Single Phase vs. Three Phase Transformers

Buy Single Phase Transformers                Buy Three Phase Transformers

With a single phase power system, power lines are used as an input source, but there is only one primary and one secondary winding that’s required to achieve the voltage transformation. The single phase transformer, therefore, uses these two windings to transform the voltage.Single phase transformers come in various models, which differ based on horsepower range, taps, mounting type (such as wall mount), dimensions, KVA and shipping weight.  You might see these labeled as ‘240/480 VAC Primary and 120/240 VAC Secondary, 1 PH, 60 Hz” when ordering, and a listing of models available for this type of transformer.

Three phase power works differently in that power is generated by rotating three windings or coils through a magnetic field within the generator.  The three windings are spaced apart by 120 degrees, and generate power as they rotate through the magnetic field.  The generated power is then sent out on three different lines, which is why it’s called “three phase” power.

For a three phase transformer to work, it must have three windings or coils connected in the proper order to match the incoming voltage.  It then transforms the incoming voltage to the voltage level needed while maintaining proper polarity and phasing.

Three Phase Power for Industrial Applications

Industrial loads are best powered by three phase electricity for efficiency purposes.  Three phase power helps heavy duty equipment to operate more smoothly because the voltage can be transmitted for long distances using a smaller conductor.  If single phase power is needed, it can be harnessed between any two phases within a three phase system.  Single phase power can be implemented between the ground and just one of the phases in some applications.

Using three conductors in a three phase system can provide approximately 170 percent more power than a single phase system, which only has two conductors.   

How Three Phase Transformers Work

Three phase transformers have a three-section iron core, with each section having a primary and secondary coil or winding.  At the plant, the three primary coils are connected to provide the proper polarity or sequence.  The configuration of the primary three windings is called “Delta.”  The three secondary windings are also connected at the plant but these will be configured as either “Delta” or “Wye” depending on the voltage requirements.

Like single phase transformers, three phase transformers come in various models and can be differentiated by KVA, Taps, horsepower range, mounting (such as wall or floor mount), dimensions and weight. These may be labeled similar to the following when ordering, “460 VAC  Primary, 230 VAC Secondary, 3 Ph., 60 Hz.”

Loads and Transformers

The type of transformer being used depends on the load.  For three phased loads, there must be a three phase supply and transformer.  The supply can be either single or three phase with a single phase load; however, the transformer must be single phase and have a connection between the primary and two lines on the three phase circuit.


If you’re in need of single or three phase transformers for your application, check out Carotron’s “Transformers” sections below:

Buy Single Phase Transformers                Buy Three Phase Transformers

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