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Introduction to 3-phase trasformer

Three-phase power is used almost exclusively for generation, transmission, and distribution, as well as for all industrial uses. It is also used on aircraft, both commercial and military. It has many advantages over single-phase power.

Three-Phase Transformer Design (Geometry, Delta/Wye Connections, and Many More)
Three-Phase Transformer Design (Geometry, Delta/Wye Connections, and Many More)

The transformer can be made smaller and lighter for the same power handling capability, because the copper and iron are used more effectively.

In circuitry, for conversion from AC to DC, the output contains a much lower ripple amplitude, and a higher frequency component, which is 3 times and 6 times the line frequency, and which, in turn, requires less filtering.


Primary Circuit

The two most commonly used primary circuits for three-phase transformers are the Star, or Y connection, as shown in Figure 1a, and the other being known as the Delta (A) connection, as shown in Figure 1b.

The design requirement for each particular job dictates which method of connection will be used.

a. Three-Phase Transformer, Connected in Star; b. Three-Phase Transformer, Connected in Delta
Figure 1 – a. Three-Phase Transformer, Connected in Star; b. Three-Phase Transformer, Connected in Delta

Comparing Transformer, Physical Size

The schematic diagram in Figure 2, shows the connection of three single-phase transformers operating from:

  1. 3-phase power source and a single three-phase transformer; and
  2. 3-phase power source connected in a delta-delta configuration.

The single three-phase transformer T4, would be lighter and smaller than a bank of three single-phase transformers of the same total rating.

Comparing Three Single-Phase Transformers Connected in Three-Phase Delta
Figure 2 – Comparing Three Single-Phase Transformers Connected in Three-Phase Delta

Since the windings of the three-phase transformer are placed on a common magnetic core, rather than on three independent cores, the consolidation results in an appreciable saving in the copper, the core, and the insulating materials.

Title:Three-Phase Transformer Design (Geometry, Delta/Wye Connections, and Many More) – Colonel Wm.; T. McLyman
Format:PDF
Size:330 KB
Pages:18
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Three-Phase Transformer Design (Geometry, Delta/Wye Connections, and Many More)
Three-Phase Transformer Design (Geometry, Delta/Wye Connections, and Many More)

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2 Comments


  1. p.k chandra
    Apr 22, 2023

    i want to know the theory of design ,for acadamic purpose only , Thanks !


  2. p.k.chandra
    Apr 14, 2023

    dear sir ,
    i want learn delta / star small transformer design .
    core area selection, T/V calculation ignoring different factores .
    thanks!
    p.k.chandra

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