RU2797718C1 - Generator for wind turbine - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: generator for a wind power plant comprises a bearing cover mounted in the centre of the round part of the housing to fix the bearing inside the generator. Inside the generator housing, two round-shaped rotor disks are mounted, along the circumference of which, in the form of a ring, with equal pitch, round-shaped magnets made of ferrimagnetic metal are placed. A round-shaped stator is mounted between the rotor discs on a common shaft, along the stator circumference on both sides, in the form of a ring, stator coils are placed. The stator coils are trapezoidal with rounded corners and holes in the central part. The holes in the central part of the stator coils are also trapezoidal with rounded corners, the smaller bases of the trapeziums of the stator coils and their holes face the stator centre. Round magnets are mounted on the sides of the rotors facing the stator. At the same time, an electric generator with a permanent magnet rotor does not have a collector and brushes.

EFFECT: increased reliability and operating time without maintenance and repair while reducing the dimensions.

1 cl, 1 dwg

Description

Generator for wind power plant refers to power generators for wind farms, power [H02K1/02, H02K1/27, H02N11/00, H02K53/00, H02K21/22].

Known in the prior art is Neodymium Iron Boron RARE EARTH STRONG MAGNETIC POWER CYCLE AND POWER GENERATION SYSTEM [CN108365734 (A) - 2018-08-03], which discloses a strong magnetic power generation system based on neodymium, iron, boron and rare earth elements . The system is characterized by a superconducting smart switch, a superconducting smart circulator, a superconducting rotor magnetic energy generator, and a rotor consisting of two to eight permanent magnets. The neodymium-iron-boron-rare earth strong magnetic power generation system comprises a case, within which a stator is installed; at the other end, inside the casing, there is a linear battery with an output voltage (220V / 380V); two ends of the central shaft are equipped with high-precision bearings; a flywheel and a gear are installed at one end of the central shaft; the rotor is equipped with a central shaft; the stator receives electrical energy when a permanent magnet generates electromagnetic induction through a positioned coil, and a permanent magnet with the same direction as the magnetic force is mounted on the rotor. Neodymium iron boron rare earth strong magnetic power cycle power generation system is simple, long life, high temperature resistant, high power conversion efficiency and wide application range, and the power conversion efficiency can reach 99% or higher. The disadvantage of this technical solution is the high weight and size requirements for its implementation.

Also known from the prior art is a PERMANENT MAGNET MOTOR [CN206595792 (U) - 2017-10-27], which refers to the technical field of the drive device, in particular, refers to a permanent magnet motor, including a housing, a setting rotor in a housing, a permanent magnet and the stator, the rotor uses non-magnetic materials, the material of the permanent magnet is neodymium-iron-boron, extremely alternative setting of the extreme point N, S is pressed against the permanent magnet on the surface of the rotor, which is equipped with an excitation coil and a power generation coil on the stator, the excitation coil includes independent excitation coil from a plurality of groups, the power generation coil includes several groups of coils that independently generate electricity, independent excitation coil with independent power generation, coil spacing adjustment and uniform arrangement in the stator, this permanent magnet motor can supply AC current, for movement, light and magnetic conductivity are not qualities of the rotor, and are further used to generate permanent magnetism. The disadvantage of this technical solution is the complexity and low reliability of the design.

The closest in technical essence is ELECTRIC MACHINE [RU2544914 (C1) - 2015-03-20 REGION], which contains a stator support housing, a lamellar stator core with slots for accommodating stator winding coils, a rotor including a housing and an inductor, and a bearing assembly. The support body is made in the form of a cylindrical barrel with the middle part of the side wall, provided with a cylindrical ledge fixed on it for the stator core. The stator is located inside the cylindrical cavity of the rotor. The rotor contains a housing and an inductor coil, which contains permanent magnets and non-magnetic wedges alternating along the perimeter. The rotor housing contains a shell made of a material with high magnetic conductivity and two removable discs made of non-magnetic material, connected by their edges to the shell and facing each other with their cavities. The inductor coil is located in the peripheral zone of the rotor housing, and its permanent magnets and non-magnetic wedges are made in the form of strips oriented along the longitudinal axis of the rotor and installed so that they form a composite ring with alternating polarity of the magnet poles made of neodymium-iron-boron material, while the strips magnetized radially. The technical result is a simplification of the design and an increase in reliability.

The main technical problem of the prototype is the weight and size requirements for the device with low remaining reliability of the device.

The objective of the invention is to eliminate the technical problem of the prototype.

The technical result of using a generator for a wind power plant is to increase its reliability and operating time without maintenance and repair while reducing its dimensions.

The claimed technical result is achieved due to the fact that the generator for a wind power plant contains a bearing cover mounted in the center of the round part of the housing for fixing the bearing inside the generator, inside the generator housing two round rotor disks are mounted, around the circumference of which, in the form of a ring, with equal step, round-shaped magnets made of ferrimagnetic metal are placed, a round-shaped stator is mounted between the rotor disks on a common shaft, around the circumference of the stator on both sides, in the form of a ring, the stator coils are placed, the stator coils are made of a trapezoidal shape with rounded corners and holes in the central parts, the holes in the central part of the stator coils are also made of a trapezoidal shape with rounded corners, the smaller bases of the trapezoid of the stator coils and their holes face the center of the stator, the round magnets are mounted on the sides of the rotors facing the stator.

Brief description of the drawings

Figure 1 schematically shows a General view of the generator.

Figure 1 indicates: 1 - bearing cover, 2 - part of the housing, 3 - bearing, 4 - rotor disk, 5 - tablet magnets, 6 - shaft, 7 - stator, 8 - stator coils.

Implementation of the invention

The generator for a wind power plant (Fig. 1.) contains a bearing cover 1 mounted in the center of the round part of the housing 2 to fix the bearing 3 inside the generator. Inside the generator housing, two circular rotor disks 4 are mounted, along the circumference of which tablet magnets 5 are placed with equal pitch, made in the form of small round magnets made of ferrimagnetic metal. Tablet magnets 5 are placed in such a way that they are located near the outer edge of the rotor disk 4, while not being located in the central part of the rotor disk 4, thereby forming a ring of magnets on the rotor disk 4. Between the rotor disks 4 on a common shaft 6 is mounted stator 7 is round. Along the circumference of the stator 7, stator coils 8 are placed on both sides. The stator coils 8 are trapezoidal with rounded corners and holes in the central part. The holes in the central part of the stator coils 8 are also made of a trapezoidal shape with rounded corners along the inside. The stator coils 8 are mounted around the circumference of the stator 7 at its edge, forming a ring of stator coils 8. The smaller bases of the trapezoids of the stator coils 8 and their internal holes face the center of the stator 7. Magnet tablets 5 are mounted on the sides of the rotors 4 facing the stator 7 .

The invention is used as follows

The most appropriate solution for the generator of a power wind turbine is an electric generator with a rotor 4 on permanent magnets (magnet tablets 5). One of the ways to solve it is a multi-pole electric generator with a rotor 4 of a sufficiently large diameter. The rotor 4 of the generator in this case can be made using permanent magnets. An electric generator with a permanent magnet rotor does not have a collector and brushes, which can significantly increase its reliability and operating time without maintenance and repair. The use of permanent magnets with high values of residual induction and coercive force can significantly improve the electrical characteristics of the generator or reduce its dimensions.

Strong permanent magnets are mounted on the rotor 4 to create a permanent magnetic field and the generated electricity is taken from the coils of the stator 8 without the use of collectors, slip rings or brushes.

Permanent magnets (tablet magnet 5) can be mounted on the rotor disc 4 made of ferrimagnetic metal to reduce costs.

The principle of operation of permanent magnet generators is similar to a synchronous generator, except that permanent magnet generators can operate asynchronously. The advantages of permanent magnet generators include the elimination of the commutator, slip rings and brushes so that the machines are strong, reliable and simple. The use of permanent magnets removes the winding field (and associated power losses), but makes field control impossible, and prime cost can be prohibitive for large machines. Because actual wind speeds are variable, permanent magnet generators cannot generate electricity at a fixed frequency. They must be connected to the mains through AC conversion using a power converter. The generated AC power (with variable frequency and magnitude) is first rectified into DC and then converted back into AC power (with fixed frequency and magnitude). It is advisable to use these generators with permanent magnets for direct drive applications. In this case, they can eliminate the problems with the transmission of mechanical motion through the shaft 6, which is the cause of most wind turbine accidents.

The technical result - an increase in reliability with a decrease in dimensions - is achieved due to the fact that stator coils are placed on both sides of the stator circumference, while the stator coils are placed one above the other on different sides of the stator, and the magnet tablets are mounted on the sides of the rotors facing the stator , while the electric generator with a permanent magnet rotor does not have a collector and brushes, which can significantly increase its reliability and operating time without maintenance and repair. At the same time, the specified form and method of placing the stator coils and tablet magnets ensures that the device directly performs its intended functions, namely, the use of a generator for a wind power plant. The shape and method of placement of the stator coils and tablet magnets are selected based on the experiments and the results of mathematical modeling, so as to ensure the required quality of the device, taking into account design changes that increase reliability while reducing the dimensions of the product.

Implementation example

As an example, below is the calculation of the output voltage of an electric generator and its electrical parameters. At the same time, its design is determined by the following data:

1. The outer diameter of the rotor of the electric generator is 0.4 m.

2. Width (or height) of the rotor 0.1 m.

3. Permanent magnets neodymium-iron-boron (Nd-Fe-B), residual induction approx. 0.8 T, coercive force approx. 900 kA/m.

4. Number of poles - 16.

5. Operating speed 4 revolutions per second.

Required to find:

1. Power output.

2. Output voltage for a given winding method.

3. Ways to optimize the generator.

Accepted designations (calculations are carried out in the SI system):

B - magnetic induction in the gap between the magnetic pole and the pole piece of the winding, T

B0 is the amplitude of the magnetic induction in the gap, T

BS is the value of the magnetic induction in the gap, averaged over the area of the pole, T

d is the diameter of the winding wire, m

E - emf of one winding of the generator, V

E0 is the amplitude of the emf of one winding of the generator, V

ED - effective value of the emf of one winding of the generator, V

E _GEN - effective output voltage of the generator (idling voltage), V

f – generator rotation frequency, Hz

j - current density in the wires of the generator windings, A / mm ²

L is the average length of the winding turn, m

n is the number of generator poles

N is the number of winding turns

PMAX is the electric power of the generator in the short circuit mode, W

PV - specific power (power per unit volume) dissipated in the generator windings, W / m ³

R - resistance of one winding of the generator, Ohm

RGEN - generator internal resistance (total winding resistance), Ohm

S is the area of the magnet pole (pole piece of the winding), m ²

t – current time, s T – generator rotation period, s

F - magnetic flux through the core of the winding, Wb

F0 - amplitude (maximum value) of the magnetic flux through the pole piece of the winding, Wb

l is winding packing factor r

E - specific electrical resistance of the winding wire, Ohm⋅m

w - circular frequency of rotation of the generator, rad / s

In accordance with Faraday's law of electromagnetic induction, the voltage at the output of each winding of the generator can be calculated by the formula:

(1)

(1)

We can assume that the magnetic flux through the winding changes according to the harmonic law:

(2)

(2)

where Ф ₀ is the maximum value of the magnetic flux, which can be found by the formula:

(3)

(3)

Then for the effective value of the voltage of one winding we obtain:

(4)

(4)

The effective value of the output voltage of the generator in idle mode (n windings connected in series):

(5)

(5)

For a wire with electric current, the power density (power per unit volume) dissipated in the wire due to the presence of electrical resistance and converted into heat can be found by the formula:

(6)

(6)

The heat dissipation power and, accordingly, the temperature of the winding depend on the current density in the winding. This temperature should not exceed the allowable for this brand of wire. The calculation of the temperature inside the winding and, accordingly, the allowable current density in the windings can be made by the finite element method.

The allowable current density in the winding wires depends on the stator design and cooling conditions, and for this design case it can reach 10 A/mm ² if the packing factor is taken equal to 0.6.

The calculation of the magnetic induction in the gap, as well as the magnetic flux penetrating the winding, can be done in different ways, in particular, by the finite element method.

The magnetic circuits of the axial and radial generators are almost the same: slots are made on the steel stator, into which the windings are laid, permanent magnets of the appropriate size are attached to the steel rotor. There is an interpolar gap between the magnets and the steel cores of the windings, the value of which is determined by the tolerances in the manufacture of generator parts and should be as minimal as possible.

The current density in the windings is 6 A/ ^mm2 , in the wires of the windings it is 10 A/ ^mm2 (packing factor 0.6). The width of the pole is 20 mm, the width of the gap is 5 mm, the depth of the slot for the winding is 10 mm. The gap between the rotor and the stator is 1 mm.

To calculate the output voltage E _GEN according to formula (5), we have: N = (4 x 60 x 0.6) / 2 = 72 turns (a wire with a diameter of 1.6 mm (section 2 mm ² ) is wound into a window measuring 30 x 50 mm ² , packing factor equal to 0.6 BS = 0.75 T S = 0.05 x 0.008 = 0.0004 m ² n ~ (3.14 x 1000) / (8 + 8) ~ 196 w = 6.28 rad / s The output voltage of the generator E _GEN according to formula (5) is equal to 307 volts at a speed of 10 rpm For a copper wire with a diameter of 1.6 mm (section approximately 2 mm ² ), the permissible current value can be 30 A. Then the output power of the generator at a speed of rotation of 1 revolution per second will be approximately 1 kW. Part of the power will be transferred to load, and part - to be dissipated by the internal resistance of the generator windings.To find what part of the power will be transferred to the load, and what part will be dissipated by the internal resistance of the generator windings, it is necessary to calculate the resistance of the windings. The resistance of one winding can be found by the formula:

(7)

(7)

In our case: рE = 1.67 * 10-8 Ohm * m (copper winding wire), d = 1.6 mm L = 2 * (8 + 4 + 50 + 4) * 12 = 1584 mm = 1.584 m. Then the resistance of one winding R ~ 0.0132 Ohm, and the internal resistance of the generator with 196 windings connected in series R _GEN = 72 * 0.0132 ~ 1 Ohm

At a current of 30 A, approximately 1 kW of power will be dissipated in the internal resistance of the generator, and the rest of the power (about 8 kW) will be transferred to the load. The load resistance for a current of 30 A should be equal to (307 / 30) - 2.6 = 7.45 ohms.

At a constant angular velocity of rotation, the output voltage of a multi-pole permanent magnet generator increases in proportion to the square of the number of poles, provided that the area of the pole does not change, that is, either a solid ring magnet of a larger diameter is used, or the number of magnets from which the ring magnet is recruited increases.

An increase in the number of poles when using a ring magnet of given dimensions leads to a decrease in the flux linkage area S in proportion to the increase in the number of poles n. If the number of turns of the coils N remains unchanged, which can be achieved by reducing the diameter of the winding wire, then the output voltage of the generator E _GEN will increase in proportion to the number of poles n.

If the coils are wound with a winding wire of a given diameter, then with an increase in the number of poles (and, accordingly, a decrease in the size of the coil), the number of turns of one coil N decreases. The output voltage of the generator will then remain approximately constant as the number of poles n increases.

The electric power of the generator does not depend on the diameter of the winding wire and grows in direct proportion to the squares of the dimensions of the ring magnet (outer diameter, ring width) and in direct proportion to the number of its poles. Thus, when designing a low-speed electric generator according to the above scheme, it is necessary to use a ring magnet with the maximum possible residual induction, the largest possible outer diameter and the width of the ring with the maximum possible number of poles, selecting, by changing the diameter of the winding wire, the number of turns of the coils so that the output generator voltage was in the required range at given speeds.

It is desirable to wind the coils with a wire with the lowest resistivity (copper) with the highest possible form fill factor (packing factor).

From the above reasoning, we can say that if the number of coils is equal to the number of magnet poles (m \u003d n), then when the coil core is opposite the pole of the ring magnet, due to attractive forces, a large moment of resistance arises, to overcome which a significant force is required (large wind force). Therefore, it is possible to increase or decrease the number of coils per unit (m = n + 1, m = n - 1), which will significantly reduce the amplitude values of the moment of resistance.

In the proposed generator scheme, the use of steel cores in the coils was abandoned; in this case, the moment of resistance in the idle mode will be close to zero at any position of the rotor. Such coils must be made with a minimum height comparable to the gap between the magnet and the coil, so that the decrease in magnetic induction in the gap is not too significant.

This technical solution was implemented in the form of a pilot plant, on which results were obtained confirming a 20 percent increase in reliability.

Claims (1)

A generator for a wind power plant, containing a bearing cover mounted in the center of the round part of the housing for fixing the bearing inside the generator, inside the generator housing, two round-shaped rotor disks are mounted, along the circumference of which, in the form of a ring, with equal pitch, round-shaped magnets are placed, made made of ferrimagnetic metal, between the disks of the rotors on a common shaft a round stator is mounted, around the circumference of the stator on both sides, in the form of a ring, stator coils are placed, the stator coils are made of a trapezoidal shape with rounded corners and holes in the central part, holes in the central part of the stator coils the trapezoid shape with rounded corners is also made, the smaller bases of the trapezium of the stator coils and their holes are turned towards the center of the stator, the round magnets are mounted on the sides of the rotors facing the stator.

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