Rex Power Magnetics has expanded the free engineering calculator suite available on its website, giving engineers, contractors, and specifiers a faster way to size transformers, estimate efficiency, and evaluate reactor and harmonic mitigation options directly online. The suite now includes nine dedicated tools, each built to answer a specific sizing or selection question that comes up during the early stages of a project.
The calculators are designed for quick, practical use — no software downloads or account sign-ups required. Enter the known values for a given application, and the tool returns the result instantly, along with the underlying assumptions so the output can be verified against project-specific requirements.
rexpowermagnetics.com/resources/calculators.
What’s Included
The expanded suite covers the calculations most frequently needed when specifying a dry-type transformer or evaluating power quality equipment:
| Calculator | What It Solves |
|---|---|
| Transformer kVA Calculator | Determines required transformer kVA from voltage, current, and phase inputs |
| kW to kVA Conversion Calculator | Converts real power to apparent power using power factor |
| HP to kVA Conversion Calculator | Converts motor horsepower to apparent power for sizing purposes |
| Transformer Fault Current Calculator | Estimates available fault current at the transformer secondary |
| K-Factor & Harmonic Loss Calculator | Calculates K-factor rating and additional losses from harmonic loading |
| Efficiency & Regulation Calculator | Models efficiency and voltage regulation across the load range |
| Savings & Payback Calculator | Compares total cost of ownership and payback period between transformer options |
| Reactor Inductance Calculator | Determines required inductance for line/load reactor applications |
| Harmonic Reactor Calculator | Sizes detuned reactors for harmonic filtering applications |
Built for the Field and the Front Office
Several of the tools go beyond a single output number. The efficiency and regulation calculator plots performance curves across the load range, and the savings and payback calculator generates a total-cost-of-ownership comparison so the financial case for a higher-efficiency unit is as clear as the technical one. Every calculator includes a brief explanation of the formula behind the result, so the tools work equally well as a quick field reference and as a way to double-check assumptions during detailed engineering.
The calculators are built to work on desktop and mobile browsers, with no plug-ins required, making them practical to use on a job site or during a client call.
Why It Matters
Transformer sizing decisions made early in a project — kVA rating, K-factor, fault current withstand — have downstream effects on switchgear selection, protective device coordination, and overall system cost. Having reliable, accessible tools to run these numbers early helps engineers and contractors catch sizing issues before they become change orders. Rex Power Magnetics developed the suite based on the calculations its own applications engineering team is asked to run most often for customers, and built each tool to reflect the same assumptions and standards used in that internal engineering work.
The calculator suite joins the Product Configurator, Knowledge Hub, and technical documentation library as part of Rex Power Magnetics’ broader set of self-serve engineering resources, all available at rexpowermagnetics.com/resources.