VisSim/Real-Time at GE Motor & Drive Division

The Motor and Drive Systems Division of General Electric (GEMIS), based out of Salem, Virginia, is one of the largest manufacturers of electrical drive systems worldwide. Using VisSim and VisSim/Real-Time, engineers recently completed prototyping a Resonance Eliminator Controller (REC) for industrial drive systems used in metals rolling applications. The goal of the controller, according to Emil Kuelz and Sandy Gurian, System Engineers for GEMIS, is to reduce resonance vibrations in the shafts and rolls of the mechanical system. Kuelz and Gurian modeled the motor and mechanical system in VisSim, and then incorporated the REC. The REC computes a motor torque correction signal from shaft torque measurement, which in turn is applied to the mechanical system at a specific resonant frequency.

To test the design, Kuelz and Gurian used two PCs, each running VisSim/Real-Time. One PC contained the motor and mechanical system simulation; the other, the REC. VisSim's A-D/D-A real-time interface allowed the two models to exchange information. This configuration verified that controller performance would not be degraded by either time delays introduced by the A-D/D-A conversions or the precision of the 12-bit DAC. "The simulation results assured us that the REC would function properly when attached to the actual motor and mechanical system," said Kuelz.

After verification, Kuelz and Gurian disconnected the PC with the REC from the PC with the motor and mechanical system simulation, and reconnected it to the real motor and mechanical system in GEMIS's in-house laboratory. The first time the REC was turned ON, it totally eliminated the mechanical system resonance.

VisSim model of GE industrial drive system with Resonance Eliminator Controller. Upper plot shows amount of correction applied to motor torque. Lower plot shows drive speed.

Real-Time I/O cards & data channels can be configured directly from VisSim via intuitive dialog boxes.

By developing and testing the REC in VisSim and VisSim/Real-Time, Kuelz and Gurian focused exclusively on proving the viability of the design. "The risks of connecting an unproved design to a large horse power electrical drive and mechanical system are great," said Kuelz. "If incorrectly designed and not thoroughly tested, it can cause motor, shaft, and coupling failure, resulting in a process outage costing millions of dollars."

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