Optimizing induction motors with corresponding three-phase balanced and symmetrical motors

Abstract

This invention presents a method for the optimal design of induction motors with multi-phase or single-phase input power. Motors with multi-phase input power can be easily designed from the basic three-phase motor using this method. Herein, motors that are fed by single-phase power supply reach the desired or complete magnetic balance by installing a capacitor in its circuit. With the help of the presented method, the design of induction motors powered by single-phase alternating voltage is done in accordance with the basic three-phase induction motors, and thus achieving the efficiency of the primary three-phase induction motor becomes possible. Three-phase induction motors have an output power of 120-3000 watts, usually with a power factor 0.6 to 0.8 and in fewer cases 0.4 to 0.6. The mentioned method is optimally used to convert these motors into induction motors are fed by single-phase power supply with two-phase or three-phase internal structures.

Description

Optimizing Induction Motors with Corresponding Three-phase Balanced and Symmetrical Motors

[0001] One of the primary objectives of this invention is to provide an approach for the efficient design of run capacitor induction motors that are fed by single-phase alternating voltage. These motors typically feature a two-phase, or in some instances, a three-phase internal configuration. In some applications, a completely single-phase internal structure with a starter winding, commonly referred to as a split phase, may be utilized, which the motor's efficiency and performance are suboptimal.

[0002] However, split phase motors pose a significant challenge as they lack the ability to achieve balanced magnetic field due to the presence of equal forward and backward rotating fields. This imbalance leads to a sharp decline in efficiency and performance. The establishment of balanced magnetic field necessitates at least two windings, prompting ongoing efforts to eliminate the reverse magnetic field in order to enhance the performance and efficiency of motors with two or three-phase internal structures that are operated using single-phase power supply.

[0003] By addressing this critical issue, the proposed method aims to eliminate inefficiencies and enhance the overall performance of these motors, ultimately paving the way for improved performance in a variety of industrial and commercial applications.

[0004] H02K 17 / 12 – H02P 6 / 08

[0005] CN102005880A

[0006] Three-winding parallel single-phase induction motor

[0007] The invention relates to a three-winding parallel single-phase induction motor. A stator winding of the single-phase induction motor adopts a three-winding parallel connection mode, so when the single-phase induction motor operates under a rated load, the single-phase induction motor has an approximately symmetrical air gap field, has the efficiency closer to that of a same-capacity three-phase induction motor and higher power factor.

[0008] The mentioned patent aims to achieve the efficiency and performance of a balanced and symmetrical three phase induction motor by changing the values of two capacitors. On the other hand, our design comprises a capacitor for the structure of the motor that has three symmetrical windings and is supposed to be powered by single-phase power supply. Moreover, the exact value of the capacitor and all other variables is completely calculable according to the Balanced and Symmetrical three-phase induction motor power factor and parameters.

[0009] KR20060055046A

[0010] Single-phase induction motor and noise reduction method thereof

[0011] The present invention relates to a single-phase induction motor and a noise reduction method thereof, and an object of the present invention is to provide a single-phase induction motor and a noise reduction method capable of realizing a low noise and low vibration motor by eliminating the imbalance of the magnetic force of the stator winding.

[0012] In this mentioned patent, motors with two-phase internal structure that are fed by single-phase power supply are studied. Therefore, it focuses primarily on reducing the contribution of the reverse magnetic field compared to the normal magnetic field and reducing the imbalance of the rotating field, to show that the amount of noise and vibration is greatly reduced. On the other hand, with our claimed method, motors with two-phase internal structure that are fed by single-phase power supply, the rotating field is almost completely normalized, and reduction amount for reverse rotating field depends on preservation of the motor performance is fully calculable.

[0013] CN201365179Y

[0014] Three-winding single-phase induction motor with novel connection

[0015] The utility model discloses a three-winding single-phase induction motor with novel connection, which can lead the efficiency of a three-winding single-phase induction motor to approach to a motor with three-phase symmetrical running in single-phase running through adopting the connection of a motor stator winding and a capacitor, and leads the efficiency to be higher than a normal single-phase induction motor with the same volume.

[0016] The purpose of the above-mentioned patent is to achieve the efficiency and performance of a balanced and symmetrical three phase motor by changing the values of two capacitors. But in our claimed one, for the structure of a motor that has three windings and is supposed to be powered by single-phase power supply, the exact value of the capacitor has been calculated, which is a function of the power factor of the balanced and symmetrical three-phase motor. This calculated value of capacitor can bring the motor to full magnetic balance.

[0017] KR101171168B1

[0018] Optimum design system and method for high efficient single induction motor, and high efficient single induction motor manufactured by It

[0019] This patent is similar to our claimed one in purpose but the methods are different. In our design, first, the characteristics of the balanced and symmetrical three-phase induction motor are determined, and then by converting the three-phase motor to two-phase and calculating a capacitor value, the magnetic balance is established in the motor. The noteworthy point is that the problem of optimization of the motor powered by single-phase power supply has been solved through the design of a basic three-phase motor that can be easily optimized. However, the mentioned patent does not have the characteristics of an optimal motor and the main idea is applied to a pre-designed motor that is not necessarily optimal and only calculates the value of capacitor for the best efficiency, which is fundamentally different from the content and claims of our statement.

[0020] CN203859597U

[0021] Single-phase induction motor stator winding connecting structure

[0022] In this mentioned invention, the motor powered by single-phase power supply has been introduced with a three-phase internal structure, which is directly connected to one of its phases and a capacitor is paralleled to another phase. Under such a structure, this motor has qualitative advantages compared to motors powered by single-phase power supply with other structures.

[0023] This circuit has also been used in our design to convert a balanced and symmetrical three-phase induction motor fed by three-phase power supply into a motor with a three-phase internal structure and fed by single-phase power supply. But this feature is not in the form of expressing qualitative advantages, and with the help of circuit analysis and applying magnetic balance conditions, it has been calculated that under the conditions that the power factor of the primary three-phase motor is between 0.4 and 0.6, it is appropriate to use this circuit, otherwise it is not suitable. Also, the value of the capacitor is calculated in a very accurate way, which is very different from this description and the mentioned patent.

[0024] CN1822477A

[0025] Single-phase induction motor with negative sequence suppression winding

[0026] Present invention discloses a single-phase induction motor with negative sequence suppress winding. It solves large problem negative sequence current in current single-phase induction motor, having advantage of effectively suppressing negative sequence current. It contains casing, shaft installed in casing, rotor stator installed on shaft, stator consisting of stator core and armature winding, said armature winding connected with compensation winding, two windings series connected in negative phase sequence.

[0027] This above-mentioned design is for induction motors powered by single-phase power supply, wherein a method is provided to neutralize the reverse rotating field with the help of an additional winding. However, in ours, no additional winding are used to remove the reverse magnetic field and in the electromagnetic design of the primary three-phase motor, which is the basis of this statement, there are conditions that by achieving them, the motor powered by single- phase power supply that is obtained from the primary three phase motor, will not have a reverse rotating field.

[0028] This innovative method allows for transformation of traditional three-phase induction motors into efficient multi-phase or single-phase induction motors, expanding their versatility and applicability in various industries. By incorporating a capacitor into the circuit, the designed single-phase induction motors can achieve optimal magnetic balance, ensuring smooth and stable operation. This method not only simplifies the design process but also enhances the overall performance and efficiency of the motors, aligning them with the attainable efficiency grade of their three-phase counterparts.

[0029] Furthermore, the versatility of this method allows for the conversion of three-phase induction motors ranging from 120 to 3000 watts into induction motors are fed by single-phase power supply with two-phase or three-phase internal structures.

[0030] Overall, this comprehensive method aims for the optimal design of induction motors with multi-phase or single-phase input power and offers a practical and efficient solution for enhancing motor performance and versatility.

[0031] The most widely used motors in the world are induction motors, whose wide application and popularity has caused the electricity consumption of these motors to account for a large amount of the world's energy consumption. In order to manage the energy consumption of these motors, instead of increasing power plant resources and electricity production, it is better to reduce their energy consumption by using the cheapest and most accessible methods.

[0032] Induction motors are responsible for approximately 40% of the world's electricity consumption, as these motors power fans, compressors, pumps, and almost any mechanical load that rotates. Every year, about 30 million new electric motors are used only for industrial applications. Despite the emergence of permanent magnet motors, induction motors (IM) have always maintained their position due to their simple and robust construction and low cost, and therefore, a small improvement in the performance of these motors can have a large effect on energy consumption and reduce greenhouse gases all over the world.

[0033] In three-phase induction motors, which have symmetrical structure and feeding, the magnetic field is completely normal and they have the most suitable energy consumption mode among all types of induction motors. But in single-phase induction motors, due to the presence of a combination of two types of normal magnetic field and reverse magnetic field (disturbing factor), energy loss actually occurs, and in order to achieve the desired balance, new design methods must be used. In the end, only the normal magnetic field remains and the reverse magnetic field is removed. Single-phase induction motors are widely used in household and sometimes industrial appliances because they usually have low power. Efficiency in single-phase induction motors (SPIM) is inherently relatively low, thus, the need to design methods that increase the efficiency of this type of motors needs to be addressed.

[0034] One of the goals of this invention is to provide a comprehensive method for the optimal design of run capacitor induction motors that are powered by single-phase alternating voltage. Such motors mainly have a two-phase, and in some cases a three-phase internal structure. In a number of limited applications, where the efficiency and performance of the motor are not optimal, they can have a completely single-phase internal structure with a starter winding, also known as split phase. Due to having equal normal and reverse rotating field, split phase induction motors basically do not have the ability to balance magnetization and a severe drop in efficiency occurs in them. Considering magnetic balance requires at least two winding, efforts are being made to achieve magnetic balance by removing the reverse magnetic field and ultimately improving performance and efficiency in motors that have two or three phase internal structures and are powered by single phase power supply.

[0035] In the present invention, a method is provided wherein motors with internal three-phase and two-phase structures that are fed by single-phase AC line power can obtain optimal magnetic balance. This is achieved through installing an auxiliary capacitor in the circuit of the induction motor and with minimized costs.Solution of Problem

[0036] Since three-phase induction motors have the highest possible efficiency among all types of induction motors with different structures, in order to improve the efficiency of induction motors powered by single-phase power supply, it is necessary to design a motor whose efficiency is similar to the efficiency of a three-phase induction motor. If three-phase balanced and symmetrical power supply is available and the induction motor is designed with three balanced and symmetrical phases optimally, the highest possible efficiency that can be achieved in induction motors will occur. Therefore, how much we approach this ideal state for the design of induction motors powered by single-phase power supply, we can logically have the highest efficiency.

[0037] Using this fact, in this statement a method is presentedbased on which, in order to achieve the highest possible efficiency in induction motors, a three-phase motor fed by three-phase power supply (primary motor) is designed first. And its parameters are determined, including the power factor (which is a unitless number between zero and one). At this stage, if the motor is designed correctly in principle, the maximum efficiency will be obtained.

[0038] At first, it will be proved that for each motor with a two-phase internal structure, whose power supplies for its phases and its windings are balanced and symmetrical, there are balanced and symmetrical n≥3 phase motors. These motors are corresponding and equivalent to each other in performance and material consumption. The first benefit of proving this theorem is that in the case of an optimal and principled design of a balanced and symmetrical three-phase motor, the response of all n≥2 balanced and symmetrical motors can be easily calculated from it (n is a natural number).

[0039] However, the main problem is increasing efficiency in those induction motors that are fed by single-phase power supply (n=1 refers to motors with single-phase input power supply whose internal structure is two-phase or three-phase). Therefore, by converting the power supply of the designed motor from three-phase to single-phase, the power factor of the primary three-phase induction motor is evaluated and used as a determining index to continue the path; In this way, if the numerical power factor is between 0.4 and 0.6, the designed motor is kept in three phases in terms of its internal structure, and to achieve magnetic balance, an auxiliary capacitor is calculated and embedded in the motor circuit. In this case, the designed motor with built-in capacitor will have approximately the same efficiency as the primary motor (with the highest possible efficiency) and at a certain point when the power factor is equal to 0.5, while removing the reverse magnetic field, and establishing complete magnetic balance in the motor, the efficiency is exactly equal to that of the primary motor.

[0040] In the second case, if the numerical power factor is between 0.6 and 0.8, the internal structure of the motor is redesigned as two-phase and the auxiliary capacitor is added to the circuit after calculation; In this case, the magnetic balance in the motor has been established to a large extent, the efficiency will correspond to the efficiency of the primary motor (which has the highest possible efficiency) and at a certain point when the power factor is equal to 0.707, while removing the reverse magnetic field and establishing complete magnetic balance in the motor, the efficiency at this particular point is exactly equal to the efficiency of the primary three-phase motor.

[0041] Now we will describe the created method completely and step by step:

[0042] As mentioned, the main objective of this statement is to provide a comprehensive method for the optimal design of induction motors with run capacitors that are fed by single-phase AC line power. For this purpose, we first prove a 2-phase induction motor with the root mean square (RMS) value of the voltage of V_2 for each phase where the angle difference between the supply voltage of its windings is 90 degrees and the electric angle difference between its windings is also 90 degrees, which we call this motor “Motor_2-Phase”, there is an identical n≥3 phase induction motor with the RMS value of the voltage of each phase V_n, where the angle difference between the power sources of its windings is 360 / n degrees and the electric angle difference between the windings is also 360 / n degrees, which we call this motor “Motor_n-Phase”.

[0043] The meaning of identical is that in a specific stator and rotor core with a specific length and the same rotor cage, both motors have the same input power, output power, power factor, torque, flux density, speed and current density [Formula. 1]. It is only the winding of the two motors are different, but they are the same in terms of wire consumption.

[0044] For simplicity in the proof, we make the RMS value of the supply voltage of the phases equal [Formula. 2].

[0045] On the other hand, since we considered the characteristics of the stator and rotor cores of both motors as well as their rotor cages to be the same, and the performance of the two motors is supposed to be the same, this means that the reluctance of the flux path is the same for both motors.

[0046] With the premise of naming the RMS value of the motors' phase currents I_2 and I_n the total number of turns of each phase of the motors N_2 and N_n, the magneto motive force of motors MMF_2 and MMF_n, by writing the sum of the magneto motive force of the phases at the spatial angle α and converting the cosine multiplication relations to the sum for the even and odd n states, [Formula. 3] is proved.

[0047] In [Formula. 3] and [Formula. 4] f is the frequency of the power source, p is the number of pole pairs and k is a constant coefficient of the core reluctance function (B-H curve) and the air gap, which is the same for both of them due to the same core and the same operation of the two motors.

[0048] Now we want to calculate how the winding of the n-phase motor should have a relationship with the two-phase motor so that the two motors match.

[0049] In order to match the motors, it is necessary that their input power and output power be equal. The magneto motive force produced by the motor is the representative of its output power and we use it instead of the output power. At first, we have two motors with equal input powers [Formula. 5].

[0050] In this way, the relationship between the phase currents of two motors is obtained. For the relationship between the wire diameters of the two motors, namely D_2 and D_n, from the equality of current densities, we will have [Formula. 6].

[0051] Through [Formula. 6], the relationship between the wire diameter of the two-phase motor and n≥3 phase motor is obtained. Now we will have the equality of the magneto motive force of two motors based on the equality of their output powers [Formula. 7].

[0052] Therefore, in order to match the two motors, the total number of turns of each phase of the n≥3-phase motor must be equal to the total number of turns of each phase of the two-phase motor [Formula. 7].

[0053] We call the obtained principle the principle of similarity of multi-phase induction motors, and the relations between the windings of two motors are obtained in [Formula. 8].

[0054] - Changing the number of stator or rotor slots

[0055] After designing a balanced and symmetrical n-phase motor, the change in the number of stator and rotor slots can be done easily and with minimal manipulation, so that if we represent the number of stator or rotor slots with S and the width of its teeth let us represent it with W and the old and new indices are the old and new values, respectively, to maintain the motor performance, from the equality of the flux under the motor poles, the new width of the stator or rotor teeth can be calculated as in [Formula. 9].

[0056] The above relationship is very important from this point of view, that the number of slots per poles per phase of the designed three-phase primary motor is an integer, but during the conversion of the number of phases, this number may become a fraction. Under such conditions, [Formula. 9] can be highly effective.

[0057] - Designing a balanced and symmetrical n-phase motor from a balanced and symmetrical 3-phase motor

[0058] With the help of what has been expanded so far in this declaration, by designing and optimizing a balanced and symmetrical three-phase motor, which is very attainable by an experienced motor designer, any n≥2 phase motor can be designed balanced and symmetrical according to the equations in [Formula. 10].

[0059] If we encounter the problem of limiting the number of slots per poles per phase in the conversion of a balanced and symmetrical 3-phase motor to a balanced and symmetrical n-phase motor (the slot per pole per phase may become an fractional number), we can change the width of teeth and the number of slots to the desired amount, according to the [Formula. 9].

[0060] - Optimum design method of induction motors powered by single-phase power supply

[0061] Now the question is, what is the effect of the obtained principle on induction motors powered by single-phase power supply. As mentioned, the main goal of this invention is to provide a comprehensive method for the optimal design of run capacitor induction motors that are powered by single-phase alternating voltage. In the following, a method will be presented for three-phase and two-phase motors that are fed by single-phase alternating voltage of the line, to reach the desired or complete magnetic balance by placing a capacitor in the circuit of such motors.

[0062] We know that today the problem of design and optimization based on performance, material and efficiency for balanced and symmetrical three-phase induction motors less than 4 horsepower, which we called Motor_3-Phase, is a routine solved problem. For a specific case, we assume that with the presence of an experienced electric motor designer, it does not contain any special complexity and we have the design solution. Under each mechanical load, such a motor has a decouple electrical equivalent circuit without magnetic coupling between phases for each of the phases, which we will use in the following.

[0063] Now, the goal is to balance the resulting three-phase induction motor by placing an auxiliary impedance in one of its phases while feeding from single-phase power supply. For this purpose, we form a circuit with three phases of the motor according toin which [Formula. 11] is the total equivalent impedance of each phase of the motor and its load, from the point of view of the network and [Formula. 12] is an auxiliary impedance in order to create a magnetic balance in the motor. It is clear that φ_3 is the same load angle related to the power factor.

[0064] As it is clear, according to the KCL law in the right part of the circuit, we will have [Formula. 13], which can be simplified as [Formula. 14].

[0065] Now that the auxiliary impedance has been calculated, to calculate the total input impedance from the point of view of the network, according to the circuitwe will have [Formula. 15].

[0066] As exhibited, with the help of impedance Z_(3+) , the load angle is improved by 30 degrees, and for example, if the load angle of the primary three-phase motor fed by three-phase power supply is 60 degrees and its power factor is 0.5, the three-phase motor obtained with this method, with the help of this impedance, is fed from single-phase power supply will have a load angle of 30 degrees and a power factor of 0.866.

[0067] Our ideal situation is that the impedance Z_(3+) be a full capacitor or close to it. It is clear that if φ_3=60, therefore, the power factor of the primary three-phase motor fed by three-phase power supply is 0.5, then the Z_(3+) is completely a capacitor and we will have [Formula. 16].

[0068] Now the calculations of [Formula. 17] shows the power factor of the primary three-phase motor powered by three-phase power supply will be with 0.1 variation, which also gives us the condition of the auxiliary impedance Z_(3+) in order to achieving very suitable magnetic balance.

[0069] In conclusion, if the power factor of the primary three phase motor powered by three phase power supply be [Formula. 18], because the non-capacitive part of the auxiliary impedance is less than 12% of its total, with only one capacitor, we can bring it to a very suitable magnetic balance and if cos (φ_3) =0.5 is the case, the perfect balance is achieved.

[0070] The problem is that normally, three-phase induction motors powered by three-phase power supply with an output power of more than 120 watts, which include the standard of the energy efficiency category, have a power factor of more than 0.6, and this method is optimally not efficient for single-phase feeding them and the application of this method becomes very limited.

[0071] The next solution that exists is the design of a two-phase balanced motor powered by two balanced voltages with a phase difference of 90 degrees, which we called Motor_2-Phase. As mentioned previously, since Motor_3-Phase is assumed to be known, we can calculate the two-phase motor based on the three-phase one in [Formula. 19].

[0072] Therefore, after designing the three-phase balanced motor, the two-phase balanced motor is easily obtained.

[0073] Now, the goal is to balance the resulting two-phase motor while feeding from single-phase power supply, by placing an auxiliary impedance in one of its phases. For this purpose, we form a circuit with two phases of the motor according toin which [Formula. 20] is the total equivalent impedance of each phase of the motor and its load from the point of view of the network, and [Formula. 21] is an auxiliary impedance to create magnetic balance in the motor. It is clear that φ_2 is the load angle is related to the power factor.

[0074] As it is clear, according to the KVL law in the right part of the circuit, we will have [Formula. 22].

[0075] Now we can write [Formula. 23] for impedance Z_(2+), which finally brings us to [Formula. 24].

[0076] Now that the auxiliary impedance has been calculated, to calculate the total input impedance from the point of view of the network or according to the circuit, we will have [Formula. 25].

[0077] As can be seen, with the help of impedance Z_(2+), the load angle is improved by 45 degrees, and for example, if the load angle of the primary three-phase motor fed by three-phase power supply is 45 degrees and its power factor is 0.707, the two-phase motor that is fed by single-phase power supply with the help of impedance in this method will have a load angle of 0 degrees and a power factor of 1.

[0078] Our ideal situation is that the impedance Z_(2+) be a full capacitor or close to it. It is clear that if the load angle is 45, or the power factor of the primary three-phase motor powered by three-phase power supply is 0.707, then the Z_(2+) is completely a capacitor and we will have [Formula. 26].

[0079] Now we check for the primary three-phase motor powered by three-phase power supply with the power factor of 0.7 with a variation of 0.1 or [Formula. 27] in order to see what becomes of the auxiliary impedance via [Formula. 28].

[0080] Therefore, if the condition of the primary three-phase motor powered by three-phase power supply is as stated in [Formula. 27], because the non-capacitive part of the auxiliary impedance is less than 14% of its total, with only one capacitor, we can bring it to a very suitable magnetic balance and if cos (φ_2) =0.707 is the case, with only one capacitor, we will reach full magnetic balance.

[0081] The interesting thing to note in the design of the mentioned motors is that three-phase induction motors powered by three-phase power supply with an output power of more than 120 watts and less than 3000 watts, which include the standard of the energy efficiency category (IEC 60034), mainly have a power factor between 0.6 and 0.8 and this method is optimally effective for converting them into a two-phase balanced motor and feeding them with a single-phase power supply. This makes the application of the discussed solution very comprehensive.Advantage Effects of the Invention

[0082] • Applicable in production of a wide range of induction motors for household and industrial appliances

[0083] • Energy efficient and cost-effective

[0084] • No need for changing the current production lines of induction motor manufacturers

[0085] • Using more available material in the manufacturing process such as aluminum magnet wire instead of copper magnet wire

[0086] • Applicable to multi-phase induction motors

[0087] Shows a general flowchart of the developed method.

[0088] Declares a diagram of the proposed circuit for three-phase induction motors.

[0089] Displays a diagram of the proposed circuit for two-phase induction motors.

[0090] Shows a general flowchart of the stages of maximizing the efficiency of all types of induction motors through the design of three-phase balanced and symmetrical induction motors.

[0091] Depicts the induction motor circuit with three-phase internal structure and powered by single-phase power supply.

[0092] Displays the induction motor circuit with two-phase internal structure and powered by single-phase power supply.Examples

[0093] The invention involves a method of optimization for induction motors and can be applied to a variety of motors. As an example of the developed method, we design and manufacture two examples of single-phase induction motors with different powers and number of poles. For this purpose, a lamination with a stator of 36 slots and an outer diameter of the stator core of 160 mm, which belongs to an induction motors manufacturing company (Motorjam Alborz Corporation), has been used.

[0094] The first case involves the design of a 4-pole induction motor is defined with an output power of 370 watts, input voltage of 230 volts (according to the standard of the power grid), a minimum power factor of 0.9 and IE4 energy grade (According to IEC 60034), which according to the standard must be at least 81.1%.

[0095] In the design of this motor, the following parameters have been obtained with the help of one of the available FEM products software for the design of three-phase induction motor.

[0096] The length of the core is 45 mm, the material is M470 sheet, the number of turns in each phase is 696 turns, the diameter of the wire in each phase is 0.55 mm, the current of each of its three phases is 0.83 amps, the power factor is 0.78 and the efficiency is 83%.

[0097] Based on the relationships obtained for converting the three-phase motor to two-phase, the number of turns of each phase of the two-phase motor is 696 turns, the wire diameter of each phase is 0.673mm (0.5mm and 0.45mm) and the current of each of its two phases will also be 1.245 amperes. According to the obtained parameters and that the power factor of the primary three-phase induction motor is 0.78, the capacitor value of the motor with a two-phase internal structure fed by single-phase power supply, according to [Formula. 26], will be equal to [Formula. 29].

[0098] Since the value of the capacitor's capacitance decreases over time, we choose its value as 12.5 microfarads.

[0099] The obtained 370-watt motor winding is according to [Table 1].

[0100]

[0101] In the second case, a 6-pole induction motor is designed with an output power of 120 watts, input voltage of 230 V (according to the standard of the power grid), a minimum power factor of 0.9 and IE4 energy grade (According to IEC 60034), which according to the standard must be at least 64.9%.

[0102] In the design of this motor, with the help of one of the available FEM products software for the design of three-phase induction motors, the following parameters have been obtained:

[0103] The length of the core is 45 mm, the material of the sheet is M470, the number of turns in each phase is 1350 turns, the diameter of the wire in each phase is 0.286 mm, the current of each of its three phases is 0.38 amps, the power factor is 0.67 and the efficiency is 68%.

[0104] According to the obtained relationships, to convert the three-phase motor to two-phase, the number of turns of each phase of the two-phase motor is 1350 turns, the wire diameter of each phase is 0.35 mm, and the current of each of its two phases will be 0.57 amperes. According to the obtained parameters and that the power factor of the primary three-phase motor is 0.67, the capacitor value of the motor with a two-phase internal structure fed by single-phase power supply, according to the [Formula. 26], will be equal to [Formula. 30].

[0105] Since the value of the capacitor's capacitance decreases over time, we choose its value as 6.3 microfarads.

[0106] The obtained 120-watt motor winding is according to [Table 2].

[0107]

[0108] The prototypes based on the mentioned designs and calculations were tested and the results included the following.

[0109] The dynamometry of the first motor sample has resulted in an output power of about 367 watts, an efficiency of 81.4%, a power factor of 0.98, a current of 2 amps, and a motor speed of 1445 rpm.

[0110] The dynamometry of the second motor sample at the output power of about 120 watts has resulted in an efficiency of 68.4%, a power factor of 0.99, a current of 0.77 amps, at a motor speed of 960 rpm.

[0111] The reason for the closeness of the dynamometric test results and the design results in the method presented in this invention is that the inventor has a long experience in designing induction motors powered by three-phase and single-phase power supply with various energy efficiency class and calibration between software design and actual testing has been done prior to this stage.

[0112] - Changing the number of turns and the diameter of the auxiliary winding conductor while maintaining the motor performance

[0113] A change in the auxiliary winding of the motor in the form of playing with the number of turns of the coils and the diameter of its wire does not change the motor, since the design and operation of the motor is based on the diameter of the wire and the total number of turns of the main winding, which is explained further:

[0114] Since the main task of the auxiliary winding is to create a phase difference and carry the current, it can be changed in such a way that the flux produced by the auxiliary winding and also its current density does not change. For this purpose, for auxiliary winding assuming current I, current density J, conductor diameter D, conductor cross section A and number of turns N, we can have [Formula. 31].

[0115] The old and new indices show the old and new values, respectively. Now, since we assume that the old and new current densities are the same so that the thermal pressure on the auxiliary winding does not change, we will have the above relationship by simplifying it in [Formula. 32]. This equation means that the volume of the wire used in the auxiliary winding is also maintained, because under the conditions of fixed geometry for a coil, the number of turns of the wire multiplied by the square of its diameter is the representative of the volume of the used wire.

[0116] Due to the increase in the inductance of the auxiliary winding, which is the result of the increase in its number of turns, we must reduce the value of the capacitor so that the motor reaches the same performance as before. Under these conditions, it is easy to determine the value of the capacitor from practical and dynamometric tests. On the other hand, by increasing the diameter of the auxiliary winding and reducing the number of turns, a similar motor can be reached, which will obviously the value of the capacitor increase this time.

[0117] Reducing the diameter of the wire and increasing the number of turns, which leads to a decrease in the value of the capacitor, is beneficial from the point of view of the capacitor price, and it is harmful from the point of view of increasing the production cost due to taking more time in winding process. On the opposite end, increasing the diameter of the wire and reducing the number of turns, which leads to an increase in the value of the capacitor, is harmful from the point of view of the capacitor price, and is beneficial from the point of view of reducing the production cost due to less time spent in winding process. In general, the final decision-maker regarding the benefits and harms of what was said will be the manufacturer.

[0118] For example, in the auxiliary winding of the 370 W motor, instead of the 0.673mm (0.5mm and 0.45mm) wire, we can use a 0.5mm wire, which under these conditions the number of auxiliary winding turns will be obtained according to [Formula 33].

[0119] The formulas mention in both solution and example sections of this statement are listed here:

[0120] [Formula. 1]

[0121] [Formula. 2]

[0122] [Formula. 3]

[0123] [Formula. 4]

[0124] [Formula. 5]

[0125] [Formula. 6]

[0126] [Formula. 7]

[0127] [Formula. 8]

[0128] [Formula. 9]

[0129] [Formula. 10]

[0130] [Formula. 11]

[0131] [Formula. 12]

[0132] [Formula. 13]

[0133] [Formula. 14]

[0134] [Formula. 15]

[0135] [Formula. 16]

[0136] [Formula. 17]

[0137] [Formula. 18]

[0138] [Formula. 19]

[0139] [Formula. 20]

[0140] [Formula. 21]

[0141] [Formula. 22]

[0142] [Formula. 23]

[0143] [Formula. 24]

[0144] [Formula. 25]

[0145] [Formula. 26]

[0146] [Formula. 27]

[0147] [Formula. 28]

[0148] [Formula. 29]

[0149] [Formula. 30]

[0150] [Formula. 31]

[0151] [Formula. 32]

[0152] [Formula. 33]

[0153] The method introduced in this statement is generally applicable to all induction motors powered by single-phase power supply that have run capacitors. Also, with the help of the method presented in this declaration, the symmetrical winding of an n-phase AC motors such as IM, BLDC, PMSM, SR, etc. motors can be converted into a corresponding motor of the same type with the desired number of phases.

Claims

A Method for optimizing all types of induction motors, through the design of three-phase balanced and symmetrical induction motors is presented, which includes:- Designing the primary three-phase balanced and symmetrical induction motor powered by three-phase power supply- Calculation of the parameters of the designed primary induction motor, including the power factor, characteristics of the windings (number of turns and diameter of the conductor) and the current of each phase- Determining the number of phases feeding the motor (n≥1), for the design of the motor corresponding to the primary induction motor- Calculation of the new values of turns and wire diameter and the current of each phase ​​for the motor corresponding to the primary induction motor- Calculation of auxiliary capacitor capacitance- The design of the motor corresponding to the primary induction motor, for the same output power and the same phase voltage, and taking into account the number of phases feeding the motor (n) and the new calculated values ​​for the windings as well as installation the Auxiliary capacitor.- improving power factor in the corresponding motorAccording to claim 1, the claimed method works through the design of three-phase balanced and symmetrical induction motors and can be used for the initial design or optimization of all induction motors powered by n-phase power supply.According to claim 1, with the assumption of n = 1 and for the power factor in the range of 0.4 to 0.6 for the primary induction motor, the number of windings and their characteristics (number of turns and conductor diameter) remain unchanged.According to claim 1 and 3, the calculation of the auxiliary capacitor capacitance is possible with this formula:.According to claim 1, 3 and 4, after designing the corresponding motor, the load angle (the angle related to the power factor) can be improved up to 30 degrees.According to claim 1, 3, 4 and 5, the designed corresponding motor has an optimal magnetic balance and at a power factor of 0.5, the magnetic balance is fully obtained.According to claim 1, with the assumption of n=1 and for the power factor in the range of 0.6 to 0.8 for the primary motor, the corresponding motor is designed with two windings.According to claim 1 and 7, the features of the corresponding motor can be calculated through these formulas:,and.According to claim1, 7 and 8, the capacitance of the auxiliary capacitor can be calculated with this formula:.According to claim 1, 7, 8 and 9, after designing the corresponding motor, the load angle (the angle related to the power factor) can be improved up to 45 degrees.According to claim 1, 7, 8, 9 and 10, the designed corresponding motor has optimal magnetic balance and at a power factor of 0.707, the magnetic balance is fully obtained.According to claim 6 and 11, the corresponding motors will be nearly equivalent in efficiency, and for those with power factor of 0.5 and 0.707, the efficiency will be completely equal to the primary three-phase induction motor.According to claim 1, the features of the corresponding motor with n≥2 can be calculated with these formulas:,and.According to claim 1 and 13, the design of the corresponding motor is done at a constant power factor without the need for an auxiliary capacitor.According to claim 1, the design of the corresponding motor fed by n-phase power supply can be done with any possible and permissible number of slots for the rotor and stator and any possible and permissible value for the length of the rotor and stator core.According to claim 1, after designing the corresponding motor fed by n-phase power supply, it is possible to change the number of slots in the stator and or rotor with this formula:.According to claim 1, after designing the corresponding two-phase induction motor fed by single-phase power supply, It is possible to change the number of turns and diameter of auxiliary winding using this formula:.

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