Product category:
Industrial Drives/Controls
News Release from: Rockwell Automation | Subject: Allen-Bradley 1336 12-pulse configured drives
Edited by the Engineeringtalk Editorial
Team on 22 November 2001
Drives part of water clean up system at
Heathrow
Rockwell Automation has supplied two 160kW Allen-Bradley 1336 12-pulse configured drives for a new water treatment system designed to handle run off water from BAA's Heathrow Airport.
Rockwell Automation has supplied two 160kW Allen-Bradley 1336 12-pulse configured drives for a new water treatment system designed to handle run off water from BAA's Heathrow Airport The drives have been installed as part of BAA's major £22m, 10 year project to improve water quality around Heathrow, the busiest international airport in the world, using an innovative system of reed beds known as the Heathrow Constructed Wetlands
Run off water from airports is often mixed with contaminants such as the glycol used to de-ice runways and aircraft in winter, and BAA has become the first airport operator in the world to use man-made reed beds to purify waste water.
Run off water from Heathrow's Eastern catchment area is collected in a BAA reservoir at Hatton Cross on the eastern side of the airport, where a new pumping station has been built.
There the Allen-Bradley 1336 drives control the speed of two pump sets, which send the untreated water through 3 km of the existing fire ring main to a one hectare floating reed bed to the south of the airport.
The reed beds digest the contaminants and the clean water is allowed to run back into the River Crane.
The variable speed drives are required to control the flow of water through the 36 inch fire main and ensure that pressures never exceed the maximum permitted 12 bar.
Water from Heathrow's Southern catchment is mixed with water from the floating reed beds before being treated in separate two hectare sub-surface flow gravel reed beds.
Although the system is mainly called upon to handle extra run off water following heavy rainfall or during winter, it forms part of BAA's overall water management strategy and is in continuous use.
The project was managed for BAA by mechanical and electrical contractor AMEC, and the drives were configured and built for the project by Rockwell Automation's drives engineering facility at Bletchley.
An expert in wetland treatment systems, Peter Worrall, produced the concept design for the scheme and worked with the framework engineers and contractors to integrate the ecological and engineering aspects of the scheme.
The Bletchley site has extensive experience and expertise in the design and assembly of high power configured drives and drive systems, and is one of the few UK centres able to offer 12-pulse drives.
Rockwell Automation can design and supply 12-pulse drives in ratings up to 600kW within six to eight weeks of receiving an order.
It does this by integrating isolating phase shifting transformers and series rectifier bridges into DC bus 6-pulse units, converting them to true 12-pulse drives.
This greatly reduces the key 5th and 7th harmonics generated by 6-pulse drives, which now have to be strictly controlled under new limits imposed by Engineering Recommendation G5/4.
These more stringent recommendations can result in low voltage 6-pulse inverters rated higher than approximately 40kW no longer being suitable for direct connection to the National Grid electrical supply.
One alternative to 12-pulse drives is to use active filters to reduce the harmonics put back in to the mains by a 6-pulse drive.
Rockwell Automation believes however that the most cost effective route to compliance with G5/4 is to install true 12-pulse technology.
Rather than install complex harmonic filters BAA chose Allen-Bradley 12-pulse drives to improve both water and electrical power quality at Heathrow. Request a free brochure from Rockwell Automation ...
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