Slitting lines are tension machines: an uncoiler holding back against the line is a brake by design, generating power all day long — the textbook case for regeneration. Notes from our 650 mm line rebuild at Galva Makina.
The system design
The line’s drive train moved to a SINAMICS S120 lineup on a shared DC bus with a regenerative infeed: the uncoiler’s braking power feeds the bus, the recoiler and line drives consume from it, and the net surplus returns to the grid instead of cooking resistor banks. A new Siemens dynamic winder motor replaced the aging recoiler machine — sized for the torque-at-diameter envelope rather than nameplate habit (see our winder torque-control guide for the control structure: diameter calculation, inertia compensation, taper tension — all of it lives here).
The energy result comes in two layers: the recovered braking energy (previously pure resistor heat), and the avoided losses of the old drive train — together a measurable double-digit percentage of the line’s consumption at production duty, visible on the meter and in the panel room’s temperature.
The retrofit choreography
Classic staging: new lineup built and simulated while the line produced, cutover in a planned window, winder commissioning per the friction/inertia/diameter sequence, and the first coils run with the trace armed. The operators’ verdict is the one we quote: tension holds through speed changes that used to mark the strip.
FAQ
Does regen make sense on every slitting line? Duty decides — multi-shift lines with heavy coils, almost always; a lightly-used line gets the resistor honesty check first (the economics post has the math).
What broke the old system, really? Nothing dramatic — spares extinction and drift. The retrofit was chosen on the obsolescence audit, not after a failure. That is the point.
Zone Otomasyon rebuilt this line end to end — drives, motor, control and documentation. More projects.