Deep Slot Axial Induction Motor

Abstract

An axial flux induction motor, of the type comprising a stator with an electrical winding and a rotor separated from the stator by an operating air gap, characterized in that: - The stator has, in cross-section, a substantially trapezoidal or wedge-shaped profile geometry, defined by a width that increases radially outwards, generating two lateral active faces with divergent inclination; - the rotor has an enveloping configuration with a channel or "U" shaped profile that surrounds the active faces of the stator laterally and inferiorly; - and in that the magnetic core of said rotor is constituted by a segmented structure formed by a succession of discrete ferromagnetic blocks with a "U" profile, separated from each other by slots that act as magnetic flux barriers, inside which conductive bars are housed forming multiple squirrel cages.

Description

DEEP SLOT AXIAL INDUCTION MOTOR TECHNICAL SECTOR The present invention falls within the field of electrical engineering, and more specifically within the field of axial flux induction electric motors. The object of the present invention is an axial flux induction motor incorporating a multiple squirrel cage configuration, designed to increase torque and power density compared to equivalent conventional motors. BACKGROUND OF THE INVENTION Induction motors are predominant in industry due to their simple construction, robustness, and high efficiency. However, their traditional architecture (radial flux) has limitations in terms of torque density and volumetric power, which hinders their integration into applications where space and weight are critical. To overcome these power density limitations, the current state of the art primarily uses permanent magnet motors, and more specifically axial flux topologies. These machines are becoming increasingly common in sectors such as electric vehicles and aerospace. However, permanent magnet motors have significant drawbacks: they rely on expensive materials (rare earth elements such as neodymium or dysprosium), which increases manufacturing costs and creates a strategic dependence on external supply chains. Furthermore, temperature management in permanent magnets is critical to prevent demagnetization. On the other hand, although there are previous developments of induction motors with axial geometry, these have not managed to achieve competitive power densities compared to permanent magnet motors, being relegated by their lower specific efficiency. Therefore, a technical solution is identified that allows achieving the torque densities characteristic of axial magnet geometry, while maintaining the robustness, low cost and absence of rare earth elements characteristic of induction motors. EXPLANATION OF THE INVENTION The present invention relates to a novel induction motor that solves the problems described above by modifying the traditional geometry of axial flux motors and internally reconfiguring their magnetic circuits. Generally, an axial induction motor consists of a stator, which produces a rotating magnetic field, and a rotor, parallel to the stator and separated by an air gap, both elements being perpendicular to the axis of rotation. Based on this premise, the motor of the present invention introduces specific geometric changes. First, the stator has a substantially trapezoidal or wedge-shaped cross-section. This section is defined by a greater width at its radially outer periphery and a narrower width at its radially inner periphery, creating two opposing active faces with a divergent outward inclination. Adapting to this shape, the stator winding is divided into at least two sections electrically connected in series, housed in the slots of these inclined faces. Additionally, the rotor adopts a wrap-around configuration with respect to the stator. This rotor profile comprises two lateral arms and a lower return yoke that connects these arms below the stator level. The rotor's lateral arms are inclined at the same angle as the stator's active faces, separated from them only by the operating air gap. Thus, the rotor's magnetic circuit surrounds the stator laterally and inferiorly. This U-shaped yoke geometry serves as the structural basis for the segmented internal construction of the rotor, which is a key novel aspect of the invention. Specifically, the rotor's magnetic core is not continuous but is formed by the sequential arrangement of a plurality of discrete, U-shaped ferromagnetic blocks, stacked along a circumferential axis around the motor's axis of rotation. This creates a discontinuous toroidal structure where magnetic blocks and wide separation slots alternate at an angle. These slots technically act as high-reluctance flux barriers, and the conductor bars of the multiple cages are housed within them: the outermost bars face directly towards the active faces of the stator, while the bars of the additional cages are distributed around the 'U' profile according to their specific geometry. The space in the slot not occupied by the bars is filled with air. As a general guideline, the width of the air column in these slots is preferably defined as slightly less than the thickness of the conductor bars themselves. This barrier configuration forces the magnetic flux to travel through the entire U-shaped profile of each block, ensuring that the field lines pass through and interact with all the squirrel cages arranged around the block, regardless of their orientation. The direct technical consequence of this increased electromagnetic interaction is the generation of greater force, resulting in a dramatic increase in the motor's torque and power density. Additionally, this arrangement offers secondary advantages: replacing ferromagnetic material with the aforementioned barriers reduces the rotor's overall weight, while the remaining air spaces in the slots act as integrated cooling channels, allowing the power increase to be managed without thermal penalty. Finally, it should be mentioned that the U-shaped rotor structure described is rigidly attached to the motor's transmission shaft by means of a support element or disc made of non-ferromagnetic material, guaranteeing the transmission of torque and the structural integrity of the rotating assembly. BRIEF DESCRIPTION OF THE DRAWINGS To complement the description being made and in order to help a better understanding of the characteristics of the invention, a set of drawings is included as an integral part of said description, in which, for illustrative and non-limiting purposes, the following has been represented: Figure 1.- Shows a front view of a wedge-shaped portion of the stator. Figure 2.- Shows a side view of a wedge-shaped stator portion. Figure 3.- Shows a front perspective view of a rotor segment with a 'U' profile, detailing the arrangement of the squirrel cage bars distributed following the contour of said geometry. Figure 4.- Shows a side perspective view of a rotor segment with a 'U' profile, detailing the arrangement of the squirrel cage bars distributed following the contour of said geometry. Figure 5.- Shows a perspective view of the assembled motor assembly, illustrating the coaxial integration of the stator with the circumferential arrangement of the multiple 'U' rotor profiles and their squirrel cages. Figure 6.- Shows a longitudinal cross-section view of the complete motor, detailing the complementary geometric coupling between the rotor's envelope profile and the stator's trapezoidal section. Figure 7.- Shows a detailed segment of the stator-rotor coupling. PREFERRED EMBODIMENT OF THE INVENTION A preferred embodiment of the invention is described below with reference to the accompanying figures. First, Figures 1 and 2 illustrate the fundamental geometry of a stator segment. Specifically, Figure 1 shows a front view or cross-section of this segment, while Figure 2 provides a perspective view of the same element to appreciate its volume. The stator consists of a plurality of these wedge-shaped modular segments. As shown in Figure 1, each segment comprises a central body (2) with a trapezoidal geometry, which constitutes the main path through which the generated magnetic flux will circulate. Figure 2 shows how two lateral protrusions or blocks (1) and (3) emerge from the sides of this central body (2), which have a smaller cross-section than the main wedge. The technical function of these protrusions (1) and (3) is to serve as a core for the stator winding; that is, it is on these blocks where the stator coils are stacked or inserted (not represented in this figure for greater clarity). This geometric configuration defines the basic structural unit of the stator. In the complete motor, this profile is repeated circumferentially as many times as there are slots designed. From a construction standpoint, the magnetic core shown in these figures is manufactured by stacking magnetic laminations. It is important to note that these laminations are arranged parallel to the direction of the magnetic flux, stacked circumferentially in a wedge shape. This specific arrangement is designed to drastically reduce eddy current losses, optimizing the overall magnetic efficiency. Additionally, the described geometry allows the coil slots on the blocks (1) and (3) adjacent to the core (2) to remain radially open to the outside. This feature allows the winding to be directly exposed to the surrounding environment or fluid, significantly improving stator cooling compared to conventional closed slots. Figures 3 and 4 illustrate the detailed configuration of a rotor segment. Figure 3 shows a front view of the profile section, while Figure 4 provides a perspective side view. The basic structural element is the magnetic core (4), which has a U-shaped profile or enveloping channel geometry. A fundamental technical requirement of this configuration is that the net cross-section of ferromagnetic material of this core (4) remains substantially constant along the entire length of the U-shape. This homogeneity of cross-section, which may involve geometric adjustments to compensate for the shorter arc length at the inner radii compared to the outer radii, is critical to ensure a uniform flux density and prevent local magnetic saturation at any point of the yoke. A series of conductor bars, referenced in this embodiment by numbers (5) to (10), are arranged around this core (4). Although six levels of bars are shown in the figures for illustrative purposes, it is understood that both the total number of cages and the cross-sectional geometry of the bars can vary depending on the specific torque and power requirements of the design. From a functional point of view, the electrical connectivity of the assembly is important to highlight. Although the figures show the section of a single segment, the bars depicted act in conjunction with their counterparts in adjacent segments. Thus, all bars located in the same relative position with respect to the U-profile along the rotor circumference are electrically connected to each other, closing the circuit by means of short-circuiting rings (not shown) or equivalent connections. Finally, to understand the functional integration and the operating principle of the set, reference is made to Figures 5, 6 and 7. Figure 5 provides a perspective view of the complete assembled motor. It shows the coaxial configuration of the assembly, where the rotor's outer shell surrounds the stator. In this view, the short-circuit rings of the cages (labeled "Cages") are identified; these protrude slightly from the rotor's ferromagnetic structure, remaining exposed for ventilation. To detail the internal coupling, Figure 6 shows a cross-section of the motor, while Figure 7 presents a detailed operating segment formed by the stator and rotor, fundamental to understanding the magnetic circuit. As shown in Figure 7, there is a precise geometric correspondence between the stator and the rotor, maintained by two symmetrical operating air gaps located between the active faces of the stator poles, (1) and (3), and the rotor's lateral arms (4). The magnetic circuit follows the following closed path: The flux generated by the winding originates from a first stator pole (1), passes through the first operating air gap, and enters the corresponding arm of the rotor core (4). At this point, it is crucial to highlight the effect of the rotor segmentation described earlier: due to the presence of air columns (high-reluctance barriers) that longitudinally separate each 'U' block, the magnetic flux is prevented from dispersing laterally and is forced to travel the entire length of the 'U' profile of the block (4), effectively interacting with all the bars of the cages housed along its path.Finally, the flux emerges through the opposite arm of the rotor, crosses the second air gap to the second pole of the stator (3) and closes the magnetic circuit through the central trapezoidal yoke of the stator (2). Additionally, Figures 6 and 7 highlight an essential constructive feature: the formation of an air chamber or free technical space (referred to as "Air" in Figure 7), located between the lower vertex of the stator wedge and the bottom of the rotor channel. This interstitial volume fulfills a critical dual function in the invention: • Connection Housing: Provides the necessary space to house the short-circuit rings that interconnect the cage bars, allowing the rotor's electrical circuit to close without mechanical interference with the static part. • Cooling System: As it is a through-duct and open, it acts as a forced ventilation channel. During motor rotation, air circulates through this space, cooling by direct convection both the short-circuit rings (which are sources of heat generation due to the Joule effect) and the internal surfaces of the magnetic core.

Claims

1. An axial flux induction motor, of the type comprising a stator with an electrical winding and a rotor separated from the stator by an operating air gap, characterized in that: - The stator has, in cross-section, a substantially trapezoidal or wedge-shaped profile geometry, defined by a width that increases radially outwards, generating two lateral active faces with divergent inclination; - the rotor has an enveloping configuration with a channel or "U" shaped profile that surrounds the active faces of the stator laterally and inferiorly; - and in that the magnetic core of said rotor is constituted by a segmented structure formed by a succession of discrete ferromagnetic blocks with a "U" profile, separated from each other by slots that act as magnetic flux barriers, inside which conductive bars are housed forming multiple squirrel cages. 2.A motor according to claim 1, characterized in that the width of the separation slots between the ferromagnetic blocks of the rotor is dimensionally greater than the width of the operating air gap of the motor, configuring high reluctance barriers that force the magnetic flux to circulate through the entire 'U' profile of the blocks.

3. A motor according to claim 1, characterized in that the conductive bars housed in the rotor slots are arranged in multiple levels, comprising a first group of bars facing directly the active faces of the stator and additional groups of bars distributed around the geometry of the 'U' profile of the rotor. 4.A motor according to claim 1, characterized in that a ferromagnetic-free technical chamber is defined in the radially internal zone between the lower vertex of the stator and the lower return of the rotor, dimensioned to house the coil heads of the stator winding and allow for their cooling.

5. A motor according to claim 1, characterized in that the succession of ferromagnetic rotor blocks is rigidly attached to the transmission shaft by means of a disc-shaped support element made of non-ferromagnetic material.

6. A motor according to claim 1, characterized in that the cross-section of the ferromagnetic material of the rotor blocks remains substantially constant along the entire "U" profile, both in the side arms and in the lower return, presenting a magnetic cross-section equivalent to that of the stator poles to prevent magnetic saturation of the core.