to the electric motor, such as the power supply lines 146 and 147 shown in Figure 1.

[0034] It should be noted that, due to the single-winding stator configuration, the lead wires 320-325 for each coil 310-312 are located at one end of the respective coil span. For example, coil A is formed by winding wire in a first direction (e.g., counterclockwise) along the circumference of the stator around a 120° span of the coil, from the first end 320 to the end of the coil span where the magnet wire forms the second end 321. Furthermore, in the single-winding stator 300, coil A is formed entirely before coils B and C are formed.

[0035] Figure 4 shows a stator 400, comprising two coils per phase per pole pair, for use in a three-phase electric motor having one pair of pole pairs, according to one aspect of the present disclosure. In this configuration, the stator 400 is a double-wound stator (or four-ply coil stator), and when implemented with individual helical coil winding patterns as depicted in Figure 2C, the stator 400 is a double-helix-wound stator similar to the completed windings shown in Figure 2G. In the stator 400, each phase A, B, and C of the three-phase electric motor comprises two coils. Therefore, phase A comprises coil 410 (labeled "A1") and coil 411 (labeled "A2"), phase B comprises coil 412 (labeled "B1") and coil 413 (labeled "B2"), and phase C comprises coil 414 (labeled "C1") and coil 415 (labeled "C2"). Furthermore, as shown in Figure 4, the stator 400 has an inner winding comprising coils A1, B1, and C1, and an outer winding comprising coils A2, B2, and C2.

[0036] Referring to the single-winding stator 300 in Figure 3, the double-winding stator 400 of this disclosure has thicker coils and may have a smaller inner diameter and / or a larger outer diameter than the single-winding stator 300. In certain embodiments, thicker magnet wire is used in the double-winding stator 400 compared to the wire used in the single-winding stator 300 in order to maintain equivalent coil resistance. Thus, if each coil 310-312 of the single-winding stator 300 comprises a winding having N turns where N is an integer and N ≥ 1, then the coils for each phase A, B, and C in the double-winding stator 400 comprise a winding having approximately 1.5N turns to approximately 2N turns, with each coil A1, B1, and C1 in the inner winding having the same number of turns and each coil A2, B2, and C2 in the outer winding having the same number of turns. However, due to the increased diameter of the double-wound stator 400, it should be noted that each coil A2, B2, and C2 in the outer winding has a greater number of turns than each coil A1, B1, and C1 in the inner winding. It should also be noted that the double-wound stator 400 is constructed with thicker magnet wire to reduce coil resistance, resulting in a double-wound stator with approximately 1.5N turns to approximately 2N turns. As described above, coils 410 to 415 are formed from helical windings with a start point and an end point, as shown by lead wires 420 to 431 in Figure 4.

[0037] The angular distribution of coils 410-415 is such that it is equally distributed around the stator 400, with each coil spanning a mechanical angle of 120 degrees around the circumference of the cross-section of the stator 400. The stator 400 is used in a three-phase electric motor having two coils per phase per pole pair, but for a typical electric motor having n phases and p pole pairs, the stator 400 comprises an inner winding and an outer winding. The inner winding comprises np coils, in which one coil for each phase is arranged next to a coil for a different phase in phase order for each pole pair, and this arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator. The inner winding provides the outer surface on which the coils of the outer winding are formed. The outer winding also comprises np coils arranged on the outer surface of the inner winding, and each coil of the outer winding is circumferentially aligned with the coils of the inner winding, which have the same phase for each pole pair, so that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross-section of the stator.

[0038] The winding patterns of the individual coils A1, B1, and C1 in the double-winding stator 400 are the same as those of the individual coils A, B, and C in the single-winding stator 300. However, in the double-winding stator 400, after the inner windings are formed, the windings of the coils 411, 413, and 415 that form the outer windings are wound on the outer surface of the coils 410, 412, and 414 that form the inner windings, extending longitudinally from the proximal end to the distal end of the stator 400 and returning to the proximal end. In this configuration, the inner and outer windings each effectively comprise two wire layers, and are therefore referred to as a four-layer coil stator. The lead wires for each coil 410-415 are located at the proximal end of the stator 400 for easy connection to the power supply lines to the electric motor, such as the power supply lines 146 and 147 shown in Figure 1.

[0039] It should be noted that, due to the configuration in which the double-winding stator 400 is formed, the lead wires 420-421, 424-425, and 428-429 for the inner windings (coils 410, 412, and 414 respectively) and the leads 422-423, 426-427, and 430-431 for the outer windings (coils 411, 413, and 415 respectively) are located at one end of the respective coil spans. For example, coil A1 is formed by winding the coil in a first direction (e.g., counterclockwise) along the circumference of the stator around a 120° span of the coil, from the first end 420 to the end of the coil span where the magnet wire forms the second end 421. After coil A1 is formed, the remaining coils of the inner windings (i.e., coils B1 and C1) are formed. Only after the inner windings are completely formed does the formation of the coils that make up the outer windings begin. Therefore, after coils A1, B1, and C1 are formed, coils A2, B2, and C2 are formed. Coil A2 is formed by winding the coil in a first direction (e.g., counterclockwise) along the circumference of the stator around a 120° span of the coil, from the first end 422 to the end of the coil span where the magnet wire forms the second end 423. After coil A2 is formed, the coils that make up the rest of the outer winding are formed. The winding sequence of this disclosure results in a winding with wires in a precise order to achieve the most compact 4-layer coil stator possible. This preserves the integrity of the wires forming each coil, as will be detailed in the following sections with respect to Figures 9A-9B.

[0040] It should be noted that the double-wound stator 400 is at least twice as thick as the single-wound stator 300. This means that the double-wound stator 400 may have a smaller inner diameter and / or a larger outer diameter than the single-wound stator 300. When the double-wound stator 400 is used in an electric motor, the fixed dimensions within the electric motor necessitate smaller magnets and / or thinner yokes. Both smaller magnets and / or thinner yokes reduce magnetic flux density, thus impairing the motor torque coefficient and motor efficiency. However, the benefits of the increased number of coil winding turns in the double-wound stator 400 compared to the single-wound stator 300 outweigh the benefits of smaller magnets and / or thinner yokes, resulting in a considerable increase in the motor torque coefficient and motor efficiency.

[0041] Figure 5 shows an exemplary cross-section 500 of the electric motor 110 of the blood pump 100 of Figure 1, which uses a double-wound stator 400 in a three-phase two-pole electric motor. For clarity, the windings forming coils 410-415 are omitted from Figure 5. The interaction between the current flowing through the coils of the stator 400 and the magnetic flux density of the two-pole rotor during operation will be explained with reference to Figure 5. As explained with respect to Figure 1, the rotor 150 is in a constant rotational state during use. Figure 5 depicts the position of the rotor 150 at the moment the rotor is in the position shown in the figure. In the illustrated position, the permanent magnet rotor 150 generates a magnetic flux density B, and each of the coils 410-415 carries a current which may be oriented vertically (into or out of the page). According to the Lorentz law, the interaction between the magnetic flux density B and the longitudinal length L of the conductive wire perpendicular to the magnetic flux density B generates a torque T within the rotor 150, causing it to rotate, which is determined by the following equation: TIFF0007855297000001.tif4128In formula, TIFF0007855297000002.tif3128 is in a direction parallel to the longitudinal axis 105 of rotor 150, TIFF0007855297000003.tif3128 is the radial direction of magnetic flux density B perpendicular to the longitudinal axis 105 of the rotor 150, and × represents the cross product of vectors. Thus, the flow of current in the stator 400 causes the rotor 150 to rotate around the longitudinal axis 105, which in turn causes the corresponding rotation of the impeller 160 connected to the distal end of the rotor shaft 153. Although accompanied by a slight reduction in magnetic flux density B, the stator 400 described herein attempts to significantly increase L in order to increase torque generation in the motor.

[0042] The dual-winding stator 400 of this disclosure increases the number of winding turns of the electric motor compared to a single-winding stator by doubling the number of coils per phase. However, as will be explained with reference to Figures 9A-9B, the dual-winding stator of this disclosure is not solely concerned with doubling the number of coils per phase. Rather, the dual-winding stator 400 of this disclosure is formed using a unique winding sequence in which the wires forming the inner winding coils are first formed sequentially, and then the wires forming the outer winding coils are formed sequentially on the outer surface of the inner windings. Such a winding sequence increases the coil mounting density between the outer diameter of the rotor 150 and the inner diameter of the yoke 113. Therefore, the dual-winding stator 400 of this disclosure significantly increases the L component of equation (1) as the number of conductive wires of the stator 400 increases, and does not require a reduction in the size of the magnets or the thickness of the magnetic yoke.

[0043] As briefly discussed with respect to Figure 1, the outer diameter of the pump 100 is limited by the inner diameter of the catheter used to position the pump within the patient's heart. Currently, the maximum inner diameter of the catheter used for Impella® pumps is approximately 14 Fr. Thus, as shown in Figure 5, the dimensions x + y + z of the electric motor, where x is the radius of the rotor 150, y is the thickness of the stator coil, and z is the thickness of the yoke 113, are limited by the inner diameter of the catheter. To increase the magnetic flux density B in the motor, (i) a larger permanent magnet may be used (i.e., x is larger), (ii) the coil may be made thinner (i.e., y is smaller), and (iii) a thicker yoke may be used (i.e., z is larger).

[0044] Regarding the design of the double-wound stator 400, compared to the single-wound stator 300, the motor's magnetic flux density B is reduced because the coils of the double-wound stator are thicker (y is greater), and as a result, the permanent magnets are smaller (x is smaller) and the yoke is thinner (z is smaller), which are required by the spatial constraints within the catheter. This reduces the B component in equation (1). However, the increase in L due to the greater number of turns in the coil windings is greater than the reduction in B for the reasons mentioned above. As a net effect, the torque generated in the rotor 150 is increased.

[0045] The coils 310-312 in the single-winding stator 300 and the coils 410-415 in the double-winding stator 400 of this disclosure may be electrically connected to any configuration for an electric motor, such as a star connection or a delta connection. Figure 6A shows the coils 310-312 of the single-winding stator 300 in Figure 3 connected to an exemplary star configuration 600. The coils 310-312 are represented by their resistances RA, RB, and RC, respectively. In Figure 6A (and subsequently in Figures 6B and 6C), "s" represents the beginning lead of the coil and "e" represents the end lead of the coil. In the star configuration 600, the endpoint "Ae" of coil 310, the endpoint "Be" of coil 311, and the endpoint "Ce" of coil 330 are connected together. The starting points "As" of coil 310, "Bs" of coil 311, and "Cs" of coil 312 are connected to the power supply lines 146, 147, etc., of the blood pump 100 in Figure 1. In this configuration, each branch of the star configuration 600 is equipped with a single load corresponding to the coil for each phase in the single-winding stator 300.

[0046] Figure 6B shows an exemplary electrical connection of coils in a double-wound stator 400 according to one aspect of the present disclosure. Figure 6B shows the coils of the stator 400 connected in a star configuration, with coils for each phase A, B, and C connected in series. Here, coils 410-411 are represented as resistors RA1 and RA2 for phase A, respectively; coils 412-413 are represented as resistors RB1 and RB2 for phase B, respectively; and coils 414-415 are represented as resistors RC1 and RC2 for phase C, respectively. As mentioned above, the stator 400 comprises coils arranged in an inner winding and an outer winding. The inner winding coils 410, 412, and 414 each have N turns, while the outer winding coils 411, 413, and 415 each have at least N turns; where N is the number of turns in each coil of the stator 300, and the total number of winding turns per phase in the double-winding stator 400 may be 1.5 to 2.0 times that of the single-winding stator 300. Therefore, the electrical resistance per phase of the double-winding stator 400 is higher than that of the single-winding stator 300. It should be noted that in some embodiments, thicker magnet wire is used in the double-winding stator 400 to achieve equivalent resistance compared to the single-winding stator 300.

[0047] As is well known, motor efficiency is defined by the motor constant K as follows: m This can be shown by: TIFF0007855297000004.tif7128, k T k is the torque coefficient, and R is the coil resistance. Furthermore, as is well known, the torque coefficient k T is the torque T per unit current I, and therefore the torque coefficient can be defined using the following relationship: In formula TIFF0007855297000005.tif4128, B is the magnetic flux density and L is the length of the conductive wire in the direction perpendicular to the magnetic flux density.

[0048] As discussed with respect to Figure 5, the double-wound stator 400 of this disclosure increases the contribution of L by approximately 1.5 to 2 times compared to the single-wound stator 300, while slightly reducing the contribution of B to the torque T generated in the rotor 150 due to a larger y (thicker coil), smaller x (smaller magnet), and / or smaller z (thinner yoke). According to equations (1) and (3), this is the motor torque coefficient k T This increases the motor constant K by approximately 20% to 50%. In other embodiments, the motor torque coefficient may be increased by approximately 25%, 30%, 35%, 40%, or 45%. Furthermore, since the number of turns per phase in the double-wound stator 400 is increased compared to the single-wound stator 300, thicker wires are used to achieve the same coil resistance as the single-wound stator 300. Thus, from equation (2), the motor constant K of the double-wound stator 400 of this disclosure is increased compared to the single-wound stator 300. m This is expected to increase [the value]. This will lead to an increase in motor efficiency.

[0049] As shown in the circuit diagram of Figure 6B, each branch of the star configuration 650 comprises two coils connected in series such that the current flowing through the coils of the same phase is in the same direction; that is, the two coils are connected in such a manner that the endpoint of one coil is connected to the starting point of the other coil. For example, for phase A, coils 410-411, represented by resistors RA1 and RA2 respectively, are connected such that their endpoint "A1e" is connected to their starting point "A2s". Similarly, for phase B, the endpoint "B1e" of coil 413 and the starting point "B2s" of coil 414, represented by resistors RB1 and RB2 respectively, are connected together, and for phase C, the endpoint "C1e" of coil 414 and the starting point "C2s" of coil 415, represented by resistors RC1 and RC2 respectively, are connected together. The starting point "A1s" of resistor RA1 of coil 410 for phase A, the starting point "B1s" of resistor RB1 of coil 412 for phase B, and the starting point "C1s" of resistor RC1 of coil 414 for phase C are connected to the power supply lines 146, 147, etc. of the blood pump 100 in Figure 1. In addition, the ending point "A2e" of resistor RA2 of coil 411 for phase A, the ending point "B2e" of resistor RB2 of coil 413 for phase B, and the ending point "C2e" of resistor RC2 of coil 415 for phase C are connected together.

[0050] The configuration in which the coils 410-415 of the double-wound stator 400 of this disclosure are connected is important because it determines how the coils 410-415 interact with the magnetic flux density generated by the rotor 150 during the operation of the electric motor. In a star configuration 650 as depicted in Figure 6B, the direction of the current flowing through coil A1 of the stator 400 is the same as the direction of the current flowing through coil A2. Similarly, the direction of the current flowing through coil B1 of the stator 400 is the same as the direction of the current flowing through coil B2, and the direction of the current flowing through coil C1 of the stator 400 is the same as the direction of the current flowing through coil C2. This means that coils A1 and A2, which have the same direction of current flowing through them, both interact with the same pole of the rotor. In addition, coils B1 and B2, which have the same direction of current flowing through them, both interact with the same pole of the rotor. Furthermore, coils C1 and C2, which have the same direction of current flowing through them, both interact with the same pole of the rotor. In other words, in the dual-winding stator 400 of this disclosure, each phase coil encounters the same polarity of the magnet for each pole pair of the rotor.

[0051] Figure 6C shows a further exemplary electrical connection of coils in a double-wound stator 400, based on one aspect of the present disclosure. In Figure 6C, the coils of the stator 400 are connected in a star configuration 660, with coils for each phase A, B, and C connected in parallel, such that the current flowing through the coils is in the same direction. This can be seen in Figure 6C; for phase A, coils 410-411, represented by resistors RA1 and RA2 respectively, are connected such that their endpoints "A1e" and "A2e" are connected to the central reference terminal, while their starting points "A1s" and "A2s" are connected to the feed line. Similarly, for phase B, coils 412-413, represented by resistors RB1 and RB2 respectively, are connected such that their endpoints "B1e" and "B2e" are connected to the central reference terminal, while their starting points "B1s" and "B2s" are connected to the power supply line. For phase C, coils 414-415, represented by resistors RC1 and RC2 respectively, are connected such that their endpoints "C1e" and "C2e" are connected to the central reference terminal, while their starting points "C1s" and "C2s" are connected to the power supply line.

[0052] Similar to the configuration 650 in Figure 6B, in the star configuration 660 as depicted in Figure 6C, the direction of the current flowing through coil A1 of the stator 400 is the same as the direction of the current flowing through coil A2. Similarly, the direction of the current flowing through coil B1 of the stator 400 is the same as the direction of the current flowing through coil B2, and the direction of the current flowing through coil C1 of the stator 400 is the same as the direction of the current flowing through coil C2. This means that coils A1 and A2, through which the current flows in the same direction, both interact with the same pole of the rotor. In addition, coils B1 and B2, through which the current flows in the same direction, both interact with the same pole of the rotor. Furthermore, coils C1 and C2, through which the current flows in the same direction, both interact with the same pole of the rotor. In other words, in the double-wound stator 400 of this disclosure, the coils of each phase encounter the same polarity of the magnet for each pole pair of the rotor.

[0053] Figure 7 illustrates another example of a cross-section of a double-wound stator 700 for use in an electric motor having three phases A, B, and C and two pairs of permanent pole pairs N1-S1 and N2-S2, according to one aspect of the present disclosure. According to the general definition above, an electric motor using stator 700 has n = 3 and p = 2. As discussed with respect to stator 400 in Figure 4, stator 700 also comprises two coils per phase per pole pair, resulting in a total of 12 coils, 710-721. In stator 700, the presence of two pairs of pole pairs within the electric motor means that each phase A, B, and C of the three-phase electric motor comprises two coils. Therefore, phase A comprises coils 710-73 (labeled "A1", "A2", "A3", and "A4", respectively), phase B comprises coils 714-717 (labeled "B1", "B2", "B3", and "B4", respectively), and phase C comprises coils 718-721 (labeled "C1", "C2", "C3", and "C4", respectively). As shown in Figure 7, the stator 700 comprises an inner winding of the coil and an outer winding of the coil. The inner winding comprises six coils; these six coils are arranged in phase order for each pole pair, with one coil for each phase next to a coil for a different phase, and this arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans 360° / (np) = 360° / (3)(2) = 60° around the cross-section of the stator 700; the inner winding has an outer surface. The outer winding also comprises six coils arranged on the outer surface of the inner winding; each coil of the outer winding is circumferentially aligned with the coil of the inner winding having the same phase for each pole pair such that each coil of the outer winding spans 60° around the cross-section of the stator 700. Furthermore, the coils of the same phase for each pole pair may be connected in series or parallel so that the current flowing through the coils is in the same direction.

[0054] Similar to the coils of stator 400, coils 710-721 may be electrically connected in either a star or delta configuration as follows: (i) coils 710-713 for phase A are connected in series or parallel along the branch for phase A of the star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil; (ii) coils 714-717 for phase B are connected in series or parallel along the branch for phase B of the star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil; and (iii) coils 718-721 for phase C are connected in series or parallel along the branch for phase C of the star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil. In such electrical connections, (i) the direction of the current flowing through coils A1 and A3 is the same as the direction of the current flowing through coils A2 and A4; (ii) the direction of the current flowing through coils B1 and B3 is the same as the direction of the current flowing through coils B2 and B4; and (iii) the direction of the current flowing through coils C1 and C3 is the same as the direction of the current flowing through coils C2 and C4. In short, whether in-phase coils are connected in series or parallel, the current flowing through in-phase coils flows in the same direction.

[0055] In this configuration, coils A1 to A4 have the same direction of current flowing through them; here, coils A1 and A3 interact with, for example, magnetic pole S1, and coils A2 and A4 interact with magnetic pole S2, which has the same polarity as magnetic pole S1, to rotate the rotor. Similarly, coils B1 to B4 have the same direction of current flowing through them; here, coils B1 and B3 interact with, for example, magnetic pole N1, and coils A2 and A4 interact with magnetic pole N2, which has the same polarity as magnetic pole N1, to rotate the rotor. Furthermore, coils C1 to C4 have the same direction of current flowing through them; here, coils C1 and C3 interact with, for example, magnetic pole S2, and coils C2 and C4 interact with magnetic pole S1, which has the same polarity as magnetic pole S2, to rotate the rotor. It should be noted that coils 710-721 may be driven by, for example, a 6-stage DC current controller that alternately supplies current to coils 710-721 in pairs of two phases at a time. Thus, the coils with each phase successively generate torque within the rotor, thereby causing continuous rotation of the rotor.

[0056] Figure 8 illustrates a further example of a cross-section of a double-wound stator 800 for use in an electric motor having five phases A, B, C, D, and E and a pair of permanent pole pairs NS, based on one aspect of the present disclosure. According to the general definition above, an electric motor using stator 800 has n = 5 and p = 1. As discussed with respect to stators 400 and 700, stator 800 also comprises two coils per phase per pole pair, resulting in a total of 10 coils, 810-819. Phase A comprises coils 810-811 (labeled "A1" and "A2" respectively), Phase B comprises coils 812-813 (labeled "B1" and "B2" respectively), Phase C comprises coils 814-815 (labeled "C1" and "C2" respectively), Phase D comprises coils 816-817 (labeled "D1" and "D2" respectively), and Phase E comprises coils 818-819 (labeled "E1" and "E2" respectively). As shown in Figure 8, the stator 800 comprises an inner winding of the coil and an outer winding of the coil. The inner winding comprises five coils; these five coils are arranged in phase order for each pole pair, with one coil for each phase next to a coil for a different phase, and this arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans 360° / (np) = 360° / (5)(1) = 72° around the cross-section of the stator 800; the inner winding has an outer surface. The outer winding also comprises five coils arranged on the outer surface of the inner winding; each coil of the outer winding is circumferentially aligned with the coil of the inner winding having the same phase for each pole pair such that each coil of the outer winding spans 72° around the cross-section of the stator 800. Furthermore, the coils of the same phase for each pole pair are connected in series or parallel so that the current flowing through the coils is in the same direction.

[0057] Similar to the coils of stators 400 and 700, coils 810-819 may be electrically connected in either a star or delta configuration as follows: (i) coils 810-811 for phase A are connected in series or parallel along the branch for phase A of the star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil; (ii) coils 812-813 for phase B are connected in series or parallel along the branch for phase B of the star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil; (iii) coil 8 for phase C (iv) Coils 14-815 are connected in series or in parallel along a branch for phase C of a star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil; (iv) Coils 816-817 for phase D are connected in series or in parallel along a branch for phase D of a star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil; and (v) Coils 818-819 for phase E are connected in series or in parallel along a branch for phase E of a star or delta connection, with the start terminal of one coil connected to the end terminal of the adjacent coil. In such an electrical connection, (i) the direction of the current flowing through coil A1 is the same as the direction of the current flowing through coil A2; (ii) the direction of the current flowing through coil B1 is the same as the direction of the current flowing through coil B2; (iii) the direction of the current flowing through coil C1 is the same as the direction of the current flowing through coil C2; (iv) the direction of the current flowing through coil D1 is the same as the direction of the current flowing through coil D2; and (v) the direction of the current flowing through coil E1 is the same as the direction of the current flowing through coil E2.

[0058] In this configuration, coils A1 to A2 have the same direction of current flowing through them; here, coils A1 to A2 interact with, for example, magnetic pole N at a given moment. Similarly, the coils for each of the other phases B to E also interact with the same polarity of the magnetic flux from the rotor at a given moment; the coils for each phase have the same direction of current flowing through them at that moment. Coils 810 to 819 are driven by a motor controller that supplies current to multiple phase coils at once. Therefore, the coils for each phase successively generate torque within the rotor, thereby causing continuous rotation of the rotor.

[0059] Table 1 shows representative data for two blood pumps equipped with electric motors featuring a single-helix winding stator and a double-helix winding stator, respectively. Specifically, the single-helix winding stator is similar to the single-helix winding stator 300 described above, implemented with a helical winding type as shown in Figure 2C. The double-helix winding stator is similar to the double-helix winding stator 400 described above, also implemented with a helical winding type as shown in Figure 2C. As can be seen in the table, the double-helix winding stator has a coil resistance increased to 5.40 Ω / phase and a torque coefficient of 1.236 × 10⁻⁶ compared to the single-helix winding stator. -3 This results in an electric motor with an increase in N·m / A, i.e., a 40.5% increase from a single-helix winding stator. The results in Table 1 confirm that the double-winding stator based on the embodiments of this disclosure reduces the Joule heating of the coil by 40%, while a motor using such a double-winding stator generates the same torque for driving a pump as a motor using a single-winding stator. It should be noted that a blood pump using the above-described stator, which has two coils per phase per pole pair, is configured to operate at flow rates of approximately 1.0 lpm and approximately 6.0 lpm; where "lpm" indicates liters per minute.

[0060] TIFF0007855297000006.tif47131 (Table 1) Performance of blood pumps with various stator coil configurations

[0061] As described above, increasing the number of magnet wires from a single-winding stator to a double-winding stator reduces the Joule heating of the coil for the same output torque, and therefore improves the overall efficiency of the motor. However, a conventional embodiment of increasing the number of winding turns will be described with reference to Figure 9A. Figure 9A shows an exemplary stator 900 having multiple magnet wire layers, in which the amount of conductors in the stator 900 is increased from that of a two-layer stator. The stator 900 is suitable for use in a three-phase electric motor having phases A, B, and C. Similar to the stator described above, phase A comprises coil "A", phase B comprises coil "B", and phase C comprises coil "C". As can be seen in the figure, the amount of conductors in each coil of the stator is increased by simply increasing the number of turns of the magnet wire in each coil in a random manner, where the wire is wound without any precision or regularity. For example, as shown in Figure 9A, coils A, B, and C are each formed by a random arrangement of turns of magnet wire, starting with turn 1 and ending with turn 65, according to the numbers shown in the figure. Since the goal is to pack a specific number of magnet wires into each coil, the turns are placed randomly and without order within each coil. For example, turns 1-4 are spaced apart from each other when arranged to form each coil. This results in the magnet wires being randomly clustered within each coil, but this random arrangement is an inefficient use of space because it leads to the formation of large gaps, such as 910, when the coils are formed; these gaps can be occupied by turns wound later in the winding sequence. This inefficient use of space within each coil results in a thick and oversized stator 900.

[0062] Figure 10A shows an exemplary random-winding multilayer stator 900 formed using the winding sequence described in Figure 9A. The random arrangement of wires forming the stator 900 can be seen in Figure 10A, and the magnet wires are irregular and excessively overlapping. As can be seen in the appearance of the outer surface of the stator shown in Figure 10A, this contributes to the irregular winding pattern on the outer surface of the stator.

[0063] An oversized random-winding multilayer stator 900 presents several problems. Firstly, it may be necessary to mechanically squeeze the stator to fit the size constraints of the motor stator. Mechanical squeezing may reduce the thickness of the stator 900 to fit within the motor yoke, which has a fixed inner diameter. Such mechanical squeezing is an additional post-processing step required after the multilayer stator 900 has been formed. Secondly, mechanical squeezing poses a risk to the integrity of the electrical insulation of the magnet wires within each coil of the stator 900. This is because the force applied to mechanically squeeze the multilayer stator may damage the insulation around each magnet wire. Such damage to the magnet wire insulation could result in short circuits within and / or between coils during operation. It will be recognized that if the random-winding multilayer stator 900 is not squeezed, the size of the magnets and / or the thickness of the yoke must be reduced, which will reduce the magnetic flux density B through the electric motor.

[0064] Figure 9B illustrates an exemplary stator 950 having four magnet wire layers formed as uniformly wound coils, based on one aspect of the present disclosure. The four-layer coil stator 950 is analogous to the double-winding stator 400 in Figures 4 and 5. As described above, the stator of the present disclosure comprises an inner winding 960 and an outer winding 965. As shown in Figures 4 and 5, each of the inner and outer windings comprises a coil. Furthermore, each of the inner and outer windings comprises two magnet wire layers formed as coils. Here, each coil A1, A2, B1, B2, C1, and C2 shown in Figure 9B is formed by winding magnet wire in an ordered sequence along a 120° span around the cross section of each coil stator between the proximal ends of the stator, using one of the coil winding patterns shown in Figures 2E to 2H, so as to extend longitudinally toward the distal end and return to the proximal end.

[0065] When the magnet wire is wound from the proximal end to the distal end of the stator to form the first turn (for example, the turn labeled "1") in each of the inner winding coils, the forward portion of the magnet wire for turn 1 is formed in the first layer, and when the magnet wire is wound back from the distal end to the proximal end, the return portion of the magnet wire for turn 1 (labeled "X") is formed in the second layer, which is radially outward and adjacent to the first layer. Here, adjacent means "immediately radially next to" (i.e., with nothing in between). Thus, the first turn is formed by a continuous copper wire wound from the proximal end to the distal end of the stator (the forward wire portion located in the first layer) and from the distal end to the proximal end of the stator (the return wire portion labeled "X", located in the second layer). This is shown in the cross-section of Figure 9B, where the forward wire portion of turn 1 has a corresponding return wire portion X that is immediately adjacent to the forward wire portion and positioned radially outward. As a result, coils with a first layer and a second layer are formed in each of the inner windings 960 and outer windings 965 of the stator 950, as shown in the cross-section of Figure 9B. This arrangement of magnet wires is seen in the cross-section of the stator 950 in Figure 9B; the turns of the inner winding 960 are precisely arranged in order from turn 1 to turn 31 in a counterclockwise direction along the span of each coil, from 0° to 120°, for each of the coils A1, B1, and C1. Since the forward wire portion of each turn is aligned in the first layer, the corresponding return wire portion is automatically aligned in the second layer, which is immediately adjacent to the forward wire portion and positioned radially outward. Thus, for each turn, the forward wire portion (in the first layer) and the corresponding return wire portion (in the second layer) are formed before the turns of the remaining portion of the subsequent coil are formed. Each turn within each coil is formed immediately adjacent to the turn that was formed before it; that is, each turn is formed right next to the previous turn with nothing in between.

[0066] As a result of the precise arrangement of turns in the stator 950, the inner winding 960 forms a uniform outer surface, on which the wires of the outer winding 965 are laid. Thus, after all the coils A1, B1, and C1 of the inner winding are formed, the coils A2, B2, and C2 of the outer winding are formed on the uniform outer surface of the inner winding in the same manner as the inner winding is formed. For each coil of the outer winding, the first turn (for example, the turn labeled "32") is formed from the proximal end to the distal end of the stator, at which point the forward portion of the magnet wire of the first turn 32 is formed in the third layer, and when the magnet wire is wound back from the distal end to the proximal end, the return portion of the magnet wire of the first turn 32 (labeled "Y") is formed in the fourth layer adjacent to the third layer radially outward. Therefore, the first turn 32 of the outer winding is formed by a continuous magnet wire wound from the proximal end of the stator to the distal end of the stator (the forward wire portion located in the third layer) and from the distal end of the stator to the proximal end of the stator (the return wire portion labeled "Y" located in the fourth layer).

[0067] This arrangement of magnet wires is seen in the cross-section of the stator 950 in Figure 9B; the turns of the outer winding 965 are precisely arranged in a counterclockwise direction along a 120° span of each coil, from turn 32 to turn 65, for each of the coils A2, B2, and C2. In this configuration, turn 32 of the outer winding is radially aligned with turn 1 of the inner winding, and turn 65 of the wire winding is radially aligned with turn 31 of the inner winding. It should be noted that the stator of this disclosure has more turns in the outer winding than in the inner winding due to the larger diameter of the outer winding compared to the inner winding. For example, in the double-winding stator 950 of Figure 9B, the outer winding has 34 turns and the inner winding has 31 turns. As a result, the stator 950 has magnet wires that are ordered to be more tightly packed compared to the irregular arrangement of magnet wires in the randomly wound multi-layer winding stator 900. The double-wound stator 950 is more compact and therefore thinner compared to the random-wound multi-layer stator 900.

[0068] An exemplary winding sequence for forming the stator 950 may have the following order: (1) forming turns 1 to 31 for coil A1; (2) forming turns 1 to 31 for coil B1; (3) forming turns 1 to 31 for coil C1; (4) forming turns 32 to 65 for coil A2 on the outer surface of coil A1; (5) forming turns 32 to 65 for coil B2 on the outer surface of coil B1; and (6) forming turns 32 to 65 for coil C2 on the outer surface of coil C1. As previously stated, each turn comprises a forward wire portion and a return wire portion automatically positioned radially adjacent to the forward wire portion.

[0069] A servo motor is used to ensure that the turns are precisely and sequentially placed along the span of each stator. It should be noted that each coil in the inner and outer windings of stator 950 has a pair of lead wires (such as lead wires 420-421 for coil A1 in Figure 4) for connection to the power supply lines 146-147 of electric motor 100.

[0070] In some embodiments, thicker wires may be used for the coils forming the inner and outer windings to minimize the increase in coil resistance of a double-winding stator compared to a single-winding stator, thereby achieving resistance equivalent to that of a single-winding stator.

[0071] Figure 10B illustrates an exemplary stator formed using the winding sequence described with respect to Figure 9B, based on embodiments of the present disclosure. As seen in the figure, the stator in Figure 10B comprises precisely arranged wires, which result in a uniform outer diameter along the length of the stator. When assembling an electric motor with the four-ply coil stator of Figure 9B, the required mechanical squeeze of the stator is considered to be minimal. Because the required mechanical squeeze is minimal, the risk of damaging the insulation of the wires forming coils A1, A2, B1, B2, C1, and C2 is minimized, thereby increasing the reliability of the double-wound stator 950.

[0072] It should be noted that, with respect to the random-winding multilayer stator 900 in Figure 9A, mechanical squeeze can only reduce the stator thickness to a limited extent. Therefore, even after mechanical squeeze, the random-winding multilayer stator 900 may be too thick for the yoke used in the electric motor compared to the double-winding stator 950. To mitigate this problem, in some embodiments, a thinner yoke is used in the random-winding multilayer stator 900 compared to the double-winding stator 950, in order to maintain the motor's outer diameter so that it can be integrated with other components that work with the motor, such as a 14 Fr catheter through which Impella® moves. In addition, it may be necessary to use smaller magnets in the random-winding multilayer stator 900 compared to the double-winding stator 950.

[0073] Compared to an electric motor with a double-wound stator 950, an electric motor with a random-wound multilayer stator 900 has a thinner yoke and / or smaller magnets, which reduces the magnetic flux density B. As shown in Figures 9A and 9B, both the random-wound multilayer stator 900 and the double-wound stator 950 have the same number of winding turns. This means that, according to equation (1), both stators 900 and 950 have the same contribution L to the motor torque T. Compared to an electric motor with a double-wound stator 950, an electric motor with a random-wound multilayer stator 900 has a lower magnetic flux density B for the same conductive wire length L, resulting in lower motor torque and lower motor efficiency.

[0074] Figure 11 illustrates an exemplary method 1100 for forming a double-wound stator, such as the stator 400 described above, according to one aspect of the present disclosure. Method 1100 is suitable for use in a slotless permanent magnet motor having p pairs of poles and n phases, where p is an integer greater than zero and n is an integer greater than 3. Method 1100 begins with a step 1110 in which an inner winding (e.g., inner winding 960 in Figure 9B) is formed, comprising np coils. In the inner winding, one coil for each phase is arranged next to a coil for a different phase in phase order for each pole pair, and this arrangement is repeated around the circumference of the stator for all pole pairs such that each coil of the inner winding spans a mechanical angle of 360 / (np) degrees around the cross-section of the double-wound stator. In some embodiments, each winding comprises two wire layers, each extending longitudinally along the length of the stator; the wires in each winding are arranged in sequence immediately adjacent to each other along the span of each winding. The inner winding, upon completion, has an outer surface.

[0075] After the completion of the inner winding, the method proceeds to step 1120 in which the outer winding is wound, such as the outer winding 965 in Figure 9B. Similar to the inner winding, the outer winding also comprises np coils arranged on the outer surface of the inner winding, and each coil of the outer winding is also aligned circumferentially with the coils of the inner winding, which have the same phase for each pole pair, so that each coil of the outer winding also spans a mechanical angle of 360 / (np) degrees around the cross-section of the double-wound stator. Similar to the inner winding, in some embodiments, each winding comprises two layers of wire, each extending longitudinally along the length of the stator; the wires in each winding are arranged sequentially right next to each other along the span of each coil. In the arrangement described above, the inner and outer windings of the double-wound stator 950 share the same angular boundary.

[0076] Once the inner and outer windings are complete, in step 1130, the in-phase coils for each pole pair are electrically connected so that the current flowing through the in-phase coils is in the same direction.

[0077] In summary, the double-wound stator of this disclosure (e.g., stator 400) improves motor efficiency compared to a single-wound stator (e.g., stator 300) due to the trade-off between the rotor magnet size, yoke thickness, and winding turn count in each stator. This increase in motor efficiency is achieved by increasing the motor torque coefficient by approximately 20% to approximately 50% while maintaining equivalent stator resistance. In certain embodiments of this disclosure, the motor torque coefficient may be increased by approximately 25%, approximately 30%, approximately 35%, approximately 40%, or approximately 45%. In addition, the double-wound stator of this disclosure (e.g., stator 950) improves motor reliability compared to a random-wound multi-layer stator (e.g., stator 900) because the compact arrangement of wires within the double-wound stator minimizes the required mechanical squeeze post-processing. Because the required mechanical squeeze is minimal, unlike random-winding multi-layer stators which require excessive mechanical squeeze, the resulting wire insulation damage is absent in double-winding stators.

[0078] From the above description and references to various drawings, those skilled in the art will recognize that certain modifications can also be made to this disclosure without departing from the scope of the disclosure. It should be understood that while the devices described herein are shown in relation to a double-wound stator for an electric motor for a blood pump, they may be applied to other systems where an electric motor with increased torque and high motor efficiency is desirable. While the drawings illustrate several aspects of this disclosure, it is not intended to be limited thereto; this disclosure is as broad as the art allows, and this specification is intended to be read as such. Therefore, the above description should be considered only as an example of a particular aspect, and not as an exemption. Those skilled in the art will also be able to imagine other modifications that fall within the scope and spirit of the appended claims.

[0079] In the above disclosure, the term “about” should be understood to mean ±20% of the described value. In addition, the term “electric motor” should be understood to be synonymous with the term “electric machine,” as is well known in the art. Furthermore, the term “adjacent” should be understood to mean being immediately next to something with nothing in between. For example, object / feature P is adjacent to object / feature Q when there is no intervening object / feature Q. All angular measures (with units of °) should be understood as mechanical angles unless otherwise stated. In the above embodiments, the wire used for winding the stator may be made of any material, such as copper. In some embodiments, the wire may be insulated.

[0080] Those skilled in the art will be able to conceive of variations and modifications after reviewing this disclosure. The features of this disclosure may be implemented in any combination and subcombinations (including multiple dependent combinations and subcombinations) with one or more other features described herein. The various features described or illustrated above, including their components, may be combined or integrated into other systems. Furthermore, certain features may be omitted or not implemented at all.

[0081] Examples of modifications, substitutions, and alterations are verifiable by those skilled in the art and can be made without departing from the scope of the information disclosed herein. All references herein are incorporated by reference in their entirety and constitute part of this application.

Claims

1. An intravascular blood pump for insertion into a patient's heart, A slender housing having a proximal end and a distal end, and a vertical axis, The housing comprises a slotless permanent magnet motor housed within the aforementioned housing, The motor has p pairs of magnetic poles and n phases, where p is an integer of 1 or more and n is an integer of 3 or more, and the motor comprises a stator that extends along the longitudinal axis of the housing and has 2np coils wound to form two coils per phase per pair of magnetic poles, The stator comprises an inner winding having np coils, where one coil for each phase is arranged next to a coil for a different phase in phase order for each pole pair, and the inner winding having an outer surface; and an outer winding having np coils, where the coils for each phase in the outer winding are circumferentially aligned with the coils of the inner winding having the same phase for each pole pair. An intravascular blood pump in which the in-phase coils of each pole pair are electrically connected such that the current flowing through the coils is in the same direction.

2. The intravascular blood pump according to claim 1, wherein each coil of the inner winding and each coil of the outer winding comprises two magnet wire layers, each extending longitudinally along the length of the stator.

3. The intravascular blood pump according to claim 2, wherein the magnet wires in each coil are arranged sequentially next to each other along the span of the coil.

4. The intravascular blood pump according to claim 1, wherein the inner winding of the coil establishes a uniform surface on which the outer winding of the coil is superimposed.

5. The intravascular blood pump according to claim 1, wherein one phase coil is electrically connected to the other phase coil in either a star configuration or a delta configuration.

6. The intravascular blood pump according to claim 5, wherein the in-phase coils are connected in either series or parallel.

7. The intravascular blood pump according to claim 1, wherein each of the 2np coils has a coil winding pattern selected from the group consisting of a helical winding pattern, a diamond winding pattern, and a hybrid winding pattern.

8. The intravascular blood pump according to claim 1, wherein the motor comprises a three-phase, one-pole pair machine.

9. The intravascular blood pump according to claim 8, wherein the motor comprises a 6-coil, 2-pole machine in which each coil spans a mechanical angle of 120 degrees around the cross-section of the stator.

10. A slotless permanent magnet electric motor having p pairs of magnetic poles and n phases, wherein p is an integer of 1 or more and n is an integer of 3 or more, and the motor has a vertical axis, A stator having 2np coils that extend along the longitudinal axis of the housing and are wound to form two coils per phase per pole pair, An inner winding comprising np coils, where one coil for each phase is arranged in phase order for each pole pair, and one coil for each phase is arranged next to coils for different phases, wherein the inner winding has an outer surface; An outer winding comprising np coils arranged on the outer surface of the inner winding, wherein each phase coil in the outer winding is circumferentially aligned with the coils of the inner winding having the same phase for each pole pair. A slotless permanent magnet electric motor comprising a stator, wherein the in-phase coils of each pole pair are electrically connected such that the current flowing through the coils is in the same direction.

11. The slotless permanent magnet electric motor according to claim 10, comprising two layers of magnet wire, each of the coils of the inner winding and each of the coils of the outer winding, each extending longitudinally along the length of the stator.

12. The slotless permanent magnet electric motor according to claim 11, wherein the magnet wires in each coil are arranged sequentially next to each other along the span of the coil.

13. The slotless permanent magnet electric motor according to claim 10, wherein the inner winding of the coil establishes a uniform base upon which the outer winding of the coil is superimposed.

14. A slotless permanent magnet electric motor according to claim 10, wherein one phase coil is electrically connected to the other phase coil in either a star configuration or a delta configuration.

15. The slotless permanent magnet electric motor according to claim 14, wherein two of the coils per phase are connected in either series or parallel.

16. The slotless permanent magnet electric motor according to claim 10, wherein each of the 2np coils has a coil winding pattern selected from the group consisting of a helical winding pattern, a diamond winding pattern, and a hybrid winding pattern.

17. The slotless permanent magnet electric motor according to claim 16, wherein the motor comprises a three-phase two-pole machine.

18. The electric motor according to claim 16, wherein the motor comprises a 6-coil, 2-pole machine, each coil extending at a mechanical angle of 120 degrees around the cross-section of the stator.

19. A method for forming a stator for use in a slotless permanent magnet motor, The motor has p pairs of magnetic poles and n phases, where p is an integer greater than or equal to 1 and n is an integer greater than or equal to 3. The stator extends in the longitudinal direction and comprises 2np coils wound to form two coils per phase per pole pair, The method is A step of forming an inner winding comprising np coils, each having a phase order for each pole pair, with one coil for each phase arranged next to coils for different phases, wherein the inner winding has an outer surface; A step of forming an outer winding comprising np coils arranged on the outer surface of the inner winding, wherein each phase coil in the outer winding is circumferentially aligned with the coils of the inner winding having the same phase for each pole pair; and A method comprising the step of electrically connecting in-phase coils for each pole pair so that current flows through the coils in the same direction.

20. The method according to claim 19, comprising the step of forming coils on an inner winding and an outer winding such that each coil comprises two layers of magnet wire extending longitudinally along the length of the stator.

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