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Tasked with replacing two ageing autotransformer starters at the Kempton Water Treatment Works of Thames Water in the UK, Varicon (3D) Drives Limited, a specialist in the service, repair, supply and installation of motor control equipment, selected Vacon NXS ac variable speed drives for the project.
The drives are used in conjunction with high-lift pumps that provide an auxiliary water feed to the low-pressure main.
As part of a project for Thames Water with a brief of identifying opportunities for saving energy, consultant Advanced Energy Monitoring Systems (AEMS) found that the autotransformer starters that were formerly used with the pumps were not only inefficient, as they allowed only a single speed of operation, they were also inconvenient to use, as they could only be operated by local pushbuttons – there was no provision for operation from the control room.
AEMS therefore approached Varicon to supply modern replacements for the obsolete starters. Varicon selected Vacon NXS drives for the application because it’s previous experience with these products had shown them to be easy to use, dependable and to offer excellent value for money. In addition, the robust design of these drives incorporates effective protection against supply network disturbances and trip-free operation is guaranteed by sophisticated motor control principles and motor/drive protection features.
For this project, Varicon used Vacon drives with ratings of 160kW. The IP21 chassis versions were chosen and were pre-installed in enclosures prior to delivery to minimise the time needed on site for installation, wiring and commissioning.
Stop/start and manual speed control facilities for the drives were provided in the plant control room, and provision was also made for future automatic control of the pump speeds from a 4-20 mA flow signal. When automatic control is ultimately implemented, use will be made of the integral PID controllers that are a standard feature of NXS drives.
The new drives have now been in use for almost four years, and are fully meeting the requirements of Thames Water in terms of both performance and reliability. Indeed, so satisfactory has their operation been that Vacon NXS drives were recently selected for another major project on the Kempton site in a plant that is used to regenerate activated charcoal.
For more information, visit www.vacon.com