Types of CRGO Laminations for Transformer Core Design

mukesh muke
Jul 29
4 min read

Types of CRGO Cut Laminations: Detailed Guide for Transformer Core Applications | S M Steels

When it comes to manufacturing high-efficiency transformer cores, the type of lamination used plays a critical role in performance, longevity, and magnetic behavior. At S M Steels, a trusted supplier and consultant for Cold Rolled Grain Oriented (CRGO) electrical steel in India, we provide a comprehensive range of CRGO lamination types tailored for both prime and secondary sheet materials.

This article explores the various types of CRGO cut laminations, their functions, applications, benefits, and how to choose the right lamination type depending on the transformer core design, magnetic circuit requirements, and material grade.

What Are CRGO Cut Laminations?

CRGO, or Cold Rolled Grain Oriented Steel, is a specialized type of electrical steel used to manufacture transformer cores. It features superior magnetic properties in the rolling direction, making it ideal for use in transformers, inductors, and reactors. Cut laminations are individual pieces of CRGO steel, precisely shaped and notched to be assembled into transformer cores.

Different cut types allow engineers to optimize magnetic flux flow, reduce core losses, prevent hot spots, and ensure ease of assembly. These lamination types are essential whether you are working with BIS-certified prime CRGO or cost-effective secondary (reclaimed or oily) CRGO.

1. Mitered CRGO Laminations

A precisely cut CRGO (Cold Rolled Grain Oriented) steel sheet with a miter edge, commonly used in transformer cores for efficient magnetic flux distribution.

Mitered laminations are cut at a 45-degree angle and are commonly used in transformer core limbs and yokes. This angled cut allows the magnetic flux to pass through the core with minimal interruption at the joints.

Functions and Benefits:

Reduces core loss and improves flux continuity
Ideal for step-lap assembly, ensuring smooth magnetic transitions
Enhances transformer performance in high-voltage applications

Recommended For: Prime-grade CRGO cores for power and distribution transformers requiring high precision and low no-load losses. Mitered laminations are standard in BIS-grade transformers.

2. Diamond Cut CRGO Laminations

Stacks of CRGO diamond-cut sheets, precision-engineered for optimal efficiency in electrical applications.

Diamond cut laminations feature precisely trimmed corners, often forming diamond-like edges. These are used to relieve stress concentration points and improve stacking precision.

Functions and Benefits:

Reduces mechanical stress at the lamination edges
Simplifies the stacking and alignment process
Prevents edge burr-induced magnetic disruptions

Recommended For: Secondary or oily CRGO steel used in medium-sized distribution transformers, reactors, and custom coil builds.

3. V Notch Laminations

The V-notch is a specific shape cut into the CRGO laminations (thin sheets) that make up the transformer core.

The V-notch lamination includes a single V-shaped punch at the end of each limb. This design allows precise alignment of limbs and yokes in a rectangular or square core configuration.

Functions and Benefits:

Improves interleaving and stacking efficiency
Enhances overall core balance and alignment
Minimizes magnetic flux distortion at limb junctions

Recommended For: Commonly used in rectangular or stacked transformer cores using both prime and secondary CRGO sheets. Suitable for CTs, PTs, and low to mid-range distribution transformers.

4. Double V Notch Laminations

CRGO steel sheets with a double V-notch design are neatly arranged on a wooden pallet, showcasing their precision engineering and readiness for electrical applications.

As the name suggests, double V-notch laminations contain two V-shaped cuts placed symmetrically. These notches allow for tighter, more accurate alignment during assembly.

Functions and Benefits:

Enhances core symmetry and reduces air gap inconsistencies
Ideal for faster stacking and industrial automation
Reduces mechanical and magnetic noise in the core

Recommended For: Prime or high-quality secondary CRGO used in power transformers and fast-paced production environments where high alignment accuracy is necessary.

5. Triple V Notch Laminations

Triple V-notch laminations feature three strategically spaced V-cuts, offering advanced alignment precision in critical transformer designs.

Functions and Benefits:

Reduces deviation and buckling in larger cores
Ensures maximum symmetry and uniform magnetic field distribution
Enhances stacking speed and reduces core losses in automated assembly lines

Recommended For: High-end transformer applications using premium CRGO material, especially in CNC-operated lamination stacking systems.

6. Gapping Laminations (Split V Notch)

CRGO gapped cut lamination sheet, precision engineered for use in electrical transformers, enhancing efficiency through reduced energy loss.

Gapping laminations are a unique variation of the V-notch design. In this case, the V-notch is precisely split in the middle, creating a deliberate air gap in the core magnetic path. This air gap is not incidental but carefully engineered.

Functions and Benefits:

Controls magnetic saturation by introducing a calibrated air gap
Essential in current transformers (CTs), potential transformers (PTs), reactors, and inductors
Enables accurate flux modulation and inductance control

Recommended For: Both prime and secondary CRGO materials where magnetic field regulation is necessary. Especially useful for energy metering, magnetic chokes, and low-flux-density applications.

7. Rectangular Laminations

CRGO rectangular cut lamination sheet used in electrical transformer cores for efficient magnetic flux conduction.

Rectangular laminations are simple, block-like shapes that can be stacked or interleaved.

Functions and Benefits:

Suitable for customized transformer core designs
Efficient in low to mid-power applications
Allows simplified core building

Recommended For:Secondary CRGO used in distribution transformers, chokes, and reactors.

8. EI Laminations

CRGO EI lamination components, featuring precision-cut and oriented grain structure for enhanced magnetic efficiency in transformers and inductors.

EI laminations are among the most common and standard transformer core shapes, consisting of an “E” section and an “I” section.

Functions and Benefits:

Easy to assemble and mass-produce
Cost-effective and compatible with both prime and secondary CRGO
Minimizes waste in cutting
Widely used in low-voltage and general-purpose transformers

Recommended For:Small distribution transformers, instrument transformers, UPS systems, and inverters.

Choosing the Right CRGO Lamination Type: Prime vs Secondary Sheets

When choosing lamination types, consider the following factors:

Material Grade: Prime CRGO is suitable for BIS-standard transformers and precision designs. Secondary CRGO may have minor defects but is cost-effective for non-critical applications.
Magnetic Requirements: Gapped and triple-notch laminations suit applications with specific magnetic field control needs.
Assembly Method: Automated assembly lines benefit from double or triple notch laminations, while manual setups can use V-notch or diamond cuts.