When drivers on a road near an ornamental lake and fountain in London’s docklands complained that they were getting an unexpected and unwanted free car wash, Carillion PME, the company in charge of maintaining the site, called in automation expert Wilson Electric for help with eliminating the problem. Two Vacon NXL AC variable speed drives proved to be the key to an efficient and cost-effective solution.

The fountain in the East India Dock area of London undoubtedly looks attractive. However, even in moderate wind conditions spray from the fountain affected vehicles on the adjacent busy roadway, a situation which was not only inconvenient for the drivers of the vehicles, but also a potential safety hazard.

One solution would have been to switch off the fountain on windy days but, as only a small amount of wind was needed to trigger the problem, this would have meant that fountain would spend much of its time out of use. Carillion PME wanted a better solution and, following discussions with Wilson Electric, it was agreed that a system would be put in place that would regulate the height of the fountain according to the prevailing wind speed.

The fountain is fed by two pumps, each with an 11 kW motor. The pumps run in parallel and, in the original arrangement, the pump motors were provided with standard direct-on-line starters. There was no provision for speed control and there was no space within the existing control panel for the addition of the variable speed drives that would be needed to control the height of the fountain. 

However, after looking closely at the application, engineers from Wilson Electric found that there was just sufficient space to accommodate two of Vacon’s exceptionally compact NXL drives within the enclosure that houses the control panel.

“The small size of the NXL drives was a key advantage in this application,” said John Brooker, Technical Services Supervisor for Wilson Electric, “but they also had other benefits including, for example, ease of use, enclosed construction and built-in EMC filters.”

To sense the wind speed, Wilson Electric fitted an anemometer that has a standard 4 to 20 mA analogue output. As might be expected, the anemometer provides a 4 mA signal at zero wind speed, increasing linearly to 20 mA for wind speeds of 30 knots or greater. However, the speed of the pumps is required to be highest at zero wind speed, decreasing as the wind speed increases. The flexible software of the NXL drives was therefore used to configure them for an inverse response to the signal from the anemometer.

Contact details

electrical industry variable speed drive news, e-lec.org