Bushing Mounting Flanges and Terminal Plates: Critical Interface Components in Transformer Design

Transformers are complex electrical systems where mechanical accuracy directly impacts electrical performance and long-term reliability. Among the many components involved, bushing mounting flanges and terminal / connector plates play a crucial role as interface elements between internal electrical assemblies and external power connections.

Although often considered secondary parts, these components demand high precision, controlled flatness, and consistent material quality to ensure safe and reliable transformer operation.

Understanding Bushing Mounting Flanges in Transformers

Bushing mounting flanges serve as the mechanical interface that secures porcelain or composite bushings to the transformer tank or cover. These flanges must maintain proper alignment and sealing to prevent oil leakage, moisture ingress, and mechanical stress on the bushing assembly.

Key Functional Requirements

• Accurate bolt-hole positioning

• Flat sealing surfaces for gasket performance

• Structural strength to support bushing loads

• Compatibility with various bushing designs

Bushing flanges are typically manufactured as custom components, as their dimensions, drilling patterns, and thickness vary depending on transformer rating, bushing type, and manufacturer standards.

Role of Terminal and Connector Plates

Terminal plates, also referred to as connector plates, provide the interface for LV and HV cable terminations and busbar connections. These components must ensure reliable electrical contact while withstanding mechanical loads, thermal expansion, and environmental exposure.

Typical Applications

• Cable termination interfaces

• Busbar mounting surfaces

• Connection points between external cables and internal conductors

Terminal plates often require custom machining to match specific busbar layouts, hole patterns, and clearance requirements defined in transformer designs.

Materials Commonly Used

Material selection depends on electrical, mechanical, and environmental requirements:

• Mild Steel (MS) – structural strength and cost efficiency

• Stainless Steel (SS) – corrosion resistance for outdoor or harsh environments

• Aluminum – lightweight and corrosion-resistant applications

• Copper & Brass – excellent electrical conductivity for terminal plates

Each material requires different machining strategies to maintain dimensional accuracy and surface integrity.

Why CNC Machining Is Preferred

CNC machining is widely used for manufacturing transformer interface components due to its ability to achieve consistent and repeatable results.

Advantages Include

• Tight dimensional tolerances

• Controlled flatness and parallelism

• Accurate drilling and tapping patterns

• Reliable repeatability for batch production

These characteristics are essential for components that must fit precisely within transformer assemblies and perform reliably over long service periods.

Custom Manufacturing in Transformer Applications

Unlike standard fasteners or generic hardware, bushing flanges and terminal plates are rarely standardized. Transformer manufacturers typically specify:

• Custom outer and inner diameters

• Non-standard bolt-hole patterns

• Specific thickness and flatness limits

• Material grades and surface conditions

As a result, drawing-based manufacturing is the most common approach for these components.

Applications Across Transformer Types

Custom bushing flanges and terminal plates are used in:

• Power transformers

• Distribution transformers

• Oil-filled transformers

• Dry-type transformers

• Retrofit and maintenance projects

Each application may impose different mechanical and environmental requirements, reinforcing the need for precise manufacturing.

Bushing mounting flanges and terminal plates may appear to be simple metal parts, but their function within a transformer is critical. Precision machining, correct material selection, and adherence to customer specifications directly influence transformer reliability and service life.

As transformer designs continue to evolve, the demand for custom-machined interface components with consistent quality and dimensional accuracy remains essential across the power industry.