Secondary Winding Bobbin: Flammability Rating UL94 V-0

Q: What is the primary function of a secondary winding bobbin in current transformers?

The bobbin provides mechanical support to maintain precise winding geometry, electrical insulation between turns and to ground, and thermal management to dissipate heat generated during operation.

Q: Why are specific materials required for medium voltage applications?

Medium voltage applications require materials with high dielectric strength, excellent tracking resistance, and thermal stability to prevent electrical breakdown and ensure long-term reliability under high voltage stress.

Q: Can secondary winding bobbins be customized for different transformer designs?

Yes, bobbins are often custom-designed with specific dimensions, flange configurations, and material formulations to match particular transformer core sizes, winding requirements, and application environments.

Component Specifications

Definition

A precision-engineered insulating component that provides mechanical support, electrical insulation, and thermal management for the secondary winding coil in medium voltage current transformers. It maintains precise winding geometry, prevents inter-turn short circuits, and ensures proper heat dissipation during transformer operation.

Working Principle

Provides rigid structural support to maintain winding geometry under electromagnetic forces, offers high dielectric strength to prevent electrical breakdown between turns and to ground, and facilitates heat transfer from the winding to the transformer core or cooling medium.

Materials

Typically made from thermosetting plastics (phenolic, epoxy, or polyester resins) with mineral fillers for improved thermal and mechanical properties. May include glass fiber reinforcement for enhanced strength. Must have high Comparative Tracking Index (CTI >600V), UL94 V-0 flammability rating, and continuous operating temperature rating of 130°C minimum.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Thermal Class	Class B (130°C) or higher
Dielectric Strength	>12 kV/mm
Flammability Rating	UL94 V-0
Dimensional Tolerance	±0.1 mm
Insulation Resistance	>10^12 Ω
Comparative Tracking Index	>600 V

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 61869, IEEE C57.13, 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

Electrical breakdown due to insulation failure
Thermal degradation under overload conditions
Mechanical deformation affecting winding geometry
Partial discharge leading to insulation deterioration

FMEA Triads

Trigger: Material impurities or voids in insulation
Failure: Partial discharge leading to insulation breakdown
Mitigation: Implement strict material quality control and vacuum impregnation processes

Trigger: Thermal cycling stress
Failure: Cracking or deformation of bobbin structure
Mitigation: Use materials with matched thermal expansion coefficients and adequate thermal class rating

Trigger: Inadequate dimensional precision
Failure: Improper winding tension and geometry affecting transformer accuracy
Mitigation: Implement precision molding with tight dimensional tolerances and regular tool maintenance

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Dimensional tolerance ±0.1mm, concentricity within 0.05mm, surface finish Ra < 3.2μm

Test Method

Dielectric strength test per IEC 60243, thermal cycling test per IEC 60068-2-14, dimensional verification with CMM, material certification with UL and RoHS compliance

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 Secondary Winding Bobbin

Manufacturer profiles associated with Secondary Winding Bobbin.

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Frequently Asked Questions

What is the primary function of a secondary winding bobbin in current transformers?