Interlayer Insulation: Thickness 0.05-0.15 mm

Component Specifications

Definition

Interlayer insulation is a critical component in medium voltage current transformer core assemblies, consisting of thin insulating material layers inserted between stacked magnetic steel laminations. Its primary function is to electrically isolate individual laminations, thereby minimizing eddy current circulation within the core during alternating current operation. This insulation reduces core heating, improves transformer efficiency by lowering no-load losses, and enhances magnetic performance by maintaining proper flux distribution. The component must withstand thermal cycling, mechanical compression forces, and maintain dielectric strength throughout the transformer's operational lifespan.

Working Principle

Works by creating electrical barriers between conductive magnetic steel laminations in transformer cores. When alternating magnetic flux passes through the core, it induces circulating currents (eddy currents) within the conductive laminations. The insulating layers interrupt these current paths, forcing eddy currents to circulate within individual laminations only, dramatically reducing their magnitude and associated I²R heating losses. This principle follows Faraday's law of electromagnetic induction and utilizes high-resistance dielectric materials to block inter-lamination current flow while allowing magnetic flux to pass through with minimal reluctance.

Materials

Typically composed of: 1. Electrical grade paper (Kraft, Nomex) with thickness 0.05-0.15mm, 2. Polyester film (PET, Mylar) 0.025-0.1mm thick, 3. Composite materials (paper-film-paper combinations), 4. Epoxy or phenolic resin coatings for enhanced bonding and moisture resistance. Materials must have dielectric strength >5kV/mm, thermal class B-F (130-155°C), low moisture absorption (<1%), and good mechanical strength under compression.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Thickness	0.05-0.15 mm
Thermal Class	B to F (130-155°C)
Compression Set	<10% after 1000h at rated pressure
Tensile Strength	>50 MPa
Dielectric Strength	>5 kV/mm
Moisture Absorption	<1%
Surface Resistivity	>10^12 ohm/sq

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

IEC 60076, IEEE C57.13, ASTM D202, ISO 9001

Parent Products

This component is used in the following industrial products

Medium Voltage Current Transformer Core Assembly

Precision wound magnetic core assembly for current measurement in electrical distribution systems

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Engineering Analysis

Risks & Mitigation

Insulation degradation from thermal cycling
Moisture absorption reducing dielectric strength
Mechanical damage during core assembly
Delamination under compression forces
Chemical contamination from transformer oil

FMEA Triads

Trigger: Thermal aging and oxidation
Failure: Reduced dielectric strength leading to inter-lamination short circuits
Mitigation: Use thermal class appropriate materials, implement temperature monitoring, regular insulation resistance testing

Trigger: Mechanical stress during core clamping
Failure: Insulation tearing or compression beyond recovery limits
Mitigation: Control clamping force, use compression-resistant materials, implement proper assembly procedures

Trigger: Moisture ingress
Failure: Decreased surface resistivity and potential tracking
Mitigation: Use moisture-resistant coatings, maintain dry storage conditions, implement vacuum drying during transformer assembly

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Thickness tolerance ±0.01mm, dielectric strength tolerance +0/-10%, dimensional stability within ±0.5% after thermal cycling

Test Method

Dielectric strength per IEC 60243, insulation resistance per IEC 60093, thermal aging per IEC 60216, compression testing per ASTM D395

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Interlayer Insulation

Manufacturer profiles associated with Interlayer Insulation.

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

Why is interlayer insulation necessary in transformer cores?

Interlayer insulation prevents eddy current circulation between laminations, reducing core heating and energy losses by up to 90% compared to uninsulated cores.

What happens if interlayer insulation fails?

Insulation failure allows eddy currents to circulate between laminations, causing excessive core heating, increased no-load losses, potential thermal damage to adjacent components, and reduced transformer efficiency.

How is interlayer insulation tested for quality?

Quality testing includes dielectric strength tests (hipot), insulation resistance measurements, thermal aging tests, compression set evaluation, and microscopic inspection for uniformity and defects.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Interlayer Insulation