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  • Küçük Resim
    Öğe
    Cogging torque minimization using skewed and separated magnet geometries
    (2020) Dalcalı, Adem; Kurt, Erol; Çelik, Emre; Öztürk, Nihat
    In the study, analytical design, analysis and optimization of a 2.5 kW 14-pole, 84-slot permanent magnet synchronous generator(PMSG) have been performed. The performance characteristics of this PMSG such as efficiency, torque, cogging torque andmagnetic flux density are assessed. Then, 3D model of the respective generator is acquired to examine the effect of magnetgeometry on the cogging torque produced. In that context, the effects of splitted and skewed magnet structures are examined. Inthe first design, the magnet is modelled with one piece and the rms value of the cogging torque is found as 436.75 mNm. In thesecond case, a certain skewed slit is made alongside the magnet and that yields a slightly reduced cogging torque of 434.58 mNm.In the other design, the magnet of the first design is divided into two sub-parts, which are then combined together in a skewedfashion. Thus, the value of cogging torque is found as 159.60 mNm. Eventually, by making two certain slits on the last model,cogging torque is further depressed down to 89.95mNm. It is concluded from the obtained results that the last design contributesan improvement in the value of cogging torque up to 80% compared to the initial design.
  • Küçük Resim
    Öğe
    Wind turbine speed control of a contactless piezoelectric wind energy harvester
    (Taylor & Francis Ltd, 2020) Celik, Emre; Kurt, Erol; Ozturk, Nihat
    Wind turbine control is an important task to make the electricity generation secure in terms of energy demand and machine safety. It also yields to control the desired power level and optimized energy because of the assignment of turbine speed. The contactless piezoelectric wind energy harvester (CPWEH) used in this study has three piezoelectric layers located around the shaft with 120 degrees apart and they are buckled by the magnetic force without any physical contact. The superiority of this device is to generate energy for low wind speeds such as 1.5 m/s. However, for high speeds, high total harmonic distortions (THDs) govern the waveforms, thus controlling the turbine speed becomes necessary for optimizing the output power. Encouraged by this, a small low inertia dc generator is coupled with the wind turbine, and the generator terminals are connected to a resistor through a power switch to generate a braking torque that opposes to wind speed direction. By controlling the switch properly, turbine speed is ensured to remain within a certain band, which accordingly prevents the turbine from rotating very fast at damaging wind speeds. Several experiments are performed on the developed CPWEH with/without the presented control scheme which prove the existence of promising performance of our proposal.