Choosing the right transformer for the mining industry

Introduction

The United States has one of the largest mining industries in the world, an industry closely tied to the economy. In the past, the discovery of resources such as gold and oil resulted in major population change and rapid growth in previously remote regions of the country such as California, Texas, and Alaska. The extraction of these resources and the search for new deposits continue to form the basis of local economies in some regions.

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

The mining and mineral extraction sector, both in the US and around the world, is highly dependent on energy to harness natural resources such as aggregates, precious metals, iron ore, oil, gas and Coal. This energy is used to drive shovels and drills to excavate these products, load them onto huge mining trucks or conveyor belts, classify, sift and crush minerals, heating and a hundred other functions. Both surface and underground mining operations rely on motorized equipment to extract materials and load trucks. In general, the mining sector could not prosper without the use of large amounts of energy.

The role of transformers

Mine ‘Energy Centers’ or ‘Load Centers’ are an essential system for surface and underground mining. Its main function is to convert the distribution voltage into the utilization voltage for the operation of the equipment, thus placing the power transformers at the heart of the load center. Proper selection of transformers is imperative and must meet the requirements for safety, reliability, and efficiency. Determining the rating is one of the first steps in selecting a power transformer for a mining load center. A general rule of thumb here is to allow 1 kVA for each connected load horsepower. Most mining processes, however, do not produce constant loads (not all machinery is connected all the time) and therefore the rule of thumb of 1 kVA per horsepower will generally result in oversizing of the transformer. According to Howard L. Hartmann’s SME Mining Engineering Handbook, “Past experience and demand factors established by manufacturers and operators, along with connected load horsepower, are essential in determining transformer capacity. within the range of 50 to 80% of connected horsepower. “

Transform losses

Standard transformers while fully loaded operate at 90 to 95% efficiency, with this figure decreasing as the load is lightened. This is due to inefficiencies in the transformer core, a major component of the transformer. 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 lost represents a higher percentage of energy wasted. Unfortunately, average transformer loads are between 34 and 50% of the total transformer capacity. With most of the electricity consumed

In the US, running through transformers with these lower loads wastes massive amounts of energy. This issue is of special relevance to the mining industry, simply because of its high energy consumption. Mining operations also involve harsh environments filled with dust, dirt, chemicals, moisture, and airborne pollutants. Load center transformers must operate reliably and efficiently in these long-term environments.

Without electrical power at mining facilities, natural materials extracted from the earth in the mining process would be much more expensive than they are today. Therefore, power transformers bring a lot of muscle, capacity and stability to an essential industry. From trenching to rock excavation, mining massive loads of materials, and mining large amounts of minerals, power transformers provide the strength and capacity you need.

Dry and Liquid-Filled Transformers – Performance Characteristics

Liquid filled transformers

While there is still a debate about the relative advantages of the types of transformers available, there are some performance characteristics that have been accepted: • Liquid-filled transformers are more efficient, have a higher overload capacity and a longer life expectancy. • Liquid-filled units are better at reducing hot spot coil temperatures, but have a higher risk of flammability than dry types. • Liquid-filled transformers sometimes require containment channels to protect against liquid leaks. • Liquid-filled transformers are smaller than dry-type units for the same power rating and have lower losses due to their better heat dissipation characteristics.

2.Dry-type transformers

Dry type transformers are generally used for lower ratings (switch point is 500 kVA to 2.5 MVA). They are usually placed indoors, serving an office / apartment building. Dry-type units generally come in louvered or sealed cabinets.

Dry-type transformers use almost no flammable materials and therefore do not constitute a fire hazard when used underground in both coal and other mines.

Dry-type transformers in the mining industry are housed in a steel tank and the core and windings are cooled by the air circulating inside the tank, transferring heat to the steel tank which is in turn cooled by the external air. In some compact designs for mounting on mining machines, water cooling is added to further improve the performance of the transformers.

The correct choice of insulating materials and an understanding of the cooling system are imperative for the transformer to be properly designed. For example, a temperature rise test performed on a transformer manufactured and sold with continuous rating may reveal that the transformer only had a continuous rating of 65% of the nameplate rating.

The need for energy efficient mining

With today’s focus on climate change and reducing environmental impact, government agencies around the world are making increasingly stringent demands on industries to reduce energy consumption and manage waste more effectively, among others. It is surprising how many mining operations still use technology from twenty years ago.

Regulatory pressures are already beginning to affect the mining industry: According to an article on ‘US Environmental Regulations and the Mining Industry’ on the International Development Research Center (IDRC) website, “Environmental Regulations have had an effect on the profitability of the US mining industry. Companies have been forced to modernize or renovate facilities or leave the market. Rising operating costs have affected their international competitiveness and, to some extent, this the global allocation of mining investment may be changing. Employment levels have fallen substantially and local economies share in this cost. “

Therefore, mining companies in the US feel the urgent need to be energy efficient, simply to remain competitive. Reducing energy consumption by adopting cost-effective, custom solutions like NEMA approved transformers and harnessing solar or wind power to meet your future energy needs can be good long-term ideas, especially as the alternative energy option will help. mining companies to stay away from fluctuations in international fuel prices. Alternative energy sources are still a small dot on the graph, in terms of actual energy provided for industries like mining, and therefore the sector as a whole needs to find more immediate ways to conserve energy.

Various types of transformers for the mining industry:

Transformers can be used in a variety of open pit and hard rock (underground) applications ranging from auxiliary lighting loads to power for cranes, drag lines, conveyors, and various other dedicated drive applications.

Benefits of energy efficient mining

• Reduced production cost

• Opening of new reserves for Conclusion

On the one hand, the mining industry is ready to grow to keep up with growing demand; on the other hand, it must remain competitive as fuel prices rise. For an energy-intensive industry, controlling fuel consumption and cost is essential. Therefore, the mining industry as a whole is looking for energy efficient technology, including power transformers.