Power Rollers for 300-Ton Generator
The project scope was to provide Siemens Energy customer DRAX Power in the UK a Power Roller System for a Parsons 660MW Generator. This project was critical for DRAX Power Station since DRAX generates 7% of UK’s power with 6x660MW units at this facility. The Power Roller System is designed to allow the stator core to be rotated as the core is wound, allowing bars to be installed at the optimum position, greatly improving manual handling, safety and quality.
The Power Roller System consisted of a 3 roller system, 2 driven and 1 center idler. The load capacity was 360 Metric Tons with a safety factor of 1.5 with a synchronized drive system and end plate bumper system both with electronic controls. Enser utilized a similar design of a set of Power Rollers for Siemens Energy in Charlotte with a load capacity of of 220 Metric Tons.
The ease of use of the power rollers has changed how the vast majority of the rewind activities are carried out. Originally planned as an improvement to the bar installation process, it has also improved access for NDT, inspections, painting and instrumentation. It has allowed removing the need for scaffolding to be installed all around the core saving time and cost.
Generator Core Rewind History
Often referred to as a power plant’s “money maker”, the generator is among the most valued asset at a facility. Generators are subjected to high electrical, thermal and mechanical stresses over the course of their service life. Continuous extreme thermo-mechanical stresses and thermal cycles can have a particularly severe impact on the stator core. Over time, this can lead to deficiencies in the core insulation. A damaged insulation can cause the formation of larger eddy currents and local hot spots, which spread out during time. A deficient bar insulation can result in a stator ground fault which can cause an unscheduled outage and blackouts for DRAX’s customers.