Abstract
In this study, the most vital characteristic properties of induction motor, motor starting, maximum and nominal torque are analyzed for what are affected. For the analysis of torque, L type, T type and IEEE 112 equivalent circuit model is employed. Torque change is investigated with the help of codes developed in MATLAB to be used in electrical machines course. First, the slip-moment characteristic curve of the induction motor is divided into three working zones and it was determined which equivalent circuit model gave the best results in these study zones. Later, such parameters as stator and rotor resistance, stator and rotor reactance, magnetization reactance, core resistance and slip are researched for how torque values are affected from. The obtained values for each of the three equivalent circuit models are given and compared with experimental results. 50 HP squirrel cage induction motor parameters are used in analysis. In the analysis, the most influential parameters on the starting torque are found as rotor resistance and stator and rotor reactance. Change of other parameters’ impact ratio depending upon right proportion and inverse proportion is observed. When nominal torque variations are investigated, again rotor resistance is the most influential parameter and by selecting proper factor effecting rotor resistance during design, the result of acquiring desired rotor resistance is obtained. When the maximum torque variations are examined, it appears that the stator and rotor reactance values are effective. Starting, maximum and nominal torque expressions change with square of voltage alters the effect on them a lot. Therefore, triangle or star connection importance arises during machine design.
Highlights
Induction machines is widely used in many applications in terms of specifications such as simple and robust structure, low cost, wide speed adjustment, low maintenance requirement, wide power range, reliable operation, mass production technology and etc
50 HP squirrel cage induction motor parameters are used in analysis
To be used in electric machinery courses, three different equivalent circuits of three-phase squirrel cage induction motor have been examined to observe the changes at starting torque, nominal torque and maximum torque
Summary
Induction machines is widely used in many applications in terms of specifications such as simple and robust structure, low cost, wide speed adjustment, low maintenance requirement, wide power range, reliable operation, mass production technology and etc. Some applications may require torque-speed characteristics outside the "design B feature", and a higher starting torque may require (e.g., for a loaded conveyor) than the capacity of "design B feature" In this case, a machine produced having "design C features" of the NEMA can be selected or machine having higher output power with "design B features" must be selected [7]. The slip-torque diagram of the induction machine has been divided into three parts, and it is determined which equivalent circuit model converges better to the experimental results in these parts It has been investigated how the starting, nominal and maximum torque values vary with changing the equivalent circuit parameters of the induction machine using three different circuit models. The parameters such as slip, stator and rotor resistances, stator and rotor leakage reactance, magnetization reactance and iron resistance have been changed at certain intervals and the change of torque values has been investigated
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