Product category:
Industrial Drives/Controls
News Release from: Lenze | Subject: Lenze smd inverters
Edited by the Engineeringtalk Editorial
Team on 20 February 2007
Inverters cut pump running costs
Modern Drives and Controls of Leicester teamed up with the Coventry Sports Centre engineers to save energy and reduce electricity bills.
Lenze smd inverters have reduced the running costs of a three-pump installation at the Coventry Sports Centre by about half The pumps return heated water to the swimming bath
A simple installation of three smd inverters immediately gave an improved power factor and site engineers are now able to adjust the flow and achieve constant bath temperature with varying weather conditions.
Pumps represent about 31% of the energy used by motor drives equipment in the UK, the largest single use.
Usually pumps are sized to cope with the maximum predicted flow, leading to the motors running at part load.
The result is low motor efficiency and a low power factor which pulls in extra reactive current.
This was exactly what was happening at the swimming baths which are part of the Coventry Sports Centre.
Built in 1963 and a listed building, little attention was paid to energy costs until the sharp rises seen in recent years.
Three pumps are installed in parallel to take water from the boilers and return it to the swimming pool.
Each pump is powered by a 5.5kW four-pole motor.
The actual working loads depend primarily on the external ambient temperature.
In summer one pump is usually adequate to maintain the pool temperature and the other two are switched off.
In colder weather, two or even all three pumps are needed, and with the pool open 18 hours per day, the pumps usually run continuously 24 hours a day and 7 days a week.
Modern Drives and Controls of Leicester teamed up with the Sports Centre engineers to save energy and reduce their electricity bills.
A site survey with an extended period of measurement revealed the opportunity to reduce running costs on these pumps.
Modern Drives fitted a small panel with three Lenze smd frequency inverters rated at 5.5kW, each with a potentiometer for manual speed control.
This simple installation was made easy by integrated RFI filers in the drives which meet EMC requirements.
The first results seen were a big improvement in power factor with each pump reducing its measured current from 9 to about 5A.
The pumps were running at about 50% load, which had resulted in a power factor below 0.7 and high currents.
Fitting the smd inverters brought the power factor back up towards 1.
This reduced the reactive current, helping the overall power factor on site and made a major reduction in the kVA electricity consumption.
The second benefit is that the site engineers now have the ability to adjust the pump speed to match the demand.
Previously pumps could only be on or off, with the result that motors were running with low loads.
Now they can adjust motor speeds individually and achieve a high load factor with higher motor efficiencies.
This also means big energy savings, as a reduction in motor speed of as little as 10% can save 27% of electrical energy.
Early indications from site indicate that a saving of 17% from reducing speed has been achieved and total saving with power factor is over 50%.
With experience, even better results are expected.
Lenze smd inverters installed by Modern Drives and Controls have made a major improvement in power factor and give the ability to adjust speed steplessly. Request a free brochure from Lenze ...
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