# US 2018/0323665 A1 · Motor with separated permanent magnet torque and reluctance torque and its optimal efficiency control

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- Number: US 2018/0323665 A1
- Document ID: US20180323665A1
- Status: Published application
- Kind: A1
- Application number: 15/544,212
- Filed: 2016-03-16
- Published: 2018-11-08
- Earliest claimed: 2016-01-26
- Assignees: Jiangsu University
- Applicants: Jiangsu University
- Inventors: Qian CHEN; Wenxiang ZHAO; Guohai LIU; Jinghua JI; Gaohong XU; Zhipeng LIN
- Web page: https://patentgrep.com/patent/US20180323665A1

## CPC

- H02K 1/27: Rotor cores with permanent magnets
- H02K 15/03: having permanent magnets
- H02K 16/00: Machines with more than one rotor or stator {(machines for transmitting mechanical power from a driving shaft to a driven shaft and comprising structurally interrelated motor and generator parts H02K51/00; permanent magnet machines with multiple rotors or stators relatively rotated for vectorially combining the excitation fields or the armature voltages H02K21/029)}
- H02P 21/00: Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P 21/16: Estimation of constants, e.g. the rotor time constant
- H02P 21/50: {Vector control arrangements or methods not otherwise provided for in H02P21/00- H02P21/36}
- H02P 25/024: controlled by supply frequency
- H02P 25/08: Reluctance motors
- H02K 1/246: {Variable reluctance rotors}
- H02K 1/276: Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
- H02K 3/28: Layout of windings or of connections between windings (windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32)
- H02K 19/103: {Motors having windings on the stator and a variable reluctance soft-iron rotor without windings}
- H02K 21/24: with magnets axially facing the armatures, e.g. hub-type cycle dynamos
- H02P 2207/05: Synchronous machines, e.g. with permanent magnets or DC excitation
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

The invention proposes a new motor with separated permanent magnet torque and reluctance torque. Meanwhile, the optimal efficiency control method for this motor is proposed. This invention belongs to the field of motor and its drive system. The proposed motor includes 3 stators and 1 rotor (composed of 2 axial rotors and 1 radial rotor), the radial stator employs distributed winding, the axial stator adopts concentrated winding. The distributed winding and the radial reluctance rotor structure contribute to higher reluctance torque, while the concentrated winding and the surface mount permanent magnet structure offer higher permanent magnet torque. In the view of the magnetic circuit, the axial magnetic circuit generates the permanent magnet torque, and the radial magnetic circuit generates the reluctance torque. By using the decoupling of axial and radial magnetic circuits, the separation and the independent control of the permanent magnet torque and the reluctance torque are realized. Each stator and rotor of the invention can be processed independently, and the modular installation can be processed, thereby reducing the difficulty of the motor processing.

## Claims

### Claim at position 1

1-10. (canceled)

### Claim 11

A motor with separated permanent magnet torque and reluctance torque, said motor comprising a casing, a radial motor inside the casing, a first axial motor and a second axial motor, the radial motor comprising the first axial motor and the second axial motor, respectively;
wherein the radial motor comprises a radial stator and a radial rotor, wherein an integer slot distributed winding is adopted in the radial stator and a synchronous reluctance rotor is employed as the radial rotor, wherein the radial motor is adapted to produce only reluctance torque;
wherein the first axial motor comprises a first axial stator and a first axial rotor, the second axial motor comprises a second axial stator and a second axial rotor, wherein in the first axial stator and the second axial stator, fractional slot concentrated windings are used;
surface mounted permanent magnets are fixed on the second axial rotor and the first axial rotor, said permanent magnets having excitation directions parallel to an axial direction of the motor, and adjacent permanent magnets have opposite excitation directions, whereupon the axial motor only produces permanent magnet torque; and
the radial motor is adapted for either an inner rotor or an outer rotor structure, the first axial motor and the second axial motor, the first axial stator and the first axial rotor being interchangeable in positions along the axial direction, and the second axial stator and a second axial rotor being interchangeable in positions along the axial direction, whereupon the radial motor generates radial flux, while the first axial motor and the second axial motor generate axial magnetic flux, and the radial flux and axial flux are perpendicular to each other, resulting in the decoupling of radial flux and axial flux.

### Claim 12 (depends on 11)

The motor of claim 11, characterized by one or more of the following features:
the radial motor is an inner rotor structure;
the inner ring of radial rotor is a shaft, the inner ring of radial stator is the radial rotor, and there is a radial air gap between them;
the two sides of the end of radial rotor are connected with a first axial rotor and a second axial rotor, respectively;
the first axial stator and the second axial stator are arranged on an outermost layer of the first axial rotor and the second axial rotor, respectively;
the permanent magnets on the first axial rotor and the second axial rotor are arranged on the side respectively close to the first axial stator and the second axial stator; and
the radial stator, the first axial stator and the second axial stator are mounted on the casing.

### Claim 13 (depends on 11)

The motor of claim 11, characterized by one or more of the following features:
the radial motor is an outer rotor structure, and the radial rotor is adapted to be directly installed in the wheel to form a hub structure;
the inner ring of radial stator is the radial rotor, and there is a radial air gap between them;
the two sides of the end of the radial rotor are set with a first axial rotor and a second axial rotor respectively;
the first axial stator and the second axial stator are arranged on the outermost layer of the first axial rotor and the second axial rotor respectively;
the permanent magnets on the first axial rotor and the second axial rotor are arranged on the side respectively close to the first axial stator and the second axial stator respectively; and
the radial stator, the first axial stator and the second axial stator are connected to the shaft.

### Claim 14 (depends on 11)

The motor of claim 11, characterized by one or more of the following features:
the radial motor is an inner rotor structure;
the inner ring of radial rotor is a shaft;
the inner ring of radial stator is set with a radial rotor, and there is a radial air gap between them;
the first axial stator and the second axial stator are placed along the axial direction, while the radial stator is nested in the core of the stator and the second axial stator along the axial direction;
the first axial rotor and the second axial rotor are arranged on the outermost layer of the first axial stator and the second axial stator respectively;
the permanent magnets on the first axial rotor and the second axial rotor are fixed on the side close to the first axial stator and the second axial stator respectively;
the first axial stator and the second axial stator are arranged on the casing; and
the radial rotor, the first axial rotor and the second axial rotor are connected with the shaft.

### Claim 15 (depends on 11)

The motor of claim 11, wherein
the rotor structure of the radial rotor comprises a shape rotor, a V type rotor, a multi-layer air slot rotor or a switched reluctance rotor structure; and
the permanent magnets are surface mounted, surface inlay and Halbach array, and the surface sticking coefficient of the permanent magnet ranges from 0.8 to 1.

### Claim 16 (depends on 11)

The motor of claim 11, wherein
the radial stator comprises an integer slot distributed winding structure: the number of slots and the number of poles need to meet the formula q=S/(2*P*m), and the value of q is integer; and
the second axial stator and the first axial stator comprise a fractional slot concentrated winding structure: the number of slots and the number of poles need to meet the formula S=2 P±2, wherein m is the phase of motor, S is the slot number of motor, p is the pole of motor, q is the number of slots per pole of motor.

### Claim 17 (depends on 12)

The motor of claim 12, wherein an outer diameter of the radial rotor is larger than that of the first axial rotor or the second axial rotor, wherein outer ratio of diameters between the first axial rotor and the radial rotor preferably is in the range from 0.7 to 0.9.

### Claim 18 (depends on 11)

The motor of claim 11, wherein outer diameters of the second axial rotor and the first axial rotor are equal, while an outer diameter of the radial rotor is unequal to an outer diameters of the first axial rotor and the second axial rotor, and wherein the ratio of outer diameters between the radial rotor and the first axial rotor or the second axial rotor is fixed, the ratio of axial thickness between the radial rotor and the first axial rotor or the second axial rotor is in the range from 0.2 to 0.8.

### Claim 19 (depends on 11)

The motor of claim 11, characterized by one or more of the following features:
the control method is divided into three regions: the first section is the low speed region, the middle and the high speed area is the second region, the third region is the high speed area;
in the first region, permanent magnet torque is used as the main driving torque, and the torque produced by second axial stator, the first and second axial stator axial rotors, and the first axial rotor plays a leading role;
in the second region, the permanent magnet torque and the reluctance torque are the driving torque together, and the radial motor, the first axial motor and the second axial motor are all involved to provide output torque;
in the third region, the reluctance torque is adopted as the main driving torque, the torque produced by the radial stator and radial rotor plays a dominant role, and the axial stator and rotor is adapted to be used to charge the power source if the permanent magnet torque is not needed in the drive system; and
an optimal efficiency control of a single radial motor or a first axial motor or a second axial motor are achieved, wherein a first relationship between dq currents and the inductances of the motor is built with the help of finite element software, a second relationship between them and iron loss is built, and, on a basis of the first and second relationships, an operation point of maximum efficiency is determined by adjusting the current angle, wherein an essence of searching for maximum efficiency point is to find the right current angle for maximum efficiency, and the current angle is modified by searching the maximum efficiency point until the right current angle is found.

### Claim 20 (depends on 19)

The motor of claim 19, wherein optimal efficiency control for the motor is achieved as follows:
A Step 1, in which a simulation results of a finite element model, the polynomial fitting is used to construct the polynomial relationship between the quadrature axis and the direct axis inductance (Lq and La) and the quadrature axis and the direct axis current (iq and id) of the motor;
A Step 2, in which stator iron loss of the motor is modeled, and a relationship between (Pfe) and (La), (Lq), (id) and (iq) is established;
A Step 3, in which using the motor iron loss model and the d, q axis voltage equation of the motor, an equivalent resistance of the iron loss (RFe) is calculated;
A Step 4, in which the given current (is) and current angle (γ), the currents of d- and q-axis (id, iq) are calculated;
A Step 5, in which a fitting polynomial with the given id and iq, the inductances of d- and q-axis (La, Lq) are calculated;
A Step 6, in which inductances of d- and q-axis obtained by step 5, the voltages of d- and q-axis are calculated;
A Step 7, in which currents and voltages of d- and q-axis, the input and output powers are calculated; and
A Step 8, in which motor efficiency is calculated and judged whether it is the biggest, and if it is, the currents of d- and q-axis is obtained; and if it is not, the current angle is modified and the process returns to Step 4 and repeated.