Reducing of the space harmonics effect for 60 slot induction motor and improving of the motor performance

In recent years, energy efficiency has come to the forefront and technological developments have led to the development of improving the performance of asynchronous motors. A lot of improvement on both the drive and design side is carried out to improve the electrical and mechanical performance of asynchronous motors. Along with improvements in electronics technology, it is possible to drive asynchronous motors with a pure sine waveform and reduce the amplitudes of the time harmonics to low levels. In induction machine, space harmonics appear as well as the time harmonics .The mmf distribution of the induction motor is not pure sinusoidal, so mmf distribution have harmonic compounds. The space harmonics are directly related to the airgap MMF distribution. The amperage distribution occurs along the machine space as a function of the stator slot position and the current flowing through the respective slot. A structural changes are necessary to change the MMF distribution in the machine space. When the space harmonics are examined; the amplitude of the double harmonics is zero due to the 3-phase current-voltage waveform. Harmonics of 3 and 3 times are insignificant because they do not form a rotational field. Space harmonics appear in every 6k ± 1. k is the level of the harmonics. The most effective space harmonics are 5th and 7th harmonics. The harmonics of level 6k-1 generate rotating field in the negative direction and the harmonics of level 6k+1 have rotating field in the positive direction. Historical development of space harmonics has started with the definition of mathematical equations for classical windings of harmonics and continue with various calculation methods have been established for all motors respectively and methods have been developed to reduce harmonics. Although there is no current method for all rotating electric machines today, there are methods to reduce harmonics under certain criteria. In this thesis study, it is aimed to eliminate the harmonics in the air gap MMF distribution by changing the stator groove positions and ampere turn of the respective slot. The first important academic research of space harmonics was carried out by B. Hague in 1917. The mathematical model of the harmonics in the MMF distribution is presented with this research. Then the effect of the space harmonics on motor torque xxii were investigated by K.L Hansen in 1922 (Torque Components Due to Space Harmonics in Induction Motors). After the concept of space harmonics has been defined, some studies have been done to calculate the harmonic components. One of the most important works was carried out by J. Stepina in 1987 (Matrix analysis of space harmonics of asymmetrical stator windings). The MMF expression is solved in these matrices and the harmonic components are obtained by opening to the fourier series. Since the position matrix is given as an input here, this method can be applied for any symmetrical or asymmetric windings. It is very important because it is the basis of the method of changing the slot locations used in this thesis study. MMF expressions obtained for different q values in the work "Reducing the Effects of Space Harmonics on Asynchronous Machines" made by Kocabaş D. A in 2004 were solved by the Newton Raphson iteration method in terms of the slot position matrix. For each q value, the stator slot locations that make the least harmonic components are calculated. In this method it is possible to eliminate harmonics as much as 1 minus the q value calculated. For example, q = 10 for the 60 poles and 2 poles used in this thesis. 9 pcs harmonics can be eliminated and the first space harmonics available is 31st harmonic. Within the scope of the thesis, 90kW 2-pole 48-Slot IE2 Efficiency class asynchronous motor is examined as the reference motor. After that, it was compared with the test results. The analytical and finite elements analysis of the reference motor were compared with the test results after analysis. It has been proven that the design outputs match the motor test results. The design of the 48 corrugated motors whose design and performance have been verified .Then reference 60 pole motor will be designed consider the same rotor geometry with 48 slot machine. The design of the 60 slot reference motor with classical winding has been verified in the analysis of the finite elements and then the design of the 60-pole 2-pole space harmonics reduced motor according to the reference motor parameters. Slot location and ampere turn distribution which is stated by D.A.Kocabaş for q/2=5 will be used for design of reduced harmonics machine. It is known that the effects of all harmonics up to 31. harmonics to be eleminated by using this method. The results of analyzes made and the equivalent circuit parameters are given comparatively for all three machines and the results obtained with the machine with reduced harmonics according to the analysis outputs are satisfactory. As a consequence of reducing the harmonic effects, the rotor currents are improved, while a more similar sine wave MMF distribution is obtained in the air gap. s a result of the reduction in rotor currents, there is a serious improvement in rotor conductor losses. With the Improvement of the destructive torque has been observed to improve the starting characteristic of the induction motor. With the new winding design being made, the coil steps have been shortened and the usage of less copper has resulted in a decrease in copper losses and an increase in motor efficiency.