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A Historical Overview, Misconceptions and Suggestive Measures of Lightning- A Bangladesh Perspective
Md Rosaidul Mawla,
Nasrin Sultana
Issue:
Volume 7, Issue 2, December 2021
Pages:
35-41
Received:
13 August 2021
Accepted:
23 August 2021
Published:
5 October 2021
Abstract: Every year Bangladesh experiences high density of lightning as it is a tropical country. In recent years, lightning related deaths and injuries have increased in Bangladesh. In 2016 due to lightning, 81 people have died in just two days. Therefore, the GoB has acknowledged lightning as natural disaster. The survey portrayed that around 70% population explain their belief that it is nothing but ray of light of God and it comes down to earth to punish the sinners. The rest people made an attempt to explain the lightning at their own way. About the lightning safety, approximately 80% of the surveyed people are still yet to acquire basic knowledge on lightning safety and around 90% interviewers acknowledge that they donot trust or relay on the forecasting and monitoring by government on weather and climate change. Still people are not educated on consequences of lightning. However, the paper reviews the lighting safety and awareness programs conducted around the world. It also portrays an overview of lightning history along with the misconceptions of lightning. It also highlighted the surveyed summary of the misconceptions of lightning. Finally, some suggestions are recommended about lightning safety and awareness for Bangladeshi people.
Abstract: Every year Bangladesh experiences high density of lightning as it is a tropical country. In recent years, lightning related deaths and injuries have increased in Bangladesh. In 2016 due to lightning, 81 people have died in just two days. Therefore, the GoB has acknowledged lightning as natural disaster. The survey portrayed that around 70% populati...
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Minimization of the Electromagnetic Torque Ripple of a Synchronous Reluctance Generator Using External Rotor Excitation
Jesus Gonzalez,
Concepcion Hernandez,
Marco Arjona
Issue:
Volume 7, Issue 2, December 2021
Pages:
42-47
Received:
10 September 2021
Accepted:
5 October 2021
Published:
15 October 2021
Abstract: This paper presents an approach to minimize the electromagnetic torque ripple of a synchronous reluctance generator (SynRG) with a magnetic field created by externally excited rotor coils. The synchronous reluctance machine is widely used in low and medium power systems such as wind power generation and new electric vehicle technologies. This paper proposes a rotor topology with flux barriers and direct current excited coils that reduce the torque ripple and replace the permanent magnets used in other reluctance rotor topologies. First, the initial rotor design, without excitation coils, is optimized to obtain a new rotor structure that reduces the electromagnetic torque ripple. In this work, the optimization of the rotor geometry was achieved by using genetic algorithms and the finite element method to optimize and parameterize the main components of the machine. In the optimized rotor model, an external electronic converter is included to feed the coils positioned between the magnetic flux barriers and the segments formed by the ferromagnetic material of the rotor. Finally, the electrical and magnetic machine variables obtained from implementing the coils into the optimized rotor are compared to the initial rotor structure operating under nominal load conditions to demonstrate the advantage of this topology in minimizing the electromagnetic torque ripple.
Abstract: This paper presents an approach to minimize the electromagnetic torque ripple of a synchronous reluctance generator (SynRG) with a magnetic field created by externally excited rotor coils. The synchronous reluctance machine is widely used in low and medium power systems such as wind power generation and new electric vehicle technologies. This paper...
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Effect of Eccentricity Factors on End Winding Electromagnetic Force in Turbo-generator
Hong Chun Jiang,
Yu Ling He,
Gui Ji Tang
Issue:
Volume 7, Issue 2, December 2021
Pages:
48-53
Received:
28 October 2021
Accepted:
19 November 2021
Published:
27 November 2021
Abstract: Static eccentricity will cause the abnormal distribution of air gap magnetic field and further affect the electromechanical characteristics of the generator. This paper comparatively studies on the end winding electromagnetic force of turbo generator under different eccentricity ratio and eccentricity angle. The analytical expression of end winding electromagnetic force is derived after eccentricity. Meanwhile, the three-dimensional transient finite element simulation is carried on under several eccentricity cases. Then the amplitude variation characteristics with eccentricity ratio and angle are analyzed. Further, the force characteristics are verified by experimental vibration acceleration of CS-5 simulating generator. It is found that the static eccentricity will not change the frequency components of the end winding force. However, it will change the amplitude of the electromagnetic force, and the increase or decrease tendency depends on the winding position, eccentricity ratio and eccentricity angle. The number of force amplitude increasing coils is close to half of the total number, and it changes slightly with the eccentricity ratio and eccentricity angle. The force increment of coil near the minimum air gap will be larger with the increase of eccentricity ratio, but it is not affected greatly by eccentricity angle. Moreover the coil with the most obvious force increase is located in the interphases position near the minimum air gap.
Abstract: Static eccentricity will cause the abnormal distribution of air gap magnetic field and further affect the electromechanical characteristics of the generator. This paper comparatively studies on the end winding electromagnetic force of turbo generator under different eccentricity ratio and eccentricity angle. The analytical expression of end winding...
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Application of New Co-simulation in System Simulation of Doubly-fed Induction Generator
Wen Jie Zheng,
De Rui Dai,
Gui Ji Tang
Issue:
Volume 7, Issue 2, December 2021
Pages:
54-60
Received:
24 November 2021
Accepted:
16 December 2021
Published:
29 December 2021
Abstract: This paper proposes a doubly-fed induction generator (DFIG) model built on three simulation platforms: Maxwell, Simplorer and Simulink. It can solve the overall modeling problem of the DFIG system effectively. In this paper, the generator physical simulation model (rotating shaft, rotor, stator and winding) are first established in Maxwell. Then, the internal (stator/rotor winding) and external circuit of DFIG are connected in Simplorer. The external circuit includes converter (generator side and grid side), filter, transformer and grid. Moreover, both the generator-side converter and the grid-side converter are controlled by Simulink. Finally, the simulation calculation study on the 5.5kW DFIG are carried out to validate the theoretical analysis. It is shown that SAGE causes distortion of the air gap magnetic field, the magnetic flux density (MFD) is inversely related to air gap changes. In addition, with the increase of SAGE, the curve of electromagnetic torque (EMT) moves down and rotor unbalanced magnetic pull (UMP) fluctuations become more obvious. The model can simulate the DFIG system accurately and effectively. And the simulation results are consistent with the theoretical derivation, which proves the validity of the model. This provides an effective method for the whole simulation and fault analysis of DFIG system.
Abstract: This paper proposes a doubly-fed induction generator (DFIG) model built on three simulation platforms: Maxwell, Simplorer and Simulink. It can solve the overall modeling problem of the DFIG system effectively. In this paper, the generator physical simulation model (rotating shaft, rotor, stator and winding) are first established in Maxwell. Then, t...
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