Alstom cuts weeks off turbine testing with variable speed drive16 December 2014

Alstom Power of Rugby, which tests 1/10th scale steam turbine blades in a large pressure vessel, has cut the time taken to change its test rig set-up from six weeks to a few hours, following the installation of an ABB variable speed drive (VSD).

The vessel uses a compressed mixture of air and refrigerant gas to simulate steam, and tests the components at low and high pressures.

Speed control of the dc motor used to achieve the different pressures was formerly achieved by gearboxes, but those introduced significant delays.

"The changeover involved replacing the gearbox of the motor so that it could drive the compressor to achieve high or low pressure as required," explains Steve Finch, project manager for Alstom.

Another challenge was the age of the dc motor, which, having been installed for some 50 years, was proving costly to maintain.

"[ABB system integrator] Iconsys offered us a lead time that was 10 weeks lower than the other bidders," says Finch.

Iconsys supplied and installed a new 4 MVA transformer, a 3.1MW water-cooled motor and a 3.1MW ACS6000 medium voltage VSD.

Finch explains that the installation involved removing the existing motor and altering the bed plate to fit the new motor.

Another aspect was modifying the incoming protection breaker, which originally had protection circuits for the liquid-cooled starter and needed to be modified to provide the required 3.1MW.

"We now have much more control," says Finch. "We can now ramp up or down easily, and the motor is working well within its capacity so we have all the power we need."

And he adds that taking away the gearboxes means the lab can make changeovers much more quickly.

"We can move between low pressure and high pressure testing in a couple of hours. rather than the weeks it took previously," he says.

"We can now test for one day and analyse the results the next day, while we are changing over to the other pressure level.

"In terms of the installation, the motor went in very well despite the tight area in which it is installed. We have received very good support from ABB and Iconsys, and have excellent spares support at good rates."

Brian Tinham

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