WO2008143598A2

WO2008143598A2 - Wind generator/motor with double rotors

Info

Publication number: WO2008143598A2
Application number: PCT/TR2008/000034
Authority: WO
Inventors: Ergun Ozakat
Original assignee: MITRA TURIZM INSAAT TICARET VE SANAYI Ltd SIRKETI
Current assignee: MITRA TURIZM INSAAT TICARET VE SANAYI Ltd SIRKETI
Priority date: 2007-05-18
Filing date: 2008-04-10
Publication date: 2008-11-27
Anticipated expiration: 2009-11-18
Also published as: WO2008143598A3

Abstract

The invention relates to a wind turbine (1) used to convert the kinetic energy formed by the wind into the electrical energy, which comprises at least one blade (10) and at least one rotor shaft (14) and a rotor (3) connected onto said rotor shaft (14), a stator (4) having coils inside which said rotor (3) rotates, and at least one generator/motor (2) having at least one secondary stator (16) with thick coils that is activated at high revolutions after the activation of said stator (4), which is the part with the thin coils, at the low revolutions and at least one secondary rotor (15) connected onto said rotor shaft (14), and exhibiting the 3-phase synchronous motor feature upon the application of an alternative voltage with variable voltage and frequency to the 3-phase coils of said stator (4) and/or secondary stator (16).

Description

WIND GENERATOR/MOTOR WITH DOUBLE ROTORS

Technical Field

The present invention relates to the PM (permanent magnet) type motors used in the wind energy generation systems and electric vehicles, employed for the electricity generation in the field of alternative energy.

The invention relates in particular to a low-revolution and low-noise wind generator/motor with multiple vanes and double rotors capable of rotating also at low wind velocities, which is developed for use in the houses, offices, yachts and the similar places where there is the need for electricity and for operation as a motor when an alternative voltage with variable voltage and frequency is applied to the stator coils.

State of the Art

In the present practice, the use of wind energy generation systems has become rather intensive, owing to the acceleration of the studies performed on the wind energy. Wind energy, by virtue of its many properties, is becoming a frequently used energy source in our century, which sees a day by day increasing energy demand. The main properties of the wind energy are its formation as a result of the sun heating up the air to set it into motion, its endless availability in the atmosphere, its low density, its ability to be converted into another energy form, its causing no environmental pollution, and its being a renewable and clean energy source. Wind energy is directly proportional to the cube of the wind velocity. In short, as the wind intensity increases, the wind energy increases with a much higher rate as compared to the wind velocity. Despite the benefit of this fact, the issue to be careful about is the importance to build the rotating part to which the wind turbine is connected and the pole in a form resistant to storms.

Today's wind-energy conversion systems, as in the way of benefiting from the rotational speed and the output energy of the wind turbine, involve the direct supply to the electricity lines or the storage for use when needed. Based on this classification, the fields where the wind turbines will be used are determined and the new development studies are carried out accordingly.

In the existing practice, the turbines used in said wind energy conversion systems comprise a generator connected to a propeller that rotates under the influence of the wind. Wind turbine catches the wind energy by means of its rotating vanes. The area occupied by the vanes as they rotate is an indicator of the collected wind energy. In other words, the collected energy increases with increasing area in square meters. In general, two or three vanes are mounted on a shaft for one rotor. Vanes have an aerodynamic form and the cross-section just as in the airplane wings, and a rotational moment is formed due to the pressure resulting from the difference in the velocity of the air passing below and above the vanes manufactured with two different surface shapes. This is the principle owing to which the airplanes can fly. This is called the Bernoulli principle. Until the invention of this principle, the airplanes were said to be impossible to fly.

Wind generators are generally made with resemblance to the car alternators by today's manufacturers. In fact, they are almost the same with regards to the structure. The rotor of the wind generator according to the invention is equipped with Neodymium type magnets called PM (permanent magnet). Thus, the carbon brushes that are available in the automobile types will not be used. In this model, there is not any part that wears out and becomes defective with time. There has been no need for maintenance in the prototype studies. It is a significant fact that there is no part that needs replacing in time, with the exception of two bearings. It takes a long time for the magnets to loose their feature, as long as the operation is carried out within their tolerances. Magnets are of the type capable of enduring a temperature of 80 - 120 degrees C, depending on the kind of magnet. Since there is no coil and electricity loss in the rotor, no heating will occur. In the existing applications, the rotation usually starts only at the moment the wind velocity reaches 2-3 meters/second. This velocity generally can not be sufficient for charging the batteries. In cases where said wind velocity is 4-5 meters/second, the battery may be charged; hence it is not possible to charge the batteries during the periods of low wind. If the diameter of the turbine vanes are increased, said low winds will also perform generation. However, this will cause an important problem at high winds. Therefore, it is necessary to provide operation within optimum range.

Wind velocity and the rotational speed of the vanes are proportional. The vanes will rotate faster with the increasing wind velocity. The fast rotation of the vanes causes sound and noise. In general, as the number of blades is increased, the rotational speed necessary to perform the same extent of generation will reduce. In our model, owing to the use of a structure with 12 blades, a high torque (rotational moment) is obtained at low revolution and the wind turbine is enabled to run in a very silent manner.

In the state of the art, it is possible to encounter many developments and many applications regarding the wind generators and the energy systems. For example, the application no. WO9929025 relates to a wind energy system, wherein some additional generators are mounted to the system and the improvements are provided in the variable speed systems.

Regarding the delivery of the electricity generated by means of the wind energy systems, the application no. WO9933165 may be mentioned as an example, which includes some developments regarding the delivery of the generated electricity to the electric network. The application no. WO186144, which is another application about the wind energy systems, relates to an apparatus developed for continuous discharge of the electrostatic charge from at least one rotor plate.

Today, there are also the practices involving different methods for generating electricity from the wind energy systems. For example, the application no. WO0215367 relates to a wind energy plant having two rectifiers and two breakers. The application no. WO0242641 relates to a system that tends to reduce to the maximum possible extent the mechanical loads resulting from the excessive wind, in cases of said excessive wind.

Today, various developments are provided for the silent operation of the vanes and such developments are encountered in the relevant applications. For example, the utility model application no. TR 2006 07311 U relates to a structure, which "comprises at least one gearbox attached to the front part of said generator, enabling to obtain maximum efficiency without the need for very fast rotation of said vanes".

When all the previous documents are examined, we observe that the studies have been made for a long time on the wind energy systems and the wind generators and that developments have been provided in many issues. However, each of said provided improvements relates to different purposes, and there exists no. application, which relates to a wind generator with double rotors and double stators enabling said generator to run at low revolutions.

As a result, the need for a motor, which runs silently at low revolution and has double rotors, and is also capable of exhibiting 3-phase synchronization feature upon the application of an alternative voltage with variable voltage and frequency to the 3-phase coils of the stator opposite said rotor, capable of being used in any field especially where electricity is required, has made it necessary to provide an improvement.

Brief Description of the Invention

The present invention relates to a generator/motor with double rotors, which satisfies the aforesaid requirements, eliminates all the disadvantages and provides some additional advantages.

The object of the invention is to enable the generator according to the invention to run at low velocities to generate electricity. It is also an object to enable the motor to generate high torque at low velocities. The object of the invention is to enable said generator to exhibit the feature of 3- phase synchronized motor upon the application of an alternative voltage with variable voltage and frequency to the 3-phase coils of the stator.

The object of the invention is to provide the magnetic isolation and to make it possible to obtain a more intensive magnetic field, by using the materials such as copper and aluminum that are not affected by the magnetic field in the connection of said rotors to the shaft.

The object of the invention is to obtain the wind energy by providing a silent operation so that the residents in the vicinity will not be disturbed.

Another object of the invention is to put forward a wind energy system that enables to generate electricity from the wind energy in an uninterrupted and independent manner.

Another object of the invention is to enable the generation of electrical energy from the wind energy in all the fields where there is electricity consumption and particularly in places where the wind velocities are low.

Another object of the invention is to enable said generator to have an ideal use also in the rivers, wherein the desired efficiency is very easily obtained owing to double rotors and double stators and to the addition of water turbine in place of the vane.

In order to achieve the aforesaid objects, the invention is manufactured with 12 blades for the wind energy.

In order to achieve the aforesaid objects, the invention is manufactured in the form of a skew stator to enable the rotation to start at the low revolutions.

In order to achieve the aforesaid objects, the invention comprises double stators, wherein the stator with thin coils is activated at low revolutions and the stator with thick coils is activated at high revolutions. These may be connected separately or according to the serial or parallel DC connection to the outlets of each other, based on the need.

The present invention provides many facilities at the stage of both installation and use owing to its mentioned characteristics, with the aim of achieving all the advantages mentioned above, which will be understood from the following detailed description.

The structural and characteristic features and all the advantages of the invention will be more clearly understood from the enclosed figures and the detailed description written with reference to said figures, and therefore, the evaluation must be made taking into account said figures and the detailed description.

Brief Description of the Figures

In order to best understand the advantages of the present invention along with its embodiments and additional elements, it must be considered together with the figures described below.

Figure 1 is a representative drawing that illustrates the operating principle of the generator/motor with double rotors according to the invention along with the other auxiliary elements.

Figure 2 is the front view of the generator/motor with double rotors according to the invention.

Figure 3 is the side view of the generator/motor with double rotors according to the invention.

Figure 4 is a representative drawing showing the structure of the double stators and double rotors.

Figure 5 is a complete two-dimensional view of the wind turbine.

Figure 6 is the two-dimensional view of the rotors. Reference Numbers Used in the Figures

1. Wind turbine

2. Generator/motor

3. Rotor

4. Stator

5. Natural (permanent) magnet

6. Apparatus

7. Wind guide

8. Inverter

9. Isolated transformer

10. Blade

11. Pole

12. Soil floor

13. Concrete surface

14. Rotor shaft

15. Secondary rotor

16. Secondary stator

Detailed Description of the Invention

In this detailed description, the wind generator/motor (2) having a secondary rotor (3) is described in a non-limiting manner only for the purpose of enabling a better understanding of the subject.

The invention comprises 12 blades (10) that perform the rotational movement depending on the wind velocity in order to convert the kinetic energy formed by the wind into the electrical energy, at least one rotor shaft (14) that rotates in connection with the blades (10) as a result of the rotation of said blades (10) and two rotors (3, 15) connected to said rotor shaft. In connecting said rotors (3, 15) with the shaft (14), the material such as copper and aluminum, which are not affected by the magnetic field, are used such that the magnetic isolation and a more intensive magnetic field may be obtained. Another characteristic of said wind generator (2) is that it exhibits the feature of 3-phase synchronized motor upon the application of an alternative voltage with variable voltage and frequency to the 3-phase coils of the stator (4). With the rotation of the rotor (3) as a result of the rotation of said blades, 3-phase alternative voltage is obtained. As for the motor, the motor is enabled to rotate by way of applying an alternative voltage with variable voltage and frequency to the 3-phase coils of the stator (4). The electricity obtained from the DC supply is converted to AC by means of a frequency converter and the motor runs. Although the motors rotating in this way are included as AC in the technical literature, they are also defined as DC motor. Although this type of motors is AC, they are also called the BLDC (Brushless Direct Current) motor, because they are fed from DC and their speed torque curve is similar to that of DC motors. They also have such names as Self synchronous, PMSM (Permanent Magnet Synchronous Motor), ECM (Electronically Commutated Motor).

Included in said generator/motor (2) are a rotor (3), a stator (4) inside which said rotor (3) rotates and a secondary stator (16). One of said stators (4, 16) may be used as generator, while the other may be used as the motor. This provides a significant advantage especially in the electric devices.

Motors are generally made of two parts, namely the stator and the rotor. Stator is the stationary part of the motor. Permanent magnets are used in the rotor in the permanent magnet synchronous motors. Since no electrical energy is used to generate magnetic field in the rotors, these have a higher efficiency.

Synchronous motors are electric machines with a vary broad field of application. Particularly, since there is no carbon brush in the permanent magnet synchronous motors, no wear and corrosion occurs and no electrical arc forms. They also need less maintenance as compared to other electric machines. In the synchronous motors, the velocity of the magnetic field formed in the stator (4) coils is the same as the rotational speed of the rotor (3). Since the rotational speed of the rotor (3) is the same as the rotational speed of the magnetic field of the stator (4), these are called the synchronous motors. In the wind generator (2) according to the invention, there is no coil in the rotor (3) and the secondary rotor (15) used. Presence of the permanent magnets (5) in the rotors (3, 15) reduces the electricity consumption. Owing to such kind of generation, the efficiency, which is the most important factor for the motors/generators (2), may be raised to high levels.

In the generator/motor (2) with a secondary rotor (15) according to the invention, the presence of the natural magnets (5) on the rotors (3, 15) enables a higher beginning torque and rotational torque as compared to 3-phase asynchronous motors. 3-phase asynchronous motors draw more current as the load increases and they may burn out as a result of the excessive current drawn. The synchronous generator/motor (2) with secondary rotor (3, 15) according to the invention does not draw excessive current even if the load increases and thus, it becomes rather economic and durable. Permanent magnet synchronous motors provide facilities to form a high and stable moment curve. However, the speed control devices to be selected for controlling said permanent magnet motors and the software within this system must be in perfect conformity with the motor behavior dynamics.

In order to perform the speed control of the generator/motor (2) with secondary rotor according to the invention, the variable voltage frequency converters are used. Said frequency converters enable precious control especially in the operations with variable revolutions. For this to be possible, it is sufficient to determine an average operating limit and to operate the frequency converter and the generator/motor (2) within these limits. For more precious operations, much more complicated control systems may also be used. Said permanent magnet synchronous motors exhibit structurally rigid and stable behavior. The permanent magnets, which constitute the main component of the permanent magnet synchronous motors, have a fixed and unadjustable force of repulsion and attraction. In order to carry out the speed controls for said motors in a reliable manner, a speed control system is necessary, wherein the magnetic power at the pole angles, by which many magnet parts within the motor are positioned, and the differences of the power angle are previously determined and the control is provided for each motor angle. However, very simple speed control systems may also prove sufficient for many applications. In our application, no sensor is used for the magnetic fields. Alternatively, with the development process of the technology with time, some applications could bring about such a requirement.

In the generator (2), Neodymium (Nd2Fe14B) (the crystal made of a mixture of Neodymium, iron and boron) super magnets (5) are present as aligned on said rotors (3,15). Said rotors (3, 15) rotate inside a coil called stator (4) and secondary stator (16) that bear windings thereon. When used as a generator, said rotation of the magnets (5) forms varying magnetic fields in the coils. Said varying magnetic fields produce electric current.

In Figure 1 , the process steps for the generation of the electrical energy from the kinetic energy of the wind and also the electronic elements used are illustrated in a representative manner. AC voltage is generated at the output of said generator (2), and the generated AC current is converted to DC current by means of a 3-phase bridge rectifier. The current rectified by means of said rectifier is transferred into the batteries of the inverter (8) with battery for storage. The energy stored in said batteries is converted to network voltage by means of the inverter (8).

According to another application used in places with the possibility to obtain electricity from the municipal network, the batteries are enabled to be charged additionally by benefiting from the fact that the electricity is cheaper during the night time use and the electricity demand of the houses or the businesses are rendered economical by an extent of up to 50%. Because, as in many other countries, the electricity is very cheap during the hours 22.00 - 06.00 in the night in our country. This has a very valid economical justification. Because, if a community can reduce the electricity use during the peak hours of 17.00 -22.00 and shift the use to the other hours, the annual investment sums of the countries in electricity may become much lower. During the nights, the generation may not be much reduced due to technical reasons necessitated by the electricity distribution. The use during such hours provides great benefits for the countries; hence the prices are kept low.

In order to enable the operation at low revolution of the generator (2) according to the invention, for which the front and side view are provided respectively in Figures 2 and 3, a skew stator (4) is obtained. The event of blockage that makes the initial rotation difficult to take place and called "cogging" is prevented in this manner.

According to another preferred embodiment of the invention, the difficulty of rotation faced in the beginning is avoided owing to the assembly of said magnets (5) in an inclined manner. However, in the product according to the invention, said stator (4) is produced with an inclination by means of an apparatus (6). Said apparatus (6) enables practical application to obtain an angled stator (4). In the present practice, no production is carried out with this method. It is more difficult and , more expensive to have special magnets manufactured suitable for the angled magnet application. Magnets are obtained from Finland and China. Some of the magnet types are subjected to shock treatment in our country.

The operation at low revolution is provided by way of obtaining the angled stator (4) and thus, the batteries may be charged for a longer time.

The generator/motor (2) according to the invention comprises a stator (4) with thin coils activated at low revolution and a secondary stator (16) with thick coils designed to be activated at high revolutions. The generation of both stators (4, 16) provide support to one another in operation with parallel connection, according to the Millman's principle of parallel generators, thus the thin coil is prevented from burning out. In other words, the thin coils do not burn out when the speed increases. The thin coil is protected upon the increase of the voltage generation by the thick coil with increasing speed. Here, the most important study to be performed involves the necessity to carry out a good adjustment of thickness for the wires of both stators (4,16). Failure to provide a good thickness adjustment for the wires prevents an ideal generation and also causes the thin coil to burn out. In said rotors (3,15), permanent magnets (5) are used in place of the electromagnets. Owing to the presence of said permanent magnets (5) in the rotors (3, 15), the efficiency of said generator/motor (2) considerably increases. There is no carbon and commutator system called the brush. Owing to the use of the permanent magnets (5) in place of the electromagnets, a generator (1) with permanent magnets is obtained.

One of the most important factors enabling a silent operation for said generator (2) is the structure and the number of the blades (10) attached to said generator (2). 12 blades (10) are used in the wind generator (2) according to the invention. The revolution reduces with the increased number of blades (10) and accordingly, said generator (2) operates in a very silent manner. In these systems established to convert the wind energy into the electrical energy, the wind velocity should not exceed 60 m/s at the blade ends, since the high velocity causes excessive sound. This sound formed constitutes a disadvantage due to the disturbance it causes in the nearby residences, especially for the systems used in the environments, in the vicinity of which there are settlement units like the houses. For example, if the diameter of a blade (10) is 40 cm., it has a perimeter of about 120 cm according to the expression 2πr. It is not possible for said blade (10) to rotate at 60/1.2, in other words, 50 times within a second (3000 rpm). In the model according to the invention, the power that normally necessitates several hundred revolutions is obtained by means of 12 blades (10). In the storms, said speed reaches 600 rev/min (rpm) or 10 rev/sec. In the other small turbines (1), the noise forms, because the revolution values of 1000 or more are reached even at normal winds. This is one of the most important differences of the wind generator (2) according to the invention from the wind generators used in the prior art.

In the big turbines, the blade diameters today vary in the range 40 to 120 meters. Since the perimeter corresponding to a blade diameter of 100 meters is about 300 meters, said turbine blades rotate 1 time within 5 seconds, considering a speed limit of 60 m/sec. Despite having a very low rotational speed, these should remain within the target of 60 m/sec as annual velocity, which comprises the sound limit on blade ends.

The blade (10) structure of said wind generator (2) is manufactured in such a way to obtain maximum generation from the wind energy at the least revolution.

In Figure 5, the complete two-dimensional view of the wind turbine (1) is provided. The wind turbine (1), which comprises the blade (10) and the generator (2) connected with said blade (10), is buried into the soil floor (12) with a depth of 1.5 meters by means of an iron pole (11) having a length of 12 meters and a wall thickness of 8 mm. By means of the surface (13) formed from concrete and iron on the soil floor (12), a stronger structure is provided.

By means of the wind guide (7) connected with the rear part of said generator (2), the optimum efficiency is provided from the wind velocity.

The protective scope of this application is set forth in the section of claims and the scope may by no means be limited to the description above provided only for exemplary purposes. It is obvious that a person skilled in the art may provide the innovation put forward by the invention also by using the similar embodiments and/or apply this embodiment to other fields with similar purpose used in the relevant art. Consequently, such embodiments would obviously lack the criteria of innovative step and particularly, exceeding the state of the art.

Claims

1. A wind turbine (1), which comprises at least one blade (10) that performs the rotational movement depending on the wind velocity, at least one rotor shaft (14) that rotates in connection with the blade (10) as a result of the rotation of said blades (10), a rotor (3) connected onto said rotor shaft (14) and a stator (4) having coils inside which said rotor (3) rotates, and is used to convert the kinetic energy formed by the wind into the electrical energy characterized in that it comprises at least one generator/motor (2) having

- at least one secondary stator (16) with thick coils that is activated at high revolutions after the activation of said stator (4), which is the part with the thin coils, at the low revolutions and

- at least one secondary rotor (15) connected onto said rotor shaft (14), and

exhibiting the 3-phase synchronous motor feature upon the application of an alternative voltage with variable voltage and frequency to the 3-phase coils of said stator (4) and/or secondary stator (16).

2. A wind turbine (1) according to Claim 1 characterized in that said stator (4) comprises at least one apparatus (6) that enables it to be manufactured with an inclined formation.

3. A wind turbine (1) according to Claim 1 characterized in that the magnets aligned on said rotor (3) are Neodymium (Nd2Fe14B) (crystal made of a mixture of Neodymium, iron and boron) super magnets.

4. A wind turbine (1) according to any one of the preceding claims characterized in that it comprises 12 blades (10), in order to convert the kinetic energy formed by the wind into the electrical energy and to enable a silent operation for said generator.

5. A wind turbine (1) according to any one of the preceding claims characterized in that it comprises the isolation material, which is not affected by the magnetic field, for use in the connection of said rotors (3,15) with the rotor shaft (14).