WO2021119196A1

WO2021119196A1 - Systems and devices of a five-phase inverter motor

Info

Publication number: WO2021119196A1
Application number: PCT/US2020/064111
Authority: WO
Inventors: Bart Dean Hibbs
Original assignee: Aerovironment, Inc.
Priority date: 2019-12-09
Filing date: 2020-12-09
Publication date: 2021-06-17

Abstract

Systems, devices, and methods for a five-phase inverter motor (110) comprising: a stator (112) comprising: at least one armature (116); at least five teeth (138); a rotor (120) comprising at least four magnets (122); at least five inverters (420); where four magnets of the at least four magnets are associated with five teeth of the at least five teeth.

Description

PATENT COOPERATION TREATY APPLICATION

TITLE: SYSTEMS AND DEVICES OF A FIVE-PHASE INVERTER MOTOR

INVENTOR: Bart Dean Hibbs

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/945,821, filed December 9, 2019, the contents of which are hereby incorporated by reference herein for all purposes.

TECHNICAL FIELD

Embodiments relate generally to motors, and more particularly to a motor for an unmanned aerial vehicle (UAV).

BACKGROUND

Unmanned aerial vehicles (UAVs), such as a high altitude long endurance aircraft, are lightweight planes that are capable of controlled, sustained flight. UAVs may be associated with ground-based operators for two-way communications. UAVs may utilize one or more motors to provide power and control to the UAV for sustained flight.

SUMMARY

An embodiment may include a five-phase inverter-driven permanent magnet motor of an unmanned aerial vehicle (UAV). In one embodiment, the UAV is a high altitude long endurance solar-powered aircraft.

A device embodiment may include a five-phase inverter motor comprising: a stator comprising: at least one armature; at least five teeth; a rotor comprising; at least four magnets; at least five inverters; where four magnets of the at least four magnets are associated with five teeth of the at least five teeth. In additional device embodiments, if one inverter of the at least five inverters fails, the four remaining inverters are able to run the five-phase inverter motor. In additional device embodiments, a maximum current is produced when each rotor tooth of the plurality of teeth associated with the rotor is lined up directly between two magnets of the plurality of magnets. In additional device embodiments, no current is produced when a tooth of the at least five teeth is directly facing a magnet of the at least four magnets. In additional device embodiments, an AC drive (420) regulates power to the at least five inverters.

In an additional device embodiment, a device embodiment may include a five- phase inverter motor comprising: a stator comprising: at least one armature containing a number of teeth divisible by five and a rotor with a number of magnets divisible by four; at least five inverters; where there are four magnets for every five teeth.

In additional device embodiments, if one inverter of the at least five inverters fails, the four remaining inverters are able to run the five-phase inverter motor. In additional device embodiments, a maximum current is produced when each rotor tooth of the plurality of teeth associated with the rotor is lined up directly between two magnets of the plurality of magnets. In additional device embodiments, no current is produced when a tooth of the at least five teeth is directly facing a magnet of the at least four magnets. In additional device embodiments, an AC drive (420) regulates power to the at least five inverters.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principals of the invention. Like reference numerals designate corresponding parts throughout the different views. Embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which:

FIG. 1 depicts an unmanned aerial vehicle with at least one five-phase inverter-driven permanent magnet motor, according to one embodiment; FIG. 2 depicts a top perspective disassembled view of a rotor and a stator of the five-phase inverter-driven permanent magnet motor of FIG. 1, according to one embodiment;

FIG. 3 depicts an elevation view of the five-phase inverter-driven permanent magnet motor of FIG. 1, according to one embodiment;

FIG. 4 depicts a schematic of an inverter of the five-phase inverter-driven permanent magnet motor of FIG. 1, according to one embodiment;

FIG. 5 depicts an alternative schematic of an inverter of the five-phase inverter-driven permanent magnet motor of FIG. 1, according to one embodiment;

FIG. 6 illustrates an example top-level functional block diagram of a computing device embodiment; and

FIG. 7 depicts a flowchart of a process of operation of the five-phase inverter- driven permanent magnet motor of FIG. 1, according to one embodiment.

DETAILED DESCRIPTION

With respect to FIG. 1, an unmanned aerial vehicle (UAV) 101 with at least one five-phase inverter-driven permanent magnet motor 110 is depicted. UAVs are aircraft with no onboard pilot and may fly autonomously or remotely. In one embodiment, the UAV 101 is a high altitude long endurance aircraft. In one embodiment, the UAV 101 may have one or more motors 110, for example, between one and 40 motors, and a wingspan between 100 feet and 400 feet. In one embodiment, the UAV 101 has a wingspan of approximately 260 feet and is propelled by a plurality of propellers 140 coupled to a plurality of motors, for example, ten electric motors, powered by a solar array covering the surface of the wing, resulting in zero emissions. Flying at an altitude of approximately 65,000 feet above sea level and above the clouds, the UAV 101 is designed for continuous, extended missions of up to months without landing. The UAV 101 may function optimally at high altitude and is capable of considerable periods of sustained flight without recourse to land. In one embodiment, the UAV 101 may weigh approximately 3,000 lbs.

A five-phase inverter-driven permanent magnet motor may propel a UAV for extended flight. Permanent magnet motors may result in compromises that reduce motor efficiency or increase weight. Some examples of the compromises considered concern the layout of the winding and the magnets. Three-phase motors are wound in several ways. A classic wind is to have each coil span three slots, forming an overlapping wind of the three phases. This has the compromise of large end turns, adding weight, resistance, and reducing efficiency.

Another way of winding the motor is the concentrated wind, as shown in FIG. 2. Here each coil spans one slot, and each tooth is wound separately. This greatly reduces the bulk of the end turns. In one embodiment, the AC power in each tooth is exactly in phase with the passage of the magnets. This can be done if three teeth are included for every two magnets. As a result, the tooth is much smaller than the magnet, and some magnetic flux leaks out to adjacent teeth, reducing motor efficiency.

Another optional embodiment is to have fewer teeth per magnet, such as a 24 tooth, 20 magnet arrangement. In this arrangement, the teeth are sized to capture all the flux from each magnet, but the AC current in every tooth will not be in phase with the passage of the magnets. There will be small phase offsets.

With respect to FIG. 2, the at least one motor 110 coupled to the UAV 101 for propulsion of the UAV 101 is shown. In one embodiment, the motor 110 is a five- phase inverter powered permanent magnet motor. In one embodiment, the motor 110 includes an out-runner rotor 120 (e.g., where the rotor, or runner, is outside the stator) with the stator 112 electrically connected with a five-way wye-configuration winding 114 about improved armatures 116. In another embodiment, each of the five phases is electrically isolated from the other phases and each phase is powered by a separate inverter power stage, allowing for redundancy in the event of a winding short or a power stage failure. The motor 110 may have a casing formed of steel or other high- strength material to enclose and protect the motor.

A rotor 120 is positioned around the perimeter of the stator 112, with the rotor 120 having a back iron to contain the magnetic field of the rotor 120. The rotor 120 may be formed of permanent magnets 122 such as neodymium and praseodymium or suitable magnet, including electromagnets. The stator 112 may have the armatures 116 built up from layers of laminated electrical steel, such as silicon steel, with an oxide film positioned between each steel layer, to reduce induced ring currents and to increase efficiency of the motor 110. Other armature materials may include iron or amorphous steel.

In one embodiment, the motor 110 is configured to have the windings 114 wound around iron teeth like a standard combustion motor. Additionally, there may be a layer of magnets on the outside of the motor 110 that may remain glued to the motor 110 down to approximately -80° Celsius. This is useful as the UAV 101 often flies at night and at high altitude with temperatures approaching -80° Celsius.

Some motors in the art may be ironless to avoid hysteresis losses and eddy current losses, which result in energy being wasted in the form of heat. In one embodiment, the motor 110 may incorporate permendur: a cobalt-iron soft magnetic alloy with equal parts iron and cobalt, such as Hiperco®. Permendur has very low hysteresis and eddy current losses, often performing better than ironless motors. Still further, iron has some very important properties that are not found in ironless motors, including; (1) mechanically supporting the winding, (2) providing inductance, thus not requiring external inductors, (3) providing a way for heat to get out of the motor, (4) gives a very thin air gap so you need far less magnetic material to make the magnetic field, and (5) keeping the magnetic field out of copper, because a magnetic field going through copper causes large energy losses in copper.

In one embodiment with an induction motor, AC supplied to the stator windings 114 energizes the windings 114 to create a rotating magnetic flux. The flux generates a magnetic field in an air gap between the rotor 120 and the stator 112 and induces a voltage, which produces current through rotor bars. The rotor circuit may be shorted and current flows in rotor conductors. The action of the rotating flux and the current produces a force that generates a torque to start the five-phase inverter-driven permanent magnet motor 110. Other embodiments may use an inrunner permanent magnet motor.

The rotor 120 may act as a field magnet, interacting with the armature 116 to create motion, or it may act as the armature 116, receiving its influence from moving field coils on the stator 112.

Embodiments of the present application disclose motors where by using five phases, for example, instead of three, a motor may be constructed with five teeth for every four magnets. Such configuration results in a tooth size closely equal to the magnet size, and allows for every tooth to be energized with AC current properly in phase with magnet passage.

With respect to FIG. 3, the five-phase inverter-driven permanent magnet motor 110 is shown. The five-phase inverter-driven permanent magnet motor 110 may have five phases 150, an "A", “B”, “C”, “D”, and Έ” phase. The teeth may be wound with the five phases, A, B, C, D, E, in the order A, C, E, B, D. If there are more than five teeth, the pattern repeats. The number of phases refers to the different combinations of poles that are energized in sequence to attract the stator 112. In one embodiment, a separate inverter 128 may be generated for every phase. With the five- phase inverter-driven permanent magnet motor 112, configuration redundancy is in place such that if one inverter 128 fails, there are still four remaining inverters 128 that are able to run the five-phase inverter-driven permanent magnet motor 110.

With respect to FIG. 4, a microcontroller 420 is shown connected to the phase “A” of FIG. 3. In one embodiment of the presently disclosed five-phase inverter- driven permanent magnet motor, the microcontroller 420 is an AC drive (e.g., an inverter). The AC drive 420 may be situated between an electrical supply and the motor 110, and the AC drive 420 may receive the electrical supply. The AC drive 420 may then regulate the power to be fed to the motor 110. The input electrical power is run through a power stage 130 of the AC drive 420, which converts the incoming DC power to AC power that is then transmitted to the motor 110. Configured as such, the AC drive 420 may adjust the frequency and voltage that is supplied to the motor 110 at the desired speed.

The windings 114 receive the AC power from the AC drive 420 and become energized. In one embodiment, a winding 114 may be wound around each of a plurality of iron teeth 138 of the stator 112 in a so-called “concentrated winding”. When the windings 114 become energized, an electro-magnet is created which attracts the magnetic flux of the rotor 120, with each electro-magnet being a single north (N) - south (S) pole. In one embodiment, there are 5 stator teeth 138 for every 4 magnets 122 of the rotor 120. In one embodiment, a maximum current is supplied when each stator tooth 138 is lined up 160 directly between two magnets 122.

A five-phase inverter motor 110 may include: a stator 112, a rotor 120, and at least five inverters 420. The stator 112 may include at least one armature 116 containing a number of teeth 138 divisible by five. The rotor 120 may include a number of magnets 122 divisible by four. There may be four magnets 122 for every five teeth 138 in some embodiments. If one inverter 420 of the at least five inverters 420 fails, the four remaining inverters 420 are able to run the five-phase inverter motor 110. A maximum current is produced when each rotor tooth 138 of the teeth 138 associated with the rotor 120 is lined up directly between two magnets 122 of the magnets. No current is produced when a tooth 138 of the teeth 138 is directly facing a magnet 122 of the magnets 122. An AC drive may regulate power to the at least five inverters 420.

Conversely, and with respect to FIG. 5, no current is supplied when a given stator tooth 138 is displaced and directly faces 162 a magnet 122. No current is supplied when a given stator tooth is displaced and directly faces a magnet, which is the ideal case for efficiency. There is a reason for the inverter to supply current to the winding when the tooth is in line with a magnet, known as “field weakening”. It is used to allow electric motors to run at higher speed. In some embodiments, the motor may use field weakening. In other embodiments, zero current at the magnet crossing is the most efficient, and this layout of teeth and magnets allows that case to occur for every tooth. In one embodiment, as the stator teeth 138 are displaced and become out of phase, the motor 110 produces torque. In one embodiment, each stator tooth 138 is approximately .75 to .8 the size of the distance from one gap or “slot” 140 between the magnets 122 and the next. The size of each stator tooth 138 is approximately the same size as each magnet 122, thus all the flux may go right through a stator tooth 138 when the stator tooth 138 is directly facing a magnet 122. In one embodiment, the motor 110 has 40 poles and 45 slots 140. In one embodiment, with 5 stator teeth 138 for every 4 magnets 122, every stator tooth 138 is energized such that each stator tooth 138 is perfectly in phase with the magnet 122 that the stator tooth 138 faces.

FIG. 6 illustrates an example of a top-level functional block diagram of a computing device embodiment 400. The example operating environment is shown as a computing device 420, such as microcontroller 420 comprising a processor 424, such as a central processing unit (CPU), addressable memory 427, an external device interface 426, e.g., an optional universal serial bus port and related processing, and/or an Ethernet port and related processing, and an optional user interface 429, e.g., an array of status lights and one or more toggle switches, and/or a display, and/or a keyboard and/or a pointer-mouse system and/or a touch screen. Optionally, the addressable memory may include any type of computer-readable media that can store data accessible by the microcontroller 420, such as magnetic hard and floppy disk drives, optical disk drives, magnetic cassettes, tape drives, flash memory cards, digital video disks (DVDs), Bernoulli cartridges, RAMs, ROMs, smart cards, etc. Indeed, any medium for storing or transmitting computer-readable instructions and data may be employed, including a connection port to or node on a network, such as a LAN, WAN, or the Internet. These elements may be in communication with one another via a data bus 428. In some embodiments, via an operating system 425 such as one supporting a web browser 423 and applications 422, the processor 424 may be configured to execute steps of a process establishing a communication channel and processing according to the embodiments described above.

With respect to FIG. 7, a flowchart 200 of a process for operating the five- phase inverter-driven permanent magnet motor 110 is shown. At step 202, an AC drive regulates the power to be fed to an inverter of the five-phase inverter-driven permanent magnet motor. At step 204, windings of the motor receive the AC power and become energized. A winding is wound around each of a plurality of iron teeth of the stator and an electro-magnet is created which attracts the magnetic flux of the rotor to the stator, at step 206. At step 208, a maximum current is produced when each stator tooth associated with the stator is lined up directly between two magnets. At step 210, there are 5 stator teeth for every 4 magnets of the motor, and if each stator tooth is lined up with a magnet, then no current is produced when a given rotor tooth is directly facing a magnet. At step 212, as the stator teeth 138 are displaced and become out of phase the motor 110 produces torque. At step 214, if one inverter of the five-phase inverter motor fails, the four remaining inverters are able to run the motor.

It is contemplated that various combinations and/or sub-combinations of the specific features and aspects of the above embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments may be combined with or substituted for one another in order to form varying modes of the disclosed invention. Further, it is intended that the scope of the present invention is herein disclosed by way of examples and should not be limited by the particular disclosed embodiments described above.

Claims

CLAIMS: What is claimed is:

1. A five-phase inverter motor comprising: a stator comprising: at least one armature; at least five teeth; a rotor comprising at least four magnets; at least five inverters; wherein four magnets of the at least four magnets are associated with five teeth of the at least five teeth.

2. The five-phase inverter motor of claim 1, wherein if one inverter of the at least five inverters fails, the four remaining inverters are able to run the five-phase inverter motor.

3. The five-phase inverter motor of claim 1, wherein a maximum current is produced when each rotor tooth of the plurality of teeth associated with the rotor is lined up directly between two magnets of the plurality of magnets.

4. The five-phase inverter motor of claim 1, wherein no current is produced when a tooth of the at least five teeth is directly facing a magnet of the at least four magnets.

5. The five-phase inverter motor of claim 1, wherein an AC drive regulates power to the at least five inverters.

6. A five-phase inverter motor comprising: a stator comprising: at least one armature containing a number of teeth divisible by five; a rotor comprising a number of magnets divisible by four; at least five inverters; wherein there are four magnets for every five teeth.

7. The five-phase inverter motor of claim 6, wherein if one inverter of the at least five inverters fails, the four remaining inverters are able to run the five-phase inverter motor.

8. The five-phase inverter motor of claim 6, wherein a maximum current is produced when each rotor tooth of the teeth associated with the rotor is lined up directly between two magnets of the magnets.

9. The five-phase inverter motor of claim 6, wherein no current is produced when a tooth of the teeth is directly facing a magnet of the magnets.

10. The five-phase inverter motor of claim 6, wherein an AC drive regulates power to the at least five inverters.