VSD retrofit

Following an appraisal, AAR Powerdrives supplied, installed and commissioned a 22kW ABB ACS550 drive for the permanent installation. The full load speed was slowed by 17% to 1185rpm and the no load speed was slowed by 42% to 830rpm.

A challenge of the application was to receive the signal from the bending machine to initiate the motor to start the hydraulic compressor.

"Initially, we used a pressure switch but we could not find the correct place on the hydraulic pack to get the right signal,” says voestalpine Metsec’s Maintenance Manager, Eddie Raymond. "We found that the drive was ramping up and down continuously, causing the part that is being bent to distort and go out of tolerance.

"To cure this, we moved to a timer on the drive. The machine controller sends an "in cycle” signal to the drive. When this signal is not present, the drive is in idle mode, which is the case for 60 percent of the time. After receiving this signal from the machine, the drive waits for two seconds then ramps up the speed for the motor.

"Sometimes the operator would press the cycle start and then finds that he wants to pause the cycle due to the part slipping between the jaws. The two seconds is the check time to allow the cycle to get in full motion and ensures the part is at the correct angle for bending.”

"As well as the energy saving, the lower pressure on the hydraulic system meant less heat build-up, giving a better lifetime, and less noise. The oil is also now lasting longer,” says Raymond. "We also predict a longer life for the motors as they are not running at full speed constantly as previously.”

Voestalpine Metsec is converting four more of its machines to VSD operation over the next few months, with a total of 50 machines being candidates for drive installation.