Examination of Electric Transformer

The basic function of Electric transformers is to transform voltage from one level to another, usually from a higher voltage to a lower voltage. This is made possible by magnetic induction between coils to convert voltage and current levels. An electric transformer usually has a ferromagnetic core and two or more coils called windings. A changing current in the primary winding creates an alternating magnetic field in the core. The core multiplies this field and couples the most of the flux through the secondary transformer windings. This in turn induces alternating voltage in each of the secondary coils.

Electrical transformers are constructed as either a single-phase or a three-phase configuration. There are several important specifications for electrical transformers such as maximum secondary voltage rating, maximum secondary current rating, maximum power rating, and output type. An electrical transformer is capable of providing more than one secondary voltage value. One can opt for either AC or DC. For Alternating Current waveform output, voltage the values are typically given in RMS values. For direct current secondary voltage output, consult manufacturer for type of rectification.

The transformer is based on two principles - electromagnetism and electromagnetic induction. In the first category, the electric current produces a magnetic field and in the second alternative, a changing magnetic field within a coil of wire induces a voltage across the ends of the coil. Changing the current in the primary coil changes the magnitude of the applied magnetic field. The changing magnetic flux extends to the secondary coil where a voltage is induced across its ends.

Let us now look into the electric current that reaches our houses and other buildings we occupy. When electricity is sent from a power plant, it is of an extraordinarily high voltage in the region of 155,000 to 765,000 volts and unfits to travel long distances comprising of many hundreds of miles. In order for a building occupant to use the electricity, it has to be reduced to a lower voltage and this lower voltage electricity is introduced into the local electric wires at a substation. The substation breaks the larger amount of power down into smaller pieces at lower voltage. Once smaller transformers take that voltage down to usually 7,200, the power leaves the substation.

For example, an electric transformer ubiquitously seen on top of a utility pole, or the ones less visibly connected to underground wires, transforms the 7,200 volts into 220-240 volts. This is then sent into households over three wires. The three wires go through the electric meter, which measures how much electricity you consume to recover costs. One of the three wires is the ground, and the other two are the positives.

Most of the electrical appliances we use like water heater, stove and oven, or air conditioner need 220-240 volts. They are provided with very special connections and plugs. But certain other devices, like TV or computer need only110-120 volts. Again, some manufacturers use higher voltage power to run big machines. So, they may not feel the need to reduce the voltage in a big way.