Calculation results
Enter project conditions, then calculate. Live results update after valid changes.
Calculation history
Formula used
The operating-current formula changes with the selected circuit. DC power uses current equals power divided by voltage and efficiency. Three-phase AC also includes square root three and power factor.
Single phase: I = P ÷ (V × PF × η)
Three phase: I = P ÷ (√3 × V × PF × η)
PV strings: I = Isc × parallel strings × combiner groups
Design current multiplies operating current by selected project factors. Corrected ampacity multiplies base ampacity by every applicable correction factor. Parallel runs increase total available ampacity when current sharing remains equal.
I_allowable = I_base × F_combined × parallel runs
Voltage drop uses conductor resistance at operating temperature. DC and single-phase circuits use the complete outgoing and return path. Three-phase circuits use the square root three relationship.
DC or 1φ: ΔV = 2 × I × L × Z ÷ 1000
3φ: ΔV = √3 × I × L × Z ÷ 1000
The thermal fault check uses the adiabatic relationship. Minimum area depends on prospective current, clearing time, and the selected k-factor. Confirm every thermal constant before approving construction documents.
I_withstand = k × S ÷ √t
How to use this calculator
Select the project reference, circuit type, and electrical system. Choose the correct current method for the available design data. Enter module current, inverter power, or measured circuit current.
Set every current multiplier according to project requirements. Do not leave default factors without checking their purpose. Double multiplication can create an unnecessarily large conductor recommendation.
Choose conductor material, cable type, and sizing mode. Automatic mode finds the first reference size passing ampacity. Selected mode checks a specific cable against entered conditions.
Enter maximum ambient temperature and cable grouping information. Select the closest installation method for preliminary comparison. Replace reference factors with approved project values when available.
Add one-way length, operating temperature, and voltage-drop limits. Manufacturer resistance improves voltage-drop and loss accuracy. AC circuits should use appropriate resistance and reactance data.
Enter protection ratings and prospective fault data carefully. The suggested device must fit between design current and cable ampacity. Module, connector, and disconnect ratings can impose lower limits.
Review every warning before using the recommendation. Compare nearby cable sizes for efficiency and voltage drop. Export results to support design review and documentation.
Understanding solar cable ampacity
A cable ampacity value represents allowable continuous current under defined conditions. Real installations often differ from those reference conditions. Temperature, grouping, routing, and terminals can reduce usable capacity.
Solar conductors may operate near rooftops with intense heating. Enclosures and grouped cables can trap additional heat. Conservative site temperatures help prevent overlooked thermal stress.
Voltage drop creates another cable-size limit. A conductor may pass ampacity yet waste significant energy. Longer circuits commonly require larger conductors for performance.
Parallel conductors can support large currents when properly designed. Each run needs matching length, size, material, routing, and termination. Unequal impedance can produce dangerous current imbalance.
Protection coordination is equally important. Protective devices must interrupt faults without exceeding cable limits. Solar equipment ratings may restrict the final protective-device selection.
Manufacturer documentation remains the preferred cable-data source. Local codes can impose different multipliers and installation rules. Qualified designers should verify every final selection before construction.
Standards and cable-data references
IEC 62548-1 addresses photovoltaic array design requirements. Its scope includes DC array wiring, protection, switching, and earthing provisions. Confirm the edition adopted for each project location.
IEC 60364-5-52 addresses wiring-system selection and installation. Its requirements can influence conductor sizing and installation methods. Local amendments may change applicable correction factors.
IEC 62930 covers specified photovoltaic cables for DC systems. Cable voltage, construction, and manufacturer ratings still require verification. Listed project cables should match actual environmental conditions.
Example design inputs
| Design item | Example value | Reason |
|---|---|---|
| PV module Isc | 13.5 A | Defines source-circuit current. |
| Parallel strings | 2 | Combines current from both strings. |
| System voltage | 600 V DC | Supports voltage-drop percentage. |
| One-way length | 35 m | Defines the conductor route length. |
| Ambient temperature | 45°C | Applies a thermal correction. |
| Voltage-drop limit | 2% | Sets the performance target. |
Frequently asked questions
Does the smallest passing cable become the final design?
Not always. Voltage drop, losses, terminals, fault withstand, availability, and project specifications can require a larger cable.
Why are there two current multipliers?
They allow separate treatment of PV source current and continuous loading. Verify both against the adopted rules before use.
Can I enter manufacturer ampacity?
Yes. Select custom ampacity mode, choose the cable size, and enter the approved base ampacity.
Why does rooftop installation reduce ampacity?
Rooftop cables may face higher surrounding temperatures. The exact adjustment depends on routing, height, code, and project conditions.
Does voltage drop use Isc?
The default uses operating current. Select design current when project criteria require a more conservative voltage-drop check.
Can aluminum cable be evaluated?
Yes. Select aluminum, then verify compatible equipment, terminations, cable listings, and installation practices.
What does the k-factor control?
It controls the adiabatic short-circuit calculation. Use a value matching conductor material, insulation, and permitted temperatures.
How are parallel runs handled?
Total ampacity is multiplied by run count. Voltage drop and losses assume equal current sharing across identical runs.
Why might no protective device be recommended?
No listed standard rating may fit between design current and corrected ampacity. A different cable or design may be needed.
Can the calculator replace cable software?
It supports preliminary design and review. Complex installations may require certified software and detailed thermal modelling.
Is the result automatically code compliant?
No. Compliance depends on adopted rules, equipment listings, manufacturer data, engineering judgment, and authority approval.