VSD Stands For Very Significant Dividend

Tailoring motor speed to the task offers a variety of important benefits.

By Seán Ottewell, Editor at Large

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Barlow cites the results achieved at one U.S. plastic sheet manufacturer that decided to replace a DC motor and drive system used on its primary extruder with a 500-hp AC vector motor and drive. The line has three extruders with its own service from the power company, so a power quality meter and analysis of the utility's bill enabled easy verification of the retrofit's impact.

"The retrofit was performed between billing cycles. The billing cycle prior to the retrofit showed an overall power factor of 0.49 with a peak power of 371 kW. After the retrofit, the bill showed a power factor improvement to 0.86 and the peak power was reduced to 360 kW. It is clear that the retrofit had an impact on the peak kW, which demonstrates an energy efficiency improvement, as well as a power factor improvement."

"The energy saving in this application was estimated at $2,500 a month, equating to $30,000/year. Combined with the maintenance costs associated with the DC motor, the estimated return on investment for this application was 1.4 years," he notes.

 For its part, Yaskawa has just added the A1000 range of VSDs to its portfolio. The company claims the A1000 is robust, flexible and user-friendly, and provides twice the calculated design life of previous generations (Figure 2).

Meanwhile, ABB, Zurich, Switzerland — which recently expanded its drive (and motor) portfolio with the purchase of Baldor, Ft. Smith, Ark. — says six main drivers spur developments in its VSD technology: making devices more user friendly, with common user interfaces across the whole range; simplifying maintenance and installation; reducing the footprint; integrating certified safety features; providing improved lifecycle services; and creating industry- and application-specific features.

"In the chemical, oil and gas (COG) industry there is reluctance to use the newest technology. So we are working closely with our customers to see what would be the best solution for them and we are giving them training to use the products in the best possible way. Also, we are working to ensure that the drives are extremely reliable," explains Markus Eklund, market manager COG.

ABB's experience at Repsol's refinery in La Plata, Argentina, highlights the benefits that VSDs can provide.

The 750-acre site contains 35 different processing unit. Originally, steam turbines handled a large number of drive applications. This posed a number of disadvantages, including the higher cost of steam versus electricity, the greater maintenance costs of gas turbines relative to electric drives, and high operating costs due to the large amount of cooling water circulating through the surface condensers.

So, Repsol replaced one of the three steam-turbine-powered blowers on fluid catalytic cracking (FCC) unit A with an electric system consisting of an ABB KTMP 4400 double secondary transformer, an ACS 1000 medium-voltage AC drive and an AMB 560 L2L motor. Benefits realized include more efficient use of power because of better speed control, far smoother torque application throughout the required power range, and improved power index (Figure 3).

"The energy intensity index of the FCC unit improved by 10.5% within one year by replacing one steam turbine with an electric drive," notes Marcelo Ruiz, manager of the FCC units at the refinery.

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