by Luis Gamboa, Rockwell Automation

For example, the simplified design of new transformerless drive technology eliminates the need for a transformer thus reducing space and weight requirements-an essential consideration in the oil & gas industry. These drives use pulse width modulated switching patterns and an integrated DC choke as an alternative to heavy and costly transformers that were once the only option for mitigating harmonics and common-mode voltage. By connecting the power supply directly to the drive without an isolation transformer, this technology results in a drive that is smaller and lighter. Transformerless medium voltage drives are ideal for tightly confined applications, such as oil platforms, refineries and pipeline pump stations.

Overall operating costs can also be reduced by the transformerless drive's high efficiency and regenerative capability that converts the variable frequency power generated to a signal that can be pushed back to the utility. The drive can provide 100 percent continuous full-current regenerative braking without putting thermal stress on the motor.

VFDs today also provide integrated control and power. Connecting these two together simplifies information gathering, configuring and programming. For example, programming wizards for drive start-ups operate much like the setup programs in new consumer PCs-after a few prompts, the wizard automatically installs the software and required drivers, sets all the parameters and recognizes the hardware devices plugged into the PC.

In a drive application, the wizard will prompt the user for information about the application, size of the motor and other critical information. It will then automatically set up all the parameters to help meet the defined application and hardware requirements. These tools also allow users to easily save all of their drive parameters and control logic in a single database. In the event of a failure, replacement and restoration of the original drive parameters is a relatively simple process.

Like any industry, the oil and gas sector is evaluating new approaches to increase performance with lower production risk. As the industry works to find new reserves, increase capacity and upgrade its existing infrastructure, it will increasingly rely on drive and power control technology to protect assets, improve motor performance and boost operational and energy efficiency.

Pumps & Systems, April 2008