Abstract- This paper deals with the circulating current distribution calculation and its resultant ohmic losses in a large synchronous generator. Circulating currents are produced by the induced voltage differences between parallel strands in a bar that cause high ohmic losses in high power synchronous generators. In this paper, three different cases are assumed for the armature end winding structure, and a 3-D finite element model is adopted to calculate the effectiveness and resultant losses of these cases. As mentioned later, by the use of an appropriate transposition in slot area, both main and leakage fluxes inside the machine are the same for all transposed strands bundle in active part and consequently the induced voltage difference in each strand in a bundle is negligible. However, the currents flowing in the end winding of the generator produce leakage flux in the slot region that causes circulating currents in strands, and consequently electrical power losses in the machine.
Index terms— Synchronous generator, slot region, end winding, circulating current, finite element method.
I. INTRODUCTION
Circulating currents are produced by the induced voltage differences between parallel strands in a bar due to different linkage magnetic flux. In large synchronous generator with high power density, the Roebel bars are used for the stator windings in which strands in a bundle are completely transposed in slot region by different arrangement.
By the use of this procedure, the overall physical position of each strand in a bundle is the same. Therefore, the both main and leakage fluxes are the same for each strand in each bundle, and consequently the induced voltage difference in each strand is negligible. Anyway, the curr...
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...gren X, Lijian T, Dangun Z, Yi X. “Calculation of end region magnetic field and circulating losses for turbo-generators using a coupled field and circuit equations method”, IEEE Trans Magn 1990;26:497–500.
[5] K. Takahashi, M. Takahashi, and M. Sato, “Calculation Method for Strand Current Distributions in Armature Winding of a Turbine Generator”, Electrical Engineering in Japan, Vol. 143, No. 2, 2003 Translated from Denki Gakkai Ronbunshi, Vol. 122-D, No. 4, April 2002, pp. 323–329.
[6] Hitachi, Ltd., Japan M. A. Mueller, “Design and Performance of a 20kW, 100rpm, Switched Reluctance Generator for a Direct Drive Wind Energy Converter”, IEEE International Conference on Electric Machines and Drives, page(s): 56-63, 2005.
[7] J. Haldemann, “Transpositions in Stator Bars of Large Turbogenerators” IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 19, NO. 3, SEPTEMBER 2004
It is well known that nowadays wind power is one of the fast developing energy sources of the world. Thats why one of the GE’s Energy business maintain a strong focus on building the wind power facility and delivering the technology in its fields and benefiting the advantages of wind power. GE has over 12,000 wind turbine operating in all around world with the countries like USA, Canada, China and Spain.
...issued on 2009 Aug 11, cited 2010 Oct 3]. [about 5 paragraphs]. Available from: http://green.blogs.nytimes.com/2009/08/11/raising-wind-output-with-longer-blades/
For an engineer to determine the feasibility of using a linear electric generator in a system’s design many comparisons between rotary and linear machines must be made. Several points to consider when making this comparison include: practicality of using linear power generation for that particular system, cost to build and design, total system efficiency, role of modern day power electronics, type of driving force (linear or rotational) applied to the generator system, system power factor, force density and force ripple on the drive components, cost to maintain, and the system’s reliability. The relative weights of these considerations will vary from one system to the next. The motivation behind this question was the decision on whether to use a linear or rotary generator on a buoy driven, ocean wave electrical generator project [6]. During this decision process, many opinions and assumptions between these competing systems were made, but finding hard data that compared the two methods was not readily available. Taking the time to thoroughly evaluate the electrical and mechanical technical aspects of this choice (rotary vs. linear) conflicted with the tight scheduling requirements of the project. This situation forced the team to make a best approximation based on limited experience instead of a deliberate and thoroughly evaluated approach.
Linear generators/motors have been around since the early 1900’s with one of the first written references being in regard to Birkeland’s Cannon, then described as a tubular motor but is more accurately described as a reluctance motor. 1
The aerofoil of the blade also very significant, the shape of the aerofoil that has been used would affect the result of the wind turbine performance. The CFD analysis result, such as pressure and velocity distribution, flow streamlines and calculation results such as rotational speed, torque, power, lift and drag coefficient , effect of TSP and angle of attack can be done. Regards for the shroud reviews, found that the differences between the bare wind turbine and the augmented shroud wind turbine affect the efficiency of power production
Since the invention of jet engines, there has always been a steady increase in their power and efficiency. As a comparison, the air temperature inside the turbine has risen from about 600 degrees Celsius to over 1500 degrees Celsius. This change has caused a 60% increase in power and a 20% decrease in fuel usage. These drastic changes have also caused a change in the materia...
Our orthocyclically-wound motor coil makes it possible to manufacture the stator windings with the highest possible copper fill factor, allowing for a shortened motor length while increasing power output by up to 80
Offshore wind power has become a need of the hour in renewable energy production due to the rising prices of oil and continually increasing demand for a separate energy sector. Offshore wind has the prospective to deliver at least four times the current U.S. demand of energy, as per mentioned by the Global Wind Energy Council. However, there are many challenges and advantages that are significant for us to comprehend.
Wilson, D. G., & Korakianitis, T. (1998). The design of high-efficiency turbomachinery and gas turbines (2nd ed.). Upper Saddle River, NJ: Prentice Hall.
It is very simple, from the name itself we can understand that there is induction process occurred. Actually when we are giving the supply to the stator winding, flux will generate in the coil due to flow of current in the coil. Now the rotor winding is arranged in such a way that it becomes short circuited in the rotor itself. The flux from the stator will cut the coil in the rotor and since the rotor coils are short circuited, according to Faraday's law of electromagnetic induction, current will start flowing in the coil of the rotor. When the current will flow, another flux will get generated in the rotor. Now there will be two flux, one is stator flux and another is rotor flux and the rotor flux will be lagging to the stator flux. Due to this, the rotor will feel a torque which will make the rotor to rotate in the direction of rotating magnetic flux. So the speed of the rotor will be depending upon the ac supply and the speed can be controlled by varying the input supply. This is the working principle of an induction motor of either
Induction Motors are widely used in industrial applications. It has been reported that they have a motor market share of approximately 80 percent. Their popularity stems from robust construction, low cost and ease of maintenance.
Engineers does not need to spend too much on maintenance as AC generators does not have any brushes unlike DC generator. An example of brushes is shown in figure 13.Therefore, it saves a lot of money.
The wind is an incredibly valuable renewable energy source and is in the forefront of renewable energy developments. It is used to convert wind energy into energy that can be harnessed and used via a variety of methods, including; wind turbines, windmills, sails and windpumps. For a renewable energy source, however, it is wind turbines that are used to generate electricity (see figure 1). Wind power has been used for this since the end of the nineteenth century, after Professor James Blyth of the Royal College of Science and Technology first attempted it (Boyle, 2012). However, It wasn’t until the 1980s that using wind power technology was sufficient enough to experience a rapid growth of the technology.
Deal, W. (n.d.). Wind power: An emerging energy resource.Technology & Engineering Teacher, 70(1), 9-15. Retrieved from http://web.b.ebscohost.com/ehost/detail?sid=a747d6c4-9f9f-4066-be3e-d7d26a427ef2@sessionmgr115&vid=1&hid=114&bdata=JkF1dGhUeXBlPWNvb2tpZSxpcCxjcGlkJmN1c3RpZD1zc2Mmc2l0ZT1laG9zdC1saXZlJnNjb3BlPXNpdGU=
... a little current. In induction motors, this present comes from the rotor conductors. The revolving magnetic earth produced in the stator cuts across the conductive bars of the rotor and induces an e.m.f. The windings of the rotor which is being used due to the force of an external resistance tend to be directly shorted or closed which will lead in changing the direction of the rotor current in the other direction of the rotating magnetic field which is resulted from the stator and at the end a torque will be resulted in the rotor. As a reult, the rotor speed will not reach the synchronous speed of the r.m.f in the stator. If the speeds match, there should be no e.m.f. generated in the rotor, no present should be flowing, and consequently no torque should be generated. The difference between the stator (synchronous speed) and rotor speeds is known as the slip.