Going from DC to AC

ALTERNATING current is the future of dragline operations.
Going from DC to AC Going from DC to AC Going from DC to AC Going from DC to AC Going from DC to AC

Illustration: Rod Emmerson

Staff Reporter

At least that is the view of electrical equipment maintenance specialist Flanders.

It has conducted North America’s first direct current to AC dragline upgrade.

Flanders president Dave Patterson said the company decided some year ago to make a commitment to develop an AC drive and motor package specifically for draglines.

“We’re a dragline service company and we knew that the future for motors, drives and controls for draglines would be AC,” he said.

In 2010 Armstrong Coal Company sent DC rotating and electrical equipment from an existing dragline to Flanders for evaluation and a repair quote.

At that stage Flanders’ electrical, mechanical and systems engineers had completed 75% of their first AC dragline conversion.

The Armstrong DC motors were in poor shape and the motor generator sets had to be replaced.

Flanders suggested an AC upgrade.

Over the next six months it customised, finished building and commissioned Armstrong’s AC dragline upgrade to fit the mine’s needs.

The Flanders’ purpose-designed drop-in AC motors and drive systems are designed for long-life operation – up to 175,000 hours or 10 million load cycles.

The company incorporated select power components with high thermal lifecycle capability.

To make them easy to repair it used easy to replace common power modules and detailed diagnostics.

Water-cooled semiconductors that remove heat from the house were chosen to help boost productivity and machine availability. This approach also allowed the cabinets to remain closed and filter free.

Armstrong reported that the AC dragline had been working well with availability in the upper 90% range since commissioning.

According to Flanders, the Armstrong dragline operators have liked the one-touch start-up – which means no need to start the motor generator sets in the house; the machine’s torque and power; the high degree of coordination between all motions; and the smoothness of operation.

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