Power transformer

Friday, 18 August 2006

A transformer is an electrical device widely used for transferring energy of an alternating current in the primary winding to that in one or more secondary windings. Transformers are utilized to step electrical voltages up or down, to couple signal energy from one stage to another, and to match the impedances of interconnected electrical or electronic components. Transformers transfer electric energy from one circuit to another circuit through magnetic induction. Electrical transformers are used extensively in electrical and electronic applications. Transformers are also used to sense current, and to power electronic trip units for circuit interrupters. Transformers may also be employed in solenoid-equipped magnetic circuits, and in electric motors. Most electrical transformers have a primary winding and a secondary winding around a ferromagnetic core. The windings are usually a primary winding through which electrical current is directed, and secondary windings which are electrically isolated from the primary winding. The ferromagnetic core provides a low reluctance path for the magnetic field. Transformers are developed to accommodate various supply and load connection configurations or various output voltage requirements. A transformer is typically designed to accommodate the layout of a particular substation. There are transformers available for powers from the 1 VA region to the 1000 MVA region and for voltages up to the highest transmission voltages.

There are two types of transformers used to convey electricity from a transmission system to a distribution system. These transformers are power transformers and distribution transformers. Distribution transformers are used to convert the high-voltage electricity delivered by power lines to the 120/240-volt supply needed for consumers. Distribution transformers are typically smaller in size and are not usually constrained by the installation site. Distribution transformers typically have high-voltage windings rated at approximately 10 kV to approximately 20 kV. The distribution transformers come in three varieties: the pole-mounted transformers; the ground-level pad-mounted transformers; and the underground transformers. Power transformers provide rated voltage and current to electric and electronic devices while isolating those devices from the AC current mains. Most electricity is produced at a power plant. The voltage of this electricity is stepped up for efficient conducting of electric power, because electricity loses some of its strength as it travels. Each substation contains a power transformer that is used to step down the voltage to lower levels for subsequent conducting through a distribution network. Distribution transformers are installed in the distribution network to lower the voltage to levels conveyed to commercial buildings, households, and other end users.

Power transformers convert an alternating current power supply of the type available in homes, offices, hotels, and the like via an ordinary wall outlet to a direct current power supply compatible with electronic devices, such as televisions, telephones, answering machines, calculators, computers, and radios. To provide the regulated power supply, the transformer includes a power converting circuit within the housing having a male connector positioned thereon. Power transformer has two types of windings, a primary winding and a secondary winding. Power switches commonly are metal-oxide semiconductor field-effect transistors. Power transformers are normally designed to conform to unique substation requirements. Power transformers installed in substations are capable of process far greater influxes of electric current and voltages than distribution type transformers. The capacity of power transformers located at substations may be impacted greatly by ambient temperature. Cooling systems and other heat dissipation devices are used.

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