A single panel design was chosen, which is easier to control and position than multi-panel designs that utilize an accordion system. In this single panel design the entire roof panel can be removed from the stadium and “parked” over the plaza area. Globe Life Field is the largest single panel retractable roof in the world.
The right drives for the job
For Uni-Systems Engineering, the company selected to design and install the roof mechanization, the Globe Life Field retractable roof was the largest they had built to date. The sheer size was impressive, weighing 24 million pounds and utilizing two sets of parallel rails with 10 bogies (train cars) per rail. Each bogey rides on six wheels, with five of the bogies on each rail powered. Six wheels on each of the powered bogies are driven by a 10 HP motor, and each powered bogie is controlled by two 40HP ACS880 regenerative drives, with each drive powering three motors, for a total of 20 ABB drives on the system.
ABB ACS880 regenerative drives were chosen to eliminate the need for 3rd party regen units to generate energy. Uni-Systems Engineering has been using ABB ACS800 drives since the mid-2000s when they first installed them in the Cardinals football stadium. Alex Krueger, Electrical Engineering Manager, explains that they have continued to use ABB drives because “Not only have the drives performed well in other installations, ABB is a good supplier – they provide local sales support and troubleshooting, as well as educational opportunities relevant to what we do daily.” For this project, Uni-Systems utilized the ACS880-11, the latest technology in the ABB regenerative drive family.
The schedule was the next biggest challenge in this build. Uni-System Engineering’s shop in Minnesota was responsible for assembling ten cabinets, each with two drives, and then mounting the cabinets to the bogies. To ensure uptime and flexibility, redundancy is built-in to the design (although the duty cycle is low as some stadiums seldom open), so the roof can move even with up to four drives inoperable. However, each drive had to be programmed for the application. To make this as simple as possible, ABB provided an ACS880 demo case to Uni-Systems Engineering. This allowed the team to develop the needed program and find the right configuration for quick and accurate drive setup. As cabinet/bogie assemblies were completed, they shipped from Minnesota to Texas to be hoisted on the roof.
Taking care of customers
ABB continuously tests products, even after release, to ensure that performance, safety and lifetime expectancy are achieved. This was an important benefit with the ACS880-11 drives since they had just been introduced to the market when they were selected for the Globe Life Field project.
Six months after Uni-Systems Engineering purchased 21 ABB ACS880 drives for the project, ABB informed them that some of the drives had failed lifecycle testing due to a component issue. This meant that all 21 of the drives could fail prematurely. “We were impressed that ABB reached out to us to let us know of a potential problem,” says Andrew Agosto, Vice President of Sports Architecture. “The fact that ABB continues to test components, and then reached out to make sure that our drives would perform reliably emphasizes their commitment to taking care of customers and watching out for their success.” ABB proactively offered to replace all the drives for new units that had passed lifecycle testing, but with some cabinets in Minnesota and some in Texas, Uni-Systems Engineering decided to wait until the roof was in place in Texas to make it easier to swap out the drives.”
ABB sent technicians to the stadium to assist in the laborious task of switching out each of the 150-pound drives. The three-person job involved creating a lifting bracket and hoist to lift the load and personnel from the concrete deck to the elevated cabinets, and then replacing the drives. The unique memory unit (ZMU) in the ACS880 allowed the techs to remove it from one drive and install it in the new drive without losing the application-specific programming that had been set by the team in Minnesota.
Ready to play ball
The initial installation was completed in early 2020, with Globe Life Field opening in summer 2020 for the Texas Ranger season. “The project was a success. The stadium roof runs really smoothly with little noise,” says Andrew Agosto. “ABB’s ACS880 drives, and the commitment to customers from the ABB team, were a big part of the project going so well because they were easy to program and worked exactly as advertised.” To close out its inaugural season, Globe Life Field hosted the 2020 World Series.
Photo courtesy of Uni-Systems Engineering 
