RU121405U1 - Brushless motor - Google Patents

Abstract

1. Brushless DC motor, including: an internal stator with electromagnets, the cores of which are parallel to the axis of rotation of the electric motor, an external rotor separated from the stator by an air gap and containing two identical circular magnetic circuits located on both sides of the stator, each of which includes evenly spaced along circumference permanent magnets with alternating magnetic field direction, rotor position sensors, electromagnet control unit, characterized in that the number of phases of the electric motor can be any number from the series N = 2, 3, 4, 6; the number of electromagnets is a multiple of the number of phases, and they are all separated by an air gap and have an independent connection to the control unit; the number of permanent magnets on each magnetic circuit is even, not a multiple of the number of phases, more than the number of electromagnets and not a multiple of their number; the number of rotor position sensors is not less than the number of phases. ! 2. An electric motor according to claim 1, characterized in that it has three phases, 9 electromagnets and 12 or 24 permanent magnets on each of the magnetic circuits. ! 3. The electric motor according to claim 1, characterized in that it has 4 phases, 12 electromagnets, the number of permanent magnets is selected from a number of numbers m = 18, 20, 26, 30, 34.! 4. An electric motor according to claim 1, characterized in that the number of phases N is even and the number of rotor position sensors is equal to N.! 5. An electric motor according to claim 1, characterized in that the number of phases N is odd and the number of rotor position sensors is equal to N + 1. ! 6. The electric motor according to claim 1, characterized in that the control unit provides sinusoidal supply to the electromagnets

Description

The utility model relates to the field of DC motors, in particular gearless brushless low voltage electric motors, and can be used as motor wheels in vehicles: electric scooters, motorcycles, electric cars, etc., as well as in other areas of technology .

The most promising for individual electric vehicles are gearless motor wheels, in which the rotation of the wheel is caused directly by the electromagnetic interaction of the magnetic systems of the rotor and stator. Such engines are environmentally friendly, compact, economical, simple and easy to operate.

Two constructive approaches are known in the creation of motor wheels: these are collector electric motors in which permanent magnets are located on the stator, and electromagnets and sliding current collectors are mounted on the rotor, which provide electrical contact with the plates of the electric collector (US 6384496 B1, 05/07/2002; US 6617746 B1 09.09.2003; RU 2129965 C1, 05/10/1999; RU 2172261 C1, 08.20.2001); and brushless motors containing an external stator with permanent magnets and a rotor with electromagnets powered from the control unit by a signal from the rotor position sensors (RU 2091969 C1, 09.27.1997; US 6727668 B1, 04/27/2004; US 6762525 B1, 07/13/2004; US 6791226, 09/14/2004; US 6853107 B2, 02/08/2005; RU 2265271 C1, 11/27/2005; RU 2343620 C2, 01/10/2009).

Brushless motors in a number of applications have advantages over brush motors, due to the absence of slip of conductive elements and greater control flexibility.

Such engines have already found their application, but there are a number of areas in which it is possible to improve their operational. Traditionally, high-torque, low-speed motor-wheel motors have lower efficiency than high-speed electric drives. This is due to an increase in the total resistance due to an increase in the number of turns on the windings. At the same time, heat generation increases and the task of cooling the electric motor arises.

Increasing the efficiency and increasing the torque is carried out by optimizing the control system (US 6727668 B1, 04/27/2004; US 6791226, 09/14/2004) and enhancing the magnetic flux by choosing the number and location of magnets and electromagnets, as well as manufacturing special-shaped cores (US 6762525 B1, 07/13/2004). All this leads to a complication of production and does not solve the final task.

Another problem in the operation of gearless electric motors in vehicles is the presence of "dead zones" and the non-optimality of their work in a wide dynamic range, especially in start / stop modes. A partial solution to this problem will be the use of several electric motors on one vehicle, each of which is optimized for its dynamic range. For example, in patent RU 2290328 dated December 27, 2006, an all-wheel drive vehicle with an accelerating and marching engine of the motor-wheel type is described. But such a solution also complicates the design and has limited application.

This utility model is aimed at creating a low-speed gearless electric motor with a universal, relatively simple design, and suitable for use in various operating conditions.

The technical result from the use of this utility model is a simultaneous increase in efficiency, due to the optimization of electromagnetic interactions; improving energy efficiency through energy recovery; improvement of work in start / stop modes; improving the manufacturability and reliability of the electric motor.

The claimed technical result is achieved in that the brushless DC motor includes: an internal stator with electromagnets, the cores of which are parallel to the axis of rotation of the electric motor; an external rotor separated from the stator by an air gap and containing two identical circular magnetic cores located on both sides of the stator, each of which includes permanent magnets evenly spaced around the circumference with alternating directions of the magnetic field; rotor position sensors; control unit for electromagnets. The number of phases of the electric motor can be any number from the series N = 2, 3, 4, 6 and depends on the area of its application. The number of electromagnets is a multiple of the number of phases, all of which are separated by an air gap and have an independent connection to the control unit. The number of permanent magnets on each magnetic circuit is even, not a multiple of the number of phases, greater than the number of electromagnets and not a multiple of their number. The used ratio of the number of permanent magnets and electromagnets, as well as the constructive separation of the cores, creates geometrically conditions that allow obtaining the most uniform magnetic flux in the core body. This makes it possible to significantly increase the value of the motor torque without increasing the number of turns and, accordingly, to do without additional power losses due to heat generation and without reducing the efficiency. The number of rotor position sensors is always no less than the number of phases. Preferably, in the case of an even number of phases N, the number of rotor position sensors is also equal to N. In the case of an odd number of phases N, the number of rotor position sensors will be N + 1. This design allows you to avoid "dead zones" and jerking when starting.

On light vehicles (bicycle, scooter) three-phase electric motors are usually used. Moreover, they will contain 9 electromagnets and 12 or 24 permanent magnets on each of the magnetic cores. For vehicles for other purposes, motors with a large number of phases can be used. For example, a 4-phase electric motor containing 12 electromagnets and permanent magnets, the number of which is selected from a number of numbers m = 18, 20, 26, 30, 34.

In any case, all electromagnets are independently connected to the control unit. It provides a sinusoidal control signal to the electromagnets, the phase displacement of which can dynamically change in the range from - 60 to 0 phase degrees.

With a significant number of electromagnets, they through the control unit can be combined into groups whose number is equal to the number of phases. A single control signal is applied to each group. Within a group, electromagnets can be connected in series or in parallel. The switching of the electromagnets is carried out by the control unit, and can occur in dynamic mode.

To implement the recovery mode, each of the windings of the electromagnets is connected to the power supply circuit through a diode bridge. Moreover, all the electromagnets in the group are connected in series. For the efficiency of the recovery process, it is preferable that the diode bridge contains two diodes with a speed of 40 to 200 ns and two capacitors with a capacity of 3000 to 10000 microfarads.

The essence of this utility model is illustrated by the following drawings:

Figure 1 presents a side view of the inventive electric motor;

Figure 2 presents a diagram of a three-phase electric motor;

Figure 3 (a) and (b) presents a diagram of control signals for a 3-phase electric motor;

Figure 4 presents the electrical circuit of the phase switching according to the type of "triangle" and "star" for a 3-phase electric motor;

Figure 5 presents the efficiency of the electric motor depending on the control method;

Figure 6 shows a diagram of energy recovery for a 3-phase electric motor.

The inventive electric motor (Figure 1) includes an internal stator 1 with electromagnets 2, the cores 3 of which are parallel to the axis of rotation of the electric motor. The electromagnets are fixed using brackets 4 made of a material with low magnetic conductivity, on a fixed axis 5 of the electric motor. Sensors 6 of the position (DP) of the rotor are also located on the stator.

In the design of the electric motor, rectangular cores 3 are usually used with mounting in grooves on the stator 1. The shape of the core eliminates the direct binding of its dimensions to the diameter of the electric motor and makes it possible to make it type-setting from pin plates. This technology allows you to create various universal electric drives by dialing the right amount of identical solenoids, which greatly improves the unification of design elements and reduces the cost of production.

The external rotor 7 is separated from the stator by an air gap and contains two identical circular magnetic circuits 8 'and 8 "located on both sides of the stator 1. Permanent magnets 9 with alternating direction of the magnetic field are uniformly placed on each of the magnetic circuits.

Each of the electromagnets is independently connected to a control unit (CU) (not shown in the figure), and position sensors 6 are also connected to it. The switching wires are usually located between the brackets 4. The control unit can be located both inside and outside the electric motor.

Typically, the entire electric motor is placed in a rotating housing 10 and is closed by a cover 11. They are made of a material with low magnetic conductivity. To ensure uniform rotation and smooth running, the housing together with the cover is mounted on bearings 12 on axis 5.

The number of phases of the electric motor is chosen equal to 2, 3, 4 or 6, depending on its functional purpose. The number of electromagnets 2 in this case is a multiple of the number of phases. The number of permanent magnets 9 on each magnetic circuit is even, not a multiple of the number of phases, greater than the number of electromagnets and not a multiple of their number.

It is known that the magnitude of the motor torque linearly depends on the total number of turns of each phase of the motor and the magnetic flux closed through the cores of the electromagnets. At the same time, the maximum speed is inversely proportional to the number of turns. Traditionally, high-torque, low-speed motor-wheel motors have lower efficiency than high-speed electric drives. This is due to the need to increase the number of turns on the motor windings to increase the magnetic. At the same time, the total electrical resistance of the windings increases, heat dissipation increases, and the useful power of the electric drive decreases. With a significant increase in magnetic flux, the problem arises of magnetic saturation of the material of the magnetic cores, which does not allow a linear increase in magnetic flux depending on the magnitude of the current consumption, which leads to an additional decrease in the efficiency of the electric machine. As our studies have shown, in well-known schemes of electric motors with a common magnetic core, saturation has a local character and a large uneven distribution of magnetic lines of force over the volume of the magnetic circuit, which significantly reduces the overall magnetic conductivity of the core.

In the motor design proposed here, the ratio of the number of permanent magnets and electromagnets used, as well as the constructive separation of the cores, creates geometrically conditions that allow obtaining the most uniform magnetic flux in the core body. This makes it possible to significantly increase the value of the motor torque without increasing the number of turns and, accordingly, to do without an increase in heat loss due to heat generation and without reducing the efficiency.

Figure 2 presents a diagram of a three-phase electric motor, in which the number of electromagnets 2 is 3, and the number of permanent magnets 9 is 4. The number of DP 6 will be 4, one more than the number of phases. All electrical elements of the device are connected to the control unit 13.

The control unit receives signals from rotor position sensors located in the electric motor. The number of main sensors is equal to the number of phases N, plus in the case of an odd number of phases, one additional sensor is used. The sensors 6 are offset relative to each other by an angle of 360 / N phase degrees, and relative to electromagnets by 180 / N phase degrees. For a 3-phase electric motor, the angle between the sensors will be 120 phase degrees, and the angle of displacement relative to the solenoids will be 60 phase degrees (Figure 3 (a), (b)). Figure 3 (a) presents diagrams of the signals of HA, HB, HC from the sensors corresponding to phases A, B, C and the signal from the additional HD sensor. Figure 3 (b) presents the output signals of PA, PB, PC with control unit for the corresponding phases.

The shift of the signal up to 60 degrees depends on the load and speed. The offset is calculated by the controller and changes constantly when the motor is running.

One of the important applications of gearless electric drives is electric wheelchairs. The disadvantages of the traditional scheme include asymmetry of the holding moment in the mode of fixing the rotor in a certain position (electromagnetic brake). If you try to rotate the rotor by external forces clockwise and counterclockwise, the holding moment of the electric motor will be different. This is due to the fact that symmetrical holding of the rotor with minimal energy consumption is possible only at the dead points of the electric motor. The fronts of the change in the signals of any of the sensors are 180 / (2 * N) phase degrees from the dead points of the solenoids, and do not provide information about the passage of the dead point. To solve this problem, in this utility model, an additional rotor position sensor is used. The signal of this DP changes when the axis of the magnetic field of the solenoid and the axis of the magnetic field of the corresponding magnet intersect, i.e. strictly in the dead spots of the motor. Also, information about blind spots allows you to implement more advanced algorithms for the operation of the switching device and practically eliminate the characteristic jerks when starting the electric motor with overload, significantly improve the characteristics of the electric motor at startup.

An electric motor with separate connection of solenoids to the control unit allows greater flexibility in the choice of modes of its rotation, as well as the implementation of effective recovery of kinetic energy. For each electric motor, there is a torque constant K _t (Nm / A) and a constant frequency of rotation K _v (rpm / V). They are determined by the combination of design features of the electric motor. Separate control of the solenoids allows you to change the constants of the electric machine at the level of the control system.

To obtain the maximum value of K _t and the minimum value of K _v in the start mode from a standstill and to reduce the amount of current consumed, the control unit provides a star-type phase connection. The maximum voltage in this case at each phase is V _P = V / (N-1), where V is the voltage of the power source, N is the number of phases of the electric motor. Phase switching of the type "triangle" allows you to get a higher value of K _v and, accordingly, a higher rotational speed at a fixed supply voltage. In cruising mode and in maximum speed mode, separate phase control with voltage on each phase V _P = V is used.

Figure 4 presents the electrical diagram of the phase switching for a 3-phase electric motor, with phases A, B, C. When the keys 23 and 24 are open, the keys 21-32 work, changing the polarity of the corresponding phase. This is a separate phase connection, when each works independently. When connecting keys 33 and 34, keys 27-32 are excluded from work, and only left keys 21-26 work and a star connection is obtained.

In the design of an electric motor with a large number of solenoids, it is possible that they are combined into groups with selected switching within the group (parallel or serial). If we take the fixed values of K _t and K _v when all the solenoids are connected in parallel in one phase of the electric drive, then when they are switched in series, the new values are K _t1 = K _t * N _p , K _vi = K _v / N _p , where N _p is the number solenoids in one phase of the electric motor. Thus, during operation, it is possible to choose between obtaining the maximum torque at the start and N _p times reducing the current consumption in this case, or increasing N _p times the motor speed. All intermediate values are also achievable. It is also important that the range of rotation frequencies at which the maximum values of efficiency are achieved are also directly dependent on the constants K _t and K _v . Figure 5 presents the dependence of the values of the efficiency of the electric motor on the speed with various switching methods. Index (a) indicates the efficiency curve for connecting phases in the form of a star, when all the windings inside the phase are connected in series; by index (b) - parallel connection of phases, when inside the phase all windings are connected in series; index (c) - parallel connection of phases, when inside the phase all windings are connected in parallel. By changing the way of switching in the process of increasing the number of revolutions, it is possible to reach maximum efficiency values all the time. This control method significantly extends the range of efficient operation of the electric machine, reducing the integrated power consumption during actual operation.

The implementation of the inventive model also allows you to effectively recover the kinetic energy of the vehicle. In this mode, all the solenoids of each phase are connected in series, and the generated voltage is rectified by separate diode bridges. The outputs of the diode bridge circuit of all phases are also connected in series.

Energy recovery to the power source is possible only if the generation voltage is higher than the voltage of the power source. In classic electric machines with a fixed Kv value, this is only possible when the electric motor has a speed higher than the maximum idle speed with this power source. In practice, this means the possibility of recovery only at a vehicle speed above the maximum speed that it can independently develop. The switching method proposed in the utility model solves this problem. Figure 6 shows a schematic diagram of a rectifier for a 3-phase electric motor. Phase windings are indicated on the diagram by the indices A, B, C. For effective operation of the electrical circuit, it is preferable to use diodes with a speed of 40 to 200 ns and capacitors with a capacitance of 3,000 to 10,000 uF.

If we take the constant value for the reference point K _v when all the solenoids are connected in phase in parallel, and the maximum rotation speed value is n _max = K _v * V, where V is the voltage of the power source, then the maximum generated voltage of the whole circuit will be V _g = N * N _p * n / K _v , where N is the number of phases of the electric motor, N _{p is the} number of solenoids in the phase, n is the frequency of rotation of the electric motor, K _v is the constant of rotation frequency. The voltage V _g can be higher than the voltage of the power source V already at a speed of n> n _max / (N * N _p ). For example, for a 4-phase electric motor with the number of solenoids in the phase N _p = 5, recovery is possible at a speed of n = 0.05 * n _max . On low-power electric drives (up to 500 W), it is possible to introduce a voltage doubler with capacitors into the rectifier stages of each phase, which allows a 2-fold increase in the generated voltage and, accordingly, a further 2-fold reduction in the minimum regeneration speed.

Technologically, the design of an electric drive with separate switching of all solenoids entails the connection of a large number of conductors to a switching device (control unit). Due to the compactness of the electric drive with the axial direction of the field, it is possible to place the switching device in one housing with an electric machine, while maintaining high adaptability, ease of assembly and operation of the entire system. Implementation Examples:

Example 1

3-phase electric drive containing 30 electromagnets and 40 pairs of permanent magnets. Each electromagnet contains 67 turns of wire with a diameter of 1 mm. The power supply voltage of the electric drive is 36 V. The rated power of the electric motor is 350 W, the rated torque is 12 Nm at a nominal speed of 280 rpm. Rated current 10 A. Maximum power 530 W at 190 rpm. Starting torque 38 Nm, starting current 16 A. Maximum current consumption 27A. The frequency of rotation of idling is 320 rpm. The maximum efficiency of the electric motor is 91%. Electric motor weight 4.9 kg, outer diameter 210 mm, width 65 mm. This electric motor was mounted on a bicycle with a diameter of 26 inches, LiFePO ₄ batteries of 36 V 12 A * h were used, while testing the bicycle showed a maximum speed of 37 km / h. Mileage on one battery charge at an average speed of 35 km / h amounted to 44 km, which corresponds to an energy consumption of 9.8 W * h / km

Example 2

3-phase electric drive containing 9 electromagnets and 12 pairs of permanent magnets. Each electromagnet contains 120 turns of wire with a diameter of 1.3 mm. The power supply voltage of the electric drive is 48 V. The rated power of the electric motor is 1100 W, the rated torque is 22 Nm at a rated speed of 580 rpm. Rated current 30A. Maximum power 1500 W at 380 rpm. Starting torque 48 Nm, starting current 40 A. Maximum current consumption 60 A. Frequency of rotation of idling 770 rpm. The maximum efficiency of the electric motor is 93%. The mass of the electric motor is 5.7 kg, the outer diameter is 220 mm, the width is 65 mm. This electric motor was installed on an electric scooter with a wheel diameter of 16 inches, LiFePO ₄ batteries were used 48 V 18 A * h, during testing the scooter showed a maximum speed of 53 km / h. Mileage on one battery charge at an average speed of 45 km / h was 68 km, which corresponds to a power consumption of 12.6 W * h / km

Example 3

4-phase electric drive containing 32 electromagnets and 50 pairs of permanent magnets. Each electromagnet contains 120 turns of wire with a diameter of 0.7 mm. The power supply voltage of the electric drive is 24 V. The rated power of the electric motor is 150 W, the rated torque is 22 Nm at a rated speed of 65 rpm. Rated current 8 A. Maximum power 165 W at 45 rpm. Starting torque 57 Nm, starting current 16 A. Maximum current consumption 18 A. Idling speed 100 rpm. The maximum efficiency of the electric motor is 92%.

The mass of the electric motor is 5.8 kg, the outer diameter is 260 mm, the width is 60 mm. Two of these motors were installed on an electric wheelchair with a wheel diameter of 23 inches, LiFePO ₄ batteries were used 24 V 12 Ah, while testing the wheelchair showed the following technical characteristics: the maximum overcome lift with a mass of 140 kg is 30% (-20 degrees) , the maximum speed on a horizontal surface is 9 km / h. The run on one battery charge at a constant speed of 5 km / h was 41 km, which corresponds to the total energy consumption of two electric motors 7 W * h / km

Claims (10)

1. Brushless DC motor, including: an internal stator with electromagnets, the cores of which are parallel to the axis of rotation of the electric motor, an external rotor separated from the stator by an air gap and containing two identical circular magnetic cores located on both sides of the stator, each of which includes evenly spaced circles permanent magnets with alternating directions of the magnetic field, rotor position sensors, control unit of electromagnets, characterized by That the number of motor phases may be any number of a series of N = 2, 3, 4, 6; the number of electromagnets is a multiple of the number of phases, all of which are separated by an air gap and have an independent connection to the control unit; the number of permanent magnets on each magnetic circuit is even, not a multiple of the number of phases, greater than the number of electromagnets and not a multiple of their number; the number of rotor position sensors is not less than the number of phases. 2. The electric motor according to claim 1, characterized in that it has three phases, 9 electromagnets and 12 or 24 permanent magnets on each of the magnetic cores. 3. The electric motor according to claim 1, characterized in that it has 4 phases, 12 electromagnets, the number of permanent magnets is selected from a number of numbers m = 18, 20, 26, 30, 34. 4. The electric motor according to claim 1, characterized in that the number of phases N is even and the number of rotor position sensors is N. 5. The electric motor according to claim 1, characterized in that the number of phases N is odd and the number of rotor position sensors is N + 1. 6. The electric motor according to claim 1, characterized in that the control unit provides a sinusoidal control signal to the electromagnets, the phase displacement of which can be dynamically changed in the range from -60 to 0 phase degrees. 7. The electric motor according to claim 1, characterized in that the electromagnets through the control unit can be connected in groups, the number of which is equal to the number of phases. 8. The electric motor according to claim 7, characterized in that the control unit provides switching between serial or parallel switching of the electromagnets in the group. 9. The electric motor of claim 8, characterized in that during serial switching, each of the windings of the electromagnets is included in the power circuit through a diode bridge. 10. The electric motor according to claim 9, characterized in that the diode bridge contains two diodes with a speed of 40 to 200 ns and two capacitors with a capacity of 3000 to 10000 μF.