Electrical steel

Magnetic steel sheet with an annual global production of around 10 million tonnes, the quantity and value of important soft magnetic material. It is divided according to its properties in grain-oriented and non- grain-oriented materials, the former being called depending on area of ​​use dynamo sheet or motor plate, the latter also transformer sheet. Electrical steel sheet and strip in the narrower sense of cold rolled strip of iron -silicon alloys, in addition, also the resulting cut or punched laminations used in the manufacture of magnetic circuits for electrical machines, ie of iron cores for dynamos, electric motors, transformers, relays, contactors, choke coils, ignition coils, electric meter and controllable bending magnets are used.

The magnetic, physical and other demands on the material are described ( 10106 S) and " grain-oriented electrical steel sheet and strip delivered in the state" ( EN 10107 ) in the standards " cold rolled non- oriented electrical steel sheet and strip delivered in the state."

Function

Iron cores are made ​​of solid material in machinery and transformers hardly makes sense to use, because under the influence of variable magnetic fields result, eddy currents. Instead of transferring electrical power, the core becomes hot due to eddy currents with increasing frequency. To avoid this, the iron cores for electric machines are only available as laminated and insulated sheets in packages or as a wound cut cores. A corresponding embodiment is also referred to as laminated.

Soft magnetic materials form under the influence of an electric field a magnet and go after the removal of the field for the most part back into the non-magnetic state. Simple dynamo sheet IV could be magnetically exploited with a maximum of 12,000 Gauss = 1.2 T ( Tesla). Evolved iron -silicon alloys allow flux densities to about 1.75 T.

Embodiments

Standard cores are made ​​of die-cut single sheets, which are used to in more modern form isolated by unilaterally glued paper layers by chemically applied Phosphatierungsschichten. The sheet thickness for normal applications is often 0.5 mm. For electrical transformers of higher frequencies or very low-loss devices thinner sheets with 0.35 mm thickness are used. Cut strip and ring cores are often wound from even thinner and also isolated bands.

A classic and widely-used sheet metal cut specifically for transformers of the EI core. With each stroke, two E and two I fall out and there is virtually no waste. Therefore, this cut is referred to as the falling loose EI- section. The plates can be unilateral or reciprocal layers. For mains transformer and push-pull transformer, the sheets are stacked alternately, ie there are alternately and once I then slid E from the left and from the right with the spool. Characterized the air gap is minimized. If only laminated on one side, we can provide a defined air gap, which is necessary for Netzsiebdrosseln and for single-ended transformer.

Circular laminations for motors and generators usually have recesses that the grooves for the Bewickelung with insulated copper wire for the coils result from layering, as well as the central circular cutout for the axle shaft.

Baked enamel sheet

The sheets can be coated with a special coating ( baked enamel ), so that plate stacks are baked later by heating or solvent together. The purpose is to improve mechanical strength and possibly a reduction in the noise due to vibrations. This method is often used as an alternative to full potions or casting.

Material

Electrical sheets usually consist of an iron-silicon alloy. Has during the non-oriented material in the sheet plane isotropic magnetic properties as possible and therefore preferably rotating equipment is used, the grain-oriented material by successive rolling and annealing a grain orientation (texture) is generated. Through these deliberately introduced anisotropy in the material are reduced with a corresponding magnetization direction, the hysteresis losses and the relative permeability increases. This textured material can therefore, compared with non-oriented materials, transformers manufacture, which have a smaller size with higher efficiency.

The following table shows the ratios for M and MD nuclei are shown as an example based on the core size M 102 B / MD 102 B and 50 Hz. For comparison, a SM- C-core is also listed. For all core sizes of the coil body type is the same.