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

instrument implementation / implementation-contract

# Fuse/Breaker Trip Time Curve Viewer implementation

A source-bound implementation contract for Fuse/Breaker Trip Time Curve Viewer; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-130

**Effect**: Computation or source lookup only

## Input and validation requirements

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.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "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."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/fuse-breaker-trip-time-curve-viewer/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/fuse-breaker-trip-time-curve-viewer/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/fuse-breaker-trip-time-curve-viewer/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`