Transformers and Power Supplies
Current Transformer Burden Calculator
Calculate CT burden from secondary current and burden impedance. The default values illustrate the workflow; replace them with measurements or ratings from one documented condition.
Inputs for this calculation
Use measurements from one operating condition.
Understanding the equation
This page evaluates VA = I²Z. Only Secondary current and Burden impedance enter the numerical result.
With the current entries, the primary answer is 5.00 VA. Preserve the raw inputs when replacing this example.
Calculate CT burden from secondary current and burden impedance. Use Current Transformer Ratio Calculator as the companion source for primary current.
Values this page needs
Identify RMS, average, peak, and rectified quantities explicitly. Do not combine a worst-case value with unrelated nominal data.
Use the displayed unit for every field and document conversions separately. The required impedance step is handled by Current-Limiting Impedance Calculator.
- Secondary current
- Default example: 5 A. Enter secondary current in A.
- Burden impedance
- Default example: 0.2 Ω. Enter burden impedance in Ω.
How to use the result
The primary answer, CT burden, describes only the entered scenario. Compare it with voltage stress, current stress, ripple, loss, regulation, and temperature.
Save the raw entries before testing another scenario. Flyback Transformer Calculator may be useful for the next related quantity.
A second scenario
Change Secondary current from 5 A to 6 A and leave all other entries untouched. The displayed value changes from 5.00 VA to 7.20 VA.
Use a separate scenario when multiple conditions change together.
Practical limits
Include leads and connected instruments.
The simple equation may need adjustment for diode loss, ESR, regulation, ripple current, and thermal resistance. Do not hide omitted behavior inside an unexplained correction factor.
Identify RMS, average, peak, and rectified quantities explicitly.
Review the case step by step
Check the source of secondary current before calculating. A credible result requires every field to describe the same physical condition and unit basis.
Use CT burden alongside voltage stress, current stress, ripple, loss, regulation, and temperature. Preserve the unrounded number until all dependent calculations and comparisons are complete.
If uncertainty remains, calculate labeled low and high cases. Include isolation, creepage, waveform shape, and manufacturer operating limits when those effects can change the decision.
When the inputs are uncertain
The calculator rejects values outside its stated field limits, but a numerically valid entry can still describe the wrong condition. Confirm secondary current and burden impedance against the original source before saving the result.
Use an additional case for isolation, creepage, waveform shape, and manufacturer operating limits when that behavior is not negligible. Keep the baseline intact so the effect of each changed assumption remains visible.