July 17, 2002

PureWave AVC^® Adaptive VAR Compensator Manages Ups and Downs in Reactive Power Flow.

Background

The latest generation of roller coasters catapult riders from 0 to 60 mph in seconds, and lets them experience upside-down turns, and vertical and compound curves. It’s all made possible by the use of linear-induction motors. Unlike old “chain-drag” designs, in which the roller coaster is pulled to the top of a hill and then released relying on gravity to accelerate the cars, the linear-induction motors provide acceleration at key points along the ride.

At one theme park in Maryland, 43 such linear-induction motor pairs are installed along a 200-foot horizontal track. Each roller coaster car carries lightweight aluminum fins, which act as motor reaction plates. This arrangement allows the cars to reach 60 miles per hour from a standing start in just 3 seconds.

But all this excitement came at a cost to the electrical supply system. To generate the torque needed to accelerate the ride, the linear-induction motors required huge amounts of real and reactive power for short periods of time.

Every time the roller coaster was launched, excessive voltage drop would occur at the motor terminals, which could prevent the cars from achieving the speed necessary to complete the cycle. And other utility customers served from the same feeder experienced voltage flicker exceeding the utility’s guidelines.

What Did They Do?

Working with the electric utility, the theme park operator installed a 4100-kVAR, 520-V PureWave AVC Adaptive VAR Compensator on the secondary side of the transformer supplying power to the ride. A second PureWave AVC rated 2400 kVAR was also installed to provide transient voltage support on the utility feeder. Both units work in tandem to support motor voltage and eliminate voltage flicker.

Results

The PureWave AVCs have provided superior performance since their installation in April 1999. Although peak reactive demand actually turned out to be much greater than expected, motor terminal voltage is now precisely maintained, so operation of the ride is consistently successful. And voltage flicker complaints from nearby neighbors have been eliminated.