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magnetic core sheet

magnetic core sheet

 

Magnetic core sheets are cold-rolled alloyed steel that is doped with silicon particles in order to increase electrical resistivity and hence decreasing core-loss and for better magnetic flux conductivity. Also, aiming flux-passing cross section reduction, reducing Eddy currents and losses consequently, the sheets are insulated against each other. With a desired cross-section, the lower the thickness and the higher the quantity, the loss would be lesser.

Important and basic parameters of magnetic cores

In order to define and compare the quality of the magnetic cores there are several noteworthy fundamental parameters, which are:

  • Silicon level: Silicon is added to reduce magnetic reluctance (better magnetic flux flow) and increase electrical resistivity (lower core loss). So, silicon doping level in chemical analysis of magnetic core sheets is a highly important factor.
  • Crystal orientation: Crystals or so-called core grains, if spread randomly without interfering their direction, would be called cold-rolled non-grain oriented (CRNGO)csheets. But, if the core crystals, during production process, are oriented in a way that majority of them are aligned in the same direction, the core will gain more flux conductivity and in turn, higher quality. Recent magnetic core sheets are called cold-rolled grain-oriented sheets (CRGO).
  • Thickness: Conforming below relation which is applied to calculate Eddy loss of a magnetic core, thinner sheets result in lesser Eddy currents and electrical loss. This is why thin sheets do better in comparison to thicker ones.

  • Magnetic Saturation Level: Magnetic cores have a particular saturation threshold for passing magnetic flux while violated, will not pass more flux and result in flux waste. This level is in accordance to the material and the grade of the sheets and the higher, the better quality would be.
  • Losses per unit weight of core: Core’s loss per kg: Silicon level, crystal orientation and thickness, as major factors of core quality, will define core-loss that is critically important while chosing the core material. Hence, companies mention in their datasheets core loss per kg and also magnetic saturation level as main criteria of core evaluation.

For more information about the specifications and various grades of magnetic core sheets, you click on the below links.

(CRGO)Cold-rolled grain-oriented magnetic sheets

(CRNGO)Cold-rolled non-grain oriented magnetic sheets

The upcoming table presents the application of different core grades:

Induction

furnace

Yoke

Grid transformers

(LV-MV_HV)

 

Transformers

and low-power

reactors

Rotary systems

(motor-generator)

→ Appication

↓ Specifications

Thickness
(mm)
Core type
0.50

CRNGO

0.35
0.35

CRGO

0.30
0.23-0.27
0.23-0.30 CRGO

Low-loss

0.23-0.27 CRGO

Ultra-low-loss

Magnetic core sheets’ production:

These sheets are produced and supplied worldwide by a limited number of companies in rolled form and customers order according to their needs. Below diagram illustrates manufacturing process and final product: