What do Step-Up and Step-Down Transformers do?

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What is a Step Up Transformer?

A step-up transformer is one whose secondary voltage is greater than its primary voltage. This kind of transformer "steps up" the voltage applied to it. For instance, a step up transformer is needed to use a 220v product in a country with a 110v supply.

What is a Step Down Transformer?

Its the opposite of the above, and would be used to run for example a 110v product in a country with a 220v mains supply.

What 'Rating' Transformer do i need?

This depends entirely on the products you will be using it with. Give the electrical retailer a detailed list of all the products you will be using with it - and also their maximum outputs. From this information he/she will be able to advise the correct transformer rating needed.

A transformer converts alternating current (AC) from one voltage to another voltage. It has no moving parts and works on a magnetic induction principle; it can be designed to "step-up" or "step-down" voltage. So a step up transformer increases the voltage and a step down transformer decreases the voltage.

How does a step up transformer or step down transformer work?

A transformer is made from two or more coils of insulated wire wound around a core made of iron. When voltage is applied to one coil (frequently called the primary or input) it magnetizes the iron core, which induces a voltage in the other coil, (frequently called the secondary or output). The turns ratio of the two sets of windings determines the amount of voltage transformation.

An example of this would be: 100 turns on the primary and 50 turns on the secondary, a ratio of 2 to 1.

Transformers can be considered nothing more than a voltage ratio device.

With a step up transformer or step down transformer the voltage ratio between primary and secondary will mirror the "turns ratio" (except for single phase smaller than 1 kva which have compensated secondaries). A practical application of this 2 to 1 turns ratio would be a 480 to 240 voltage step down. Note that if the input were 440 volts then the output would be 220 volts. The ratio between input and output voltage will stay constant. Transformers should not be operated at voltages higher than the nameplate rating, but may be operated at lower voltages than rated. Because of this it is possible to do some non-standard applications using standard transformers.

Single phase transformers 1 kva and larger may also be reverse connected to step-down or step-up voltages. (Note: single phase step up or step down transformers sized less than 1 KVA should not be reverse connected because the secondary windings have additional turns to overcome a voltage drop when the load is applied. If reverse connected, the output voltage will be less than desired.)

Step up transformers and step down transformers have a long life.

The primary components for voltage transformation are the transformer's core and coil. The insulation is placed between the turns of wire to prevent shorting to one another or to ground. This is typically comprised of mylar, nomex, kraft paper, varnish, or other materials.

As a transformer has no moving parts, it will typically have a life expectancy between 20 and 25 years.

Reference: 72
Created: 14th March 2007
Modified: 14th March 2007

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