Step Down Transformers

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State-of-the-Art Step Down Transformer Sales

We offer a variety of sizes, brands, and types of high quality step down transformers at discount prices direct to the public These include:

Acme Step Down Transformers - Full line of high quality transformers available.
Amveco Step Down Transformers - Full line of high quality transformers available.
TEMCo Step Down Transformers - Full line of high quality transformers available.
Hammond Step Down Transformers - Full line of high quality transformers available.
GE Step Down Transformers - Full line of high quality transformers available.

Whatever size, type, or brand you need, just call our Step Down Transformers Specialists  at
1-800-613-2290 to help you order the electrical transformers to meet your needs.

What is a step down transformer?

A step-down transformer is one whose secondary voltage is less than its primary voltage.  The step down transformer is designed to reduce the voltage from the primary winding to the secondary winding.  This kind of transformer "steps down" the voltage applied to it.

On the converse, a transformer designed to increase the voltage from the primary windings to the secondary windings is a step up transformer.  This kind of transformer "steps up" the voltage to a higher voltage

Step down transformers often range in voltage sizes from 0.5 kva to 500 kva. 

How does a step down transformer work?

A power transformer is a electrical device with one winding of wire placed close to one or more other windings, used to couple two or more alternating-current (AC) circuits together by employing the induction between the windings. The winding connected to the power source is called the primary winding, and the other windings are known as secondary. A transformer in which the secondary voltage is higher than the primary is call a step-up transformer; if the secondary voltage is less than the primary, the device is known as a step-down transformer. The product of current times voltage is constant in each set of windings, so that in a step-up transformer, the voltage increase in the secondary is accompanied by a corresponding decrease in the current.  For more calculations on how step down transformers work mathematically and other details see further down this page.

What is a step down transformer used for?

There is many uses for step-down transformer and the larger devices are used in electric power systems, and small units in electronic devices. Industrial and residential power transformers that operate at the line frequency (60 Hz in the U.S., and 50Hz in much of Europe and South America), may be single phase or three-phase, are designed to handle high voltages and currents. Efficient power transmission requires a step-up transformer at the power-generating station to raise voltages, with a corresponding decrease in current. Line power losses are proportional to the square of the current times the resistance of the power line, so that very high voltages and low currents are used for long-distance transmission lines to reduce power losses. At the receiving end, step-down transformers reduce the voltage, and increase the current, to the residential or industrial voltage levels, usually between 110V and 600V output.

Considerations in choosing a step down transformer:

Power transformers must be efficient and should dissipate as little power as possible in the form of heat during the transformation process. Efficiencies are normally above 99 percent and are obtained by using special steel alloys to couple the induced magnetic fields between the primary and secondary windings. One of the most important considerations to increase transformer efficiency and reduce heat is choosing the metal type of the windings.  Copper windings are much more efficient than aluminum and many other winding metal choices, but it also costs more.  Transformers with copper windings cost more to purchase initially, but save on electrical cost over time as the efficiency more than makes up for the initial cost.  The dissipation of even 0.5 percent of the power transmitted in a large transformer generates a large amount of heat, which requires special cooling. Typical power transformers are installed in sealed containers that have oil or another substance circulating through the windings to transfer the heat to external radiator-like surfaces, where it can be discharged to the surroundings.

Details on a typical step down transformer:

A transformer is a device for stepping-up, or stepping-down, the voltage of an alternating electric signal. Without efficient transformers, the transmission and distribution of ac electric power over long distances would be impossible. The description below details the circuit diagram of a typical transformer.

There are two circuits; the primary circuit, and the secondary circuit. There is no direct electrical connection between the two circuits, but each circuit contains a winding which links it inductively to the other circuit. In transformers, the two windings are wound onto the same iron core. The purpose of the iron core is to channel the magnetic flux generated by the current flowing around the primary winding, so that as much of it as possible also links the secondary winding. The common magnetic flux linking the two windings is conventionally denoted in circuit diagrams by a number of parallel straight lines drawn between the windings.

Although the mutual inductance of the two windings is entirely responsible for the transfer of energy between the primary and secondary circuits, it is the self inductances of the two windings which determine the ratio of the peak voltages and peak currents in the primary and secondary circuits.  In other words, the ratio of the peak voltages and peak currents in the primary and secondary circuits is determined by the ratio of the number of turns in the primary and secondary windings: this latter ratio is usually called the turns ratio of the transformer. If the secondary winding contains more turns than the primary winding then the peak voltage in the secondary circuit exceeds that in the primary circuit. This type of transformer is called a step-up transformer, because it steps up the voltage of an ac signal. Note that the peak current in the secondary circuit is less than the peak current in the primary circuit in a step-up transformer (as must be the case if energy is to be conserved). Thus, a step-up transformer actually steps down the current. Likewise, if the secondary winding contains less turns than the primary winding then the peak voltage in the secondary circuit is less than that in the primary circuit. This type of transformer is called a step-down transformer. Note that a step-down transformer actually steps up the current (i.e., the peak current in the secondary circuit exceeds that in the primary circuit).

Power distribution requires high voltages and thus step up and step down transformers:

Ac electricity is generated in power stations at a fairly low peak voltage (i.e., something like 440V), and is consumed by the domestic user at a peak voltage of 110V or 220V for households and many businesses in the U.S. However, ac electricity is transmitted from the power station to the location where it is consumed at a very high peak voltage (typically 50,000V). In fact, as soon as an ac signal comes out of a generator in a power station it is fed into a step-up transformer which boosts its peak voltage from a few hundred volts to many tens of kilovolts. The output from the step-up transformer is fed into a high tension transmission line, which typically transports the electricity over many tens of miles, and, once the electricity has reached its point of consumption, it is fed through a series of step-down transformers until, by the time it emerges from a domestic power socket, its peak voltage is often reduced down to only 110V.

If ac electricity is both generated and consumed at comparatively low peak voltages, why go to the trouble of stepping up the peak voltage to a very high value at the power station and then stepping down the voltage again once the electricity has reached its point of consumption? Why not generate, transmit, and distribute the electricity at a peak voltage of 110V? Well, consider an electric power line which transmits a peak electric power between a power station and a city. We can think of , which depends on the number of consumers in the city and the nature of the electrical devices which they operate, as essentially a fixed number. Suppose that and are the peak voltage and peak current of the ac signal transmitted along the line, respectively. We can think of these numbers as being variable, since we can change them using a transformer. However, since , the product of the peak voltage and the peak current must remain constant. The resistance of the line causes power loses at greater percentages at lower voltages over distance. The peak rate at which electrical energy is lost due to ohmic heating in the line is high.

Thus, if the power transmitted down the line is a fixed quantity, as is the resistance of the line, then the power lost in the line due to ohmic heating varies like the inverse square of the peak voltage in the line. It turns out that even at very high voltages, such as 50,000V, the ohmic power losses in transmission lines which run over tens of kilometers can amount to up to 20% of the transmitted power. It can readily be appreciated that if an attempt were made to transmit ac electric power at a peak voltage of 110V then the ohmic losses would be so severe that virtually none of the power would reach it destination. Thus, it is only possible to generate electric power at a central location, transmit it over large distances, and then distribute it at its point of consumption, if the transmission is performed at a very high peak voltage (the higher, the better). Transformers play a vital role in this process because they allow us to step-up and step-down the voltage of an ac electric signal very efficiently (a well designed transformer typically has a power loss which is only a few percent of the total power flowing through it).

Experienced since 1968 with electrical power distribution products, AAA Acme General Electrical Power Transformer Distribution started as a family owned and run company. Today we have grown to be a National Supplier of quality brand name power transformers. We distribute a wide variety of high quality single and three phase power transformers daily from regional warehouses at wholesale prices.

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Supplying transformers constructed to the strictest UL and Canadian electrical code requirements. Enjoy the security of using the best power products from GE and Acme.

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Contact us and our support team at Tower at 510-490-2187 to get your quote, place your order and arrange for shipping.