PureWave AVC® Permits Metals Recycler to Expand Operations.

Background

When a metals recycler in Arizona began planning a facilities expansion featuring a new 6,000-HP car shredder, the local utility expressed concern about the potential for voltage flicker from the large current surges.

A car shredder is a huge hammer mill, with rotating hammers driven by a large motor. Shredders are used to separate the ferrous material in vehicles, which is then sold to steel mills. When a vehicle is shredded, the load on the motor fluctuates rapidly. And this rapid fluctuation in current demand causes a condition known as voltage flicker.

Voltage flicker is a predominantly reactive (VAR) phenomenon. Flicker on an electrical system can cause perceptible changes in the intensity of electric lights. Depending on the frequency, voltage flicker can go from being a mere visual annoyance to causing eye strain or illness in some people. Voltage flicker can also cause equipment malfunctions. Because the voltage flicker with the existing equipment was already severe, the utility insisted that the recycler find a resolution before allowing the facility expansion.

What did they do?

An S&C PureWave AVC Adaptive VAR Compensator was proposed. S&C performed field measurements to determine the size of the system and prepared a study to predict its performance, then presented the proposed solution to the utility and the customer.

The PureWave AVC provides transient reactive current that compensates for the VAR demand changes. It mitigates flicker, provides power-factor correction, and provides real-time voltage support for voltage sags and dips caused by rapidly changing dynamic loads.

S&C ’s proposal was accepted. S&C provided turnkey engineering, procurement, manufacturing, and installation services for an 8000-kVAR, 4160-volt PureWave AVC Adaptive VAR Compensator.

Results

The metals recycler was able to expand its operations and run their new 6,000-HP car shredder while meeting the utility’s strict requirement for voltage flicker of ±0.15% at their 69-kV feeder! These two graphs show the voltage flicker response to the current demand on the 4160-volt side before and after the facilities expansion. With the PureWave AVC in operation, double the load current demand results in less than half the voltage drop . . . greater than a four-fold improvement! In addition, the voltage recovery time is now more than three times faster. According to the facilities manager, “The AVC is doing the job we need, it allows us to operate at maximum capacity and the utility is happy.”

Applications

The PureWave AVC has been applied to heavy commercial and industrial processes having rapidly fluctuating loads, which create rapidly varying reactive power demand. Applications have included such diverse processes as rock crushing, automobile manufacturing, pulp and paper processing, steel manufacturing, elevators, conveyors, and even amusement park rides.

Before Facilities Expansion

After Facilities Expansion,with PureWave AVC

Actual field measurements of system voltage measured on the
4160-volt bus at metals recycler.