Speed Reference Generator with
Load Sharing

OVERVIEW

Co-Bar Corporation produces steel bars which are sold to the automotive industry to produce coil springs for suspensions. Co-Bar asked another vendor to double the horsepower of the Motors and Drives that powered their steel feed roll line. The additional horsepower meant that the customer could draw a wider range of steel, creating a more versatile machine. As a result of the increase HP and revised control scheme, the machine was unable to create straight bars. "Waves" or ripples that occur in the bars strike the sides of the induction heaters as the bars pass through, destroying a portion of the fabrication device. The customer called an independent consulting firm to evaluate the machine. The firm’s conclusion was that the waves were caused by the drive system. After months of downtime, Co-Bar contacted Galco Industrial Electronics for a solution to the problem.

SOLUTION

Galco was determined to succeed where the other vendor had failed. Galco provided engineering, design, manufacture, and programming for the interface of new DC Drives. The new design included three new Control Techniques 50 horsepower, Quantum III, DC drives along with the installation of a high-speed communication network to link the three drives to a new HMI (Human Machine Interface). The space-saving drives were compatible with existing drive isolation transformers, DC motors, and feedback encoders. The HMI unit allowed operators to change system parameters for a variety of product. This solution provided state-of-the-art technology with a higher level of access to the drives and system status.

After a brief start-up period, the machine produced two product bundles. Each of these bundles passed the customer's inspection.

During evaluation of the new drive system, Galco used a data recorder to monitor the load current of each 50 HP motor. Upon evaluation of the data it was noted a slight “wave” in the steel mirrored a similar wave pattern occurring in the load current for one of the 50 HP motors. Further evaluation revealed that one complete waveform was produced during a single revolution of the feed roll. The problem was isolated to four sheered bolts at one of the machine stands. The bolts were replaced and the system produced exceptionally straight bars for the customer.

Steel feed line before upgrade

Steel before upgrade

Steel after drives upgrade

Panel after drive replacement