Keywords:
Electrical Steel / Silicon Steel
CRGO / Grain Oriented Silicon Steel
CRNGO / Non-Grain Oriented Silicon Steel
Core Loss / Iron Loss
Transformer Core
Laminated Core
Motor Core
Transformer Steel
High-Efficiency Transformer

Introduction

In today’s electrical industry, core materials are indispensable components for both power equipment and motors. Whether it is a transformer responsible for energy transmission or a motor driving industrial production and transportation, the performance of the core directly determines the energy efficiency and reliability of the equipment.

The key material for manufacturing cores is electrical steel (also called silicon steel). It offers excellent magnetic properties and low iron loss, making it the only core material currently used on a large scale.

Electrical steel is divided into two categories: Grain Oriented Silicon Steel (CRGO) and Non-Grain Oriented Silicon Steel (CRNGO). The main difference lies in the grain orientation: CRGO is optimized for magnetic performance in one direction, making it ideal for transformer cores, while CRNGO has uniform magnetic properties in all directions, making it more suitable for motor cores.

This article will analyze the differences and applications of transformer cores and motor cores from four perspectives—material principles, structural forms, application scenarios, and commonly used grades—while also highlighting MOOPEC’s strengths and future outlook.

Transformer Core

2.1 Principle

The working principle of transformers is electromagnetic induction, where the core provides the magnetic path. An alternating current in the primary winding creates a changing magnetic field, and the flux passes through the core to the secondary winding, enabling voltage and current transformation. The core material must have high permeability and low loss; otherwise, energy waste will be significant.

The uniqueness of CRGO lies in its grain alignment along the rolling direction, with magnetic domains arranged accordingly. This results in peak permeability and reduced hysteresis loss along the rolling direction. Since transformer flux is essentially confined to one direction, CRGO is the ideal choice.

2.2 Structure and Features

Transformer cores, also known as transformer steel, are usually laminated structures composed of thin CRGO sheets. Each sheet is coated with an insulating layer to prevent interlayer short circuits and reduce eddy current loss. The thickness of CRGO typically ranges from 0.18–0.30 mm. The thinner the sheet, the lower the iron loss—but manufacturing costs increase accordingly.

Transformer cores are classified as follows:

By structure:

• Shell type core: The core surrounds the winding like a shell. Advantages include fewer sheet specifications, large and short core sections, easy clamping, low leakage flux, and good heat dissipation. Drawbacks include complex coil insulation, poor short-circuit resistance, and high steel consumption.

• Core type core: The windings surround the core columns (inner core type). Advantages are cylindrical windings for easy winding, stable short-circuit performance, and simple insulation. Disadvantages include more sheet specifications and strict assembly requirements. Most domestic transformers use core-type structures.

(a)  Shell type core ;  (b)  Core type core

By lamination method:

• Laminated cores: Built from stacked CRGO sheets, common in various transformers.

• Wound cores: Formed by winding strip steel, used mainly in small transformers.

(a) Laminated cores;  (b) Wound cores

By phase number:

• Single-phase cores (for single-phase transformers)

• Three-phase cores (for three-phase transformers)

(a) (b) Single-phase cores ;  Three-phase cores

Other types:

• Shell-type radial cores

• Core-type involute cores

• Single-frame cores

• Double-frame cores

Core-type laminated cores are the most common in China, offering simple structure, low cost, and stable performance—suitable across voltage and capacity ranges.

2.3 Applications

Different structures serve different purposes:

• Power transformers: Used in transmission and distribution networks, requiring extremely low losses.

• Distribution transformers: Installed in cities and factories, requiring compact size and high efficiency.

• Special transformers: Such as furnace, traction, and rectifier transformers, each with unique operating conditions and material demands.

With the push for energy savings, High-Efficiency Transformers are becoming mainstream, placing higher demands on CRGO.

2.4 Common CRGO Grades

• Standard grades: B18P060, B23P080, B27P095 – for small to medium power transformers.

• High-induction grades: B23G085, B27G095 – higher magnetic induction, suited for high-efficiency distribution transformers.

• Ultra-high induction grades: B27H100, B30H120 – used in large power transformers and specialized equipment, offering ultra-low loss and high efficiency.

Differences mainly lie in thickness, iron loss, and magnetic induction intensity, allowing customers to select based on transformer rating and efficiency needs.

Motor Core

3.1 Principle

The operating principle of motors is based on electromagnetic induction and torque generation. The core not only forms part of the magnetic circuit but also bears mechanical stress. Since motors rely on a rotating magnetic field where flux direction constantly changes, the core material must maintain consistent properties in all directions.

CRNGO, with its random grain orientation, provides uniform magnetic performance in all directions, ensuring efficient operation under rotating flux. It also offers good punchability and mechanical strength, making it ideal for motor laminations.

3.2 Classification

Motor cores can be categorized as follows:

By motor type:

• DC motor cores: For precise speed/torque control (e.g., EV drive motors).

• AC induction motor cores: Widely used in industry, such as fans and pumps.

• Synchronous motor cores: For applications requiring stable speed, such as large generators.

By motor structure:

• Rotor cores: The rotating part, typically laminated CRNGO sheets.

• Stator cores: The stationary part, also laminated, producing the magnetic field.

By core presence:

• With cores: Coils wound on laminations to enhance flux.

• Coreless motors: Coils suspended directly in the magnetic field, used in special designs.

By application:

• Automotive motors: Starter motors, EV drive motors.

• Generator motors: Wind and hydro generators.

• Industrial motors: Fans, pumps, and machinery.

Since motor performance directly impacts efficiency, stability, and lifespan, choosing the right core material and structure is critical.

3.3 Common CRNGO Grades

• Medium-frequency grades: B15AV1000, B20AV1200, B25AV1300 – for standard industrial and household motors.

• High-efficiency grades: B27M1300, B30M1500 – for EV drive motors and high-speed motors, optimized for high frequency and low loss.

The key differences are thickness, iron loss, and magnetic induction strength, allowing optimization for speed and efficiency requirements.

Comparison and Summary

4.1 Material principles:

• CRGO: Grain alignment provides peak permeability in one direction, ideal for transformers.

• CRNGO: Random orientation ensures uniform magnetic performance in all directions, ideal for motors.

4.2 Structural and application differences:

• Transformer cores: Laminated or wound, emphasizing low core loss and efficiency.

• Motor cores: Laminated punchings, emphasizing mechanical strength and isotropic performance.

4.3 Industry trends:

• Transformers: Moving toward ultra-low loss and higher efficiency, demanding more advanced CRGO.

• Motors: With the rise of EVs, demand for high-frequency, low-loss CRNGO is surging.

MOOPEC: Company Profile and Advantages

5.1 Positioning

MOOPEC specializes in electrical steel materials, including CRGO and CRNGO. We serve transformer manufacturers, motor producers, and new energy companies with one-stop material solutions.

5.2 Services and Advantages

• Small-batch customization: Sample supply, rapid prototyping, and early-stage small-lot orders.

• Fast delivery: 72-hour production and 7-day delivery, aligning with customer R&D and production cycles.

• Global presence: Headquartered in Singapore with branches in Shanghai, Wuhan, and Dalian, supporting multi-currency transactions and global logistics.

• Quality assurance: Supervised by PhD material scientists and senior experts, ensuring stable and reliable performance.

5.3 Customer Value

• Reduced R&D and prototyping costs.

• Improved efficiency and reliability of products.

• Shortened development cycles, helping customers seize market opportunities.

Conclusion

Although both transformer cores and motor cores rely on electrical steel, their design principles and applications differ significantly. Transformer cores emphasize low loss and directional permeability, thus using CRGO, while motor cores require isotropy and strength, thus using CRNGO.

With the global growth of energy-saving initiatives and new energy industries, demand for high-performance electrical steel continues to rise. Leveraging its flexible small-batch services, rapid delivery, and global network, MOOPEC is well-positioned to provide customers with competitive material solutions and become a trusted partner in the industry.

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