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King’s Island
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 Products Used

Square D ReactiVar™ AV9000 Real-
Time Reactive Compensation System

Square D solves a Roller Coaster’s Voltage Sag Problem

The massive inrush current associated with starting a large inductive load
typically causes a momentary voltage sag. The magnitude of this sag
depends on the available fault current and the impedance of the network.
In many cases, voltage sags created by inductive load starting within one
customer’s facility may be disruptive to other nearby utility customers.To
effectively solve this problem, the installation of a high speed reactive
power comprensation system is required to offload the utility. Schneider
Electric / Square D manufactures the Square D AV9000 Real-Time
Reactive Compensation (RTRC) system featuring solid-state switched
capacitor stages to supply instantaneous reactive power. This application
note describes an AV9000 installation that corrected the voltage sag
experienced by neighbors of a theme park due to a linear induction
motor used in a roller coaster.
Paramount King’s Island amusement park near Cincinnati, Ohio was
one of the first parks in the world to install a roller coaster which uses a
linear induction motor (LIM) to electro-magnetically accelerate its
vehicles. The Flight of Fear indoor ride’s LIM is used to launch a vehicle
with 24 riders from 0 to 54 mph in under four seconds. The LIM launch
replaces the traditional lift-hill and its relative quietness is ideal for indoor
use. Riders are sent through four inversions and more than 50 horizontal
and vertical curves in complete darkness. The ride launches a vehicle
every other minute creating a voltage sag.

The voltage sags created with each launch on the 12.47 kV feeder line by the inrush current during vehicle acceleration were severe enough to generate
complaints to the utility, Cinergy, by customers neighboring the park. Furthermore, the sags also caused problems for other loads within the park
grounds.The Schneider Electric Power Quality Correction Group was called in to investigate.

The ride is fed from a dedicated 12.47kV to 480V transformer rated 2.5 MVA. Measurements taken on the ride show a balanced three phase load with peaks of 4200 – 4500 Amps depending on vehicle loading. The load profile reaches full peak in less than 3 cycles. After one second the load settles to 3000 – 3500 Amps for three seconds and then drops to 500A for approximately 3 seconds before dropping off to zero. Nominal voltage on the transformer secondary was 519.6V (line-to-line) but sagged to 458.0 Volts at peak load. The total voltage drop was 61.6 Volts or 11.86%.

In addition to neighbor complaints, voltage sags created by LIM launches can have safety concerns on the ride itself: there have been several widely publicized cases where a LIM type ride failed to accelerate to sufficient speed due to the electrical grid’s inability to support such a large and cyclical load. In at least two cases, a LIM ride’s train got stuck in an inversion (upside down) and riders had to be rescued by local emergency response personnel.

Schneider Electric / Square D proposed and built a Square D 3150 kVAR AV9000 Real-Time Reactive Compensation system to provide the LIM’s reactive starting current and eliminate the voltage drop problem. The unit was built in an outdoor enclosure with two main breakers. The AV9000 monitors the main bus via three current transformers to determine the amount of compensation required. The system was installed and commissioned in April, 2001.

Two controllers operate 21 stages of 150 kVAR as required by load conditions. This allows for redundancy and good compensation resolution. Each step consists of SCR controlled deltaconnected capacitors with series connected reactors to prevent resonance and reduce harmonics on the network. The system can respond in less than one cycle (16.7ms), energizing as many of the stages as necessary to support the ride’s launch without creating voltage transients.
In recent months, Schneider Electric has introduced a new product for applications requiring hih speed injection of reactive power. Called the Hybrid VAR Compensator (HVC), the product joins together two existing technologies: ReactiVar capacitor systems and AccuSine active harmonic filters. In a HVC, the capacitor portion can be energized at all times while the variation in reactive power injection is provided by the AccuSine active filter in Electronic VAR Control (EVC) mode of operation.

For example, an HVC could consist of 2 x 300 Amp RMS AccuSine units in conjunction with 500 KVAR of fixed tuned capacitance. This system could provide infinitely variable VAR injection from 0-1000 KVAR at 480 Volts varying its output on a cycle by cycle basis.

Compared to the AV9000 system employed at King’s Island, the HVC topology has several advantages including:
  • Faster response to load fluctuations
  • Single phase independent VAR injection for unbalanced loads(ideal for single phase spot welding)
  • Infinite variability of control rather than discrete step injection for better overall voltage regulation
HVC systems have been successfully been used in applications in the oil & gas, automotive, appliance manufacturing and steel processing sectors.

For more information, contact the Schneider Electric Power Quality Correction Group at (905) 678-6699 or or visit


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