Choosing the Right Transformer for the Mining Industry
The mining industry occupies a significant position in the US economy. With no shortfall in the demand for
minerals and ore, one can only expect the industry to keep growing.
One worrisome aspect of the mining industry in the US, however, is its excessive demand and
dependence on energy. Highly automated, the industry demands trillions of Btu (British Thermal Units) of
energy every year; the industry’s high demand for energy has also made it easily affected by the
fluctuating international prices of fossil fuel. While other sectors of the US economy are searching for
greener, more cost-effective energy options, the mining industry has also come under pressure to follow
Transformers are a key element in collecting and transporting energy on the national grid and their
efficiency has always been a source of debate. This whitepaper seeks to address this crucial question of
selecting the right transformer for the mining industry.
While the mining industry is critical to the economy, it is, by its very nature, full of hazards for both
manpower and machines. The transformers used have to be robust and technologically advanced to
function in dust, dirt, chemicals, and in the presence of high levels of moisture both above and below
ground. Despite the high levels of automation in this industry, it is also manpower intensive in certain
areas, which means that people are often working around all kinds of dangerous machinery; transformers
should not have to be included in that category.
This whitepaper delivers useful information about the role of transformers in the mining industry, the
various types of transformers and some tips on how to select the right one. The whitepaper also takes a
look at the need for energy-efficient mining, and Pacific Crest Transformers’ offerings to the industry.
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 20 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
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.
Energy Requirement for a hypothetical Iron Ore Mine
Process Btu/ton of Ore
Source: U.S Department of Interior, Office of Surface Mining, The Effects of Increasing Costs on the Future Relation Between Open
Pit and Underground Mining, Michigan Technology University, Department of Mining Engineering
Electrical systems for this industry must meet some basic standards, as stipulated by the Institute of
Electrical and Electronics Engineers (IEEE):
• Safety to personnel and property
• Reliability of operation
• Adequate interrupting ability
• Current-limiting capacity
• Selective-system operation
• Voltage regulation
• Potential for expansion
• First cost
The Role of Transformers
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.
Liquid Filled and Dry Transformers: Performance Characteristics
1. Liquid-Filled Transformers
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
• 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.
2. Dry Type Transformers
Dry type Transformers are usually used for lower ratings (the changeover point being 500kVA to
2.5MVA). They are usually placed indoors, serving an office building/apartment. Dry type units
typically come in enclosures with louvers, or sealed.
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 air circulating within 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.
Correct choice of insulating materials and an understanding of the cooling system is imperative if the
transformer is to be correctly designed. For example, a temperature rise test conducted on a transformer
manufactured and sold as continuously rated, can reveal that the transformer only had a continuous
rating of 65% of the nameplate rating.
The Need for Energy-Efficient Mining
With the current focus on climate change and reduction of 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
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 US mining industry's profitability.
Companies have been forced to retrofit or renovate installations or leave the market. Increasing
operational costs have affected their international competitiveness, and to some extent, this may be
changing the world allocation of mining investment. Employment levels have fallen substantially, and local
economies have borne part of this cost.”
Benefits of energy-efficient mining
Mining companies in the US are thus feeling the pressing
need to be energy-efficient, simply to stay competitive. • Reduced cost of production
Reducing energy consumption by adopting customized, • Opening up of new reserves for
cost-effective solutions like NEMA-approved transformers
• Positive response to new
and harnessing solar or wind energy to meet their future
government regulations on
energy needs can be good ideas in the long run, improving safety performance
especially since the alternate energy option will help • Reduced impact on climate
mining companies keep away from fluctuating international
fuel prices. Alternate sources of energy are still a very
small blip on the graph, in terms of actual power provided for industries like mining, and thus the sector as
a whole needs to come up with more immediate ways to conserve energy.
Pacific Crest Transformers and the Mining Industry
Pacific Crest Transformers (PCT) has been providing solutions to the mining industry since its inception in
1919. Over the last 90 years PCT has had over a 100 clients from this industry across the world. PCT has
experience in building Padmount, Station and Secondary Unit Substation Transformers, and today
specializes in environmentally friendly and efficient liquid-filled distribution transformers.
PCT designs custom transformers after elaborate consultative process with clients. PCT transformers are
all based on client specifications and are designed to fit into existing infrastructure.
PCT custom builds various types of transformers for the mining industry:
PCT transformers can be used in various open
PCT Transformers can be: pit and hard rock (subterranean) applications that
range from auxiliary lighting loads to power for
• Designed to operate on a tilt
cranes, drag lines, conveyor belts and other
• Designed for skid mounting
• Designed for movement over rough ground miscellaneous dedicated variable speed drive
• Designed for severe motor starting applications. PCT also ensures reliable
• Designed for harmonic loads transformer operation in hostile environments
• Designed for corrosive atmosphere containing moisture, dust, dirt, chemicals and
• Designed for high elevations other contaminants.
• Designed for special impedance
On one hand the mining industry is all set to grow to keep up with increasing demand; on the other it has
to stay competitive as fuel prices zoom upwards. For an energy intensive industry, keeping a check on
fuel consumption and cost is critical. Thus the mining industry as a whole is looking for energy efficient
technology, including power transformers.
As companies in the mining industry explore more energy-efficient possibilities, PCT has the expertise
and long experience to provide custom-designed energy-saving transformers for all load center