Power transformers convert power-level voltages from one level or phase configuration to another. They can include features for electrical isolation, power distribution, and control and instrumentation applications. Transformers typically rely on the principle of magnetic induction between coils to convert voltage and/or current levels.
Power transformers can be configured as either a single-phase primary configuration or a three-phase configuration. The size and cost of a transformer increases when you move down the listing of primary windings. Single-phase primary configurations include single, dual, quad (2+2), 5-lead, and ladder. A 5-Lead primary requires more copper than a Quad (2+2) primary. A Ladder is the least economical primary configuration. Three-phase transformers are connected in delta or wye configurations. A wye-delta transformer has its primary winding connected in a wye and its secondary winding connected in a delta. A delta-wye transformer has its primary winding connected in delta and its secondary winding connected in a wye. Three phase configuration choices include delta - delta, delta - wye (Y), wye (Y) wye (Y), wye (Y) delta, wye (Y) single-phase, delta single phase, and international. Primary frequencies of incoming voltage signal to primaries available for power transformers include 50 Hz, 60 Hz, and 400 Hz. 50 Hz is common for European power. 60 Hz is common in North American power. 400 Hz is most widely used in aerospace applications. The maximum primary voltage rating is another important parameter to consider. A transformer should be provided with more than one primary winding if it is to be used for several nominal voltages.
Other important specifications to consider when searching for power transformers include maximum secondary voltage rating, maximum secondary current rating, maximum power rating, and output type. A transformer may provide more than one secondary voltage value. The Rated Power of the transformer is the sum of the VA (Volts x Amps) for all of the secondary windings. Output choices include AC or DC. For Alternating Current waveform output, voltage the values are typically given in RMS values. Consult manufacturer for waveform options. For direct current secondary voltage output, consult manufacturer for type of rectification.
Power transformers can be constructed as either a toroidal or laminated transformer. Toroidal transformers typically have copper wire wrapped around a cylindrical core so the magnetic flux, which occurs within the coil, doesn't leak out, the coil efficiency is good, and the magnetic flux has little influence on other components. Laminated transformers contain laminated-steel cores; they are also called E-I transformers. These steel laminations are insulated with a nonconducting material, such as varnish, and then formed into a core that reduce electrical losses. Power transformers can be one of many types. These include autotransformer, control transformer, current transformer, distribution transformer, general-purpose transformer, instrument transformer, isolation transformer, potential (voltage) transformer, power transformer, step-up transformer, and step-down transformer. Mountings available for power transformers include chassis mount, dish or disk mount, enclosure or free standing, h frame, and PCB mount.