Source: https://guthlabs.ai/docs/instruments/transformer-turns-ratio-sizing-calculator/

instrument / verified-clean

# Transformer Turns Ratio & Sizing Calculator

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/transformer-turns-ratio-sizing-calculator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/transformer-turns-ratio-sizing-calculator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/transformer-turns-ratio-sizing-calculator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/transformer-turns-ratio-sizing-calculator/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab

**Tranche**: tranche-4

**Evidence ID**: t4-054

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The core ideal-transformer relationships are standard, but the instrument fails its stated feature set because % regulation has no defined formula and required VA sizing is conflated with load apparent power. The honest-label text appropriately discloses ignored losses, but the UI must explicitly identify all results as ideal-model values and must not imply a certified or thermally sufficient transformer rating.

### Formula and scope findings

- The turns-ratio identity a=N1/N2=V1/V2=I2/I1 is correct only for an ideal transformer with RMS AC quantities, negligible losses, and consistent primary/secondary labeling.

- No formula is provided for the claimed % regulation estimate. In the stated ideal model, regulation would conventionally be 0%, but that assumption and the regulation definition are not specified; a real-transformer regulation estimate requires additional parameters.

- VA=V·I correctly computes apparent power, but it does not by itself determine a required transformer VA rating. A sizing rating normally requires a design margin, duty cycle, temperature/thermal constraints, and possibly inrush considerations.

- The input alternatives are underspecified: the spec does not state how to derive missing V2 from N1,N2 and V1, or missing current from a supplied VA, nor how conflicting simultaneous inputs are handled.

### Unit assumptions

- V1 and V2 are RMS AC voltages in volts, measured on consistently labeled primary and secondary windings.

- I1 and I2 are RMS currents in amperes; N1 and N2 are winding turns and therefore dimensionless counts.

- The transformer operates at the same frequency on both windings and is modeled as ideal, so V1/V2=N1/N2 and I2/I1=N1/N2.

- VA is apparent power in volt-amperes, calculated using RMS voltage multiplied by RMS current, with power factor excluded.

- A supplied load current is treated as secondary load current I2; a supplied VA value is treated as secondary apparent load power unless explicitly stated otherwise.

- A current ratio or voltage ratio must not use a zero denominator, and all voltage, current, and turns inputs must be positive for normal transformer operation.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The zero-turn secondary input produces an undefined ratio and must be rejected. Signed-voltage inputs also expose an unresolved polarity/sign convention: signed and magnitude interpretations produce different ratio and current signs.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "V1_V": 120,
    "V2_V": 12,
    "load_current_A": 5
  },
  "expected_outputs": {
    "ratio_a": 10,
    "secondary_voltage_V": 12,
    "secondary_current_A": 5,
    "primary_current_A": 0.5,
    "required_VA": 60
  },
  "working": "a=V1/V2=120/12=10. I1=I2/a=5/10=0.5 A. VA=V2·I2=12·5=60 VA."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`