Significant investment allows for replacement of PWT Main Drive power equipment

  • Published
  • By Bradley Hicks
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  The heart of the Propulsion Wind Tunnel Combined Test Force at Arnold Air Force Base may soon beat stronger than ever once ongoing, multimillion-dollar upgrades to the equipment that make up the PWT Main Drive Facility are complete.

Some work has already been finished, as brand new switchgear units have been installed along the PWT Main Drive. The Main Drive contains the motors that power the two large wind tunnel compressor systems found at Arnold AFB – the 16-foot Transonic wind tunnel and the soon-to-be-reactivated 16-foot Supersonic wind tunnel. The tunnels in the Flight Systems CTF as a whole offer aerodynamic ground-test capabilities from very low subsonic speed through Mach number 10.

The replacement of electrical exciters, which provide excitation voltage and current to the two 83,000 horsepower motors in the Main Drive have also been completed. Of the two new 83,000 horsepower motors, one has been built and purchased within the last two years, and the other is in the planning stages of being built.

Those involved with the undertaking expect the efforts will help alleviate testing downtime for AEDC customers and enhance safety for the PWT workforce.

Capital received from two sources was utilized to fund the approximately $100 million project. Around 70 percent of the funding was awarded through Test Investment Planning and Programming. TIPP is a resource planning process managed by Air Force Test and Evaluation which identifies and prioritizes projects, including infrastructure needs that could receive various DOD funding.

The remainder of the funding came from the Service Life Extension Program, which extends funding to facilities and equipment in an effort to increase their lifespan over the amount originally planned. The five-year SLEP program began at AEDC during the 2017 fiscal year.

“It’s a substantial investment,” said Flight Systems CTF Operations Officer Edward Mickle. “We haven’t seen an investment like this in two decades.”

The project to replace high-voltage switchgear in the PWT Main Drive facility began in the fall of 2017 and was completed in January of this year. Switchgear is equipment used to power, protect and/or isolate electrical equipment such as the Main Drive large synchronous motors, unit subs, motor control centers, and other electrical equipment from the PWT Main Drive Yard.

“The amount of man hours we put in on this switchgear was a lot of hours to say the least,” said Electrical Systems Engineer Drew Owen. “There were a lot of people involved.”

Along with increasing reliability, the new switchgear has also eliminated the potential for arc blast and arc flashes, creating a safer work environment for PWT personnel.

Electrical exciters have also been replaced on M-1 and M-4, two of the four motors found in the PWT Main Drive. Checkouts were completed in May.

The combination of the switchgear and exciters is necessary for PWT operations.

“The safety was a big thing, but the prevention of lost test time to the customers was major as well,” Craft Supervisor David Reep said.

Test Support Division Engineering Section Project Manager Jennifer Daugherty said the equipment replaced was original to AEDC and was no longer being manufactured. This meant that PWT crews could not acquire parts when repairs were necessary. Prior to the replacement of the switchgear and exciters, downtime and lost test time at PWT was a frequent occurrence.

“Making those two pieces of equipment reliable was vital to meeting the testing requirements for this area,” Daugherty said.

A new stator has been installed in M-4, and this same work is planned for M-1 in the future. Stators drive the rotating components of the motors.

The other two Main Drive motors – M-2 and M-3 – received upgrades around 18 years ago and, according to Mickle, are still in good shape.
The PWT Main Drive Motors have a combined horsepower rating of 290,000 and up to 247 megawatts available to either the 16T or 16S compressors.

It’s not just PWT electrical equipment that has received or will receive upgrades. Earlier this year, a new 20-ton crane trolley and bridge drive was installed within the Main Drive facility, replacing the original bridge crane installed in the 1950s. The crane is used to lift smaller equipment within the Main Drive Facility for facility maintenance or work.

A contract to replace the 150-ton and 75-ton crane trolleys and bridge drives, located exterior to the PWT facility, has been awarded and work is currently underway. These two cranes provide the capability to remove the rotating portion of a compressor or one of the large motors from the driveline.