I have seen many using U-T core laminations which have about 72% yield during punching. This results in more utilization of steel and also results in higher carbon foot print as a conseqeunce. Here is some sugegstion for improving punching yield. Hope it benefits someone and hope teh world as whole has smaller carbon emmissions.

ADVANTAGES OF J-I OR L-U DESIGN

• 100% yield
• Lesser steel consumption and smaller carbon foot print.
• Smaller window has smaller average perimeter and hence lesser wire length, lesser wire resistance and lower wire losses.
• Smaller window and hence suitable for copper wire too.
• Simpler stamping pattern.
• Simpler assembly effort on shop.
• Can have near cubic dimension. Current design is always 6a x 4a. But with new design it will be 6a wide x any height (=x + 2a).
• Winding window = can be any size (=x) x a.
• Hence bigger winding window can also mean higher turns, lesser steel and lower costs.
• Near cubic shape results in optimal combination for least overall losses = wire loss + steel loss.