Test · IEC 60034-27

ELCID Test — Electromagnetic Core Imperfection Detection

Diagnosis of stator magnetic cores in synchronous generators and turbogenerators. The ELCID test induces reduced magnetic flux (4% of nominal) and detects anomalous eddy currents with a Chattock sensor — identifying lamination shorts and air-gap degradation before rewind, without energizing the core to full flux.

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Electromagnetic Core Imperfection Detection

IEC 60034-27IEEE 56CFE LAPEM W4200-12ISO 9001:2015

Technical definition

What is the ELCID test

ELCID (Electromagnetic Core Imperfection Detection) is a non-destructive diagnostic technique for the magnetic core of generator stators. Unlike the High-Flux Ring test (which requires energizing the core to nominal flux with hazardous currents), ELCID induces a very low magnetic flux (4% of nominal) and measures the induced eddy currents with a Chattock sensor that traverses every stator slot. It is the modern replacement for legacy full-flux testing on most service applications.

Reference standards: IEC 60034-27 and IEEE 56 (non-destructive testing of rotating machines)
Magnetic flux induction at 4% of nominal — safe, no thermal damage
High-sensitivity Chattock sensor maps eddy currents across all slots
Full mapping of the air gap and every slot of the stator
Quantitative detection of anomalous currents (mA) by stator zone
Graphical report with severity map per section of the stator core

Operational opportunity

When the ELCID test is recommended

ELCID is applied before costly decisions on the magnetic core — rewind, restacking or replacement. The test prevents wrong investments and prioritizes the right scope of intervention.

Before stator rewind — to validate that the core is recoverable
After a severe electrical event (phase short-circuit, overtemperature)
On generators with several decades of service — accumulated degradation evaluation
As part of major turbogenerator maintenance
To evaluate the trade-off between rehabilitation and full stator replacement
Before commissioning a legacy generator relocated to a new site

Client value

What the ELCID test detects

Lamination shorts in the magnetic core (between adjacent laminations)

Insulation degradation between laminations

Surface damage to the air gap from rotor contact or particles

High eddy-current zones that would generate overheating in service

Exact location of the defect (slot, row, approximate depth)

Quantitative severity to prioritize partial restacking vs full rewind

Deliverables

What we deliver at the end of the test

Each test is delivered with a signed documentation package under IEC 60034-27 and ISO 9001:2015. Full traceability by work-order number and signature of the responsible engineer.

1Signed protocol under IEC 60034-27 with methodology and stator map
2Graphical map of eddy currents per zone (air-gap heat map)
3Prioritized list of defects by severity (mA measured vs acceptable threshold)
4Diagnosis: core recoverable / partial restacking needed / replacement required
5Technical recommendation with cost-benefit of rehabilitation vs replacement
6ISO 9001:2015 traceability with raw data for independent verification

Typical case

Pre-rewind evaluation on a hydroelectric generator stator

IEC 60034-27

Applicable standard

Core recoverable

Diagnosis

Restack + rewind

Executed plan

Hydroelectric generator with decades of service and an insulation fault. Before quoting the full rewind, ELCID was applied to validate the magnetic core. The test detected zones with mild eddy-current anomalies — the recommendation was partial restacking plus rewind, avoiding complete stator replacement. Estimated savings versus a full replacement were significant, and the result was delivered with a signed technical report under IEC 60034-27 and ISO 9001:2015 traceability.

FAQ

Frequently asked questions — ELCID test

Preguntas que recibimos con frecuencia. ¿No encuentras la tuya? Escríbenos a ventas@temisa.mx.

Why ELCID and not the traditional High-Flux Ring test?

High-Flux Ring requires energizing the core at 100% of nominal flux — hazardous, requires a high-current source and can damage marginal laminations. ELCID induces only 4% of nominal flux — it is safe, non-damaging, and maps each stator zone quantitatively. It is the modern test recognized by IEC 60034-27.

Does the rotor need to be removed for ELCID?

Yes. The ELCID test requires unobstructed access to the stator air gap from the rotor side — the Chattock sensor traverses the slots manually. Rotor removal is included in the work scope.

How long does an ELCID test take on a large turbogenerator?

Between 12 and 24 hours onsite for setup, full stator mapping and data capture. The time depends on the number of slots (a 200 MW turbogenerator may have 60 to 84 slots) and on air-gap accessibility.

Can the ELCID test replace visual inspection of the core?

No. ELCID is complementary. Visual inspection detects macroscopic damage (impacts, thermal staining, bent fingers); ELCID detects electromagnetic degradation invisible to the eye. Combined, they deliver a complete diagnosis.

What happens if ELCID detects severe lamination shorts?

We document severity quantitatively (mA measured vs acceptable threshold). If defects are localized, we recommend partial restacking. If they are extended, we evaluate major restacking or full stator replacement. The decision belongs to the client, with data in hand.

Do you perform ELCID on large turbogenerators or only on smaller machines?

We perform ELCID at any capacity under CFE LAPEM W4200-12 — from 1 MVA synchronous generators to turbogenerators up to 350 MW. The equipment is portable and adapts to any stator size.

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