Fuse/Breaker Trip Time Curve Viewer mechanism

Model scope

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.

• 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.

Units and conventions

• 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.

Inspectable vector

One of 4 source-bound review vectors:

{
  "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."
}

Failure boundary

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.

Other records

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
• BOUNDARY_HAZARD_CATALOG.json