Customized Transformer Stacked Cores with Beveled Silicon Steel Sheets
Oct 21, 2025
Leave a message
What Is a Transformer Stacked Core
A transformer's stacked core is a common construction method where thin, laminated steel sheets are stacked to form the core, with insulating material between each sheet to minimize energy loss from eddy currents. This design is built from a frame of stacked laminations, typically using a mitred or step-lap joint for a more circular cross-section and an efficient magnetic flux path.
Construction and Purpose
Laminated sheets: the core is built by stacking many thin sheets of silicon steel.
Insulation: each sheet is insulated with a varnish or other material to reduce electrical current loops.
Eddy current reduction: when the alternating current in the transformer windings creates a changing magnetic field, it induces small currents (eddy currents) in the core itself, which cause heating and energy loss. The laminated, insulated layers force these eddy currents to flow through a very narrow path, increasing resistance and greatly reducing this loss.
Material: the steel often includes silicon to increase its electrical resistivity, further reducing eddy current losses.
Joints: the sheets are stacked to form a frame of limbs and yokes, which are joined together. Various joint methods, such as mitred joints, are used to approximate a circular cross-section for better magnetic flux utilization.
Key Components and Assembly
Laminations: thin, cut sheets of silicon steel, supplied with beveled or mitred edges for the joint design.
Stacking: the process of assembling the core by layering the laminations together with insulation between sheets.
Joints: the method used to join the laminations, with mitred and step-lap joints being common for rounder shapes and lower joint loss.
Clamping: securing the stacked core with clamps and frames to maintain tightness and prevent gaps.
Automation: modern manufacturing uses automated machines for precise cutting and stacking of the laminations.
Material Specifications
A wide spectrum of grades is available, including B30P120, B30P105, B30R100, 27QG120, 27QG100, 23Q110, 23QG100, 23QG095, 23RK090, 23RK085, 23QG085, 23RK080, 23RK075, B23R070, 20QG085, 20RK080, 20RK075, B20R070, B20R065, M0H, M1H, M2, M3, M4, and M5. Each grade is engineered to provide the required loss and induction performance.
| Type | Grade | Width | Max core loss at 1.7T/50Hz | Lamination factor (%) | Min induction at B800 |
|---|---|---|---|---|---|
| Common | 23Q110 | 35-1200 mm | 1.10 W/kg | 97.2 | 1.82 T |
| Common | 27Q120 | 35-1200 mm | 1.20 W/kg | 97.5 | 1.82 T |
| Common | 30G120 | 35-1200 mm | 1.20 W/kg | 98 | 1.82 T |
| High induction | B20P085 | 35-1200 mm | 0.85 W/kg | 97 | 1.86 T |
| High induction | B23P095 | 35-1200 mm | 0.95 W/kg | 97.2 | 1.88 T |
| High induction | B30P105 | 35-1200 mm | 1.05 W/kg | 98 | 1.89 T |
| Domain refined (laser) | B20R070 | 35-1200 mm | 0.70 W/kg | 97 | 1.86 T |
| Domain refined (laser) | B23R085 | 35-1200 mm | 0.85 W/kg | 97.2 | 1.88 T |
| Domain refined (laser) | B27RK085 | 35-1200 mm | 0.85 W/kg | 97.5 | 1.89 T |
Customization
Stacked cores can be customized to customer drawings: core geometry (single-phase or three-phase), limb and yoke dimensions, joint type (mitred, step-lap, bevel), lamination thickness, grade selection, clamping arrangement, and the number of laminations per step. A precise quotation is prepared from the drawings, and production follows the confirmed design.
Frequently Asked Questions
Q: Why is the core laminated? A> Thin insulated sheets confine eddy currents to narrow paths, greatly reducing eddy current loss and heating.
Q: What is a mitred joint? A> A 45-degree cut joint that approximates a circular cross-section and improves magnetic flux utilization.
Q: Why is silicon added to the steel? A> Silicon increases electrical resistivity, further reducing eddy current losses.
Q: What grades are available? A> Common, high-induction, and laser domain-refined grades from 20QG085 to B30P120.
Q: How are cores secured? A> By clamping with frames and bolts to maintain tightness and prevent gaps.
Q: Can cores be made to customer drawings? A> Yes, geometry, joints, lamination thickness, and grade are customized to the design.
Need a customized transformer stacked core? Contact us with your drawings and grade requirements for a quotation.