Example Data Table
| Input |
Example Value |
Meaning |
| Source Voltage |
240 V |
Supply voltage before feeder conductors. |
| Feeder Length |
45 m |
One-way distance from source to branch node. |
| Feeder Area |
25 mm² |
Cross-sectional conductor size. |
| Branch Lighting |
18 A, 30 m, 6 mm² |
First parallel load branch. |
| Branch Sockets |
22 A, 38 m, 10 mm² |
Second parallel load branch. |
| Branch Motor |
16 A, 25 m, 6 mm² |
Third parallel load branch. |
Formula Used
Temperature corrected conductor resistance:
R = ρ × L ÷ A × [1 + α × (T - 20)] ÷ N
DC voltage drop:
Vdrop = I × 2R
Single phase voltage drop:
Vdrop = 2 × I × (R × PF + X × sinφ)
Three phase voltage drop:
Vdrop = √3 × I × (R × PF + X × sinφ)
Final branch voltage:
Vload = Vsource - Vfeeder drop - Vbranch drop
Voltage drop percent:
Drop % = Total voltage drop ÷ Source voltage × 100
Here, ρ is resistivity, L is one-way length, A is conductor area, α is temperature coefficient, T is conductor temperature, N is parallel conductors per path, I is current, PF is power factor, and X is reactance.
How to Use This Calculator
- Enter the source voltage and choose the circuit type.
- Select copper, aluminum, or custom conductor material.
- Enter feeder length, feeder size, and feeder power factor.
- Add current, length, area, and power factor for each parallel branch.
- Use zero current for unused branch rows.
- Press the calculate button.
- Review feeder drop, node voltage, branch voltage, and loss.
- Use CSV or PDF download for records.
Understanding Parallel Voltage Drop
A parallel circuit often looks simple because each load connects across the same supply. In real wiring, the conductors are not perfect. They have resistance. Current moving through that resistance creates voltage drop and heat. This calculator separates the shared feeder drop from each branch drop. That makes the result clearer than a single rough estimate.
Why Parallel Circuits Need Care
In a parallel layout, branch currents add together at the feeder. A small branch may have a low drop, but the feeder may still carry a large combined current. Long cable runs make this effect stronger. Warm conductors also add more resistance. The tool includes temperature, material, conductor area, power factor, and optional reactance. These details help when checking lighting strings, control panels, DC buses, machine branches, and distribution boards.
What the Result Means
The feeder voltage drop is removed first. The remaining node voltage becomes the starting point for every branch. Each branch then loses more voltage through its own conductors. The final load voltage shows what the device may actually receive. The percent drop compares total drop against the source voltage. Many designs try to keep important final circuits near three percent. Whole feeders and final circuits are often reviewed near five percent. Local codes and equipment manuals should always decide the final limit.
Better Design Choices
Voltage drop can be reduced in several ways. Use a larger conductor area. Shorten the cable route. Split heavy loads across closer panels. Reduce current where possible. Improve power factor on alternating current loads. For DC systems, check both positive and negative conductors. For three phase systems, check balanced loading before trusting one branch result.
Useful Review Notes
This page is an estimating aid. It does not replace a licensed electrical design. Actual installations may need derating, conduit fill checks, insulation ratings, termination limits, and overcurrent protection review. Still, a transparent calculator is useful early. It helps compare options before ordering wire or building panels. Save the result, export the table, and keep the assumptions with your project notes. Recheck every branch after changing loads. A small edit can move shared current, feeder loss, and final voltage. Good records make later troubleshooting much easier for teams.
FAQs
1. What is voltage drop in a parallel circuit?
It is the voltage lost in conductors before power reaches each parallel load. The shared feeder drop affects all branches. Each branch can also have its own extra drop.
2. Do parallel branches have the same voltage?
Ideal parallel loads have the same voltage at the connection node. Real branch conductors cause extra drop, so final load voltage can differ between branches.
3. Why does feeder current matter?
The feeder carries the combined branch current. Higher total current increases feeder voltage drop and conductor heating, even when individual branches seem small.
4. Should I enter one-way or round-trip length?
Enter one-way length only. The calculator applies the correct multiplier for DC, single phase, or three phase calculations.
5. What does power factor change?
Power factor changes the alternating current voltage drop estimate. Lower power factor can increase drop when reactance is included.
6. Can this calculator size protective devices?
No. It estimates voltage drop and conductor loss only. Breaker, fuse, grounding, and code checks need separate design review.
7. What is a good voltage drop limit?
Many designs aim near three percent for final circuits and near five percent overall. Always follow local rules and equipment requirements.
8. Why include conductor temperature?
Conductor resistance rises as temperature increases. A warm cable can drop more voltage than the same cable at room temperature.