Accurate voltage drop calculations

Provides the accurate equations

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Accurately calculating voltage drop results in lower voltage drops which leads to smaller cable sizes and saves money.

To accurately calculate voltage drop in cables utilise:

  • Conductor resistance (Rc) values based on actual cable operating temperature (percent loading).
  • Conductor reactance (Xc) values. Xc = 0 for d.c. installations.
  • Load power factor (cosθ).
  • Accurate cable route length (L).
  • Actual maximum operating load current (I).

For single phase:

For three phase:

The values for Rc and Xc are provided in the Standards.  They can also be calculated.

References

Standard AS/NZS 3008.1.1 Electrical Installations-Selection of cables

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