Wiring and Protection
Contact Resistance Loss Calculator
The purpose of Contact Resistance Loss is to turn current and contact resistance into contact power loss. Keep the source condition with the saved result so later comparisons remain meaningful.
Inputs for this calculation
Replace the examples with values from the same case.
From inputs to result
This page evaluates loss = I²Rcontact. Its variables correspond to Current and Contact resistance.
The initial scenario returns 5.00 W. Re-enter field data before using the answer in a design or comparison.
Calculate contact power loss from current and contact resistance. A separate cord loss result is available from Extension Cord Power Loss Calculator.
Sensitivity check
Change Current from 50 A to 60 A with the rest of the inputs held constant. The comparison runs from 5.00 W to 7.20 W.
The comparison demonstrates sensitivity, not a guaranteed field response.
Preparing the calculation
Use the installed route length, conductor material, and actual current path. If operating conditions changed between readings, calculate separate cases.
A prefix error can move the result by several orders of magnitude.
- Current
- Default example: 50 A. Enter current in A.
- Contact resistance
- Default example: 0.002 Ω. Enter contact resistance in Ω.
Checks that catch bad inputs
Values recorded at different operating points should not share one case.
Compare the magnitude with a quick independent estimate.
How to use the result
The primary answer, Contact power loss, describes only the entered scenario. Compare it with the applicable installation and equipment requirements.
Store the measurement state and conversion notes with the answer.
Assumptions and limitations
Milliohm-level readings require suitable four-wire measurement.
Additional checks may be needed for fault duration, protective-device curves, and conductor thermal limits. Do not hide omitted behavior inside an unexplained correction factor.
Use the installed route length, conductor material, and actual current path.
Using this result in a larger analysis
Check the source of current before calculating. A credible result requires every field to describe the same physical condition and unit basis.
The displayed contact power loss should be checked against the applicable installation and equipment requirements. Investigate an unexpected magnitude before changing the model or adding margin.
Keep a baseline and vary the least certain measurement first. A separate analysis may be needed for termination heating, installation method, ambient temperature, and grouping.
Before relying on the answer
Which source values should I use for Contact power loss?
Choose entries that describe the same case. Use the installed route length, conductor material, and actual current path.
What should I verify beyond the displayed inputs?
Milliohm-level readings require suitable four-wire measurement. Also consider code rules, manufacturer instructions, and field installation details.
What can cause a different contact power loss reading?
Differences can come from code rules, manufacturer instructions, and field installation details, measurement uncertainty, or values taken under different conditions.
What is the cleanest way to test another scenario?
Use separate labeled cases when more than one condition changes. Record ambient temperature, bundling, insulation class, and termination conditions.