HIGH TORQUE DENSITY ELECTRIC MOTOR

Abstract

HIGH TORQUE DENSITY ELECTRIC MOTOR The invention relates to electrical engineering, can be used in aircraft electric motors, and concerns a high torque density electric motor comprising an annular stator (1) with a coil (2) and a rotor (4) with a plurality of teeth and a plurality of magnets located between the teeth, the magnets being tangentially polarized, the teeth (3) of the stator (1) and the annular rotor core with the rotor teeth (4) being made of grain-oriented steel, the coil wire (2) having a rectangular cross-section, the stator (1) having an open structure, and the stator coil (2) being wrapped with a high thermal conductivity insulating paper, which is impregnated with varnish. The invention makes it possible to provide a high specific torque per unit volume and a high torque density necessary for its efficient use as an aircraft motor. Figure to be published with the abstract: Fig. 1

Description

Title of the invention: HIGH TORQUE DENSITY ELECTRIC MOTOR Technical field

[0001] The present invention relates to electrotechnics and can be used in electric motors for aircraft, drones and vertical takeoff and landing aircraft. Prior state of the art

[0002] An equivalent to the present invention is known - electric motor - US7679256, 10 / 06 / 2005, having the first section of the rotor's magnetic pole magnetized in the radial direction, and the second section of the rotor's magnetic pole magnetized in the direction of the axis of rotation; and a stator having a first stator magnetic pole section for generating a magnetic flux in the radial direction and a second stator magnetic pole section for generating a magnetic flux along the direction of the axis of rotation.

[0003] The disadvantage of this equivalent is the low specific torque per unit volume and unit mass of the electric motor, which makes its use as an aircraft engine inefficient.

[0004] A close equivalent of the device is known - flux concentration type motor - US20060061228A1, 16 / 09 / 2005, adopted as prototype of the device, containing an annular stator in which the coil is wound on a plurality of radially spaced teeth and a rotor located at the center of the stator, and the rotor contains an annular rotor core, a plurality of teeth projecting from the annular rotor core towards the stator and a plurality of magnets located between the teeth, while, in the connecting section between the annular rotor core and the tooth, a small diameter hole is made, designed to insert a guide pin, and, in the bridge connecting adjacent teeth, or in the end section of the tooth, adjacent to the annular rotor core, a barrier is formed for the magnetic flux of the magnets in order to prevent its dispersion.

[0005] The disadvantage of the prototype is the relatively low specific torque per unit volume and unit mass of the electric motor, which makes its use as an aircraft engine inefficient.

[0006] The technical result of the present proposed invention aims to provide a high specific torque, relative to equivalents, per unit volume and, consequently, per unit mass of the electric motor, i.e. to provide a high torque density necessary for its efficient use as an aircraft engine. Disclosure of the present invention

[0007] The technical result is obtained by means of a high torque density electric motor, comprising an annular stator, in which a coil is wound on a plurality of radially arranged teeth, and a rotor located at the center of the stator, the rotor comprising an annular rotor core, a plurality of teeth projecting from the annular rotor core towards the stator, and a plurality of magnets located between the rotor teeth, the magnets being tangentially polarized, the stator teeth and the annular rotor core with the rotor teeth being made of grain-oriented steel, the coil wire having a rectangular cross-section, the stator having an open structure, and the stator coil being wrapped with insulating paper having high thermal conductivity, which is impregnated with varnish. Brief description of the drawings

[0008] [Fig-1] is a cross-section of the high torque density electric motor.

[0009] [Fig.2] is a cross-section of the high torque density electric motor without side walls.

[0010] [Fig.3] is an enlarged fragment of a section of the electric motor with density of high torque, representing magnetic induction lines.

[0011] [Fig.4] is an enlarged view of the high torque density electric motor representing the arrangement of the reel.

[0012] [Fig.5] is a section of the optional assembly of the coaxial arrangement of two High torque density electric motors with propellers attached to them.

[0013] [Fig.6] is the stator assembly.

[0014] [Fig.7] is the optional assembly of the coaxial arrangement of two electric motors with high torque density with propellers attached to them.

[0015] The high-torque-density electric motor comprises an annular stator 1, as shown in [Fig. 1], in which a coil 2 is wound over a plurality of radially arranged teeth 3 of the stator 1, and a rotor 4 located at the center of the stator 1. The rotor 4 comprises an annular rotor core 5, as shown in [Fig. 2], a plurality of teeth 6 projecting from the annular rotor core 5 towards the stator 1, and a plurality of magnets 7 located between the teeth 6, the magnets 7 having tangential polarization, as shown in [Fig. 3]. The teeth 3 of the stator 1 and the annular rotor core 5 with the teeth 6 of the rotor 4 are made of grain-oriented steel. The wire of the coil 2 has a rectangular cross-section as shown in [Fig. 4]. The stator 1 has an open structure, and the coil 2 of the stator 1 is wrapped. of an insulating paper having high thermal conductivity, impregnated with varnish.

[0016] Best embodiment of the present invention

[0017] Let us consider an example of an implementation of the high-torque-density electric motor. The annular stator 1 is in the form of a ring, composed of steel sectors 8, connected by a dovetail locking mechanism 9, as shown in [Fig. 4]. The copper coil 2 is wound on a plurality of radially arranged teeth 3. The steel teeth 3 are fixed to the sectors 8 of the stator casing 1 by a dovetail locking mechanism 10. The coil 2 consists of a copper wire with a rectangular cross-section, as shown in [Fig. 2] and [Fig. 3]. Such a wire increases the coil space filling factor by 70%, which increases the current density in the coil and increases the specific torque. Ohmic losses in the coil are calculated using the formula L = R * 12, where R is the coil resistance and I is the current.Due to the rectangular cross-section of the coil in the implementation example, the resistance R is 2 to 2.5 times lower than that of existing motor equivalents with a circular coil cross-section. Furthermore, the rectangular wire dissipates heat much better than a standard rounded or multi-strand wire.

[0018] Side walls 11, 12 are fixed by screws to the sides of the stator ring 1, as shown in [Fig. 3]. Bearings 13, 14 are installed in the side walls 11, 12, as shown in Figures 1 and 2. A rotor 4 is arranged on said bearings 11, 12. A plurality of teeth 6 projecting towards the stator 1 are fixed to the annular rotor core 5 of the rotor 4 by a dovetail joint 15, as shown in [Fig. 3]. These parts are made of steel. The magnets 7 are fixed between the teeth 6 by virtue of their wedge shape. The magnets 7 are tangentially polarized as shown in [Fig. 3]. Consequently, the magnetic induction lines 16 in them are directed tangentially to the direction of rotation of the rotor 4. The tangential polarization of the magnets concentrates the magnetic field more intensely than a Halbach array of magnets.Combined with the positioning of the rotor 4 inside the stator 1, tangential biasing allows for a higher specific torque per unit volume and unit mass than a motor with an external rotor of the same diameter and weight. Tangential biasing increases the magnetic field in the gap between the rotor and the stator by 1.2 to 1.3 times compared to motors using surface-mounted magnets.

[0019] The stator teeth 2 and the annular rotor core 5 with the rotor teeth 6 are made of grain-oriented steel. Due to the higher magnetic conductivity of grain-oriented steel, as well as the possibility of using a smaller tooth width to achieve the same effect and a large coil cross-sectional area, the use of grain-oriented steel increases the specific torque per unit volume and unit mass of the electric motor by approximately 5%.

[0020] The stator 1 has an open design. This means that the stator is not housed within the casing, but rather the stator housing is the only casing the motor possesses. This is achieved by the fact that the steel teeth 3 are fixed to the sectors 8 of the stator housing 1 by a dovetail locking mechanism 10.

[0021] The rotation of the rotor 4 ensures efficient heat transfer by convection. In addition, the coil 2 of the stator 1 is wrapped with insulating paper having high thermal conductivity, which is impregnated with varnish. Standard Nomex® is used as the insulating paper. High thermal conductivity ST6000 paper can also be used. The described means for cooling the motor are necessary to efficiently remove heat from the considered high torque-density electric motor per unit volume and specific mass, given that it dissipates a higher specific heat per unit volume. The more heat that can be removed from the motor, the more current can be used, and the higher the motor torque will be.

[0022] The open stator also significantly reduces the motor design cost, since the outer casing, which is the most expensive part of the motor, is no longer required. The motor is hermetically sealed and conforms to the IP67 standard. Industrial application

[0023] The above description proves the possibility of implementing the present proposed invention using known industrial technologies.

[0024] The combination of the aforementioned characteristics of a high torque density electric motor, namely a tangential polarization of magnets, stator teeth and an annular rotor core with rotor teeth made of grain-oriented steel, an elongated rectangular coil wire cross-section, an open stator design with a coil wrapped in insulating paper, which has high thermal conductivity, impregnated with varnish, makes it possible to obtain a high specific torque value and to use the motor effectively as an aircraft motor.

[0025] Aviation and drones require motors that offer maximum torque per unit volume and mass. The larger the propeller diameter and the slower its rotation, the more efficient the motor is in a given application. The proposed technical solution exhibits these characteristics. Furthermore, due to its small volume, it creates less resistance to the oncoming airflow during flight, and the motor's low mass allows for greater energy efficiency.

[0026] Figure 5 illustrates an example of such a motor application. It comprises two Electric motors 17, 18 with high torque density are coaxially mounted and secured with screws. A shaft 19 supports the motor stators. Propellers are attached to the motor by folding propeller couplings 20, 21 to generate thrust for aircraft movement.

[0027] The characteristics of the high torque density electric motor listed above have led to a range of motors exhibiting the following characteristics:

[0028] 1) a motor with a mass of 1.2 kg, a diameter of 100 mm, with a torque specific per unit mass of 6 Nm / kg;

[0029] 2) a motor with a mass of 5 kg, a diameter of 150 mm, with a torque specific per unit mass of 12 Nm / kg;

[0030] 3) a motor with a mass of 15 kg, a diameter of 250 mm, with a torque specific per unit mass of 17 Nm / kg.

[0031] The specific torque values ​​are given for nominal motor operation, and peak values ​​can be up to 2 times higher.

Claims

Claims

1. A high torque density electric motor, comprising an annular stator (1), in which a coil (2) is wound on a plurality of radially arranged teeth (3), and a rotor (4) located in the center of the stator (3), the rotor (4) comprising an annular rotor core (5), a plurality of teeth (6) projecting from the annular rotor core (5) toward the stator (1), and a plurality of magnets (7) located between the teeth (6) of the rotor (4), characterized in that the magnets (7) are tangentially polarized, the teeth (3) of the stator (1) and the annular rotor core (5) with the teeth (6) of the rotor (4) are made of grain-oriented steel, the wire of the coil (2) has a rectangular cross-section, the stator (1) has an open structure, and the coil (2) of the stator (1) is wrapped with an insulating paper having a thermal conductivity raised, which is impregnated with varnish.

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