Design of IE4 efficiency level line start permanent magnet synchronous motor

Today, it is abviously clear that energy sources are rapidly consumed and the use of energy is increasing seriously. This relationship between use and reserves has led to a dramatic increase in energy costs, together with the need to optimize the use of available resources. Because of these facts, energy efficiency has reached a turning point with increasing interest in recent years. The use of energy efficient products has been enforced in a certain timetable with regulations in all developed countries and most of developing countries. A large part of electricity is consumed in the industry. The electric energy used in the industry is mostly consumed in electric motors. This has made electric motors one of the important points of energy regulations. Definitions of energy efficiency in motors are based on the end of 90's in Europe. According to the declaration of the European Committee of Manufacturers of Electrical Machines and Power Electronics (CEMEP) and the European Commission in 1998, electric motors were classified according to their efficiency classes. These classes are low efficiency motors (EFF3) which were not recommended for use in the European Union countries after 2000, efficient motors (EFF2) and increased efficiency motors (EFF1). There was no obligation and regulation related the usage and production of efficient motors. Motor manufacturers' compliance with these efficiency classes and their declaration were based on volunteerism. The first steps on efficiency in electric motors were laid by the publication of the efficiency test standard (IEC 60034-2-1:2007 and IEC 60034-2-1:2014), which describes how the motor efficiency should be tested and calculated. Afterwards, another IEC standard (IEC 60034-30:2008 and IEC 60034-30-1:2014), which describes the motor efficiency values according to power and speed, published. The basis for the development of standards is based on the principle of increasing the efficiency level and expanding the scope. When the IEC 60034-30 standard was first published in 2008, IE3 efficiency class was the highest efficiency class that had the efficiency values. By revision of standard in 2014, IE4 efficiency values have been added. With the addition of IE4 efficiency values, motor manufacturers have had to review their road maps. It is necessary to use different design methods and work on different motor technologies to achieve high efficiency values. Induction motors (IM) are highly preferred in the industrial arena due to their many advantages such as their ease of use and long life. However, it has not been easy for induction motors to achieve these efficiency values in the permitted mechanical dimensions after description of high efficiency values in IE4. With this fact, different accepted more in the long run, PMSM and SynRM, are compared with each other according to their advantages and may be proposed for different applications accordingly. Among these motor types, line start permanent magnet synchronous motors (LSPMSM), one of the derivatives of permanent magnet synchronous motors, have taken a step forward because they do not need an electronic driver. The aim of this thesis study is designing a 3 kW, 4p, IE4 LSPMSM according to IEC 60034-30-1:2014. The motor supply voltage is 400 V by star connection and the motor frequency is 50 Hz. The aimed efficiency value is 90,4% according to the IEC standard. One of the distinguishing features of this study is achieving IE4 efficiency value with only a new rotor design without changing the existing IE3 induction motor stator lamination design. Firstly, a detailed literature search was conducted at the beginning of the study. LSPMSM are a kind of hybrid motors that contain both magnets and aluminum bars in the rotor. Because the magnets are embedded in rotor, the mechanical strength and reliability of LSPMSM are good when comparing to other types of PMSM. Besides, the production process is more complicated and difficult than the asynchronous motors or other synchronous motors. Because of two active material, aluminium and magnet, process definitions and process order more critical in serial production conditions. It is seen that there are mainly two subjects which studies are mostly done. These topics are the position of magnets and the shapes of aluminium slots. It has been seen that the same stator lamination design has been used in some studies. Achieving a succesfull start-up characteristic and synchronization under load is one of the most challenging process during the design of LSPMSM. This feature is directly influenced by the rotor design. LSPMSM start-up characteristic is like an induction motor. After start-up period they operate as synchronous motor. One of the most important ways of achieving a succesfull start-up is through rotor slot design. Thanks to the appropriate slot design, the braking moment created by the magnets during starting is overcome. For that purpose, deep grooved aluminum rotor bars are preferred in this design. Magnet arrangement, which is another important design criteria, has been decided after literature investigations and motor benchmarking. After that, rectangular magnet array and NdFeB magnet type has been choosen. Design and two-dimensional electromagnetic analysis were carried out with Flux 2D magnetic analysis program. The IE3 efficient asynchronous motor, initially taken as a reference, has been modeled and verified. Because of using the same stator lamination, design of rotor lamination were carried out. Rotor slots, array and size of magnet were designed and analyzed. During these analyzes, different magnet sizes were studied and performance parameters such as motor current, power factor and efficiency were examined. Besides these performance parameters, start-up characteristic of the motors and synchronization behaviors under nominal load compared. After analyzing of five different magnet sizes, one of them which had the highest efficiency level of 90.6% was choosen for prototyping. In the prototyping phase, NdFeB type magnets had been ordered firstly. Rotor laminations were prepared by laser cutting. Because of two active material (aluminium and magnet) in the rotor, production processes had been decided according to serial production conditions. First of all, aluminium injection were applied to the sequenced rotor laminations and die cast rotor core prepared. Secondly, rotor shaft was placed into the rotor core. Lastly, magnets were placed in the rotor and the surfaces of the magnets on both sides was covered by epoxy. It is obvious that magnetized NdFeB should be used due to presence of aluminium slots. After the balancing process, the motor assembly was done by using the same wound stator of IE3 efficient asynchronous motor. The related test of prototype motor such as performance and efficiency test was performed according to IEC 60034-2-1, Section 7. According to this method, the input and output powers of the motor under the nominal load are measured. The output value is calculated by dividing the output power by the input power. This method is called as direct measurement method and recommended for synchronous motors. In order to determine the efficiency value of the motor, it is firstly required to operate at the nominal load until reaching the thermal stability. After reaching the thermal regime, the motor is loaded to six different load values and basic parameters such as current, speed, input power are measured. Thus, performance test is conducted. After tested in this way, the efficiency value of the prototype motor was calculated as 90,2% which is in tolerance of IE4 efficiency class. After the performance tests, the induced voltage in the stator windings of the motor was seen in waveform by oscilloscope. Wave shapes are consistent with the results of the analysis. At the end, a motor prototype which achieves the desired IE4 efficiency level and which can be started and synchronized under load is obtained. One of the most important advantages of this design is that it uses the same wound stator as IE3 efficient asynchronous motor. It should be underlined that the prototype was produced with processes which is fully proper serial production conditions.