Three-Phase Banking and Output Voltages

  • Three-Phase Banking: In electrical systems, three-phase banking refers to the configuration and connection of three single-phase transformers or one three-phase transformer to create a three-phase power system. This setup is commonly used in industrial and commercial applications for efficient power distribution.
  • Three-Phase Output Voltages: The voltages produced by a three-phase system can be measured in two ways: line-to-line (phase-to-phase) and line-to-neutral (phase-to-ground). These measurements help determine the system’s voltage ratings and configurations.
Three-Phase Banking and Output Voltages
Configuration TypeTransformer ConnectionLine-to-Line Voltage (VL-L)Line-to-Neutral Voltage (VL-N)Common Applications
Wye (Star)Wye-WyeVL-L = VL-N × √3VL-N = VL-L / √3Distribution systems, industrial loads
DeltaDelta-DeltaVL-L = VphaseVL-N = VL-L × 1/√3Heavy machinery, motors
Wye-DeltaWye-DeltaVL-L = VL-N × √3VL-N = VL-L / √3Long-distance transmission
Delta-WyeDelta-WyeVL-L = VphaseVL-N = VL-L × 1/√3Distribution systems, step-up/step-down transformers

Wye (Star) Connection:

  • Line-to-Line Voltage (V_L-L): This voltage is the voltage between any two of the three phases. It is higher than the line-to-neutral voltage by a factor of √3​.
  • Line-to-Neutral Voltage (V_L-N): This is the voltage between any one phase and the neutral point. It is the same as the phase voltage in a wye connection.

Delta Connection:

  • Line-to-Line Voltage (V_L-L): This voltage is the same as the phase voltage since each winding is connected directly between two phases.
  • Line-to-Neutral Voltage (V_L-N): This voltage is not typically measured in a delta system, but if needed, it can be derived as VL-L × 1/√3

Wye-Delta and Delta-Wye:

  • These configurations are used in transformers to step-up or step-down voltages between different parts of the power distribution network. The calculations for voltages remain consistent with the wye and delta principles.

Practical Tips:

  • Always ensure proper grounding in three-phase systems to maintain safety and stability.
  • When calculating power in three-phase systems, use the formula
    P=√3 × VL-L × I × cos(ϕ) for line-to-line measurements, where ϕ is the phase angle.
  • Understand the specific voltage requirements of your equipment to choose the appropriate transformer configuration.

Common Questions:

  • Why use a Wye configuration?
    • It allows for multiple voltage levels from the same transformer and is suitable for distributing power over long distances.
  • Why use a Delta configuration?
    • It is robust and provides a higher line-to-line voltage, making it suitable for heavy machinery.
Three-Phase Input and Output Voltages

Three-Phase Input and Output Voltages

Three-Phase Voltage SystemLine-to-Line Voltage (L-L)Line-to-Neutral Voltage (L-N)
400Y/230V (Europe)400V230V
380Y/220V (Asia)380V220V
415Y/240V (Australia)415V240V

Explanation of Voltage Configurations:

  1. 208Y/120V System:
    • Line-to-Line Voltage (L-L): 208V
    • Line-to-Neutral Voltage (L-N): 120V
    • Commonly used in North America for commercial buildings and light industrial applications.
  2. 240Y/120V System:
    • Line-to-Line Voltage (L-L): 240V
    • Line-to-Neutral Voltage (L-N): 120V
    • Typically used in residential applications.
  3. 480Y/277V System:
    • Line-to-Line Voltage (L-L): 480V
    • Line-to-Neutral Voltage (L-N): 277V
    • Often used in industrial settings and large commercial buildings.
  4. 600Y/347V System:
    • Line-to-Line Voltage (L-L): 600V
    • Line-to-Neutral Voltage (L-N): 347V
    • Common in Canadian industrial environments.
  5. 400Y/230V System:
    • Line-to-Line Voltage (L-L): 400V
    • Line-to-Neutral Voltage (L-N): 230V
    • Standard voltage in Europe for commercial and industrial applications.
  6. 380Y/220V System:
    • Line-to-Line Voltage (L-L): 380V
    • Line-to-Neutral Voltage (L-N): 220V
    • Used in various Asian countries for both commercial and industrial applications.
  7. 415Y/240V System:
    • Line-to-Line Voltage (L-L): 415V
    • Line-to-Neutral Voltage (L-N): 240V
    • Standard voltage in Australia and New Zealand for industrial and commercial use.

Key Points:

  • Line-to-Line Voltage (L-L): This is the voltage measured between any two of the three phases in a three-phase system.
  • Line-to-Neutral Voltage (L-N): This is the voltage measured between any one of the phases and the neutral point in a three-phase system.

These configurations are critical for ensuring compatibility with electrical equipment and safety standards in different regions.

Three-Phase and Output Voltages in the Philippines

Three-Phase Voltages in the Philippines
Voltage TypeNominal Voltage (V)Description
Three-Phase Line-to-Line (Phase-to-Phase)380V, 400V, 415VCommon industrial and commercial voltage
Three-Phase Line-to-Neutral (Phase-to-Ground)220V, 230V, 240VStandard for residential and small commercial use


  • Line-to-Line Voltage: This is the voltage measured between any two phases in a three-phase system. In the Philippines, common line-to-line voltages are 380V, 400V, and 415V. These voltages are typically used for industrial and large commercial applications where three-phase power is required for heavy machinery and equipment.
  • Line-to-Neutral Voltage: This is the voltage measured between any one phase and the neutral point. In the Philippines, common line-to-neutral voltages are 220V, 230V, and 240V. These voltages are standard for residential and smaller commercial use where single-phase loads are prevalent.
  • Nominal Voltage Range: The actual voltage can vary slightly due to factors such as load conditions and distribution network design. The given values are nominal and represent the standard or typical values used in the electrical distribution system in the Philippines.


380V, 400V, 415V Line-to-Line: These voltages are used for three-phase systems in industrial and commercial settings where equipment and machinery operate on higher voltages to handle larger power requirements efficiently.

220V, 230V, 240V Line-to-Neutral: These are the standard voltages for residential appliances and small commercial applications, ensuring compatibility with a wide range of devices and equipment designed for these voltage levels.

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