3 Phase Power Tutorial

Three-phase power is often designated by a color code, according to country of origin.
Three-phase power is often designated by a color code, according to country of origin. (Image: Liquidlibrary/liquidlibrary/Getty Images)

Three phase power refers to three currents, or voltages, that differ from each other by 120 electrical degrees, or a third of a cycle. This type of electrical power is commonly used for alternating current in its generation, distribution and transmission. Used by grids across the world in power transfer, this patented polyphase system was first introduced by Nikola Tesla in 1887. Generally supplied over three wires, 3 phase power is considered more cost effective than single or 2 phase systems, since a lower level of conductor material is used.

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Perform a network analysis to calculate power, currents and voltages. Analyze 3 phase power systems using the symmetrical components method. For example, draw a diagram of a 3 phase Y-connected generator with a 500 voltage phase and a 60 Hz frequency. Connect it through power lines to a balanced load consuming 400 kW of power, with lagging of 0.77 pf. Finally, calculate the power it consumes in one load phase, the voltage phase and the line current. This provide a general 3 phase power scenario.

Learn about 3 phase power electricity color code wiring. The conductors are generally identified by color code to accurately reflect load balancing and to ensure that the correct power level rotation phase occurs. While color codes may exist according to old standards, the National Electrical Code typically only requires neutral colors with a white or colored stripe to designate conductors. For example, green or green with a yellow stripe correlates with grounding wires. The high leg in the delta system is colored orange.

Consider 3 phase power generation that is spaced equally, providing a separation of 120 degrees. In Europe, the frequency is usually approximately 50 Hz, while in the United States it is 60 Hz. At a power station, mechanical power is converted by an electrical generator into alternating electric currents. These currents each come from the winding of the generator and an electromagnetic coil. Each current operates at the same frequency, but comes from a different phase.

Identify 3 phase power distribution and transmission methods. Power is ultimately transformed to the household standard voltage level, after numerous conversions within the electrical network. Connect loads to three wires in three equal parts, across three wire pairs. This ensures that the symmetry is kept in place. Compare the connection to a triangle, known as a "delta load."

Use a Y-configuration, where one side of each load is connected together, through the ends of the three other wires. This so-called wye load can remain constant, since it is an equal distance from each line voltage. The benefits of 3 phase power are best realized through balanced symmetrical connections.

Tips & Warnings

  • Correct complex load balance issues by using computer circuit analysis.
  • Always adhere to the National Electrical Code when designing 3 phase power strategies. Otherwise, electrical fires and other undesirable situations may arise.


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