4 Important Reasons To Calculate Voltage Drop
There is great value in using a voltage drop calculator.
Calculating voltage drop is essential when determining the best electrical cable size.
How can you quickly and precisely compute voltage drop?
Use the CableHero app. Register for a free trial of this latest voltage drop calculator.
Definition of Terms
Firstly, let us define some terms used in relation to calculating voltage drop.
- Voltage Drop – is the decrease in voltage in an electrical circuit due to the resistance in the conducting line.
It occurs when the voltage at the end of a run of cable is lower than at the beginning.
- Voltage – is the force of an electric current, measured in volts (V).
- Current – a measure of the quantity of charge passing any point of the wire per unit of time.
This is calculated in amperes (amps).
- Resistance – is also known as ohmic resistance or electrical resistance.
It is a measure of the opposition to current flow in an electrical circuit.
What Causes Voltage Drop
Secondly, let us state the cause of voltage drop.
Voltage drop happens because of increased resistance in a circuit.
This electrical resistance is due to:
- A bigger load when adding connections.
Additional loads create more distance which adds more resistance.
- More components than intended that will use energy.
- A high-resistance conductor.
An electrical cable increases in resistance when there is a longer distance for the current to travel or a smaller cross section for it to travel through.
How To Calculate Voltage Drop
Ohm’s law indicates that the voltage drop across a conductor or load is equivalent to the product of current and resistance (V = I x R).
However, the voltage drop formula changes depending on the number of phases in the circuit (single-phase or three-phase).
In the following sample equations, the variables used are:
- Z = Impedance of the conductor (ohms per 1,000 feet, or ohms / kft)
- I = Load current (amperes)
- L = Length (feet)
| Installation Type | Formula for Voltage Drop |
| Single-phase system3-phase system | Voltage Drop = 2 x Z x I x L / 1000Voltage Drop = 1.73 x Z x I X L / 1000 |
The formulas are divided by 1,000. The basic impedance values are provided for every 1,000 feet. And by this method, they are converted to ohms per foot.
Want a more convenient way to determine voltage drop?
Try using the CableHero app which also features a voltage drop calculator.
Try the beta version for free by registering for our cable size calculator online.
Finally, let’s enumerate some important reasons to calculate voltage drop.
4 Important Reasons To Calculate Voltage Drop
- To Hinder System Inefficiency
AS/NZS 3008 in Australia and New Zealand specifies the following acceptable voltage drop values:
- 3% final sub-circuit only.
- 5% from point of supply to final load.
- 7% from terminals of a transformer to the final load.
Calculating the voltage drop is worth doing in order to discover where problems exist and a way to correct them.
- To Avert Safety Issues
When the voltage drop increases, so will heat build up.
This can then cause materials to weaken and allow conductors to arc and ignite a fire within the insulation or closest combustible material.
In addition, if the insulation tears or melts away, it exposes conductor wires and users can accidentally touch it and receive an electrical shock.
- To Avoid Untimely Electrical Cable Damage
As previously explained, voltage drop can generate heat.
Too much of it can damage insulation and cause the breakdown of the insulating material, causing it to melt or tear.
Therefore, the lifespan of an electrical cable will likely be reduced.
- To Prevent Equipment Issues
Voltage drop limits the voltage and overall power that should be available to the equipment.
When voltage is lost, some equipment may function incorrectly or not even function at all.
Some large devices that use compressors can be affected with even the smallest loss of voltage it requires.
With these reasons, we understand the value of calculating voltage drop when picking the right cable size.
AS/NZS 3008 Regulations and Requirements
The Australian government has electrical cabling requirements in place. Thus, it is wise to check and follow safety and voltage drop calculation standards based on AS/NZS 3008.
CableHero: Cable Size and Voltage Drop Calculator
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Disclaimer: Although CableHero provides important and accurate tips and information through this website, CableHero does not make any representations or warranties as to the completeness, precision, trustworthiness, or timeliness of such information, and CableHero does not claim any duty to be held liable from the usage of the information.
