Transformers 3 part 05

Power transformers are at the heart of electrical transmission and distribution systems, and as competition increases within the energy sector, so does the pressure on transformer manufacturing industry to improve reliability and reduce costs of transformers.

The power transformer concept was conceived and developed in the late 1800's and since then, the basic concept of transformer has remained the same. However, design and construction techniques have improved to increase both - the overall efficiency and cost effectiveness of manufactured units.

With superior expertise in designing coupled with extensive R&D efforts, modern transformers are much smaller in size, lower in cost, and are able to promise a remarkable increase in efficiency and reduce lost energy.

Especially for countries like the US, modern transformer design can play a significant role in reduction of energy loss. The U.S. has only 4% of the world's population but produces 25% of its greenhouse gases. The country has over 9,200 electricity generating units much of them old, needing replacement and thus largely inefficient. Since 1982, growth in peak demand for electricity in the U.S. has exceeded transmission growth by almost 25% each year, even while a majority of the energy transformers in the country continue to waste away large amounts of energy.

Better transformer design and the use of superior grade electrical steel can drastically reduce no-load loss, one of the prime components of loss in an energy transformer. No-load loss can be further reduced in some cases if conventional electrical steel can be replaced with amorphous metal.

Transformer life expectancy is based on a number of factors, the most important being the quality of its insulation system. Two things that damage transformer insulation are moisture and excessive heat. Addressing these two factors, modern transformer designs are developed to preserve overall insulation quality of the transformer. Some of these designs include open style, sealed tank, conservator style, and automatic gas pressure.

With the cost of energy increasing and pressure mounting to reduce transformer losses, attention is on modern transformer design that incorporates technology to lower energy losses in transformers. Most transformers are inherently efficient when they function at 100% load. However, 100% load is an ideal situation, and many transformers need to function at far lower loading. As transformer loading changes so does its efficiency. Low loss transformers with modern designs are said to be 30-50% more energy efficient and their losses are designed to be 30% less at 35% loading.

Newer transformer designs with conservator tanks incorporate an air bag in the expansion tank, which virtually eliminates moisture egress from oil contact with the outside atmosphere.

Numerous transformer design tools have been developed also such as artificial intelligence (AI) techniques in combination with finite element method (FEM). Today, AI is widely used for modeling nonlinear and large-scale systems, especially when explicit mathematical models are difficult to obtain or completely lacking. Moreover, AI is computationally efficient in solving hard optimization problems. On the other hand, FEM is particularly capable of dealing with complex geometries, and also yields stable and accurate solutions.

Thermal deterioration of transformer insulation material reduces dielectric strength and reduces its ability to withstand short-circuit events. Innovative hybrid high-temperature insulation however can improve insulation temperature tolerance, improve winding mechanical strength, and reduce costs of maintaining and replacing transformers. Hybrid insulation consists of using layers of aramid papers and cellulose papers. Additional global design modifications include reducing the number of cooling ducts between layers and reinforcing the frame of the transformer to improve short-circuit withstand strength. Higher reliability and longer life anticipated by hybrid-insulation manufactured transformers results in cost savings to the utility.

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Transformers 3 part 04

The US has one of the largest mining industries in the world - an industry closely linked with the economy. In the past, the discovery of resources such as gold and oil resulted in a major population shift and rapid growth for formerly remote regions of the country, such as California, Texas, and Alaska. Extraction of these resources, and finding new deposits, continues to provide the foundation for local economies in some regions.

Some of the minerals mined in the US are coal, uranium, copper, gold, silver, iron, lead, zinc and others. Most of the mines in the US are highly automated and thus energy intensive. To provide an example, even in the last decade of the 20th century, iron ore mining alone consumed 62.3 trillion Btu of energy across a calendar year. Because mining is such a large industry and makes a sizable contribution to the national income, mines must have a dependable source of power - a crucial resource for mining processes.

The mining and mineral extraction sector both in the US and worldwide relies heavily on energy to harness natural resources such as aggregates, precious metals, iron ore, oil, gas, and coal. This energy is used to power shovels and drills for excavating these products, loading them into enormous mining trucks or onto conveyer belts, sorting, sifting and crushing ores, heating, and a hundred other functions. Both surface and underground mining operations rely on powered equipment to extract materials and load trucks. Overall, the mining sector could not flourish without the use of vast amounts of energy.

Mine 'Power Centers' or 'Load Centers' are an essential system for underground and surface mining. Their primary function is to convert distribution voltage into utilization voltage for equipment operation, thus placing power transformers at the heart of the load center. Proper selection of transformers is imperative, and must fulfill safety, reliability, and efficiency requirements. Determining capacity rating is among the first steps for selection of a power transformer for a mining load center. A rule of thumb here is to allow 1 kVA for every horsepower of connected load. Most mining processes, however, do not produce constant loads - all machinery is not connected all the time - and therefore the 1 kVA per horsepower thumb rule will typically result in transformer oversizing. According to the SME Mining Engineering Handbook by Howard L. Hartmann, "Past experience and demand factors established by manufacturers and operators, along with the horsepower of the connected load, are essential for determining transformer capacity. For typical underground mining sections, the kVA rating may lie within the range of 50 to 80% of the connected horsepower."

Standard transformers while under full load operate at 90 to 95% efficiency, with this figure dropping as the load lightens. This is due to inefficiencies in the transformer's core, a main component of the transformer. The losses in the core remain the same throughout the transformer's operating range. At 100% load, the amount of comparative loss is negligible. However, at reduced loads, the same amount of energy loss represents a higher percentage of energy being wasted. Unfortunately, average transformer loads run between 34 and 50% of the transformer's total capacity. With the majority of the electricity used

in the US being run through transformers at these lower loads, massive amounts of energy are being wasted. This issue is of special relevance to the mining industry, simply because of its high energy usage. Mining operations also involve hostile environments full of dust, dirt, chemicals, moisture and airborne contaminants. Load center transformers need to function reliably and efficiently in these environments over a long term.

Without electric power at mining facilities, the natural materials extracted from the earth in the mining process would be much more costly than they are today. Thus, power transformers provide a lot of muscle, capacity, and stability to an essential industry. From drilling trenches to busting up rock, carting out huge loads of materials and pulling up heavy amounts of minerals, power transformers provide the strength and capability needed.

While there is still debate on the relative advantages of the available types of transformers, there are some performance characteristics that have been accepted: • Liquid-filled transformers are more efficient, have greater overload capability and longer life expectancy. • Liquid-filled units are better at reducing hot-spot coil temperatures, but have higher risk of flammability than dry types. • Liquid-filled transformers sometimes require containment troughs to guard against fluid leaks. • Liquid filled transformers are smaller in size than dry-type units for the same power rating capacity and have lower losses because of their better thermal dissipation characteristics.

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Transformers 3 part 03

In the rush to cash-in on wind energy, developers are often trading low first costs for higher total costs of ownership to be shouldered later by the wind farm owners and operators.

Converting wind energy to electrical power is the fastest growing segment of the US energy sector. Today, wind energy represents less than 5% of the US electrical generation and is targeted to reach 20% in the foreseeable future. For this to happen, new sites need to be developed in spite of a down turning economy.

Bolstered by available federal stimulus dollars, we are seeing a virtual modern day 'land-rush'. In the words of one industry leader, 'if there is a site that has a viable wind profile, access to network connections, and access for delivery of materials, and we don't develop it, some one else will.'

This head long rush to install more and more wind turbines has outstripped the usual developmental learning curve, where new technologies mature by a process of trial and error, resulting in defining equipment suited for the job at hand.

The added economic pressure of today's market has made an already competitive market even more demanding. This has, in the view of many industry insiders, resulted in purchasing decisions for equipment based largely on the lowest initial cost solutions and not solutions that will provide the best choice in terms of total cost of ownership, network stability, less down time and lost revenue from high maintenance issues. This is nowhere as apparent as in the case of Wind Turbine Generator (WTG) transformers.

Historically this WTG transformer function has been handled by conventional, 'off the shelf' distribution transformers, but the relatively large numbers of recent failures would strongly suggest that WTG transformer designs need to be made substantially more robust. The practice of using conventional 'off the shelf' distribution transformers as a low cost solution is folly. In some cases site operators are maintaining a quantity of spare transformers to combat the frequent outages caused by standard distribution transformers being used where they are not suitable.

The role of the Wind Turbine Generator (WTG) transformer in this process is critical and, as such, its design needs to be carefully and thoughtfully analyzed and reevaluated.

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Transformers 3 part 02

Sale of transformers to the people is in more numbers and they are sold for reasonable and competitive prices. Transformers fetch more demand among the business people and general customers around the world. Transformers are available in different kinds and they are the only instrument which is used to measure or to transfer current or energy from one circuit to another. Transformers are kind of electrical instrument used to transfer energy from source to another without any hindrance. Transformers are available in more number and at the same time they are available in different kinds.

Some of the kinds of transformers are current transformer, isolation transformer, power transformer, electric transformer, audio transformer, flyback transformer, high voltage transformer, low voltage transformer, step down transformer. Transformers are sold for reasonable and affordable prices to enable the customers to pay off the price consideration. The different kinds of transformers satisfy the requirement of the customers and meet their demand at the time of requirement. Some of the kinds of transformers are displayed below.

Electric transformer is inclusive of different kinds of transformers manufactured. Electric transformer is used to transfer current from one circuit to another with the help of electromagnetic induction. Electric transformer is provides current effectively and efficiently. Electric transformers are sold for reasonable prices to enable people to purchase it.

Current transformer is also the other kind of transformer which is used to obtain current. The main purpose of using current transformer is to obtain current from the secondary circuit and also it measures the alternate current with the help of the conductor. Current transformers transfer current without influence over other process and supplies current directly.

Isolation transformer is a kind of transformers used to supply current for equipments. Isolation transformer helps to decouple two circuits and supplies current from one circuit to another circuit. Isolation transformer suits for wide applications and helps to prevent influence one section to another. Isolation transformers are designed specifically to meet the requirements of the customers around the world.

High voltage comes under the different kinds of transformers manufactured. High voltage transformers are used for more number of applications and they come up with standard features. High voltage transformer can be used in power transmission applications. High voltage transformers transfer the energy directly from one circuit to another circuit with fine voltages. They transfer the energy from one circuit to another and supplies sufficient voltage to the customer.

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