Service
Transformer magnetic core repair
Repair of the magnetic core: shorted laminations, core ground faults and restacking, diagnosed with excitation current and core-loss testing.
The magnetic core carries the flux that makes a transformer work, and its defects — shorted laminations, a defective core ground, mechanical loosening — cause overheating and rising losses. TEVKO diagnoses and repairs core problems on transformers of any manufacturer, validated with excitation current and core-loss testing.
The core is built from thin insulated steel laminations to keep eddy-current losses low. When the inter-laminar insulation degrades and laminations short together, or when the core develops an unintended second ground, circulating currents flow and the core overheats locally — generating gases, raising losses and, left unattended, damaging the surrounding insulation. These are exactly the faults that excitation current and core-loss measurements expose.
Repair depends on the defect: clearing or isolating shorted laminations, locating and correcting a defective or multiple core ground, and re-tightening or restacking sections of the core that have loosened mechanically. Core work is often done together with a rewind, since accessing the core means lifting the windings — which is why a precise diagnosis up front decides the scope efficiently.
TEVKO repairs transformer cores in its 5,600 m² plant, diagnosing with excitation current, core-loss and insulation tests using Omicron and Megger instrumentation, and validating the repair under IEEE C57 and IEC 60076 before reassembly. As an independent multi-brand provider, TEVKO does not manufacture transformers; it restores the core so the unit returns to the performance the manufacturer specified, with a documented protocol.
Scope of core repair
Shorted laminations / core ground
Clearing or isolating shorted laminations and correcting defective or multiple core grounds.
When it applies: Local overheating, rising core loss, gas generation.
Restacking
Re-tightening or restacking sections of the core that have loosened mechanically.
When it applies: Mechanical loosening after transport or through-faults.
How we execute the repair
Diagnosis
Excitation current, core-loss and core-ground insulation tests to characterize the defect.
Access
Controlled disassembly to reach the core, often combined with winding work.
Repair
Lamination/ground correction or restacking to specification, with drying.
Acceptance testing
Excitation current and the full protocol verified before reassembly and return to service.
Frequently asked questions — transformer magnetic core repair
What core faults can a transformer develop?
Shorted laminations (from degraded inter-laminar insulation), a defective or unintended second core ground, and mechanical loosening of the core stack. All of them cause local overheating and rising losses, detectable with excitation current and core-loss testing.
How are core problems diagnosed?
Mainly with excitation current and core-loss measurements, complemented by core-ground insulation tests and dissolved gas analysis (overheating generates characteristic gases). The pattern points to whether the issue is laminations, grounding or mechanical.
Is core repair done together with a rewind?
Often, yes. Accessing the core requires lifting the windings, so core work is frequently combined with a rewind. A precise diagnosis up front defines the efficient scope before disassembly.
Does TEVKO manufacture cores or transformers?
No. TEVKO is an independent, multi-brand service provider: it diagnoses and repairs magnetic cores and other components, but does not manufacture transformers. The repair restores the unit to its specified performance.
Transformer magnetic core repair in images
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