The design transition of an induction motor from IE2 efficiency class to IE4

Rapid increase in population and rapid industrialization are accompanied by the increased energy consumption. Day after day, new energy production facilities are being set up to meet new energy needs. However, it should not be forgotten that these plants need fuels such as oil, natural gas, coal to produce energy and the use of these raw materials is increasing the amount of carbon released to the environment day by day, which triggers global warming. Under these conditions, it is necessary to use the existing power in a better way and increase the efficiency value of the energy used. Considering both domestic applications and industrial applications, a large part of electricity is consumed by electric motors. For this reason, it will be the right approach to save energy in electric motors in order to use the existing energy more efficiently. Energy consumption classes are defined in almost all products that work with electricity. For the industrial motors, there are efficiency classes which are defined by some organizations such as International Electrotechnical Commission (IEC) , National Electrical Manufacturers Association (NEMA). The efficiency levels of the motors are classified as IE1, IE2, IE3 and IE4 in IEC 60034-30-1 standard. One of the most important issues of today's energy politics in electric motors is to increase the efficiency to IE3 and above efficiency classes as a result of the regulations announced by these organizations. IE3 efficiency class should be satisfied for the motors which have the power ratings of 0.75 kW and above and used in the industrial applications due regulations published by the European Union and Turkey as of January 1, 2017. In this perspective, the motor designers are aimed to increase the efficiency values of the motors that have IE1 or IE2 efficiency classes, to IE3 or IE4 efficiency classes by using various methods. It is necessary to reduce losses in order to increase motor efficiency. Literature review shows that there are several ways to reduce losses. There are two general approaches. The first one is the improvement of the materials. The other approach is to redesign the stator and rotor layouts. The thesis work was carried out in two steps. First, the reference motor and its parameters are introduced to the design programs to be used. Both analytical calculation and numerical (Finite Element Method) were used to analyze the reference motor and the new designed motors. The analytical and Finite Element Method (FEM) results of the reference motor are compared to the test results of the motor. The tests are performed due to the rotating electrical motor standards and the results are coherent. The main changes in the motor are simulated by using a commercial software based on FEM before the prototyping to save both time and money. First of all, material and winding improvements were made on the reference motor' stator and rotor laminations. Later, a new stator and rotor layouts was designed for different models. Different designs have shown that losses can be reduced in many ways. Due to limitations of production technology, some design layouts could not be manufactured. Only analytical results of them are given in the thesis. To improve the efficiency of the reference motor, the stator copper ratio is designed to be more than the reference motor on design 1 motor to reduce the winding resistance. Reduction of copper resistance will reduce copper losses, and it will increase the motor efficiency level. In design 2, in addition to design 1 the sheet material that will form the laminations will be converted from M700 to M270. As a result of these changes, in addition to the improvements achieved in design 1, the iron losses will be reduced. For design 2, motor bearings will change with friction loss decreased bearings then the friction loss of the motor will also be reduced. Motor efficiency level will increase with these changes. In design 3, in addition to the design 2, the stator and rotor package size of the motor will be extended a little. Due to the increase of package size of the design 3 than design 2, the magnetic flux density will decrease and it reduce the iron and stator losses in design 3 than design 2. The reduction of losses will allow to increase the efficiency value. In design 4, the package size of the design 3 will increase a little more. The iron and stator losses will be further reduced due to the more reduction of the magnetic flux density. With the new laminations design, the package size will be reduced a little compared to the reference motor. For design 5, new stator and rotor lamination will be made. Steel type will be M700 for new lamination. In this way, comparison of the laminations can be made without changing the steel type between design 5 and reference motor. However, the amount of copper used in the stator will be increased compared to the reference motor, but the stator slots will not be fully filled for design 5. Unlike the reference motor bearings, the loss-optimized bearings will be used for new lamination design motors. The design 6 includes improvements of the design 5. The stator and rotor length have been slightly increased and the stator filling ratio has been increased. The copper losses of the motor are reduced according to this change. The copper losses of the motor are reduced due to this change, so more efficiency motor can be get. In design 7 to reduce the rotor leakage currents, the design 6th motor's rotor is thermal shocked and additional losses are reduced. Reduction of additional losses is one of the ways of improving the efficiency of the motor. In this method, the rotor is heated in industrial ovens at high temperatures and then cooled instantaneously. Sudden heat exchange contributes to increased rotor resistance and reduced leakage currents. Design 8, design 9, and design 10 are obtained from design 1, design 4, and design 6 motors. The difference is that new rotors bars are replaced by copper bars. The conductivity of copper is higher than aluminum. The use of copper in rotor bars significantly reduces rotor copper losses and increases rotor speed. Designs reach the highest efficiency value at this point. There are two ways to use the copper application for rotor bars. The first one is to melt the copper and drain it into the rotor slots. The second is to take the prepared copper bars from any supplier and place them in the rotor slots. Both methods have the advantage and disadvantage compared to each other. Melting and draining requires hard work and hight factory investment costs, but unit production cost is lower than buying a prepared rotor bar. When the prepared rotor copper bars are bought there is no initial investment cost, but the purchase cost is high. The comparison of all the new designs is presented in the last section of the thesis. Different methods bring different improvement factors. It is clear that the reduction of copper losses and iron losses affects the efficiency of the motor directly. Production and cost constraints must be taken into consideration while efficiency studies are being carried out. The optimization should be realized by balancing production and cost. Increasing the stack length, using more efficient steel lamination, using more efficient bearings and increasing the filling factor of the stator slots boost the motor efficiency. Beside all, using the copper rotor bars and end rings also increases the efficiency significantly.