Variable Speed drives (VSDs, frequency inverters) in Pumping industry
Case study on use of Variable speed motors in pumping industry. Environmental influence and financial aspects of use of variable speed drives (VSDs, frequency inverters, AC drives).
Concerned project has been carried out on high specifications residential site that was constructed in two phases. In phase 1, the first building has been developed and made ready for occupation. During this period a booster set was installed and sized for the initial part of development.
During phase 2 of the construction, previously installed booster set found to be too small to support both sections of the project. Therefore, second set of pumps had to be fitted and used in order to supply water to the phase 2.
We were approached by the property management after several faults related to booster set operation which caused water supply interruptions to both developments. During surveying the site for long term solutions, we identified a potential energy and running maintenance cost saving modifications of current system. By using one booster set (supplying phase 2) to supply both sections of the development and by retrofitting Lowara Hydrovar Inverters, we would be able to save our client a substantial amount of money on energy costs, servicing and potential repairs. For calculation and testing purposes, the conversion process was carried out over a 3 week period.
In week one our client arranged to have a Kilowatt hour recorder fitted, so the power consumption on 2 booster sets running in their normal state would be monitored. On the third day of this period an electrical error caused a control fault which made pumps running in manual mode. This is illustrated by spike' in the energy consumption graph which provides good reference point. The second week of the test we fitted Hydrovar inverters to phase 2 booster set and allowed phase 1 booster to continue running as usual.
During third week, the phase 1 booster was removed from service and the entire development supplied from the phase 2 booster set with variable speed drives fitted.
On the day 4 pumps were running uncontrolled; therefore 302 kilowatts have been used. At this moment, the site serviced by the variable speed Hydrovar set consumes around 20 kilowatts per day.
AUTHOR: M. Starczewski, T. Shearer
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