The firm announced this month that it had completed a brushless exciter retrofit at SSE’s 20 MW Mucomir run-of-river plant (pictured) on Loch Lochy. The plant has been in continuous operation since 1962 and features a Kaplan turbine that drives a 3300 V, 40-pole, 150 rpm AC synchronous generator.
The contract included refurbishing an existing generator stator and rotor as well as designing, building and commissioning a new AC brushless exciter to replace the old DC exciter.
SSE was looking to eliminate dust as well as maintenance time and cost, while reducing the risk of extended outages from brush and commutator wear, Quartzelec said, adding that the existing commutator was suffering badly with uneven wear issues, due in part to the intermittent loading and the humid environment at the site.
The brief for the company’s design team was to retrofit a new AC brushless exciter solution into the existing footprint. Work began in summer 2016 to characterize the available space, existing cooling circuit and fan performance curve. A 3-phase AC synchronous generator and rotating rectifier hub could then be designed to fit into the modified exciter housing while retaining the existing mounting interfaces.
The designs were fabricated at Quartzelec’s engineering facilities in Rugby, England and installed at the plant during a scheduled maintenance window in June.
“The new solution is a bespoke brushless exciter to meet the duty of this site, whilst retaining the original fan, shaft interfaces and housing,” Quartzelec said. “Critically, however, it eliminates the risk and maintenance overhead of the original brush gear.”
The firm said it has seen a significant increase in demand for retrofit solutions in recent months, along with preventative maintenance and inspections. This reverses a trend which began a decade ago with the last economic downturn, when companies looked to defer upgrades in order to cut costs.