Voltage Drops

Figure 1: Auto Design Options – Voltage Drop

Auto design lets you select cables of higher rating if the voltage drop at the downstream end of the cable is greater than a user-specified value. The voltage drop is defined as follows:

Voltage Drop = (Base kV – Calculated Voltage)/ Base kV * 100%

Option Descriptions
Option Description

Assumed Locked Rotor Mult (LRM)

This value, multiplied by the full load amps of motors, provides the starting (inrush) current. This value is used for all motor circuits for voltage drop calculation while sizing cables.

Assumed Source Vpu

The per-unit voltage at the source end of the cable.

Assumed Load

Type of amps calculation to use for voltage drop calculation. Choices are:

  • Downstream Code Factors Load
  • Downstream Connected Load
  • Downstream Demand Load
  • Downstream Design Load

Upsize Conductor if Volt Drop >

If the voltage drop due to load is greater than the specified value, the program selects the next larger cable in order to keep the voltage drop within specified limits. To avoid upsizing cables based on voltage drop, the edit field must be blank.

Upsize Conductor if Motor Starting Voltage Drop >

If the voltage drop due to motor starting is greater than the specified value, the program selects the next larger cable so that the voltage drop is kept within specified limits.

Important: To avoid upsizing cables based on motor starting voltage drop, the edit field must be blank.

Next: Bus

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