The installation of an inverter-driven 415 V motor at Cockenzie power station has given such large maintenance savings that additional energy savings are seen as a bonus.

The 1200 MW coal-fired power station use two pairs of 250 kW duty/standby slurry pumps to convey the coal ash and precipitator fly ash produced during generation. Mitsui Babcock, the operations and maintenance contractor for coal and ash plants at the power station called in Danfoss Drives partner Fraser & MacDonald after the complete failure of a hydraulic coupling in the system.

The reliability of the drives had caused problems for some time, with the replacement cost of a coupling around £30 000 and quarterly refurbishment costs for the existing four drives being around £40 000 per year. The gearboxes also frequently failed due to the combination of oil, ash and sea water used.

By eliminating the gearboxes and hydraulic units and coupling an inverter motor directly to the slurry pump benefits were immediate. Three pre-set speed levels selected from the control room feed the drives. A 38% reduction in energy costs has been achieved.

Source

Electrical and Mechanical Contractor