Core

 
 

Core Slitting and Cutting

ETS specializes in the manufacture and supply of step-lap cut cores & stacked cores. The iron cores are manufactured with cold rolled grain oriented electrical sheet steel having thicknesses of 0.30 mm, 0.27 mm and 0.23 mm. In power transformers, these are also of the HiB variety (including laser-etched material), depending upon the required no- load loss levels. The most economical cross section is achieved by proper selection of particular widths. All our cores are of cruciform section and are of the core type (3 limbs with no outer return paths). The laminations are thinly insulated on both sides, allowing for a good stacking factor for the core. The equipment for cutting comprises multiple fully automatic CNC core-cutting machines, supplied by GEORG, Germany. It can handle upto 600mm widths. Laminations are automatically stacked using a brake hammer.

All the cores are mitred and step lap cut which gives a benefit in no-load losses and noise level. For ratings up to 8MVA, we can have wooden clamping structure made up of compressed resin bonded wood pressure plates and beams. In higher ratings, the clamping structure is a combination of wooden compression rings pressed and held in position by steel clamps. The limbs have no compression bolts (core bolts). In their place, we use glass fiber bonds (tightened insulated bonds). The compression at the ends of the clamping structure is maintained by core end bolts.

Styles of Cut
Size
Mitre - 45° [Conventional or Step Lap (3, 5 or 7)] Minimum plate width: 50mm
Maximum Plate width: 640mm
Plate Length Minimum - 250 mm
Maximum – 3475 mm
Hole Punching Typical Hole Size – 10 & 26mm (1 or 2)
 
Width
Length
Burr
Tolerances
50 - 150 ± 0.2 mm 250 - 500 ± 0.3mm ±0.035 mm max.
>150 < 400 ± 0.3mm >500 < 1000 ± 0.5mm
>400 < 640 ± 0.5mm >1000 < 2500 ± 0.75mm
  >2500 < 3475 ± 1.00 mm
Grade
Thickness
Specific Total Loss (Maximum Guaranteed): vvabv
Typical Induction At 800 A/m, 50 Hz
    1.5 T 50 Hz 1.7 T 50 Hz  
  mm Watts/kg Tesla
TCHO 0.23 ± 0.02 - 0.80 1.83
M3 0.23 ± 0.02 0.80 - 1.83
M4 0.27 ± 0.03 0.89 - 1.83
M5 0.30 ± 0.03 0.97 - 1.83