Source: https://guthlabs.ai/docs/instruments/fuse-breaker-trip-time-curve-viewer/

instrument / verified-clean

# Fuse/Breaker Trip Time Curve Viewer

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/fuse-breaker-trip-time-curve-viewer/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/fuse-breaker-trip-time-curve-viewer/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/fuse-breaker-trip-time-curve-viewer/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/fuse-breaker-trip-time-curve-viewer/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-7

**Evidence ID**: t7-130

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The honest-label text is appropriate but not sufficient to make the computation uniquely defined. NEEDS_REVIEW is required because the spec names IEC 60898 B/C/D and generic fuse families without supplying a normative table or an exact mathematical model. The four vectors use explicitly marked illustrative parameters solely to make arithmetic testable; they must not be presented as manufacturer, IEC, UL, or fuse-standard trip times.

### Formula and scope findings

- The specification does not provide numerical curve parameters, breakpoint tables, tolerances, or a defined equation, so an estimated trip time cannot be uniquely computed.

- IEC 60898 B/C/D classifications define characteristic instantaneous-trip current bands, not one exact trip time at each overcurrent multiple. A B/C/D label alone is insufficient for a time-current plot.

- An I²t model normally gives t = K/I², or t = K/M² when expressed using current multiple M. The alternative inverse-time form t = K/(M² - 1) is not universally standard and requires an explicit, instrument-specific definition and fitted K values.

- Breaker thermal-magnetic curves and fuse pre-arcing/clearing curves are different phenomena; one generic formula cannot honestly represent both without separate curve models and definitions.

- The specification does not distinguish fuse pre-arcing time from total clearing time, nor breaker trip mechanism time from total interruption time.

### Unit assumptions

- Rated current and fault current are in amperes; fault-current multiple M is dimensionless and equals fault current divided by rated current.

- Estimated trip time is in seconds.

- For the illustrative vectors below, the explicitly supplied generic model is t = K/(M² - 1), with K in seconds and M > 1.

- Rated current must be greater than zero; fault current is computed as rated current multiplied by M.

- The IEC 60898 B/C/D values are characteristic-band boundaries, not exact trip-time guarantees.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The generic viewer specification has undefined behavior at M = 1, requires explicit handling at the zero-overcurrent boundary, switches between inverse-time and instantaneous branches, and can produce a different validity result if signed current is interpreted literally instead of by magnitude.

## 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": {
    "rated_current_A": 20,
    "curve_type": "B",
    "fault_current_multiple": 3
  },
  "expected_outputs": {
    "fault_current_A": 60,
    "estimated_trip_time_s": 0.15,
    "curve_point": {
      "x_multiple": 3,
      "y_time_s": 0.15
    }
  },
  "reference_data": {
    "iec_60898_1_curve_band": {
      "class": "B",
      "instantaneous_trip_band_multiple": "3 to 5 x In",
      "lower_boundary_multiple": 3,
      "upper_boundary_multiple": 5,
      "source_convention": "IEC 60898-1 characteristic band"
    },
    "generic_model_parameter": {
      "curve_type": "B",
      "K_s": 1.2,
      "source_convention": "illustrative generic parameter supplied for verification; not a normative IEC value"
    },
    "model": "t_s = K_s/(M^2 - 1)"
  },
  "working": "M = 3, so fault current = 20 A × 3 = 60 A. M² - 1 = 3² - 1 = 9 - 1 = 8. t = 1.2 s / 8 = 0.15 s. M = 3 is exactly the widely memorized IEC 60898-1 B-curve lower instantaneous-band boundary; that boundary does not itself guarantee a 0.15 s trip time."
}
````

## 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-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`