Cable Voltage Drop (AC3) — fast.engineer

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Cable Voltage Drop (AC3)

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Load type *

Load current *

Full load current in amps

Motor power *

Power unit

Power factor (cos φ)

Range: 0.01 to 1.0

Motor efficiency

Range: 1 to 100%

Conductor material

Conductor size (mm²) *

Cable type

Cable formation

Insulation type

Multicore arrangement

Singlecore arrangement

Cu operating temp (°C)

R_c column of AS/NZS 3008.1.1:2017 Tables 34–37. Use the insulation's rated temperature (PVC 75, XLPE 90, elastomer 110 °C) for a fully loaded cable; 80 °C is single-core only.

Al operating temp (°C)

R_c column of AS/NZS 3008.1.1:2017 Tables 34–36 (aluminium is tabulated to 90 °C; 80 °C single-core only).

MIMS conductor temp (°C)

MIMS voltage grade

Cable length *

Length unit

System voltage *

Phase-to-phase voltage (100-1000V)

Parallel circuits

Number of parallel cable runs (1-10)

Maximum voltage drop

Allowable voltage drop limit (0.1-20%)

Report style

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Calc number

Tag number

Title

Description

Revision

Company name

Project number

Prepared by

Project name

Client company

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Your Company

Calculation No.: Calc-001
Revision: A
Description:
Created By: Engineer Name

Project: Project Name
Project No.: P001
Client: Client Name

Input Parameters

The following cable and circuit parameters were used for this calculation:

Parameter	Symbol	Value	Notes
Conductor Material	Metal	Cu	Copper or Aluminum
Conductor Size	CSA	50	Cross-sectional area
Cable Length	L	100 Meter	Length in Meter
System Voltage	V_pp	415 V	Phase-to-phase voltage
Load Current	I	17.7 A	Load current

Calculations

All calculations performed in accordance with AS/NZS 3008.1.1:2017.

Step 1: Cable Resistance and Reactance

From AS/NZS 3008.1.1:2017: R_c = 0.494 Ω/km at 90 °C (Table 35, Column 5), X_c = 0.0751 Ω/km (Table 30, Column 10)

Step 2: Cable Impedance (Z_c)

The cable impedance is calculated from resistance and reactance: This represents the total opposition to current flow in the cable.

Formula: $$ \begin{aligned} Z_c &= \sqrt{R_c^2 + X_c^2} \\ &= \sqrt{(0.494)^2 + (0.0751)^2} \\ &= 0.4997 \; \Omega/\text{km} \end{aligned} $$

Step 3: Voltage Drop (V_d)

The voltage drop is calculated using the three-phase formula with the current per cable (I / 1 parallel circuit(s)): This is the voltage lost over the length of the cable run.

Formula: $$ \begin{aligned} V_d &= \frac{\sqrt{3} \times I_{cable} \times L \times Z_c}{1000} \\ &= \frac{\sqrt{3} \times 17.69 \times 100 \times 0.4997}{1000} \\ &= 1.531 \; \text{V} \end{aligned} $$

Step 4: Voltage Drop Percentage

The voltage drop as a percentage of supply voltage: This is compared against the maximum allowable voltage drop.

Formula: $$ \begin{aligned} V_{d\%} &= (V_d / V) \times 100 \\ &= (1.531 / 415) \times 100 \\ &= 0.369 \; \% \end{aligned} $$

Compliance Check

The calculated voltage drop of 0.37% is less than or equal to the maximum allowable 5%. The installation complies with the requirements.

Summary of Results

Below is the summary of calculated values:

Parameter	Symbol	Value	Notes
Cable Resistance	R_c	494 mΩ/km	AC resistance at 50Hz, 90 °C conductor
Cable Reactance	X_c	75.1 mΩ/km	AC reactance at 50Hz
Cable Impedance	Z_c	500 mΩ/km	Total cable impedance
Phase Current	I	17.7 A	Line current
Voltage Drop	V_d	1.53 V	Absolute voltage drop
Voltage Drop Percentage	V_d%	0.369 %	As percentage of supply
Compliance Status	Status	PASS	Within acceptable limits

Approval:

This calculation has been reviewed and approved by:

Created By
Engineer Name
Date: ..........................

Checked
By: .............................
Date: ..........................

Approved
By: .............................
Date: ..........................

Client Approved
By: .............................
Date: ..........................

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