Verified calculation capability

Voltage drop Calculation Capability

Estimate conductor voltage drop from current, one-way length, and Ω/km for DC / resistive 1φ or balanced 3φ (resistance-only, PF≈1). Always returns conductor I²R loss P_loss. Optional V_system adds percent drop and estimated load voltage; optional u_* compose expanded uncertainty on V_drop via Uncertainty Engine. · Electrical

Capability ID electrical.voltage_drop · version 1.5.2

Open calculator REST API MCP Evidence Evidence JSON CVP Manifest Review policy

Model

One-way resistance

One-way resistance: R = L(m) × Rₖₘ / 1000
DC / resistive 1φ: Vdrop = I × 2R
Balanced 3φ · resistive: Vdrop = √3 × I × R
Percent: %drop = 100 × Vdrop / Vsystem
Cable loss · DC / 1φ: Ploss = I² × 2R
Cable loss · 3φ: Ploss = 3 × I² × R

Solve modes: dc · three

Inputs / Outputs

Canonical symbols for this capability. Agent schemas remain the contract.

Symbol	Quantity	Unit	Role
`I`	Load current (A)	—	input
`length`	One-way conductor length (m)	m	input
`R_ohm_per`	Conductor resistance (Ω/km)	km	input
`V_system`	Optional source voltage (V). For 3φ this is line-to-line. Adds percent_drop and V_load.	—	input
`u_I`	Optional standard uncertainty of I (A)	—	input
`u_length`	Optional standard uncertainty of length_m (m)	m	input
`u_R_ohm_per`	Optional standard uncertainty of R_ohm_per_km (Ω/km)	km	input
`uncertainty_k`	Coverage factor for expanded U on V_drop; default 2 when any u_* is set. Mutually exclusive with confidence.	—	input
`confidence`	Optional coverage probability instead of uncertainty_k. Mutually exclusive with uncertainty_k.	—	input
`V_drop`	Estimated voltage drop (V)	—	output
`R_one_way`	One-way conductor resistance (Ω) = L(m)·R_km/1000	—	output
`R_loop`	Go-and-return loop resistance (Ω) = 2·R_one_way; present for dc / resistive 1φ only	—	output
`P_loss`	Conductor I²R loss (W). DC / resistive 1φ: I²·2R. Balanced 3φ: 3·I²·R.	—	output
`percent_drop`	Present when V_system is set: 100·V_drop/V_system. 3φ uses line-to-line V_system.	—	output
`V_load`	Present when V_system is set: estimated load voltage V_system − V_drop (same basis as V_system)	—	output
`uncertainty`	Present when any u_* is provided; UncertaintySummary via engineering.uncertainty.propagate (sensitivity on V_drop)	—	output

Assumptions / Validity

Declared scope for this capability. Do not use it outside this domain.

Assumptions

Constant resistance; temperature neglected.
AC estimate assumes PF ≈ 1 and neglects conductor reactance.
DC / resistive 1φ uses round-trip path; 3φ assumes balanced line-to-line drop.
V_system for 3φ is line-to-line; V_load = V_system − V_drop on that same basis.
User supplies an appropriate Ω/km for the conductor and conditions.
When u_* are set, first-order GUM sensitivity with independent inputs (no ρ on this page).

Example

One numerical check. The calculator page holds worked steps and FAQ.

20 A, 50 m, 5 Ω/km, DC / resistive 1φ, V_system=230 → V_drop = 10, percent_drop ≈ 4.35%, V_load = 220, P_loss = 200

Open this example in the calculator

Trust

CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance. Computational verification is defined by CVP. Supplemental domain review (internal) and named expert review are defined by the Review policy and do not by themselves determine CVP conformance.

CVP: CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance· View Manifest · CVP overview · Specification
Assurance: Engineering
Declared partition coverage: PASS · 5/5 declared partitions (dc, three, with-V_system, with-uncertainty, invalid-domain)
Calculation version: 1.5.2
Verification: 38/38 calculation tests · 12/12 legacy golden · 12/12 legacy boundary · 14/14 legacy property
Production surface contract: 6/6
Versions: Calculation 1.5.2 · CVP protocol 1.0.0-proposed · Evidence 2026-09-11.schema-coverage-u
Verification revision: 2026-09-11.schema-coverage-u · 14/14 property · digest e4ca53248b8b
Reference: O1 model · O2 expected_values · O2 numerical_behavior
Interfaces: PASS · UI (SSR) / REST / MCP
ui-ssr is query-result HTML, not a live browser session.
CVP suite: 4/4 golden · 11/11 CVP boundary · 10/10 invalid · 14/14 property · 4/4 metamorphic · 1/1 cross-interface · 6/6 CVP contract
Supplemental domain review: Not performed
Named expert review: Not performed
Version lock: Supported (409 VERSION_MISMATCH)
Artifact consistency: Build verified · 1.5.2 (workspace artifacts agree)
Review-policy tier: Engine tested — catalog token engine_tested; supplemental; not CVP status

This calculator CURRENT · Public schema 1.5.2 matches · Semantic contract ✓ · Production attested · Public/cache ✓ · Origin ✓

Call this capability

Human page, REST, and MCP share the same engine and calculation_version. Build verified hashes workspace artifacts only. After deploy, attest:production GETs canonical URLs twice — the public/cached view an Agent actually hits, and origin — including every /capabilities/{id} HTML page. Public Capability HTML version must match catalog before production attestation passes. Live Trust rows above fetch /.well-known/calculatorx-production-attestation.json and the output schema const. Build hashes: release integrity. That proves currently published page / engine / schema / evidence / MCP agree — not that a historical version is independently immutable. Reference Calculation Standard — Production surface contract 6/6.

Tool id: voltage-drop
Engine: voltage-drop
REST: POST /api/v1/calc/voltage-drop
MCP: execute_calculation with capability_id: "electrical.voltage_drop"
Agent input schema: Canonical (MCP / Agent)
Output schema: JSON Schema (latest)
Versioned input schema: Immutable pin (1.5.2)
Versioned output schema: Immutable pin (1.5.2)

Operations

Declared calculation modes for this capability.

dc
three

References

Human-readable sources plus CVP reference evidence classes.

Sources

Reference evidence classes: O1 model · O2 expected_values · O2 numerical_behavior

Try with an agent

Inspect this capability via same-origin MCP, then call execute_calculation.

curl -sS -X POST 'https://www.calculatorx.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: tools/call' \
  -H 'Mcp-Name: inspect_capability' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"inspect_capability","arguments":{"capability_id":"electrical.voltage_drop"}}}'

Inspect the trust tier and required assurance level before execution. Pin calculation_version (1.5.2) when reproducibility matters. Full protocol notes: MCP docs.