DC Motor Starting Current & Back-EMF Estimator

Inspectable records

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

t4-102

Ledger rows

1

No ledger note is attached.

Review findings

The simplified separately-excited DC motor label is honest only if the instrument clearly states that it uses a steady-state model with supplied speed and combined SI-compatible motor constant K_e=kΦ. Define the warning rule, the speed unit, the motor-constant definition, the locked-rotor condition, and the allowed sign/range constraints before release.

Formula and scope findings

• Ia=(V−Eb)/Ra is the standard steady-state armature-current relation for a separately excited DC motor, provided Ra is the total armature circuit resistance and Ra>0.
• The back-EMF relation is standard as Eb=K_e·ω, or Eb=k·Φ·ω when k·Φ is not already combined. The specification writes Eb=kΦN without defining whether N is angular speed in rad/s or rotational speed in rpm; using rpm requires a 2π/60 conversion or an rpm-specific motor constant.
• The listed inputs provide a motor constant but do not explicitly provide flux Φ. The formula is complete only if motor constant means the combined constant kΦ, equivalently K_e.
• The claimed locked-rotor current requires the explicit condition speed=0, giving Eb=0 and I_start=V/Ra; this condition is implied but not stated as a separate formula.
• The claimed armature current under load is only estimated from a supplied speed. No load torque, mechanical losses, or speed-dynamics relation is included, so the instrument does not calculate speed or current from load.
• The starting-current warning has no defined threshold, trigger condition, or output semantics, so it cannot be verified.

Unit assumptions

• V is terminal armature voltage in volts.
• Ra is total armature-circuit resistance in ohms and must be strictly greater than zero.
• The motor constant used in these vectors is K_e=kΦ in volts per radian per second, numerically V·s/rad.
• Speed is angular speed ω in rad/s unless explicitly converted from rpm.
• Eb is in volts and Ia is in amperes.
• For rpm input, ω=rpm·2π/60 must be used before applying Eb=K_e·ω.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The specification provides no stated validation for Ra=0, which makes Ia undefined. It also leaves the speed and motor-constant units unspecified, allowing materially different back-EMF and current results.

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": {
    "V_V": 240,
    "Ra_ohm": 1.2,
    "motor_constant_Vs_per_rad": 0.8,
    "speed_rad_per_s": 0
  },
  "expected_outputs": {
    "Eb_V": 0,
    "Ia_A": 200,
    "starting_current_warning": null
  },
  "working": "Eb=K_e·ω=0.8·0=0 V. Ia=(V−Eb)/Ra=(240−0)/1.2=240/1.2=200 A. Speed is zero, so this is the locked-rotor case; the warning result is null because the specification defines no warning policy."
}

Related workflows

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