SPSU Photovoltaic (PV) Solar Converter Step-up Transformer

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Published: 13th January 2011
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Difficulty in procuring non renewable fossil fuel, fluctuating global prices and growing environmental consciousness is pushing a growing number of industries in the United States to explore the profitability of alternate energy like wind and solar.

Thankfully, the US gets solar energy in abundance and an increasing number of industries are waking up to its advantage. Recently, the country too has taken affirmative steps towards harnessing solar energy. The United States has many utility-scale solar power plants, the largest installation in the world being the Solar Energy Generating Systems facility, located in California. There are other solar power plants of varying sizes scattered over the country such as in Nevada, Florida and south-eastern California.

In the Solar Energy Industries Association's "2008 U.S. Solar Industry Year in Review" it was noted that U.S. solar energy capacity increased by 17% in 2007, reaching the total equivalent of 8,775 megawatts (MW).

In 2008, the Department of Energy (DOE) announced its decision to invest $17.6 million, in early-stage photovoltaic (PV) projects. More recent reports from the Solar Energy Industries Association (SEIA) and GTM Research show solar installations in 2010 are up more than 100% over 2009, and it's looking to be a very real possibility that when accounting for both solar electric and solar thermal installations, the industry could surpass the 1 GW mark for annual installations in 2010.

While these are extremely positive signs that push towards greater reliability and affordability of solar energy, work is still on to increase technological advancement.

In the area of power infrastructure, namely in the area of production and distribution of solar energy, it is energy transformers that play a critical role. Thus far energy transformers were built to step up or step down energy from non renewable sources, however transmitting and distributing energy from renewable sources like the sun come with their own challenges to energy transformers.

The differentiation in a solar energy transformer comes in areas like

Loading - solar power facilities experience a steady state loading when inverters are operating. When the sun comes out, there is a dampened reaction process and loading on the transformer is more constant.

Low voltage (LV) fault ride through - Fault ride through has yet to be defined for solar systems, this could be because it is easier to turn solar power systems on and off quickly.

Harmonics - The solar inverter system's typical harmonic content is less than 1 percent, which has almost no impact on the system. The lower harmonic profile is because there are no generators and switching and protective controls such as those found on wind turbines.

Generator step-up duty - With solar transformers, step-up duty is required, but without the problems associated with over-voltages caused by unloaded generators. The inverter converts DC input from the photovoltaic array and provides AC voltage to the transformer, giving a steady and smooth transition, with no over-voltage caused by unloaded circuits.

Voltage - Solar transformers operate at a steady voltage, with the rated voltage controlled by inverters. Therefore, voltage and load fluctuations are considerably reduced.

Nominal loading average - Solar power systems typically operate very close to their rated loads.

Special design issues - Solar power systems use inverters to convert DC to alternating current (AC). Since the largest practical inverter size, to date, is about 500 kilovolt-ampere (kVA), designers are building 1000 kVA transformers by placing two inverter connected windings in one box. In this way the transformer has to have two separate windings to accept completely separate inputs. Design issues also stem from running cables long distances to convert from DC to AC.

Size of installation - the size of solar farm is limited by inverter technology, since inverters can currently only be built to about 500 kVA. This means that nearly all solar applications use pairs of 500 kVA inverters to drive the transformer and produce about 1000 kVA. Increasing the size by adding more inverters into one transformer box is extremely difficult, due to complexities associated with the size of the box required and the practicalities of running cabling to convert from DC to AC.

Inverter technology has been slow to advance, because it is an electronic technology. It remains to be seen whether this comparative disadvantage will be a fatal flaw in the advancement of solar technology to the same level as wind farms in the renewable energy arena.

The duty cycle seen in solar farms may not be as severe as seen in wind farms, but solar power has its share of special considerations that affect transformer design. Those engaged in harnessing solar energy need to pay heed to these special needs to ensure that the solar installation is cost effective and reliable.

Some core needs of a solar inverter transformer are

* Efficient heat management: The heat generated due to uneven cooling of the coils leads to creation of hot spots. This leads to premature breakdown of the transformers

* Lower harmonic and Grid disturbances

* Ability withstand harsh weather conditions

SPSU photovoltaic (PV) solar converter step-up transformers

The SPSU is designed for the additional loading associated with non sinusoidal harmonic frequencies often found in inverter-driven transformers, and it has an innovative system of multiple windings which reduce transformer costs and minimize your transformer footprint.

Designed and constructed to meet and exceed earthquake standards, The SPSU model features circular windings that spread the radial forces evenly over their circumference and have cooling ducts throughout the coils, eliminating hot spots that lead to premature breakdown and ultimately to transformer failure. The coil end blocking with heavy duty 3 gauge steel bracing and proprietary pressure plates take on the axial forces exerted during a fault condition. These forces can cause telescoping of the coils, shortening transformer life.

The Model SPSU features an innovative design that includes round coils, a cruciform, mitered core with heavy-duty clamping and a proprietary pressure plate design, as well as a premium no-load tap changer.

To know more about SPSU photovoltaic (PV) solar converter step-up transformers and energy transformers Visit Pacific Crest Transformers website

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